A Geomorphic Classification System
U.S.D.A. Forest Service
Geomorphology Working Group
Haskins, Donald M.1, Correll, Cynthia S.2, Foster, Richard A.3, Chatoian, John M.4,
Fincher, James M.5, Strenger, Steven 6, Keys, James E. Jr.7, Maxwell, James R.8 and
King, Thomas 9
February 1998
Version 1.4
1
Forest Geologist, Shasta-Trinity National Forests, Pacific Southwest Region, Redding,
CA; 2 Soil Scientist, Range Staff, Washington Office, Prineville, OR; 3 Area Soil
Scientist, Chatham Area, Tongass National Forest, Alaska Region, Sitka, AK; 4
Regional Geologist, Pacific Southwest Region, San Francisco, CA; 5 Integrated
Resource Inventory Program Manager, Alaska Region, Juneau, AK; 6 Supervisory Soil
Scientist, Southwest Region, Albuquerque, NM; 7 Interagency Liaison for Washington
Office ECOMAP Group, Southern Region, Atlanta, GA; 8 Water Program Leader,
Rocky Mountain Region, Golden, CO; and 9 Geology Program Manager, Washington
Office, Washington, DC.
A Geomorphic Classification System
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Table of Contents
Abstract.......................................................................................................................................... 5
I.
INTRODUCTION................................................................................................................. 6
History of Classification Efforts in the Forest Service ............................................................... 6
History of Development .............................................................................................................. 7
Goals of the Geomorphology Working Group ............................................................................ 8
II.
GEOMORPHIC CLASSIFICATION .......................................................................... 10
Geomorphic Process ................................................................................................................. 10
Landform ................................................................................................................................... 11
Morphometry............................................................................................................................. 12
Geomorphic Generation ........................................................................................................... 14
III.
APPLICATION OF GEOMORPHIC CLASSIFICATION ....................................... 16
Application of the Classification at a Site................................................................................. 16
CRITERIA ............................................................................................................................ 17
CHARACTERISTIC ............................................................................................................ 17
Geomorphic Mapping and Map Units ...................................................................................... 17
Map Unit Concepts ............................................................................................................... 17
Application of the Classification for a Polygon.................................................................... 19
IV. USING THIS CLASSIFICATION FOR EXISTING MAPPING .................................. 21
V.
LINK TO NATIONAL TERRESTRIAL AND AQUATIC HIERARCHIES .......... 23
VI.
SUMMARY ..................................................................................................................... 26
VII.
REFERENCES ............................................................................................................ 27
References Cited ....................................................................................................................... 27
References used for the classification but not cited .................................................................. 29
References by Geomorphic Process.......................................................................................... 31
APPENDICES ............................................................................................................................. 35
Appendix A : Reference List of Existing Geomorphic and/or land Classification Systems ...... 35
A Geomorphic Classification System
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Appendix B; A Hierarchical Classification of Geomorphic Processes and Landforms .......... 36
FLUVIAL ............................................................................................................................. 36
GLACIAL ............................................................................................................................. 39
PERIGLACIAL .................................................................................................................... 42
LACUSTRINE ...................................................................................................................... 43
TECTONIC ........................................................................................................................... 44
VOLCANIC .......................................................................................................................... 45
MASS WASTING ................................................................................................................ 46
COASTAL MARINE ........................................................................................................... 51
SOLUTION........................................................................................................................... 53
EOLIAN ................................................................................................................................ 54
Appendix C: Landscape Terms ................................................................................................. 55
Appendix D: Common landforms.............................................................................................. 56
Appendix E: Microfeatures ....................................................................................................... 57
Appendix F: Morphometry........................................................................................................ 58
Appendix G: List of Reviewers.................................................................................................. 63
Appendix H: Codes for Geomorphic Processes and Landforms .............................................. 64
Used in this Geomorphic Classification ................................................................................... 64
Appendix I: Glossary of Geomorphic Processes and Landforms ............................................. 77
A............................................................................................................................................ 77
B ............................................................................................................................................ 78
C ............................................................................................................................................ 83
D............................................................................................................................................ 86
E ............................................................................................................................................ 90
F ............................................................................................................................................ 92
G............................................................................................................................................ 96
H............................................................................................................................................ 97
I ............................................................................................................................................. 98
K.......................................................................................................................................... 100
L .......................................................................................................................................... 101
M ......................................................................................................................................... 104
N.......................................................................................................................................... 106
O.......................................................................................................................................... 108
P .......................................................................................................................................... 109
R .......................................................................................................................................... 113
S .......................................................................................................................................... 117
T .......................................................................................................................................... 124
U.......................................................................................................................................... 128
V.......................................................................................................................................... 128
W ......................................................................................................................................... 130
Y.......................................................................................................................................... 130
U
A Geomorphic Classification System
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List of Tables
Table 1:
Table 2:
Table 3:
Table 4:
Table 5:
An example of the hierarchical link between Geomorphic Process and Landform. 11
Example of a Geomorphic Site Characterization...................................................... 17
An Example of a Geomorphic Map Unit .................................................................. 20
Summary of Linkage of the Geomorphic Classification System to ......................... 24
Use of Geomorphic Classification at the Site Scale ................................................. 25
A Geomorphic Classification System
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Abstract
Geomorphic Classification is the categorization and description of the nature, origin and
development of landforms. The fundamental framework of this classification is that a
geomorphic unit can be classified based collectively on its origin and development
(process), on its general structure and shape (landform), on measurements of its
dimensions and characteristics (morphometry) and on the presence and status of
process overprinting (geomorphic generation). Geomorphic Process has two
hierarchical elements within this classification: Geomorphic Process Type and
Geomorphic Subprocess. In addition, Subprocess Modifier is used as a further
refinement for some Geomorphic Subprocesses. The Landform component of the
classification is directly linked to the Process components in a hierarchical manner. The
Landform portion of the classification consists of two hierarchical components:
Landform and Element Landform. The following classification terms are not a part of
the hierarchical framework for Landform, but are important constituents of the
classification: Landscape Term, Common Landform and Microfeature. Morphometry
consists of measurements or characterizations of landforms or portions of landforms
including: relief, elevation, aspect, slope gradient, slope position, position/landform
modifier, slope shape vertical, slope shape horizontal, slope complexity, ground surface
shape, landform width, microfeature relief, dissection frequency, dissection depth,
drainage pattern, drainage density and stream frequency. Finally, Geomorphic
Generation is meant to describe the presence and status of geomorphic process
overprinting, and is characterized as active, dormant or relict. Applications of this
classification, which are described, include geomorphic and surficial geology mapping,
geomorphic map units and geomorphic site characterization. This classification was
designed to link with the USDA Forest Service’s ecological unit concepts, including the
“National Hierarchical Framework for Ecological Units” (USDA, 1993), as well as the
“Hierarchical Framework of Aquatic Units” (Maxwell et al, 1995). Geomorphic Process
and Landform can be described at all scales within these frameworks. Morphometry is
most often applied at the Landscape or Land Unit scales for terrestrial units, and at the
Watershed and lower scales within the Aquatic Framework. This classification is also
useful at the most specific scale, the Site.
A Geomorphic Classification System
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I.
INTRODUCTION
As used in this document, Geomorphic Classification is the categorization and
description of the nature, origin and development of landforms. The fundamental
framework of this classification scheme is that a geomorphic unit can be classified
based collectively on its origin and development (process), on its general structure and
shape (landform), on measurements of its dimensions and characteristics
(morphometry), and on the presence and status of process overprinting (geomorphic
generation). This paper will document the components of each of these elements as
well as how the classification can be used.
The primary purposes of this classification are to:
♦ Standardize geomorphic information throughout the Agency;
♦ Provide a consistent framework for collection of geomorphic information at the site
level and at broader scales; and
♦ Through the concept of geomorphic mapping and map units, provide a model for
the use of geomorphic information as a line determinant, rather than a descriptor,
in mapping efforts.
History of Classification Efforts in the Forest Service
Traditionally in the Forest Service, geomorphic information has been collected (mapped
and described) and used by a variety of resource specialists, for a multitude of
purposes. Hydrologists, geologists, soil scientists, geomorphologists and others have
all participated in various classification development efforts (See Appendix A for a
partial list of existing geomorphic and/or landform classification systems). Some of the
primary reasons for which geomorphic information has been traditionally collected are:
♦ As an attribute of Soil Resource Inventories or soil survey map units;
♦ To help characterize or define the physical parameters of a site, such as a
vegetation plot, soil pedon description, bridge site, heritage resource site, or
recreation site;
♦ To define geologic hazards;
♦ As a primary component of Land-systems Inventory map units; and
♦ Most recently, as a primary component of integrated ecological map units.
However, geomorphology has not been standardized by the Agency either within or
across functional specialist areas. From a mapping standpoint, geomorphology has
most commonly been used as a general descriptor of the landscape. Mapping where
geomorphology is a significant line determinant for surveys on National Forest System
Lands has been limited.
A Geomorphic Classification System
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The most extensive geomorphic mapping within the Forest Service over the past
several decades has been conducted in the western Regions with the specific purpose
of delineating mass wasting features and identifying landslide hazard areas,
and as a primary component of Land-systems Inventory and Integrated Resource
Inventory mapping efforts. More recently, comprehensive geomorphic mapping has
become more widespread nationally since it is one of the fundamental components
used to identify ecological types and ecological map units for the Ecological Unit
Inventory program.
Throughout all of these efforts, no single system has been used to classify
geomorphology. Some Forests, groups of Forests or Regions have compiled
geomorphic classifications, but they have not received widespread use. For the most
part, various disciplines have used a variety of geomorphic process, landform and
morphometry terms and concepts interchangeably, though inconsistently and
sometimes inaccurately, in order to describe and map landforms.
Over the past decade there have been efforts to adopt a geomorphic classification
system which would unify all the different schemes being used by different disciplines
and various agencies. Several attempts have been made by individuals or groups
within agencies to accomplish classification systems. However, each of the schemes
was incomplete, useful to only a single discipline or of limited utility in local or regional
applications.
In 1994, an interagency USDA team consisting of geologists, soil scientists and
geomorphologists from the Forest Service and Natural Resources Conservation Service
began discussing the merits of compiling a unified geomorphic classification system
using these premises. This effort continues, however, due to requests from the field,
this version of the Geomorphic Classification was developed in the interim and ideas
discussed by the interagency group incorporated as appropriate.
History of Development
Development of this classification began in 1995 through work performed for several
related projects. The Common Survey Data Structure Project (CSDS), an inter-regional
Forest Service effort to develop a corporate information structure and data standards,
began to evaluate the Lands module in 1995. The Lands module includes geology,
geomorphology, soils, minerals and geotechnical engineering. The CSDS land team,
consisting of Forest Service soil scientists and geologists, agreed that geomorphology
needed to be elevated to an equal status with other resource specific themes, rather
than be an attribute of other themes.
A unified classification system needed to be employed to support current analysis
needs, ongoing hierarchical ecosystem classification and mapping initiatives.
A Geomorphic Classification System
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Under the umbrella of CSDS, a geomorphology working group was formed, which
includes geologists, soil scientists, integrated inventory specialists and hydrologists.
The goal of this group was to compile a geomorphic classification system which could
be broadly applied. The group used a combination of methods to compile the
classification: using existing classification systems, where possible, for the individual
geomorphic process types; joined several schemes together; and modified schemes to
ensure consistency within the classification system. This project was completed
through the support of the Terrestrial Ecological Unit Inventory Group, sponsored by the
Washington Office Ecosystem Management Corporate Team.
Goals of the Geomorphology Working Group
The primary goals established by the geomorphology working group for development of
a geomorphic classification are as follows:
1. The classification must address multiple scales;
2. The classification must be flexible while providing a consistent structure and
definitions;
3. The classification should be used for: a) delineating geomorphology as a separate
theme, b) delineating the geomorphic component of an ecological unit, and c) for
describing the geomorphology of a site;
4. The classification would serve as a service-wide standard for geomorphology, and
therefore must accommodate existing information and needs, as well as provide
a consistent structure for the future;
5. The classification should use existing service-wide standards and accepted
definitions wherever possible and available; and
6. The classification should be consistent with the National Hierarchical Framework
of Ecological Units (USDA, 1993) and a Hierarchical Framework of Aquatic
Ecological Units in North America (Maxwell et al, 1995).
It is desirable that a geomorphic classification system be based on geomorphic process
in order to associate related landforms and processes and to define linkages. This is
beneficial for performing landscape-scale ecosystem analyses. The purpose of
ecosystem analysis is to study and assess the condition of ecosystem functions,
processes and inter-relationships in order to recommend management activities which
maintain or restore ecosystem function. Classifying geomorphic systems according to
process assists in inventories better serving the needs of these analyses.
It should be noted that in practice the recognition and identification of geomorphic
process is often done by first mapping and identifying landforms or element landforms.
Because of the hierarchical nature of this classification, and the link between process
and landform, application of the classification can occur either by beginning with
process and working down through the landforms or (and perhaps more commonly) by
identifying the landform and thereby linking to process.
A Geomorphic Classification System
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The geomorphic classification system also needs to be hierarchical in order to address
related landforms at various scales; to illustrate the relationships to both higher-order or
more finite geomorphic processes, landforms and landform components; and to link at
all scales to the National Hierarchical Framework of Ecological Units (USDA, 1993).
The classification system must also allow for retrofitting of existing geomorphic
information through the use of existing terms to the extent possible.
This classification is meant to provide a national standard for geomorphic classification
which can be used by all disciplines within the Forest Service. It is therefore designed
to meet a broad spectrum of needs. It is also meant to be an iterative classification,
which is updated and modified on a regular basis or as the need arises.
Finally, this paper describes data standards, not data requirements. Our goal is to
provide a unified scheme which can be used if classification or data collection for
geomorphology is conducted. These are not data requirements which require that all of
the information and data elements described need to be collected. Data requirements
need to be determined on an individual project basis.
Following this introduction, there are seven other sections to this document. The
second section contains the definitions and relationships of the various elements of the
classification. The third section describes applications of the classification while the
fourth section describes how the classification can be used to retrofit existing mapping.
The fifth section describes how the classification is used to define ecological units at
various scales, consistent with the National Hierarchical Framework of Ecological Units
(USDA, 1993) and a Hierarchical Framework of Aquatic Ecological Units in North
America (Maxwell et al, 1995). The sixth part is a summary, while the seventh part is a
reference list of the sources of information used for the classification and specifically for
each of the different process types. The final section is comprised of appendices which
include references for other geomorphic classification systems used within the Forest
Service, the complete hierarchical classification system for geomorphic process and
landforms, a listing of common landforms, landscape terms and microfeatures, and
definitions for the morphometry elements. It also includes codes which can be used for
data collection or data entry into corporate data bases and finally a complete glossary of
terms used in this classification.
A Geomorphic Classification System
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II.
GEOMORPHIC CLASSIFICATION
There are four components to the Geomorphic Classification System: Geomorphic
Process, Landform, Morphometry and Geomorphic Generation. The following
discussion describes these components.
Geomorphic Process
Geomorphic Process is the dominant internal or external geologic force that has
interacted with the existing geologic structural framework to shape the Earth’s surface.
Geomorphic Process has two hierarchical elements within this classification:
Geomorphic Process Type and Geomorphic Subprocess. In addition, a Subprocess
Modifier is used as a further subdivision for some Geomorphic Subprocess Types. The
definitions for each are as follows:
Geomorphic Process Type - A general description of the dominant geomorphic
process responsible for the nature, origin and development of the landforms.
Geomorphic Process Types are Fluvial, Glacial, Periglacial, Lacustrine, Tectonic,
Volcanic, Mass Wasting, Coastal Marine, Solution, and Eolian.
Geomorphic Subprocess - A subdivision of Geomorphic Process which groups
related landforms. For example, the Glacial Geomorphic Process type is
subdivided into Ice Erosion, Meltwater Erosion, Water Deposition (in close
proximity to ice), Ice Deposition, Active Ice and Snow Features, and Proglacial
Deposition.
Subprocess Modifier1 - A subdivision of Subprocess used for the Fluvial and
Glacial Process types. For example, Alpine and Continental are Subprocess
Modifiers for each of the Glacial Subprocesses.
Not all Geomorphic Process types have Subprocess or Subprocess Modifiers due either
to the simplicity of the classification system adopted or the nature of the Geomorphic
Process Type. Appendix B contains the Geomorphic Process Types and related
Subprocesses, Subprocess Modifier, and Landforms.
1
Some readers may find the use of this category a rather awkward and perhaps
artificial accommodation. However, since all attempts at classification are inherently
imperfect, the authors have chosen to use Subprocess Modifier as a way to maintain
the simplicity of the classification structure, while providing for some necessary
refinements of the glacial and fluvial geomorphic process types.
A Geomorphic Classification System
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Landform
A landform is defined as "Any physical feature of the Earth's surface having a
characteristic, recognizable shape and produced by natural causes" (Bates and
Jackson, 1995). The Landform component of the Geomorphic Classification is directly
linked to the Geomorphic Process element described above in a hierarchical manner.
The landform portion of the classification consists of two hierarchical components:
Landform and Element Landform. Following are definitions of each.
Landform - A landform that exists within a single Geomorphic Process Type, and which
can be delineated at scales at or above the Land Unit (Landtype and Landtype Phase)
level. For instance, under the Subprocess of proglacial depositional, Landforms include
outwash plain, outwash fan, outwash terrace kettled outwash plain, valley train and
outburst floodplain.
Element Landform - A spatial component of a Landform at the level immediately below,
and hierarchical to Landform, which can be delineated at scales at or above the Land
Unit (Landtype and Landtype Phase) level. A beach ridge is a subdivision of a beach
and a toe zone is a subdivision of an earth flow. Table 1 is an example of Element
Landforms associated with a glacial trough landform.
Geomorphic
Process
Subprocess
Subprocess
Modifier
Landform
Active Ice
and Snow
Processes
Alpine
Glacier
Element
Landforms
Moulin
Serac
Pressure Ridge
Crevasse
Bergshrund
Ice Apron
Drainage Channel
(Undifferenctiated)
Fosse
Table 1: An example of the hierarchical link between Geomorphic Process and
Landform.
Not all Landforms have Element Landforms due either to the relative simplicity of the
classification system adopted for that particular Geomorphic Process Type, or the
nature of the Geomorphic Process Type. Appendix B contains a listing of landforms
within the hierarchical classification system, linked to their related geomorphic
Processes and Subprocesses. Appendix I is a glossary which defines all of the
Geomorphic Processes and Landforms used in this classification.
A Geomorphic Classification System
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The following classification constituents are not hierarchically linked to the classification,
but are important components of the classification system:
Landscape Term - A general or descriptive term used to describe collections of
landforms, generated from a variety of geomorphic processes, on a subregional or
landscape basis, e.g., basin and range, bolson, glaciated uplands, valleys,
canyonland, plateau, and ridge and valley. Appendix C contains a list of
Landscape Terms, which are defined in Appendix I.
Common Landform - Landforms that commonly occur as components of a variety
of larger landforms. These are landforms not clearly tied to a single Geomorphic
Process Type or Landform. For instance, the Common Landform swale may occur
on moraines, toe zones, eroding hillslopes, or alluvial fans. They represent terms
that are "common usage" or "generic" such as mound, knob, or bench. Common
Landforms should be used in conjunction with a process landform unless they are
used to describe a site (point or plot) where the process and landform cannot be
determined. See Appendix D for a list of Common Landforms which are defined in
Appendix I.
Microfeature - Small, local forms on the land surface with an aerial extent (for
individual features) of less than a few meters, that can be described by vertical
changes in elevation measurable in centimeters, or at most several meters, that
are superimposed upon a Landform, Element Landform or Common Landform.
Individually these features are either too small to be delineated (and are therefore
used to describe a site), or they occur grouped in a repeating pattern which are
mappable (such as patterned ground features). See Appendix E for a list of
Microfeatures, which are defined in Appendix I.
Morphometry
Morphometry is defined as "The measurement and mathematical analysis of the
configuration of the Earth's surface and of the shape and dimensions of its landforms"
(Bates and Jackson, 1995). It is most often applied to a geomorphic map unit to provide
the quantification needed to ensure consistent application for mapping, correlation, and
interpretation purposes. The following measurements or characterizations of elements
of the landforms are used in the Morphometry portion of this Geomorphic Classification
System:
Relief, elevation, aspect, slope gradient, slope position, position/landform modifier,
slope shape vertical, slope shape horizontal, slope complexity, ground surface
shape, landform width, microfeature relief, dissection frequency, dissection
frequency class, dissection depth value, dissection depth class, drainage pattern,
drainage density and stream frequency.
A Geomorphic Classification System
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Not all parameters are applicable at all scales. Also, these parameters can be
expressed as ranges of values, averages or means as an application of the
classification.
Following are the various morphometry parameters which can be measured or
described. A list of valid values for applicable parameters is contained in Appendix F.
Relief - Differences in elevation of a land surface or specific geomorphic feature,
measured in meters or feet.
Elevation - The elevation of a land surface, measured in meters or feet from the
average of the mean high and mean low tide.
Aspect - Direction in which a slope faces, measured in degrees of azimuth or
cardinal direction.
Slope Gradient - The gradient of the inclined surface of any part of the Earth's
surface, measured in percent or degrees.
Slope Position - A description of the two dimensional position on the slope profile
of the landform, e.g., summit or backslope.
Position/Landform Modifier - A modifier which may be used to better describe the
slope position or position on a landform, e.g., upper, second, windward, distal, and
landward.
Landform Width - Measurement of the width of landforms, such as terraces,
floodplains, stream channels, and glacial troughs, measured in meters or feet.
Slope Shape Vertical - Refers to the vertical slope shape of the land surface, e.g.,
concave, linear, and broken.
Slope Shape Horizontal - Refers to the horizontal slope shape of the land surface,
e.g., concave, linear, and broken.
Slope Complexity - Refers to the complexity of slope shape for a point or polygon.
Simple slopes may be further described as linear/planar, concave, or convex.
Complex slopes may be further described as broken, undulating, or patterned.
Ground Surface Shape - Shape of the ground surface (as opposed to the land
surface), expressed as either hummocky or uniform. May be further described by
identifying the microfeature influencing the surface shape.
Dissection Frequency - The number of stream channels per linear mile or
kilometer, within a polygon.
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Dissection Frequency Class - The frequency class for dissections in landforms
with slope components.
Dissection Depth Class - The dissection depth class for landforms with slope
components.
Dissection Depth Value - The actual measured value of dissection depth in feet or
meters.
Drainage Density - The density or total length of stream channels on a landform
expressed in terms of miles of channel per square mile of land or kilometers of
stream per hectare of land.
Drainage Pattern - The configuration or arrangement in plan view of the natural
stream courses in an area, e.g., dendritic, trellis, angulate, contorted.
Microfeature Relief - Refers to the vertical change in elevation of the land surface
at scales measurable in centimeters to a few meters, or inches and feet, that are
superimposed upon a larger landform and are too small to delineate on a
topographic map or aerial photograph, at commonly used scales.
Stream Frequency - The measurement of the total number of stream channels of
all orders, divided by the area of a basin, watershed, or polygon.
Geomorphic Generation
Geomorphic Generation is a component of the classification that allows for the
recognition and documents the status of more than one geomorphic type at any given
location on the ground (overprinting). Overprinting occurs when two or more dissimilar
geomorphic processes have operated on an area at different time periods due to the
influences of climatic changes and/or tectonics. For instance, an extensive uplifted
Tertiary river terrace has a mass wasting translational slide landform superimposed on
it. Determination of the Geomorphic Generation of each landform will identify the
genesis of each of the landforms, the relationship between the landforms, and the
status of the process which formed or continues to form the landforms.
A polygon or point can be attributed for “Geomorphic Generation” using the following
terms:
Active - A landform which is continuing to develop under the contemporary
processes that formed it, such as a floodplain, where tectonic or climatic “events”,
which are influencing the landform, occur on the scale of hundreds of years, and
are expected to continue to occur. Examples include Holocene fault landforms,
recently active mass wasting landforms, alluvial fans, and Holocene volcanic
composite cones.
A Geomorphic Classification System
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Dormant - A landform which evolved or developed under different geologic and
climatic influences which do not occur in contemporary times. Processes which
formed these landforms could re-occur, but the cycles responsible for them occur
on the order of thousands or tens of thousands of years. Examples would be
glacial, periglacial and eolian landforms which evolved in the Pleistocene, when
climatic conditions were cooler and/or wetter.
Relict - Landforms or remnants of landforms which developed in previous geologic
periods which remain recognizable well past the period of their development which
are unlikely to renew development under contemporary conditions. Examples
would include volcanic landforms which developed in the Tertiary which have not
exhibited volcanic activity for several million years, eroded fault scarps in
tectonically stable areas, and deeply incised coastal plains.
For mass wasting landforms, attributing for geomorphic generation must not be
confused with either natural or human induced slope stability hazard evaluation. A
mass wasting feature which is considered “active” from a geomorphic generation
perspective, may well have a generally low natural slope stability hazard, while a
“dormant” mass wasting feature may have a high susceptibility to be re-activated by
certain human activities such as road construction. Determining slope stability hazards
requires complete analysis of many factors, including identification of the geomorphic
process and landform, morphometry, material characteristics, groundwater conditions,
bedrock structure, as well as other local factors.
A Geomorphic Classification System
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III.
APPLICATION OF GEOMORPHIC CLASSIFICATION
The classification can be applied in the following ways:
♦ At a site, by selecting appropriate terms from the classification; and
♦ For a polygon, by selecting an appropriate term or combination of terms. The
combination of terms generally results from a mapping design that incorporates
the concept of geomorphic map units and scale of mapping.
The following sections describe the application of the classification at a site, and as part
of a mapping exercise, with or without geomorphic map units.
Application of the Classification at a Site
This Geomorphic Classification system can also be used to help characterize sites in a
consistent manner. Site characterizations are commonly used for vegetation plots,
paleontology sites, heritage resource sites or at soil pit sites.
Geomorphology has been used to model locations of heritage sites based on observed
relationships between various landforms and the presence of historic sites.
Geomorphology has also been used to describe the geomorphic locations of soils to
record relationships that would be useful in predicting further occurrence and making
interpretations. It has also been used to assist in determining the relationship of plant
communities to landforms or morphometric variables.
Site descriptions of geomorphology have also been used for specific geotechnical
investigations to provide design criteria for projects including foundations, bridgesites, surface and subsurface drainage, road cuts and location, sewage disposal
systems and remedial landslide stabilization measures. Finally, site analysis of
geomorphology is used for the study of natural hazards. Table 2 is an example of
how geomorphology is used to characterize a site.
A Geomorphic Classification System
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CRITERIA
Landscape
Landform Description
Geomorphic Process
Geomorphic Subprocess
Process Modifier
Landform
Element Landform
Common Landform
Microfeature
Slope Complexity
Slope Gradient
Slope Position
Position/Landform Modifier
Horizontal Slope Shape
Vertical Slope Shape
Landform Dissection
Frequency
Landform Dissection Depth
CHARACTERISTIC
Mountains
Landslide Toe slope
Mass Wasting
Complex
N/A
Slump-Earthflow
Nested Toe Zone
Swale
Tree Tip Mound
Complex, Broken
55 percent
Toe Slope
Lower
Convex
Concave
Dissected
Moderate
N/A
Table 2: Example of a Geomorphic Site Characterization
Geomorphic Mapping and Map Units
Map Unit Concepts
Geomorphic classification at a site is relatively “pure” because the variability of
ecosystem components is limited or reduced. Once the concept of mapping is
introduced to the classification, “inclusions” become inherent due to the natural
variability of the landscape (i.e., large areas of “pureness” rarely exist). This variability
led soil scientists to develop the concept of map units, a concept now applied by
specialists in other resource areas, as defined in the Soil Survey Manual (USDA,
1993b).
A map unit recognizes that even relatively homogeneous areas of land have “included”
areas that are unlike the pure component (e.g., an aspen tree in a stand of Douglas fir).
The concept of map unit is based on the following assumptions:
♦ Relationships of components within a map unit can be described and classified
(e.g., as a complex or association);
♦ The extent of each recognized component within a map unit can be defined by
percent (in a relative sense);
A Geomorphic Classification System
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♦ At each scale a certain homogeneity of the landscape exists that allows map units
to be defined and applied repeatedly within a given set of parameters or ranges
of characteristics;
♦ Similar components are less important to distinguish than dissimilar components;
and,
♦ Identification of mapping objectives precedes identification of map unit concepts.
Identification of map unit concepts usually precedes mapping and numerous
iterations refine the concepts.
Each map unit differs in some respect from other map units in an area (subregion or
landscape). Map unit design incorporates the following principles:
1.
2.
3.
4.
The map unit can be mapped consistently;
The map unit is needed to meet the objectives of the inventory;
The map unit occurs with enough frequency to warrant distinction;
Delineation of the map unit is useful in understanding, or provides the basis
for understanding, relationships to other integrated resource components;
and
5. The size of the map unit is appropriate to the mapping scale.
These criteria need to be met in order to validate the necessity for each map unit.
Geomorphic map units can be designed as stand-alone map units, or as one of the
components of an integrated ecological map unit. A geomorphic map unit represents a
collection of landforms defined in terms of their individual or collective geomorphology.
Each map unit differs in some respect from all other map units in a survey area and is
uniquely identified in the survey legend. Map units may consist dominantly of one
geomorphic component or of two or more components, each of which generally
comprise at least 15 percent of the map unit. Components of minor extent are
inclusions and may comprise up to 10 percent of the map unit. All components,
including inclusions which are important to the interpretation or understanding of the
map unit, are described in the map unit description. In an ecological map unit
description, the geomorphology components are correlated to the appropriate bedrock
and surficial geology, soil and vegetation components.
The arrangement of components within a map unit is referred to as the map unit type.
Four types of geomorphic map units are used to show the relationships: 1)
consociations, 2) associations, 3) complexes and 4) undifferentiated groups. The
concepts for these types are derived from the Soil Survey Manual (USDA, 1993b).
Consociations are map units which delineate a single geomorphic process or landform,
depending on scale. Consociations allow for up to 15 to 25 percent inclusions of
another landform depending on the scale of the mapping, as long as it is not too
dissimilar, and only if the interpretation for the unit would not be adversely affected.
A Geomorphic Classification System
18
Complexes and associations consist of two or more different geomorphic processes or
landforms, depending on scale, which occur in a regularly repeating pattern. The
distinction between complexes and associations is a function of scale. The dominant
components of a complex cannot be mapped separately at commonly used scales,
while the major components of associations can be mapped at that scale. Complexes
and associations can generally have up to three major components with 15 to 25
percent inclusions depending on scale. At very broad scales or for reconnaissance
surveys there may be more than twenty components and inclusions due to the nature
and intent of the survey.
Undifferentiated groups consist of two or more different geomorphic processes or
landforms that are not consistently associated geographically, and therefore, do not
always occur together in the same delineation. These different landforms
are included in one map unit because the interpretations are the same or very similar.
Generally, they occur together because some common process such as Glacial Alpine
Ice Erosion (scoured basin, roche mountennee, hanging valley, nunatak, trough)
determines the interpretation.
A percent composition for each major component and inclusions within a map unit, as it
occurs across the landscape, is also assigned. The percent composition is a relative
comparison of the likely proportion (dominance/codominance) of each component within
a map unit. The percent composition may be expressed either as a single value or as a
range of values.
Map units are designed generally using the following components: Landscape Term,
Geomorphic Process, Subprocess and Subprocess Modifier, Landform and Element
Landform, Common Landform, Geomorphic Generation, and morphometry elements
including slope gradient, slope shape, slope position, position/landform modifier, and
dissection class frequency and depth. The minimum required components are
Geomorphic Process, Subprocess and Landform. Table 3 is an example of a map unit
description.
Each map unit is assigned a name that represents a common, short, descriptive label
which people can relate to. Map units may also be assigned a code, defined by each
Region.
Application of the Classification for a Polygon
The primary purposes for which geomorphic mapping might be performed are:
1. Development of a pure geomorphic map as one layer in an integrated
resource inventory or geomorphic inventory;
2. Mapping of geologic hazards, or geomorphic features as special interest or
interpretive areas; and
A Geomorphic Classification System
19
3. Development of an ecological unit inventory (or an integrated inventory)
map using geomorphic map units.
The application of this classification through geomorphic map units and mapping can
assist in the development of rigorous standards for classifying and delineating
landforms and geomorphology. Combining process, landform, morphometry and
geomorphic generation into standard “regional” map units ensures the consistent
recognition and delineation of landforms, and provides a standard to correlate landforms
to ensure a reliable product for use in analysis and decision-making.
Geomorphic map units can be designed as stand-alone map units, or as one of the
components of an integrated ecological map unit. A geomorphic map unit represents a
collection of landforms defined in terms of their individual or collective geomorphology.
Geomorphic map units designed and applied on a subregion or landscape basis are
customized to reflect local differences in landform, morphometry and lithology (e.g., the
characteristics of a mountain slope may vary dramatically from one landscape to the
next even though the geomorphic history or processes are similar). Map units designed
for a particular subregion or landscape also provide a framework for correlating
ecological units and types.
Dry Lake Shoreline Complex
Landscape: Bolson
Ecological Unit: Landtype
Map Unit Type: Complex
Geomorphic
Process
Subprocess
Landform
Lacustrine
Tectonic
Lake
Terrace
Beach
Eolian
Deposition
Slope
Position
Horizontal/
Vertical
Slope
Shape
Dissection
Frequency/
Depth
Geom
Gen
%
Comp
Footslope
Linear/
Linear
Slightly
Dissected/
Shallow
D
25
Beach
Plain
Toeslope
Linear/
Linear
Undissected
D
40
Backshore
Terrace
Toeslope
Linear/
Linear
Undissected
D
20
Toeslope
Broken/
Broken
Undissected
A
15
Element
Landform
Dune
Field
Table 3: An Example of a Geomorphic Map Unit
A Geomorphic Classification System
20
IV. USING THIS CLASSIFICATION FOR EXISTING MAPPING
One of the goals of the authors is to ensure that the geomorphic classification will be
able to accommodate exiting geomorphic information. The following section describes
how geomorphic mapping has been performed by various individuals, institutions and
agencies for the past century. An understanding of the different types of geomorphic
mapping will help determine how to best integrate earlier survey work with this
classification. It will be desirable for existing geomorphic mapping to be cross walked
into this classification for future applications. The following discussion is meant to
describe various types and uses of geomorphic mapping.
Geomorphic mapping has generally been documented in two manners: most commonly
as components of bedrock and/or surficial geology maps, and less frequently as
landform maps. Geomorphology has also been mapped as a component of Ecological
Unit Inventories, or Integrated Inventories; however, as previously described,
geomorphology has not consistently been a mapped attribute in these types of
inventories.
The fundamental purpose of traditional bedrock and surficial geology maps is to identify
the location and extent of lithostratigraphic units, gain an understanding of the
geochronology for each of the lithostratigraphic units, the geologic structures related to
them or that control them, to characterize the lithology and material characteristics of
each unit, and to
ascertain the geologic history and resources of the investigated area. Surficial
lithostratigraphic units traditionally mapped include undifferentiated alluvium, river sand
and gravels, dune sand, beach sand, marine terrace deposits, alluvial terrace deposits,
alluvial fans, landslide deposits, marsh and swamp deposits, ground moraine deposits,
terminal moraine deposits, kame-delta deposits, colluvium and a variety of coastal
marine deposits including barrier islands and sand spits. These maps can be used to
display stratigraphic relationships between the different types of surficial deposits, or
between similar deposits, such as a series of Quaternary stream terrace deposits, from
oldest to youngest, Qt1, Qt2 and Qt3. Emphasis for characterizing the surficial deposits
has generally been focussed on the material characteristics, not necessarily the
landform or the geomorphic processes which formed it. Good examples of surficial
geology mapping include Fuller (1914), Jahns (1953 ), Koteff (1966), Colton and Fitch,
(1974), Huffman et al, (1975) and Carrara (1990).
Geomorphic or landform mapping has been performed far less frequently compared to
bedrock and surficial geology mapping. Geomorphic mapping has generally been
performed to develop land use control by local and county government related to issues
such as human induced beach and sea cliff erosion, landsliding and ground
displacement due to active faulting (Atwater, 1978), river engineering and floodplain
management (Brookes and Gregory, 1988), and urban issues related to sinkholes
including fill construction, groundwater withdrawal, increased ground loading from
A Geomorphic Classification System
21
buildings, and drainage increases related to storm water runoff and sewer systems
(Tan, 1986). In addition, geomorphic mapping has been employed by State agencies to
help evaluate landslide hazards related to timber harvest plan reviews for private lands
(Bedrossian, 1983). State agencies have also used geomorphic mapping to identify
sites for developing sand and gravel resources (Schwochow et al, 1974).
As previously discussed, geomorphic mapping has also been employed by the Forest
Service to help identify mass wasting features and related natural slope stability
hazards. General geomorphic mapping has been performed to identify geomorphic
terranes and slope stability hazards for use in broad Forest Planning (USDA Forest
Service, 1994). In addition, more detailed geomorphic mapping has been performed on
National Forests in California, Oregon and Washington for the purpose of identifying
geomorphic processes and responses for landscape scale Watershed Analyses (de la
Fuente and Haessig, 1993, USDA Forest Service 1995a, 1995b).
Detailed geomorphic mapping has also been used by the Forest Service to determine
specific mass wasting features and the potential for instability related to the construction
of roads and timber harvest activities (Seidelman et al, 1977, Borum, 1980, Haskins, et
al, 1980, Jasso, 1984, and Smith, 1990). Mass wasting landforms were also mapped
by Gallegos et al (1995) to help guide Burned Area Emergency Rehabilitation measures
for the El Monte Fire in southern California. Mapping of glacial landforms for analysis
as “Special Features” has also been performed on several National Forests (Long,
1977, Haskins, 1986).
Analysis of existing geomorphic mapping indicates that it can be cross-walked into the
geomorphic classification framework described in this paper. Bedrock and surficial
mapping cannot be easily cross-walked, since it has a different purpose. However,
when geomorphic maps are used in conjunction with bedrock and surficial maps,
enhanced characterizations of landforms and geomorphic history can be performed.
Geomorphic mapping and attributing for geomorphic generation can be used in
conjunction with bedrock and surficial geologic maps to provide a more complete
geomorphic and stratigraphic history for an area. It can also be used to provide a
complete characterization of the landforms and the materials that comprise them, and
an appraisal of the activity status of the geomorphic processes for specific landforms.
A Geomorphic Classification System
22
V. LINK TO NATIONAL TERRESTRIAL AND AQUATIC
HIERARCHIES
This Geomorphology Classification System was designed to link with both the National
Hierarchical Framework for Ecological Units (USDA, 1993) and the Hierarchical
Framework of Aquatic Units in North America (Maxwell et al, 1995).
Geomorphic Process can be described at many scales within the National Hierarchical
Framework of Ecological Units. At the Ecoregion and Subregion scale, they are the
dominant internal or external geologic forces that have interacted with the existing
geologic structural framework to produce the overall pattern of landscapes within a
terrane during the late Cenozoic era. At the Landscape scale they are the combination
of geologic, climatic and gravitational forces acting to shape specific landforms during
the Pleistocene and/or Holocene epochs and may overprint the general regional
processes. At the Land Unit scale geomorphic processes describe the effect of local
and Recent tectonic, atmospheric and gravitational forces over a small area of the
surface, such as an element landform, common landform or microfeature, and within a
broader landform. Table 4 illustrates these concepts.
Landforms also can be described within the context of the National Hierarchical
Framework of Ecological Units at a variety of scales. At the Ecoregion and Subregion
scale they are generally a system or complex of landforms which reflect similar geologic
structure and climate. Patterns differ from adjacent regions. At the Landscape scale
they reflect any physical feature of the earth's surface having a characteristic,
recognizable shape and produced by natural causes. At scales below the Landscape
level, component parts may be described or a more rigorous identification of the
features can be made (Table 4).
A Geomorphic Classification System
23
Scale
Ecological
Units
Geomorphic
Process
Landform
Morphometry
Ecoregion/
Subregion
Province,
Sections and
Subsections,
River Basins,
Sub-basins and
Watersheds
A Collection
of Process
Types
Landscape
Terms
Drainage Density,
Drainage Pattern,
Dissection and
Relief
One or two
Geomorphic
Process
Types
Consociation,
Association or
Complex of
Landforms
Drainage Density,
Slope Gradient,
Elevation,
Drainage Pattern,
Stream
Frequency, Relief
Process,
Subprocess
and
Subprocess
Modifier
Consociation,
Association or
Complex of
Landforms,
Element
Landforms
and Common
Landforms
Slope Position,
Slope Shape,
Slope Gradient,
Elevation, Slope
Complexity,
Width Class,
Drainage Density,
Dissection
Frequency,
Dissection Depth,
Relief, Aspect
Landscape Landtype
Association,
Subwatershed
Land Unit
Landtype or
Landtype Phase
Table 4: Summary of Linkage of the Geomorphic Classification System to
The National Hierarchical Framework of Ecological Units (USDA, 1993) and the
Hierarchical Framework of Aquatic Units in North America (Maxwell et al, 1995).
The classification scheme for the Fluvial Geomorphic Process Types, especially stream
processes, was constructed to conform to the parameters described in the Hierarchy of
Aquatic Ecological Units in North America (Maxwell et al, 1995). In particular, the
distinction between eroding, transporting and depositional stream channel processes
was intended to blend the work of Montgomery and Buffington (1993), Rosgen (1994)
and Schumm (1977). This was done to nest aquatic valley segments and stream
reaches within this geomorphic classification system and to consistently link aquatic
systems with terrestrial ones.Morphometry is most often applied at the Landscape or
Land Unit scales within the National Hierarchical Framework of Ecological Units, and at
the Watershed and lower scales within the Aquatic Hierarchy. At Ecoregion and
Subregion scales it is used to describe the measurement of features (primarily elevation
and/or relief) over a large area, and describes qualitatively the description of patterns
A Geomorphic Classification System
24
and geologic textures, particularly the characteristics of River Basins, Subbasins and
Watersheds. At the Landscape or Subwatershed scale it is the measurement of the
shape and dimensions of landforms or groups of related landforms. At the Land Unit
scale, it is the measurement of single landforms or element landforms.
The most specific scale, Site, is not a scale addressed by the National Hierarchical
Framework of Ecological Units, but is an important scale at which to classify
ecosystems or ecosystem components. Morphometry, at the site level, is the
measurement of a specific component of a landform, or a description of a point on that
landform. Table 5 illustrates how the Geomorphic Classification can be used to classify
an ecological type at the site scale.
Scale
Application
Geomorphic
Process
Landform
Morphometry
Site
Vegetation
Plot, Soil Pit,
Site Note,
Ecological
Unit Modal
Site or
sample
Process,
Subprocess
and
Subprocess
Modifier
Landform or
Element
Landform,
Common
Landform,
and
Microfeature
Slope Position,
Position/Landform
Modifier,
Microfeature
Relief, Relief,
Aspect, Elevation,
and Slope
Table 5: Use of Geomorphic Classification at the Site Scale
A Geomorphic Classification System
25
VI.
SUMMARY
This geomorphic classification system is based on the definition of four elements: 1)
Geomorphic Process; 2) Landform; 3) Morphometry; and 4) Geomorphic Generation.
The definition of each of these elements collectively defines the geomorphology of the
feature or area. Process and Landform are linked in a hierarchical manner which allows
for the association of related landforms and geomorphic processes. It also allows the
classification system to be used at all scales. However specific morphometric attributes
may only be applicable at certain scales. The selection of specific morphometric
parameters which need to be collected should be made at the project design stage and
documented in a work plan. Geomorphic generation is a part of the classification that
allows for the recognition of more than one geomorphic process type or landform at any
given location due to process overprinting.
This geomorphic classification system links to both the National Hierarchy of Terrestrial
Ecological Units and the National Hierarchy of Aquatic Ecological Units. It can be used
to describe and delineate geomorphic features as a separate theme or as a component
of an ecological unit.
Application of the classification, including geomorphic mapping, use of the concept of
geomorphic mapping units and site characterization will help provide a more uniform
approach to geomorphology and better integration into Ecological Unit Inventories.
Analysis indicates that cross walking of existing geomorphic mapping can be performed,
and when used in conjunction with surficial mapping, can provide a desirable
characterization of not only the geomorphology but also the material characteristics and
qualities of the landforms.
This classification can be used by all resource disciplines describing or mapping
geomorphology. It provides a scientifically-based framework designed to be suitable for
the needs of all disciplines. Geomorphology is considered a distinct theme or layer of
information. This classification scheme maintains the integrity of this theme while
allowing application by a number of disciplines in a variety of ways.
Finally this classification provides a common framework for all disciplines to exchange
geomorphic information. This system will provide for more effective and efficient
integration of inventories and analyses between the various disciplines. It will also
provide for more accurate and consistent correlation of various resource information
with geomorphology.
A Geomorphic Classification System
26
VII. REFERENCES
References Cited
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A Geomorphic Classification System
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Gallegos, A.J., Levitan, F., and DeGraff, J.B., 1995, Slope Stability Conditions in
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A Geomorphic Classification System
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A Geomorphic Classification System
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A Geomorphic Classification System
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A Geomorphic Classification System
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Geological Survey, Washington, DC, 429 pp.
Ward, A.W. and Greeley, R., 1984, Evolution of yardangs at Rogers Lake, CA,
GSA Bull. v.95, pp. 829-837, Geological Society of America, Boulder, CO
Fluvial
Howard, A.D., 1967, Drainage analysis in geologic interpretation: a summation;
Am. Assoc. Petroleum Geologists Bull. v. 51, pp. 2246-1159
Leopold, L.B., Wolman, M.G. and Miller, J.P., 1964, Fluvial Processes in
Geomorphology, W.H. Freeman and Company, San Francisco, CA, 522 pp.
Maxwell, J.R., Edwards, C.L.,Jensen, M.E., Paustian, S.J., Parrott, H. and Hill,
D.M., 1995, A Hierarchical Framework Of Aquatic Ecological Units In North
America (Nearctic Zone); ECOMAP, USDA Forest Service, Washington DC, 72
pp.
Montgomery, D.R. and Buffington, J.M., 1993, Channel Classification, Prediction
of Channel Response and Assessment of Channel Condition; Report TFWSH1093-002, SHAMW Committee of the WA State Timber/Fish/Wildlife
Agreement, 84 pp.
Rosgen, D.L., 1987, Proceedings, Riparian Ecosystems and their Management:
Reconcilling Conflicting Uses, Tuscon, AZ
Rosgen, D.L., 1994, A Classification of Natural Rivers, Catena, v.22, no.3, pp.
169-199.
Schumm, S.A., 1987, The Fluvial System; John Wiley and Sons, N.Y., 338 pp.
Scott, A.J. and Fisher, W.L., 1969, Delta Systems and Deltaic Deposition, in
Deltas in the Exploration for Oil and Gas, W. Fisher and L. Brown, A.Scott and
J.McGowen, eds.; Bureau of Economic Geology, Univ. of Texas, Austin
Glaciation
Dewry, D., 1986, Glacial Geologic Processes; Edward Arnold, Ltd., London
A Geomorphic Classification System
32
Fahey, B.D. and Thompson, R.D., eds., 1973, Resarch in Polar and Alpine
Geomorphology, 3rd Guelph Symposium on Geomorphology, GEO Abstracts Ltd.,
Univ. of East anglia, Norwich, NOR88C, England, 206 pp.
Sugden, D.E. and John, B.S., 1976, Glaciers and Landscape: A Geomorphological
Approach; Halsted Press, N.Y.
Lacustrine
Hutchinson, G.E., 1957, A Treatise on Limnology, v.1; John Wiley and Sons, N.Y.,
1015 pp.
Maxwell, J.R., Edwards, C.L.,Jensen, M.E., Paustian, S.J., Parrott, H. and Hill,
D.M., 1995, A Hierarchical Framework Of Aquatic Ecological Units In North
America (Nearctic Zone); ECOMAP, USDA Forest Service, Washington DC, 72
pp.
Solution
Ford, D.C. and Williams, P.W., 1989, Karst Geomorphology and hydrology; Unwin
Hyman Ltd., London, 601 pp.
Jennings, J.N., 1985, Karst Geomorphology, 2nd ed.; Basil Blackwood Inc., N.Y.,
293 pp.
Monroe, W.H., 1970, Glossary of Karst Terminology; Water-Supply Paper 1899-K,
U.S. Geological Survey, Washington Dc, 26 pp.
Sweeting, M.M., 1973, Karst Landforms; Columbia Univ. Press, N.Y., 362 pp.
White, W.B., 1988, Geomorphology and Hydrology of Karst Terrains: Oxford Univ.
Press, New York, 464 pp.
White, W.B., 1990, Surface and near surface karst landforms, in Groundwater
Geomorphology, the Role of Subsurface Water in Earth-Surface Processes and
Landforms, Higgins, C.G. and Coates, D.R., eds, Geological Society of America
Special Paper 252, pp 157-176.
Mass Wasting:
Coates, D.R., 1977, ed; Landslides, Reviews in Engineering Geology, Vol III, Geol
Soc of Amer.; 278 pp.
Hansen, M.J., 1984, Strategies for Classification of Landslides; in Slope Instability,
Brunsden, D. and Prior, D.B., eds., John Wiley and Sons Ltd, Chichester, 620 pp.
A Geomorphic Classification System
33
Selby, M.J., 1982, Hillslope Materials and Processes, Oxford University Press,
Oxford, 264 pp.
Varnes, D.J., 1978, Slope Movement Types and Processes; in Schuster, R.L., and
Krizek R.J., eds., 1978, Landslides: Analysis and Control, National Academy of
Sciences, Transportation Research Board, National Research Council,
Washington, D.C., pp 12-33.
Periglacial:
Washburn, A.L., 1970; An Approach to a Genetic Classification of Patterned
Ground. Acta Geogr. Lodz., 23:437-446.
Washburn, A.L., 1973, Periglacial Processes and Environments, St. Martins Press,
New York, 1973.
Tectonics:
Holmes, A., 1965; Principles of Physical Geology, 2nd ed.: Ronald Press, New
York, 1288 pp.
Jackson, M.D. and Pollard D.D., 1988, the Laccolith-stock Controversy: New
Results from the Southern Henry Mountains, Utah: Geol Soc America, v. 100, pp.
117-139.
Kelley V.C., 1955, Monoclines of the Colorado Plateau; Geol Soc America Bull., v.
66, pp. 789-804.
Volcanics:
McDonald, G.A., 1972; Volcanoes, Prentice Hall, Inc., Englewood Cliffs, New
Jersey, 510 pp.
Nichols, D.R. and Yehle, L.A., 1961, Mud Volcanoes in the Copper River Basin,
Alaska, in Raasch, G. O., ed., Geology of the Arctic; Univ of Toronto Press,
Toronto, pp. 1063-1087.
deSilva, S.L., Self, S., and Francis, P.W., 1988, The Chao Dacite Revisited (abst.):
EOS, v. 69, no. 44, pp 1487-1488.
Thorarinsson, S., 1951, Laxargljufur and Laxarhraun: A Tephra-chronological
Study; Feograf. Annaler, v. 33, pp 1-88.
Williams, H., and McBirney, A.R., 1979, Volcanology; Freeman, Cooper and
Company, San Francisco, 397 pp.
A Geomorphic Classification System
34
APPENDICES
Appendix A : Reference List of Existing Geomorphic and/or land
Classification Systems
Following is a partial list of existing geomorphic and/or landform classification
systems or glossaries commonly used in the Forest Service:
Brock, T., West, R, and Paustian, S.J., 1996, A Landform Classification Guide for
the Alaska Region, USDA Forest Service; Region 10 in-house publication, 56
pages plus plates
Haskins, D.M., and Chatoian, J.M., 1993, Geology Data Standards for Ecological
Unit Inventories for the Pacific Southwest Region, USDA Forest Service, Region 5,
Technical Paper 05-008, 56 pp.
Hawley, J.W., and R.B. Parsons, 1980, Glossary of Selected Geomorphic and
Geologic Terms. West Technical Service Center, Soil Conservation Service,
Portland, Oregon. 30 p.
Holdorf, H., and J. Donahue, 1990, Landforms for Soil Surveys in the Northern
Rockies. Miscellaneous Publication No. 51. Montana Forest and Conservation
Experiment Station, School of Forestry, University of Montana, Missoula, Montana.
26 p.
Palmquist, R.C., 1990, Numerical Classification of Landform Elements, Prepared
for the Shoshone National Forest, Draft #4.
Peterson, F.F., 1981, Landforms of the Basin and Range Province Defined for
Soil Survey. Nevada Agricultural Experiment Station, Reno, Nevada. 52 p.
Peterson F.F., 1990, A manual for Describing NSSL Soil-Sampling Sites: Terms
and Concepts for Identifying Physiographic Position and Other Sampling-Site
Descriptors, Draft Version 1.0. Department of Range, Wildlife, and Forestry,
University of Nevado-Reno, Reno, Nevada. 53 p.
Soil Conservation Service, 1993, Glossary of Landform and Geologic Terms. in
National Soil Survey Handbook 430-VI-NSSH. USDA Soil Conservation Service,
Washington, D.C. pp. 627-I to 627-59.
USDA Forest Service, Southwestern Region, 1986, Terrestrial Ecosystem Survey
Handbook.
A Geomorphic Classification System
35
Appendix B; A Hierarchical Classification of Geomorphic Processes
and Landforms
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
FLUVIAL
Fluvial Slope Processes
(Subprocess Modifier: Uniform Fluvial Erosion w/o Structural
Control)
Surface Eroding Slope
Monadnock
Inselberg
Pediment
Badland
Ballena
Fan Remnant
Partial Ballena
Non-Buried Fan Remnant
Erosion Fan Remnant
(Subprocess Modifier: Differential Fluvial Erosion With Complex
Structural Control)
Cuesta
Dipslope
Scarpslope
Hogback
Dipslope
Scarpslope
Louderback
Dipslope
Scarpslope
Butte
Mesa
Dike
Hoodoo
Structural Bench
Bajada
A Geomorphic Classification System
36
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Mountain Valley Fan
Alluvial Fan
The following
element landforms
can be used with
the previous two
landforms:
Fanhead Trench
Fanhead Collar
Inset Fan
Fan Skirt
Fan Apron
Fan Piedmont
Stream Processes
(Subprocess Modifiers: Undifferentiated, Eroding, Transporting or
Depositional)
Stream
Thalweg
Channel
Cutoff Channel
Bar
Point Bar
Longitudinal Bar
Bank
Island
Floodplain
Alluvial Flat
Meander Scar
Meander Scroll
Oxbow
Levee
Flood Plain Playa
Flood Plain splay
Stream Terrace (Undifferentiated)
Depositional Stream Terrace
Erosional Stream Terrace (Strath)
(Subprocess Modifier: Terminal Deposition)
Delta
A Geomorphic Classification System
Delta Plain
37
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Basin Processes
Bolson
Playa
Semi-Bolson
Valley Floor
Valley Flat
(Alluvial Flat)
Basin-Floor
Remnant
Playa
(See Lacustrine
Process for
additional playarelated landforms)
A Geomorphic Classification System
38
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
GLACIAL
Ice Erosion
(Subprocess Modifiers: Continental or Alpine)
Scoured Basin
Roche Mountonnee
Hanging Valley
Nunatak
Trough (Glacial Valley)
Trough Wall
Trough Floor
Riegel
Sidewall
Cirque
Cirque Headwall
Glacial Quarry
Flute
Cirque Floor
Arete
Horn
Col
Meltwater Erosion
(Subprocess Modifiers: Continental or Alpine)
Tunnel Valley
Ice Margin Channel
Spillway
Coulee
Water Deposition (Close Proximity to Ice)
(Subprocess Modifiers: Continental or Alpine)
Esker
Kame
Kame Terrace
Collapsed Ice-Floored Lakebed
Collapsed Ice-Walled Lakebed
Crevasse Filling
A Geomorphic Classification System
39
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Ice Contact Deposition
(Subprocess Modifiers: Continental or Alpine)
Fluted Surface
Drumlin
Crag and Tail
Moraine (Undifferentiated)
Ground Moraine
Interlobate Moraine
Lateral Moraine
Medial Moraine
Recessional Moraine
Terminal Moraine
Kame Moraine
Disintegration Moraine
End Moraine
Kettle is an
element landform
for each of the
moraine types
Active Ice and Snow
Processes
(Subprocess Modifiers: Continental or Alpine)
Glacier
Moulin
Serac
Pressure Ridge
Crevasse
Bergshrund
Ice Apron
Drainage Channel
(Undifferentiated)
Fosse
Snowfield
Nivation Hollow
Nivation Ridge
A Geomorphic Classification System
40
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Proglacial Deposition
(Deposited from Meltwater
Not in Close Proximity to Ice)
(Subprocess Modifiers: Continental or Alpine)
Outwash Plain
(Plain Sandur)
Outwash Fan
Outwash Terrace
Kettled Outwash Plain
(Kettled Sandur)
Valley Train
(Valley Sandur)
Outburst Floodplain
Giant Ripples
A Geomorphic Classification System
41
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
PERIGLACIAL
Frost Action
Patterned Ground (Undifferentiated)
Patterned Ground (mappable areas):
Circles
Polygons
Nets
Steps
Stripes
Permafrost
Tor
Block (Rock) Field
Pingo
Palsa
Thermokarst
A Geomorphic Classification System
42
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
LACUSTRINE
Undifferentiated
Tectonic
Sag Pond
Volcanic
Landslide
Slump Pond
Glacial
Paternoster Lakes
Tarn
Solution
Fluviatile
Oxbow Lake
Shoreline
Eolian
Organic
Meteoric
Anthropogenic
Beaver
The following landforms can
be described for any of the
above processes:
Lake
Lake Plain
Lake Bed
Lake Terrace
Beach
Beach Plain
BackshoreTerrace
(Berm)
Beach Ridge
Island
Shoreline
A Geomorphic Classification System
43
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
TECTONIC
Faulting
Fault Scarp
Compound Fault Scarps
Scarp Slope
Fault Trace
Fault Terrace
Graben
Horst
Tilt Block
Fissure
Shutter Ridge
Folding
Folds
Monocline
Dome
Anticline
Syncline
Homocline
Structural
Structural Basin
Structural Domes (Undifferentiated)
Diapir
Laccolith
Batholith
Stock
A Geomorphic Classification System
44
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
VOLCANIC
Constructional
Volcanic Cone (Undifferentiated)
Shield Volcano
Composite Cone (Stratovolcano)
Parasitic Cone
Pyroclastic Cone (Undifferentiated)
Cinder Cone
Pumice Cone
Mud Volcano
Fissure Vent
Volcanic Dome (Undifferentiated)
Exogenous Dome
Pelean Dome
Intrusive Dome
Upheaved Dome
Plug Dome
Steptoe
Lava Flow (Undifferentiated)
AA Flow
Pahoehoe Flow
Block Flow
The following Element
Landforms can be
used for all lava flows:
Pressure Ridge
Trench
Spatter Cone
Pyroclastic Flow (Ash Flow)
Lahar
Air-Fall Tephra Field
Fumarole Field
Mud Pot Field
Destructional
Caldera
Collapse Caldera
Explosion Caldera
Crater
Maar
A Geomorphic Classification System
45
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
MASS WASTING
Fall
Fall-Prone Slope
Source Area
Deposit (Talus)
Topple
Topple-Prone Slope
Source Area
Deposit (Talus)
Slide
Rotational Slide
Main Scarp (Undiff)
DS-Prone Main
Scarp
Nested Main Scarp
Secondary
Scarp(Undiff)
DS-Prone
Secondary
Bench (Undiff)
Eroded Bench
Nested Bench
Toe Zone (Undiff)
Nested Toe Zone
DS-Prone Toe Zone
A Geomorphic Classification System
46
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Translational - Block Slide
Main Scarp (Undiff)
DS-Prone Main
Scarp
Nested Main Scarp
Secondary Scarp
(Undiff)
DS-Prone
Secondary Scarp
Nested Secondary
Scarp
Bench (Undiff)
Eroded Bench
Nested Bench
Toe Zone (Undiff)
Nested Toe Zone
DS-Prone Toe Zone
Translational - Debris Slide
Main Scarp
Secondary Scarp
Bench
Eroded Bench
Toe Zone
A Geomorphic Classification System
47
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Rotational-Translational
Slide
Main Scarp (Undiff)
DS-Prone Main
Scarp
Nested Main Scarp
Secondary Scarp
(Undiff)
DS-Prone
Secondary Scarp
Nested Secondary
Scarp
Bench (Undiff)
Eroded Bench
Nested Bench
Toe Zone (Undiff)
Nested Toe Zone
DS-Prone Toe
Zone
Lateral Spread
Rock Spread
Earth Lateral Spread
Flow
Debris Flow
Source Area
Transport Zone
Deposit
Debris Avalanche
Source Area
Transport Zone
Deposit
Snow Avalanche Slope
Source Area
Transport Zone
(Chute)
Runout Zone
Avalanche Talus
A Geomorphic Classification System
48
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Soil Creep Slope
Ridgetop Bedrock
Outcrop (Source)
Hillslope Bedrock
Outcrop (Source)
Colluvial Shoulder
Colluvial Slopes
Earth Flow
Main Scarp
Secondary Scarp
Bench
Eroded Bench
Toe Zone
Periglacial Flows
(Undifferentiated)
Solifluction Lobe
Solifluction Sheet
Solifluction Terrace
Frost Creep Slope
Rock Glaciers
Rock Stream
Dry Sand Flow
Ravel Cone
Loess Flow
Complex
Rock Fall Avalanche
Source Area
Transport Zone
Deposit
Slump and
Topple-Prone Slope
Source Area
Transport Zone
Deposit
A Geomorphic Classification System
49
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Rock Slide-Rock Fall
Source Area
Transport Zone
Deposit
Slump-Earth Flow
Main Scarp (Undiff)
DS-Prone Main
Scarp
Nested Main Scarp
Secondary Scarp
(Undiff)
DS-Prone
Secondary Scarp
Nested Secondary
Scarp
Lateral Scarp
(Undiff)
Nested Lateral
Scarp
DS-Prone Lateral
Scarp
Bench (Undiff)
Eroded Bench
Nested Bench
Toe Zone (Undiff)
Nested Toe Zone
DS-Prone Toe
Zone
Internested RotationalTranslational Slides
Debris Slide Basin
Valley Inner Gorge
A Geomorphic Classification System
50
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
COASTAL MARINE
Shoreline Processes
Beach
Beach Plain
Beach Ridge
BackshoreTerrace
(Berm)
Dunes (See Eolian Geomorph Process Type)
Sea Cliff
Tombolo
Tidal Flat
Spit
Longshore Bar
Barrier Island
Barrier Flat
Barrier Beach
Storm Berm
Washover Fan
Headland
Stack
Island
Organic Reef (Undifferentiated)
Fringing Reef
Barrier Reef
Platform Reef
Patch Reef
Corral Pinnacle
Oceanic Atoll
Shelf Atoll
Faros
Lagoon
Backwater
Estuary
Mud Flat
A Geomorphic Classification System
51
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
Emergence
Coastal Plain
Strand Plain
Carolina Bay
Marine Terrace (Undifferentiated)
Wave Built Terrace
Wave Cut Platform
Relict Coastline
Raised Beach
Raised Beach
Ridge
Raised Inner
Beach
Raised Estuary
Raised Tidal Flat
Chenier
Chenier Plain
A Geomorphic Classification System
52
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
SOLUTION
General Chemical Weathering
Chemically Denuding Surface
Karstification
Sinkhole (Undifferentiated)
Solution Sinkhole
Collapse Sinkhole
Subsidence Sinkhole
Subjacent Karst Collapse Sinkhole
Cockpits
Uvala (Karst Valley)
Karst Window
Blind Valley
Poljes
Kegel karst
Tower Karst
Karst Tower
A Geomorphic Classification System
53
GEOMORPHIC
GEOMORPHIC
LANDFORM
ELEMENT
PROCESS
SUBPROCESS
LANDFORM
_____________________________________________________________________
EOLIAN
Erosion
Yardang
Yardang Trough
Deflation Basin
Desert Pavement
Deposition
Sand Sheet
Sand Ramp
Sand Seas
Dune Field
Dune (Undifferentiated)
Barchan Dune
Parabolic Dune
Parna Dune
Seif Dune
Transverse Dune
Barchanoid Ridge
Blowout Dune
Reversing Dune
Star Dune
Foredune
Interdune Flat
Loess Deposit (Undifferentiated)
Paha
A Geomorphic Classification System
54
Appendix C: Landscape Terms
Following is a list of Landscape Terms used in this Geomorphic Classification.
For definition of these terms, refer to the glossary, Appendix I.
Badlands (LF)
Bajada (LF)
Barrier Islands
Basin (LF)
Basin and Range
Basin Floor
Bolson (LF)
Bottomland
Break
Canyon (LF)
Canyonland
Coast
Coastal Plain (LF)
Delta (LF)
Dune Field (LF)
Drumlin Field
Fan Piedmont (LF)
Flatlands
Foothills
Front
Glaciated Uplands
Highland
Hills (LF)
Intermontane Basin
Island (LF)
Karst
Lava Plain
Lava Plateau
Lowlands
Meander Belt
Mountains (LF)
Peninsula
Piedmont
Plains (LF)
Plateau
Range
Ridge and Valley
Rift Valley
Sandhills
Scabland
Semi-Bolson (LF)
Tableland (LF)
Thermokarst
Till Plain
Upland
Valleys
Volcanic Mountains
LF - also a landform
A Geomorphic Classification System
55
Appendix D: Common landforms
The following Common Landforms are used in this Geomorphic Classification.
For definition of these terms, refer to the glossary, Appendix I.
Arroyo
Bald
Ballon
Bay
Bayou
Bench
Blowout
Bluff
Break
Channel
Cliff
Depression
Drainage
Draw
Escarpment
Faceted Spur
Flat
Floor
Fluve
Free Face
Gap
Gorge
Gulch
Gully
Hummock
Interfluve
Knob
A Geomorphic Classification System
Knoll
Ledge
Mound
Mountain
Mountain Valley
Noseslope
Pinnacle
Pothole
Ravine
Ridge
Rim
Riser
Saddle
Scarp
Scour
Seep
Shoal
Slough
Splay
Step
Swale
Talus
Terracettes
Tread
Trench
V-Notch
Wash
56
Appendix E: Microfeatures
The following Microfeatures are used in this Geomorphic Classification.
For definition of these terms, refer to the glossary, Appendix I.
Bar
Channel
Earth Pillar
Frost Boil
Gilgai
Ice Wedge
Lava Blister
Patterned Ground Microfeatures (single features)/Periglacial:
Circle
Non-sorted Circle
Sorted Circle
Polygon
Frost Mound
Net
Earth Hummock
Turf Hummock
Mima Mound
Pimple Mound
Step
Stripe
Stone Stripe
Pedestal
Rill
Ripple Mark
Sand Boil
Scour
Shrub-Coppice Dune
Terracette
Tree-tip mound
Tree-tip pit
A Geomorphic Classification System
57
Appendix F: Morphometry
Following are Morphometry parameters, definitions and valid values used in this classification:
Slope Position - A code for the two dimensional position on the landform.
Value
Meaning
SU
SH
BS
FS
TS
Summit
Shoulder
Backslope
Footslope
Toeslope
Position/Landform Modifier - A modifier which may be used to better describe
the primary slope position and landform.
Value
Meaning
UP
MD
LR
FR
SC
TH
FT
IN
OT
LW
WW
DS
PR
SW
LD
Upper
Mid
Lower
First
Second
Third
Fourth
Inner
Outer
Leeward
Windward
Distal
Proximal
Seaward
Landward
Landform Width Class - Measurements of valley bottom, ridges and shoulders derived
from ECODATA.
Value
Meaning
1
2
3
0-100 feet wide
100-300 feet wide
>300 feet wide
A Geomorphic Classification System
58
Slope Shape - Refers to the shape (either horizontal or vertical) of the land surface
Value
Meaning
CV
CX
L
P
Concave (also depression)
Convex (also raised)
Linear/Planar (also straight, even, smooth)
Patterned - relief of hummocks and swales within
several feet)
Undulating (also rolling) - pattern of one or more low
relief ridges or knolls and draws
Broken - cliffs, knobs, and/or benches interspersed with
steeper slopes - generally characterized by sharp,
irregular breaks
Unable to assess
U
B
X
Slope Complexity - Refers to the complexity of slope (shape and gradients) for a point
or polygon. Simple slopes may be further described as linear/planar, concave or
convex. Complex slopes may be further described as broken, undulating or patterned.
Value
Meaning
S
SL
SCV
SCX
C
CP
CU
CB
Simple
Simple, Linear/Planar
Simple, Concave
Simple, Complex
Complex
Complex, Patterned
Complex, Undulating
Complex, Broken
Ground Surface Shape - Shape of the ground surface (as opposed to the land
surface). May be further described according to the type of features causing the
shape by a term from the microfeature table.
Value
Meaning
H
U
Hummocky
Uniform
A Geomorphic Classification System
59
Dissection Frequency Class - The frequency class for dissections in landforms with
slope components.
Value
Meaning
U
S
M
Undissected (0 channels/mile)
Slightly Dissected (1-3 channels/mile)
Moderately Dissected (3-10
channels/mile)
Highly Dissected (>10 channels/mile)
H
Dissection Depth Class - The dissection depth class for landforms with slope
components.
Value
Meaning
S
D
Shallowly incised (0-50 feet)
Deeply incised (>50 feet)
Drainage Pattern - The configuration or arrangement in plan view of the natural stream
courses in an area.
Value
Meaning
DN
Dendritic - Type pattern resembles spreading oak or
chestnut tree
Subdendritic - minor secondary control
Pinnate - A dendritic drainage pattern in which the main
stream receives many closely spaced, subparallel
tributaries that join it at acute angles, resembling in
plan a feather; it is believed to indicate unusually steep
slopes on which the tributaries developed. Found in
fine-textured, easily erodible materials.
Anastamotic - Pertaining to a network of branching and
rejoining channel pattern of a braided stream. Found
on floodplains, deltas and tidal marshes.
Distributary - A divergent stream flowing away from the
main stream and not returning to it, as in a delta or on
an alluvial fan. It may be produced by stream
deposition choking the original channel
DNSD
DNPN
DNAS
DNSD
A Geomorphic Classification System
60
Value
Meaning
PR
Parallel - A drainage pattern in which the streams and
their tributaries are regularly spaced and flow parallel
or subparallel to one another over a considerable area.
It is indicative of a region having a pronounced,
moderate to steep uniform slope and a homogeneous
lithology and rock structure. Also found in areas with
parallel, elongate landforms.
Subparallel - Found on intermediate slopes or
controlled by subparallel landforms.
Colinear - Occur between linear loess and sand ridges.
PRSP
PRCO
TR
TRST
TRDT
TRRT
TRJT
RC
RCAN
Trellis - A drainage pattern characterized by parallel
main streams intersected at or nearly at right angles by
their tributaries, which in turn are fed by elongated
secondary tributaries parallel to the main streams,
resembling in plan the stems of a vine on a trellis. It is
commonly developed where the beveled edges of
alternating hard and soft rocks outcrop in parallel belts,
as in a rejuvenated folded-mountain region or in a
maturely dissected belted coastal plain of tilted strata; it
is indicative of marked structural control emphasized by
subsequent and secondary consequent streams.
Subtrellis - Parallel elongate landforms.
Directional Trellis - Occurs on gentle homoclines or
gentle slopes with beach ridges.
Recurved Trellis - Occurs on plunging folds.
Joint Trellis - Occurs in areas having straight parallel
faults or joints
Rectangular - A drainage pattern in which the main
streams and their tributaries display many right-angle
bends and exhibit sections of approximately the same
length; it is indicative of streams following prominent
fault or joint systems that break the rocks into
rectangular blocks. It is more irregular than the trellis
drainage pattern, as the side streams are not perfectly
parallel and not necessarily as conspicuously
elongated, and secondary tributaries need not be
present.
Angulate - Occurs in areas having joints and faults at
other than a right angle
A Geomorphic Classification System
61
Value
Meaning
RD
Radial - A drainage pattern in which consequent
streams radiate or diverge outward, like the spokes of a
wheel, from a high central area; it is best developed on
the slopes of a young, unbreached domal structure or
of a volcanic cone.
Centripetal - Occurs in craters, calderas and other
depressions.
RDCN
AN
Annular - A drainage pattern in which subsequent
streams follow a roughly circular or concentric path
along a belt of weak rocks, resembling in plan a
ring-like pattern. It is best displayed by streams
draining a maturely dissected structural dome or basin
where erosion has exposed rimming sedimentary strata
of greatly varying degrees of hardness.
MB
Multibasinal - Drainage pattern expressed in areas
having hummocky surficial deposits, differentially
scoured or deflated bedrock, areas of recent
volcanism, limestone solution or permafrost where
there is a multiple depression pattern.
Glacially Disturbed - Glacial erosion or deposition.
Karst - Limestone
Thermokarst - Permafrost
Elongate Bay - Coastal plains and deltas.
Contorted - A pattern lacking regional orderliness,
discontinuity of ridges and valleys and generally smaller
scale.
MBGD
MBKS
MBTK
MBEB
CT
A Geomorphic Classification System
62
Appendix G: List of Reviewers
Version 1.0 of the Geomorphic Classification was sent to Regional Foresters and
Station Directors for agency-wide review. In addition, draft copies were sent directly to
specific individuals for their review. Version 1.0 of the classification was also presented
to several groups of Forest Service specialists and productive discussion and critique
occurred. Versions 1.1 and 1.2 also received internal review. The following individuals
responded with substantive written comments:
Terry Brock
George Bush
Carl Davis
Don Elder
Juan de la Fuente
James Jordan
Tom Keter
Dr. Thomas Lisle
Linda Lux
Dr. R. Meurisse
Dr. Jerry Miller
John Nesser
John Nichols
Steve Paustian
Dr. Dale Ritter
Wayne Robbie
Joe Seney
Dr. Mark Smith
Desi Zamudio
Regional Soil Scientist
Soil Scientist
Forest Soil Scientist
Geologist
Forest Geologist
Acting Regional Soil Scientist
Forest Archaeologist
Research Hydrologist
Regional Office
Siuslaw National Forest
Wenatchee National Forest
Klamath National Forest
Klamath National Forest
Regional Office
Six Rivers National Forest
Redwood Sciences Laboratory,
U.S. Forest Service, PSW
Research Station, Arcata, CA
Heritage Resource Prog. Ldr. Regional Office
Soil Group Leader
Regional Office
Geomorphologist
Desert Research Center,
University of Nevada, Reno
Regional Soil Scientist
Regional Office
Geologist
Ouachita National Forest
Supervisory Hydrologist
Chatham Area, Tongas
National Forest
Geomorphologist
Desert Research Center,
University of Nevada, Reno
Eco. Unit Inventory Coord.
Regional Office
Soil Scientist
Grand Mesa, Uncompahgre
and Gunnison National
Forests
Forest Geologist
Six Rivers National Forest
Soil Scientist
Humboldt-Toiyabe
National Forests
A Geomorphic Classification System
63
R-10
R-6
R-6
R-5
R-5
R-9
R-5
R-5
R-6
R-1
R-8
R-10
R-3
R-2
R-5
R-4
Appendix H: Codes for Geomorphic Processes and Landforms
Used in this Geomorphic Classification
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
aa flow
aa flow
active ice and snow
processes
air-fall tephra field
alluvial fan
alluvial flat
alpine glaciation
anthropogenic
anticline
arête
avalanche talus
backshore/backbeach
processes
backshore terrace
Volcanic Landform
Volcanic Landform
Glacial Subprocess
AAFL
AAFL
AISF
Volcanic Landform
Fluvial Landform
Fluvial Element Landform
Glacial Subprocess Modifier
Lacustrine Subprocess
Tectonic Landform
Glacial Element Landform
Mass Wasting Element Landform
Coastal Marine Subprocess
AFTF
ALFA
ALFL
ALPI
ANTH
ANTI
ARET
AVTA
BABP
Coastal Marine and Lacustrine Element
Landform
Coastal Marine Landform
Landscape Term and Fluvial Landform
Landscape Term and Fluvial Landform
Common Landform
Fluvial Landform
Common Landform
Fluvial Landform
Fluvial Landform and Microfeature
Eolian Landform
Eolian Landform
Coastal Marine Element Landform
Coastal Marine Element Landform
Landscape Term (plural), Coastal Marine
Landform (singular)
Coastal Marine Landform
Landscape Term
Fluvial Subprocess
Landscape Term
Landscape Term
Fluvial Element Landform
Fluvial Landform
Common Landform
BATE
backwater
badlands
bajada
bald
ballena
ballon
bank
bar
barchan dune
barchanoid ridge
barrier beach
barrier flat
barrier island(s)
barrier reef
basin
basin processes
basin and range
basin floor
basin-floor remnant
batholith
bay
A Geomorphic Classification System
BACK
BADL
BAJA
BALD
BALL
BALO
BANK
BAR
BADU
BARI
BABE
BAFL
BAIS
BARE
BASI
BAPR
BAAR
BAFL
BAFR
BATH
BAY
64
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
bayou
beach
beach plain
Common Landform
Coastal Marine and Lacustrine Landform
Coastal Marine and Lacustrine Element
Landform
Coastal Marine and Lacustrine Element
Landform
Lacustrine Subprocess
Mass Wasting Element Landform
Common Landform
Glacial Element Landform
Solution Landform
Periglacial Landform
Volcanic Landform
Common Landform
Eolian Landform
Landscape Term and Fluvial Landform
Landscape Term
Landscape Term and Common Landform
Fluvial Landform
Volcanic Landform
Landscape Term
Landscape Term
Coastal Marine Landform
Fluvial Landform and Microfeature
Solution Landform
BAYO
BEAC
BEPL
beach ridge
beaver
bench (undifferentiated)
bench
bergschrund
blind valley
block field
block lava flow
blowout
blowout dune
bolson
bottomlands
break
butte
caldera
canyon
canyonlands
carolina bay
channel
chemically denuding
surface
chenier
chenier plain
cinder cone
circle(s)
cirque
cirque floor
cirque headwall
cliff
coast
coastal marine
coastal plain
cockpits
col
collapse caldera
collapse sinkhole
colluvial shoulder
Coastal Marine Landform
Coastal Marine Landform
Volcanic Landform
Periglacial Element Landform (groups)
and Microfeature (single)
Glacial Element Landform
Glacial Element Landform
Glacial Element Landform
Common Landform
Landscape Term
Geomorphic Process
Landscape and Coastal Marine Landform
Solution Landform
Glacial Element Landform
Volcanic Landform
Solution Landform
Mass Wasting Element Landform
A Geomorphic Classification System
BERI
BEAV
BENC
BNCH
BERG
BLVA
BLFI
BLLF
BLOW
BARI
BOLS
BOTT
BREA
BUTT
CALD
CANY
CALA
CABA
CHAN
CHDS
CHEN
CHPL
CICO
CIRC
CIRQ
CIFL
CIHE
CLIF
COAS
CM
COPL
COCK
COL
COCA
COSI
COSH
65
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
colluvial slope
complex
composite cone
compound fault scarp
constructional
continental glaciation
coral pinnacle
coulee
crag and tail
crater
crevasse
cuesta
debris avalanche
debris flow
debris slide basin
debris slide-prone lateral
scarp
debris slide-prone main
scarp
debris slide-prone
secondary scarp
deflation basin
delta
delta plain
deposit
deposition
Mass Wasting Element Landform
Mass Wasting Subprocess
Volcanic Landform
Tectonic Landform
Volcanic Subprocess
Glacial Subprocess Modifier
Coastal Marine Landform
Glacial Landform
Glacial Landform
Volcanic Landform
Glacial Element Landform
Fluvial Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Element Landform
COSL
COMP
COCO
COFS
CONS
CONT
COPI
COUL
CRTA
CRAT
CREV
CUES
DEAV
DEFL
DESB
DSPL
Mass Wasting Element Landform
DSPM
Mass Wasting Element Landform
DSPS
Eolian Landform
Fluvial Landform and Landscape Term
Fluvial Element Landform
Mass Wasting Element Landform
Fluvial Subprocess Modifier and Eolian
Subprocess
Fluvial Process Modifier
DEBA
DELT
DEPL
DEPO
DEPS
Fluvial Landform
DEST
Common Landform
Eolian Element Landform
Volcanic Subprocess
Tectonic Landform
Fluvial Subprocess Modifier
DEPR
DEPA
DEST
DIAP
DFEC
Fluvial Landform
Fluvial Element Landform
Glacial Landform
Tectonic Landform
Common Landform
DIKE
DISL
DIMO
DOME
DRAI
deposition stream
channel system
depositional stream
terrace
depression
desert pavement
destructional
diapir
differential fluvial erosion
with complex structural
control
dike
dip slope
disintegration moraine
dome
drainage
A Geomorphic Classification System
DESS
66
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
drainage channel
(undifferentiated)
draw
drumlin
dry sand flow
dune (undifferentiated)
dune field
earth flow
earth hummock
earth lateral spread
earth pillar
emergence
eolian
eolian
eroded bench
eroding stream channel
system
erosion
erosion fan remnant
erosional stream terrace
escarpment
esker
estuary
exogenous dome
explosion caldera
faceted spur
fall
fall-prone slope
fan apron
fan-head collar
fan piedmont
fan remnant
fan skirt
fan-head trench
faros
fault scarp
fault terrace
fault trace
faulting
fissure
fissure vent
flat
flatland
Glacial Element Landform
DRCH
Common Landform
Glacial Landform
Mass Wasting Landform
Eolian Element Landform
Eolian Landform and Landscape Term
Mass Wasting Landform
Microfeature
Mass Wasting Landform
Microfeature
Coastal Marine Subprocess
Geomorphic Process
Lacustrine Subprocess
Mass Wasting Element Landform
Fluvial Subprocess Modifier
DRAW
DRUM
DRSF
DUNE
DUFI
EAFL
EAHU
EALS
EAPI
EMER
EOLI
EOLL
ERBE
ESCH
Eolian Subprocess
Fluvial Landform
Fluvial Landform
Common Landform
Glacial Landform
Coastal Marine Landform
Volcanic Landform
Volcanic Landform
Common Landform
Mass Wasting Subprocess
Mass Wasting Landform
Fluvial Element Landform
Fluvial Element Landform
Landscape Term and Fluvial Landform
Fluvial Landform
Fluvial Element Landform
Fluvial Element Landform
Coastal Marine Landform
Tectonic Landform
Tectonic Landform
Tectonic Landform
Tectonic Subprocess
Tectonic Landform
Volcanic Landform
Common Landform
Landscape Term
EROS
ERFR
ERST
ESCA
ESKE
ESTU
EXDO
EXCA
FASP
FALL
FAPS
FAAP
FAHC
FAPI
FARE
FASK
FAHT
FARO
FASC
FATE
FATR
FAUL
FISS
FIVE
FLAT
FLLA
A Geomorphic Classification System
67
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
floating block
flood plain
floor
flow
flute
fluted moraine surface
fluve
fluvial
fluvial slope processes
fluviatile
fold
folding
foothills
foredune
fosse
free face
fringing reef
front
frost action
frost creep slope
frost boil
frost mound
fumarole field
gap
general chemical
weathering
giant ripples
gilgai
glacial
glacial
glacial quarry
glaciated uplands
glacier
gorge
graben
ground moraine
gulch
gully
hanging valley
headland
highland
hills
Mass Wasting Element Landform
Fluvial Landform
Common Landform
Mass Wasting Subprocess
Glacial Element Landform
Glacial Landform
Common Landform
Geomorphic Process
Fluvial Subprocess
Lacustrine Subprocess
Tectonic Landform
Tectonic Subprocess
Landscape Term
Eolian Landform
Glacial Element Landform
Common Landform
Coastal Marine Landform
Landscape Term
Periglacial Subprocess
Mass Wasting Landform
Microfeature
Microfeature
Volcanic Landform
Common Landform
Solution Subprocess
FLBL
FLPL
FLOO
FLOW
FLUT
FLMS
FLUV
FL
FLSP
FLVT
FLDS
FOLD
FOOT
FORE
FOSS
FRFA
FRRE
FRON
FRAC
FRCS
FRBO
FRMO
FUFI
GAP
GECW
Glacial Element Landform
Microfeature
Geomorphic Process
Lacustrine Subprocess
Glacial Element Landform
Landscape Term
Glacial Landform
Common Landform
Landscape Term and Tectonic Landform
Glacial Landform
Common Landform
Common Landform
Glacial Landform
Coastal Marine Landform
Landscape Term
Landscape Term
GIRI
GILG
GL
GLAC
GLGU
GLUP
GLCR
GORG
GRAB
GRMO
GULC
GULL
HAVA
HEAD
HIGH
HILL
A Geomorphic Classification System
68
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
hillslope bedrock outcrop
hogback
homocline
hoodoo
horn
horst
hummock
ice apron
ice contact deposition
ice erosion
ice margin channel
ice wedge
inselberg
inset fan
interdune flat
interfluve
interlobate moraine
intermontane basin
internested rotationaltranslational slides
intrusive dome
island
Mass Wasting Element Landform
Fluvial Landform
Tectonic Landform
Fluvial Landform
Glacial Element Landform
Tectonic Landform and Landscape Term
Common Landform
Glacial Element Landform
Glacial Subprocess
Glacial Subprocess
Glacial Landform
Microfeature
Fluvial Landform
Fluvial Element Landform
Eolian Landform
Common Landform
Glacial Landform
Landscape Term
Mass Wasting Landform
HIBO
HOGB
HOMO
HOOD
HORN
HORS
HUMM
ICAP
ICCD
ICER
ICMC
ICWE
INSE
INFA
INFL
INTE
INMO
INBA
INRT
Volcanic Landform
Coastal Marine, Fluvial and Lacustrine
Landform and Landscape Term
Glacial Landform
Glacial Landform
Glacial Landform
Landscape Term
Solution Subprocess
Solution Landform
Solution Landform
Solution Landform
Glacial Element Landform
Glacial Landform
Common Landform
Common Landform
Tectonic Landform
Geomorphic Process
Lacustrine Subprocess
INDO
ISLA
KAME
KAMO
KATE
KRST
KARS
KATO
KAWI
KEKA
KETT
KEOP
KNOB
KNOL
LACC
LA
LACU
Coastal Marine Landform
Volcanic Landform
Lacustrine Landform
Lacustrine Landform
LAGO
LAHA
LAKE
LABE
kame
kame moraine
kame terrace
karst
karstification
karst tower
karst window
kegel karst
kettle
kettled outwash plain
knob
knoll
laccolith
lacustrine
lacustrine
(undifferentiated)
lagoon
lahar
lake
lake bed
A Geomorphic Classification System
69
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
lake plain
lake terrace
landslide
lateral moraine
lateral scarp
(undifferentiated)
lateral spread
lava blister
lava flow
(undifferentiated)
lava plain
lava plateau
ledge
levee
loess deposit
(undifferentiated)
loess flow
longitudinal bar
longshore bar
louderback
lowland
maar
main scarp
(undifferentiated)
marine terrace
(undifferentiated)
mass wasting
meander belt
meander scar
meander scroll
medial moraine
meltwater erosion
mesa
meteoric
mima mound
monadnock
monocline
moraine
(undifferentiated)
moulin
mound
mountain(s)
Lacustrine Landform
Lacustrine Landform
Lacustrine Subprocess
Glacial Landform
Mass Wasting Element Landform
LAPL
LATE
LAND
LAMO
LASC
Mass Wasting Subprocess
Microfeature
Volcanic Landform
LASP
LABL
LAFL
Landscape Term
Landscape Term
Common Landform
Fluvial Element Landform
Eolian Landform
LAPL
LAPL
LEDG
LEVE
LODE
Mass Wasting Landform
Fluvial Element Landform
Coastal Marine Landform
Fluvial Landform
Common Landform and Landscape Term
Volcanic Landform
Mass Wasting Landform
LOFL
LOBA
LONB
LOUD
LOWL
MAAR
MASC
Coastal Marine and Lacustrine Landform
MATE
Geomorphic Process
Landscape Term
Fluvial Element Landform
Fluvial Element Landform
Glacial Landform
Glacial Subprocess
Fluvial Landform
Lacustrine Subprocess
Microfeature
Fluvial Landform
Tectonic Landform
Glacial Landform
MW
MEBE
MESR
MESC
MEMO
MEER
MESA
METE
MIMO
MONA
MONO
MORA
Glacial Element Landform
Common Landform
Common Landform (singular), Landscape
Term (plural)
MOUL
MOUN
MTNS
A Geomorphic Classification System
70
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
mountain valley
mountain-valley fan
mud flat
mud pot field
mud volcano
nested bench
nested lateral scarp
nested main scarp
nested secondary scarp
nested toe zone
net(s)
Common Landform
Fluvial Landform
Coastal Marine Landform
Volcanic Landform
Volcanic Landform
Mass Wasting Element Landform
Mass Wasting Element Landform
Mass Wasting Element Landform
Mass Wasting Element Landform
Mass Wasting Element Landform
Periglacial Element Landform (groups),
Microfeature (single)
Glacial Element Landform
Glacial Element Landform
Fluvial Landform
Microfeature
Common Landform
Glacial Landform
Coastal Marine Landform
Lacustrine Subprocess
Coastal Marine Landform
MOVA
MOVF
MUFL
MUPF
MUVO
NEBE
NELS
NEMS
NESS
NETZ
NET
Glacial Landform
Glacial Landform
Glacial Landform
Glacial Landform
Fluvial Element Landform
Eolian Landform
Volcanic Landform
Periglacial Landform
Eolian Landform
Volcanic Landform
Eolian Landform
Fluvial Landform
Coastal Marine Landform
Lacustrine Landform
Periglacial Landform (groups),
Microfeature (single)
Fluvial Landform
Microfeature
Volcanic Landform
Landscape Term
Geomorphic Process
OUFL
OUFA
OUPL
OUTE
OXBO
PAHA
PAFL
PALS
PADU
PACO
PADU
PABA
PARE
PALA
PAGR
nivation hollow
nivation ridge
non-buried fan remnant
non-sorted circle
noseslope
nunatak
oceanic atoll
organic
organic reef
(undifferentiated)
outburst floodplain
outwash fan
outwash plain
outwash terrace
oxbow
paha
pahoehoe flow
palsa
parabolic dune
parasitic cone
parna dune
partial ballena
patch reef
paternoster lakes
patterned ground
(undifferentiated)
pediment
pedestal
pelean dome
peninsula
periglacial
A Geomorphic Classification System
NIHO
NIRI
NBFR
NOSC
NOSE
NUNA
OCAT
ORGA
ORRE
PEDI
PEDE
PEDO
PENI
PERI
71
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
periglacial flows
(undifferentiated)
permafrost
piedmont
pimple mounds
pingo
pinnacle
plain
plateau
platform reef
playa
plug dome
point bar
polje
polygon
Mass Wasting Landform
PEFL
Periglacial Subprocess
Landscape Term
Microfeature
Periglacial Landform
Common Landform
Landscape Term
Landscape Term
Coastal Marine Landform
Fluvial Element Landform
Volcanic Landform
Fluvial Element Landform
Solution Landform
Periglacial Element Landform (groups),
Microfeature (single)
Common Landform
Volcanic Element Landform
Glacial Landform Element
Glacial Subprocess
Volcanic Landform
Volcanic Landform
PERM
PIED
PIMO
PING
PINN
PLAI
PLAT
PLRE
PLAY
PLDO
POBA
POLJ
POLY
Volcanic Element Landform
Coastal Marine Landform
Coastal Marine Element Landform
Coastal Marine Element Landform
Coastal Marine Landform
Coastal Marine Landform
Coastal Marine Landform
Landscape Term
Mass Wasting Landform
Common Landform
Glacial Landform
Coastal Marine Landform
Eolian Landform
Common Landform
Landscape Term
Mass Wasting Element Landform
Glacial Element Landform
Landscape Term
Microfeature
Common Landform
PYFL
RABE
RABR
RAIB
RAES
RAMU
RATF
RANG
RACO
RAVI
REMO
RECO
REDU
RIDG
RIAV
RIBO
RIEG
RIVA
RILL
RIM
pothole
pressure ridge
pressure ridge
proglacial deposition
pumice cone
pyroclastic cone
(undifferentiated)
pyroclastic flow
raised beach
raised beach ridge
raised inner beach
raised estuary
raised mudflat
raised tidal flat
range
ravel cone
ravine
recessional moraine
relict coastline
reversing dune
ridge
ridge and valley
ridgetop bedrock outcrop
riegel
rift valley
rill
rim
A Geomorphic Classification System
POTH
PRRI
PRRD
PRDE
PUCO
PYCO
72
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
ripple mark
riser
roche mountonnee
rock fall avalanche
rock glacier
rock slide-rock fall
rock spread
rock stream
rotational slide
rotational-translational
slide
runout zone
saddle
sag pond
sand boil
sandhills
sand ramp
sand sea
sand sheet
scablands
scarp
scarp slope
scarp slope
scour
scoured basin
sea cliff
secondary scarp
(undifferentiated)
seep
seif dune
semi-bolson
serac
shelf atoll
shield volcano
shoal
shoreline
shoreline
shoreline processes
shrub-coppice dune
shutter ridge
sidewall
sinkhole
(undifferentiated)
Microfeature
Common Landform
Glacial Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
RIMA
RISE
ROMO
ROFA
ROGL
RSRF
ROSP
ROST
ROSL
ROTS
Mass Wasting Element Landform
Common Landform
Lacustrine Landform
Microfeature
Landscape Term
Eolian Landform
Eolian Landform
Eolian Landform
Landscape Term
Common Landform
Fluvial Element Landform
Tectonic Landform
Common Landform and Microfeature
Glacial Landform
Coastal Marine Landform
Mass Wasting Element Landform
RUZO
SADD
SAPO
SABO
SAND
SARA
SASE
SASH
SCAB
SCAR
SCSL
SCSP
SCOU
SCBA
SECL
SESC
Common Landform
Eolian Landform
Landscape Term and Fluvial Landform
Glacial Element Landform
Coastal Marine Landform
Volcanic Landform
Common Landform
Lacustrine Subprocess
Coastal Marine Landform
Coastal Marine Subprocess
Microfeature
Tectonic Landform
Glacial Element Landform
Solution Landform
SEEP
SEDU
SEBO
SERA
SHAT
SHVO
SHOA
SHOR
SHLI
SHPR
SHCD
SHRI
SIDE
SINK
A Geomorphic Classification System
73
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
slide
slip face
slough
slump and topple prone
slope
slump earth flow
slump pond
snow avalanche slope
snowfield
soil creep slope
solifluction lobe
solifluction sheet
solifluction terrace
solution
solution
solution sinkhole
sorted circle
source area
spatter cone
spillway
spit
splay
stack
star dune
step
step(s)
Mass Wasting Subprocess
Common Landform
Common Landform
Mass Wasting Landform
SLID
SLFA
SLOU
STPS
Mass Wasting Landform
Lacustrine Landform
Mass Wasting Landform
Glacial Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Mass Wasting Landform
Geomorphic Process
Lacustrine Subprocess
Solution Landform
Microfeature
Mass Wasting Element Landform
Volcanic Element Landform
Glacial Landform
Coastal Marine Landform
Common Landform
Coastal Marine Landform
Eolian Landform
Common Landform
Periglacial Element Landform (groups)
and Microfeature (single)
Volcanic Landform
Tectonic Landform
Microfeature
Coastal Marine Landform
Coastal Marine Landform
Fluvial Subprocess
Fluvial Landform
SLEF
SLPO
SNAS
SNOW
SOCS
SOLO
SOSH
SOTE
SO
SOLU
SOSI
SOCI
SOAR
SPCO
SPIL
SPIT
SPLA
STAC
STDU
STP
STEP
STTO
STOC
STST
STBE
STPL
STPR
STTE
Periglacial Element Landform (groups)
STRI
steptoe
stock
stone stripe
storm berm
strand plain
stream processes
stream terrace
(undifferentiated)
stripe(s)
A Geomorphic Classification System
74
GEOMORPHIC TERM
structural
structural basin
structural dome
subjacent karst collapse
sinkhole
subsidence sinkhole
surface eroding slope
syncline
swale
tableland
talus
tarn
tectonic
tectonic
terminal deposition
terminal moraine
terracette(s)
thalweg
thermokarst
tidal flat
till plain
tilt block
toe zone
(undifferentiated)
tombolo
topple
topple prone slope
Stor
tower karst
Atranslational block slide
Stranslational-debris
slide
Stransport zone
transporting stream
channel system
transverse dune
tread
tree-tip mound
tree-tip pit
trench
PROCESS/LANDFORM
CODE
and Microfeature (single)
Tectonic Subprocess
Tectonic Landform
Tectonic Landform
Solution Landform
STRU
STBA
STDO
SKCS
Solution Landform
Fluvial Landform
Tectonic Landform
Commom Landform
Landscape Term
Common Landform
Lacustrine Landform
Lacustrine Subprocess
Geomorphic Process
Fluvial Subprocess Modifier
Glacial Landform
Common Landform (groups) and
Microfeature (single)
Fluvial Landform
Landscape Term and Periglacial
Landform
Coastal Marine Landform
Landscape Term
Tectonic Landform
Mass Wasting Element Landform
SUSI
SUES
SYNC
SWAL
TABL
TALU
TARN
TECT
TE
TEDE
TEMO
TERR
Coastal Marine Landform
Mass Wasting Subprocess
Mass Wasting Landform
Periglacial Landform
Solution Landform
Mass Wasting Landform
Mass Wasting Landform
TOMB
TOPP
TOP
TOR
TOK
TRB
TRD
Mass Wasting Element Landform
Fluvial Subprocess Modifier
TRZO
TRSC
Eolian Landform
Common Landform
Microfeature
Microfeature
Volcanic Element Landform
TRDU
TREA
TRTM
TRTP
TREN
A Geomorphic Classification System
THAL
THER
TIFL
TIPL
TIBL
TOZO
75
GEOMORPHIC TERM
PROCESS/LANDFORM
CODE
trench
trough
tunnel valley
turf hummock
undifferentiated stream
channel system
uniform fluvial erosion
without structural control
upheaved dome
upland
uvala
valley
valley floor
valley flat
valley inner gorge
valley train
v-notch
volcanic
volcanic
volcanic cone
(undifferentiated)
volcanic dome
(undifferentiated)
volcanic mountains
wash
washover fan
water deposition in close
proximity to ice
wave-built terrace
wave-cut platform
yardang
yardang trough
Common Landform
Glacial Landform
Glacial Landform
Microfeature
Fluvial Subprocess Modifier
TRNC
TROU
TUVA
TUHU
UNSC
Fluvial Subprocess Modifier
UNFE
Volcanic Landform
Landscape Term
Solution Landform
Landscape Term
Fluvial Element Landform
Fluvial Element Landform
Mass Wasting Landform
Glacial Landform
Common Landform
Geomorphic Process
Lacustrine Subprocess
Volcanic Landform
UPDO
UPLA
UVAL
VALL
VAFO
VAFL
VAIG
VATR
VNOT
VO
VOLC
VOCO
Volcanic Landform
VODO
Landscape Term
Common Landform
Coastal Marine Landform
Glacial Subprocess
VOMO
WASH
WAFA
WADE
Coastal Marine Landform
Coastal Marine Landform
Eolian Landform
Eolian Landform
WABT
WACP
YARD
YATR
A Geomorphic Classification System
76
Appendix I: Glossary of Geomorphic Processes and Landforms
A
aa flow. [Volcanic Landform] A Hawaiian term for lava flows typified by a rough, jagged,
spinose, clinkery surface. (Bates and Jackson, 1995)
active ice and snow processes. [Glacial Subprocess] Geomorphic processes related
to present day glacial and snow features.
air-fall tephra field. [Volcanic Landform] A blanket-like deposit of fragmental ejecta
from volcanoes, which can range from several hectares in size to hundreds of square
kilometers, and from several centimeters in thickness to many meters, depending on the
distance and direction from the source vent and the extent and number of eruptions.
(Modified from Bloom, 1991)
alluvial fan. [Fluvial Landform] A low, outspread, relatively flat to gently sloping mass of
loose rock material, shaped like an open fan or a segment of a cone, deposited by a
stream (esp. in a semiarid region) at the place where it issues from a narrow mountain
valley upon a plain or broad valley, or where a tributary stream is near or at its junction
with the main stream, or wherever a constriction in a valley abruptly ceases or the
gradient of the stream suddenly decreases; it is steepest near the mouth of the valley
where its apex points upstream, and it slopes gently and convexly outward with
gradually decreasing gradient. (Bates and Jackson, 1995)
alluvial flat. [Fluvial Element Landform] A small alluvial plain bordering a river, on
which alluvium is deposited during floods. (Bates and Jackson, 1995)
alpine glaciation. [Glacial Subprocess Modifier] Glaciation which occurs or has
occurred in the past in mountain ranges except as related to a more extensive ice cap
or ice sheet.
anthropogenic. [Lacustrine Subprocess] Lakes formed by engineered dams, waterfilled excavations and subsidence hollows created by humans. (Hutchinson, 1957)
anticline. [Tectonic Landform] A fold, generally convex upward, whose core contains
the stratigraphically older rocks. (Bates and Jackson, 1995)
arête. [Glacial Element Landform] A narrow serrate mountain crest or rocky
sharp-edged ridge or spur, commonly present above the snowline in rugged mountains
sculptured by glaciers, and resulting from the continued backward growth of the walls of
adjoining cirques. (Bates and Jackson, 1995)
arroyo. [Common Landform] A term applied in the arid and semi-arid regions of the
southwest U.S. to the small deep flat-floored channel or gully of an ephemeral stream or
of an intermittent stream, usually with vertical or steeply cut banks of unconsolidated
A Geomorphic Classification System
77
material at least 60 cm high; it is usually dry, but may be transformed into a temporary
watercourse or short-lived torrent after heavy rainfall. (Bates and Jackson, 1995)
avalanche talus. [Mass Wasting Element Landform] An accumulation of rock
fragments of any size or shape, derived from snow and ice mixed with soil, vegetation
and rock debris avalanched from a cliff or rocky slope above. It usually occurs on the
downwind side of a ridgetop or arête, in mountains where drifting snow builds cornices
that collapse and bring down snow, ice, and rocks. Angle of slope is much less than 30°
and the slope profile is concave upward. (Bates and Jackson, 1995)
B
backshore/backbeach processes. [Coastal Marine Subprocess] A collection of
processes which occur in the backshore and backbeach coastal marine environments.
backshore terrace. [Coastal Marine and Lacustrine Element Landform] (berm) A low,
impermanent, nearly horizontal or landward-sloping bench, shelf, ledge, or narrow
terrace on the backshore of a beach, formed of material thrown up and deposited by
storm waves. Some beaches have no berms; others have one or several. (Bates and
Jackson, 1995)
backwater. [Coastal Marine Landform] An arm of the sea, or series of connected
lagoons, usually parallel to the coast, separated from the sea by a narrow strip of land
but communicating with it through barred outlets. (Bates and Jackson, 1995)
badlands. [Landscape Term and Fluvial Landform] Intricately stream-dissected
topography, characterized by a very fine drainage network with high drainage densities
and short steep slopes with narrow interfluves. (Bates and Jackson, 1995)
bajada. [Landscape Term and Fluvial Landform] A broad, continuous alluvial slope or
gently inclined detrital surface extending from the base of the mountain ranges out into
and around an inland basin, formed by the lateral coalescence of a series of separate
but confluent alluvial fans, and having an undulating character due to the convexities of
the component fans. (Bates and Jackson, 1995)
bald. [Common Landform] A local term, especially used in the southern U.S., for an
elevated, grassy area, as a mountain top or high meadow, that is devoid of trees.
(Bates and Jackson, 1995)
ballena. [Fluvial Landform] A landform comprising distinctively round-topped ridgeline
remnants of fan alluvium. The ridge’s broadly rounded shoulders meet from either side
to form a narrow crest and merge smoothly with the concave backslopes. In ideal
examples, the slightly concave footslopes of adjacent ballenas merge to form a
smoothly rounded drainageway. (Peterson, 1981)
A Geomorphic Classification System
78
ballon. [Common Landform] A rounded, dome-shaped hill, formed either by erosion or
by uplift. (Bates and Jackson, 1995)
bank. [Fluvial Landform] The sloping margin of, or the ground bordering, a stream, and
serving to confine the water to the natural channel during the normal course of flow. It is
best marked where a distinct channel has been eroded in the valley floor, or where
there is a cessation of land vegetation. A bank is designated as right or left as it would
appear to an observer facing downstream. (Bates and Jackson, 1995)
bar. [Fluvial Landform and Microfeature] A ridge like accumulation of sand, gravel, or
other alluvial material formed in the channel, along the banks, or at the mouth, of a
stream where a decrease in velocity induces deposition. (Bates and Jackson, 1995)
barchan dune [Eolian Landform] An isolated crescent-shaped sand dune lying
transverse to the direction of the prevailing wind, with a gently sloping convex side
facing the wind, wings or horns of the crescent pointing downwind, and a steep concave
leeward slope inside the horns; it can grow to heights of greater than 30 m and widths
up to 350 m from horn to horn. A barchan forms on a flat, hard surface where the sand
supply is limited and the wind is constant with only moderate velocity. It is among the
most common of the dune types, characteristic of very dry, inland desert regions the
world over. (Bates and Jackson, 1995)
barchanoid ridge [Eolian Landform] Dunes which are oriented perpendicular to the
wind which form a sinuous asymmetrical ridge which is composed of connected
crescents. (Ritter et al, 1995)
barrier beach [Coastal Marine Element Landform] A narrow, elongate sand ridge rising
slightly above the high-tide level and extending generally parallel with the shore, but
separated from it by a lagoon, estuary, or marsh; it is extended by longshore transport
and is rarely more than several kilometers long. (Bates and Jackson, 1995)
barrier flat [Coastal Marine Element Landform] A relatively flat area, often occupied by
pools of water, separating the exposed or seaward edge of a barrier from the lagoon
behind it. (Bates and Jackson, 1995)
barrier island(s) [Coastal Marine Landform (singular), Landscape Term (plural)] A long,
narrow coastal sandy island, representing a broadened barrier beach that is above high
tide and parallel to the shore, and that commonly has dunes, vegetated zones, and
swampy terrains extending lagoonward from the beach. Also, a long series of barrier
beaches. (Bates and Jackson, 1995)
barrier reef [Coastal Marine Landform] A long, narrow coral reef roughly parallel to the
shore and separated from it by a lagoon of considerable depth and width. It may
enclose a volcanic island (either wholly or in part), or it may lie a great distance from a
continental coast (such as the Great Barrier Reef off the coast of Queensland,
A Geomorphic Classification System
79
Australia). Generally, barrier reefs follow the coasts for long distances, often with short
interruptions, termed passes or channels. (Bates and Jackson, 1995)
basin [Landscape Term] An areally extensive depressed area with no surface outlet.
(Bates and Jackson, 1995)
basin processes [Fluvial Subprocess] A collection of fluvial processes which occur in
basins.
basin and range [Landscape Term] Said of a topography, landscape, or physiographic
province characterized by a series of tilted fault blocks forming longitudinal, asymmetric
ridges or mountains and broad, intervening basins; specifically, the Basin and Range
physiographic province in the southwest U.S. (Bates and Jackson, 1995)
basin floor [Landscape Term] A generic term for the nearly level, lower-most major
physiographic part of intermontane basins, i.e., of both bolsons and semi-bolsons. The
floor includes all of the alluvial, eolian, and erosional landforms below the piedmont
slope. (Peterson, 1981)
basin-floor remnant [Fluvial Element Landform] A flattish topped, erosional remnant of
any former landform of a basin floor that has been dissected following the incision of an
axial stream. (Peterson, 1981)
batholith [Fluvial Landform] A large, generally discordant plutonic mass that has more
than100 km2 of surface exposure and no known floor. (Bates and Jackson, 1995)
bay [Common Landform] (a) A wide, curving open indentation, recess, or arm of a sea
or lake into the land or between two capes or headlands, larger than a cove, and usually
smaller than, but of the same general character as, a gulf. (b) A large tract of water that
penetrates into the land and around which the land forms a broad curve. By
international agreement (for purposes of delimiting territorial waters), a bay is a water
body having a baymouth less than 24 nautical miles wide and an area that is equal to or
greater than the area of a semicircle whose diameter is equal to the width of the
baymouth. (Bates and Jackson, 1995)
bayou [Common Landform] (a) A term variously applied to many local water features in
the lower Mississippi River basin and in the Gulf Coast region of the U.S., esp.
Louisiana. Its general meaning is a creek or secondary watercourse that is tributary to
another body of water; esp. a sluggish and stagnant stream that follows a winding
course through alluvial lowlands, coastal swamps or river deltas. (b) An effluent branch,
esp. sluggish or stagnant, of a main river, e.g., a distributary flowing through a delta.
Also, the distributary channel that carries floodwater or affords a passage for tidal water
through swamps or marshlands. (c) A bayou lake or an oxbow lake. (d) A slough in a
salt marsh. (e) An estuarine creek (generally tidal), or an inlet, bay, or open cove on the
Gulf Coast. (f) A term used in northern Arkansas and southern Missouri for a clear
brook or rivulet. (Bates and Jackson, 1995)
A Geomorphic Classification System
80
beach [Coastal Marine and Lacustrine Landform] The unconsolidated material that
covers a gently sloping zone, typically with a concave profile, extending landward from
the low-water line to the place where there is a definite change in material or
physiographic form (such as a cliff), or to the line of permanent vegetation (usually the
effective limit of the highest storm waves); a shore of a body of water, formed and
washed by waves or tides, usually covered by sand or gravel, and lacking a bare rocky
surface. (Bates and Jackson, 1995)
beach plain [Coastal Marine and Lacustrine Element Landform] A continuous and level
or undulating area formed by closely spaced successive embankments of
wave-deposited beach material added more or less uniformly to a prograding shoreline,
such as to a growing compound spit or to a cuspate foreland. (Bates and Jackson,
1995)
beach ridge [Coastal Marine and Lacustrine Element Landform] A low, essentially
continuous mound of beach or beach-and-dune material (sand, gravel, shingle) heaped
up by the action of waves and currents on the backshore of a beach beyond the present
limit of storm waves or the reach of ordinary tides, and occurring singly or as one of a
series of approximately parallel deposits. The ridges are roughly parallel to the shoreline
and represent successive positions of an advancing shoreline. (Bates and Jackson,
1995)
beaver [Lacustrine Subprocess] Lakes behind dams built by beavers. (Hutchinson,
1957)
bench (undifferentiated) [Mass Wasting Element Landform] A relatively level or gently
inclined strip or platform of land, earth, or rock, bounded by steeper slopes above and
below, and formed by mass wasting processes.
bench [Common Landform] A long, narrow, relatively level or gently inclined strip or
platform of land, earth, or rock, bounded by steeper slopes above and below, and
formed by differential erosion of rocks of varying resistance or by a change of base-level
erosion; a small terrace or step like ledge breaking the continuity of a slope; an eroded
bedrock surface between valley walls. The term sometimes denotes a form cut in solid
rock as distinguished from one (as a terrace) cut in unconsolidated material. (Bates and
Jackson, 1995)
bergschrund [Glacial Element Landform] A deep and often wide gap or crevasse, or a
series of closely spaced crevasses, in ice or firn at or near the head of an alpine glacier
or snowfield, that separates moving ice and snow from the relatively immobile ice and
snow (ice apron) adhering to the confining headwall of a cirque. It may be covered by or
filled with snow during the winter, but visible and reopened in the summer. (Bates and
Jackson, 1995)
A Geomorphic Classification System
81
blind valley [Solution Landform] A valley in karst that ends abruptly downstream at the
point at which its stream disappears underground as a sinking stream. (Bates and
Jackson, 1995)
block field [Periglacial Landform] (rock field) A thin accumulation of usually angular
blocks, with no fine sizes in the upper part, over solid or weathered bedrock, colluvium,
or alluvium, without a cliff or ledge above as an apparent source. Block fields occur on
high mountain slopes above treeline, and in polar regions; they are most extensive
along slopes parallel to the contour; and they exist on slopes of less than 5°. Blocks
may be subround to subangular suggesting abrasion during transport or in-situ
derivation. (Bates and Jackson, 1995)
block lava flow [Volcanic Landform] A lava flow which has a surface of angular blocks;
it is similar to aa but the fragments are more regular in shape, somewhat smoother, and
less vesicular. (Bates and Jackson, 1995)
blowout [Common Landform] (a) A butte, the top of which has been blown out by the
wind until it resembles a volcanic crater. (b) A shallow basin formed where vegetation
has been destroyed by fire or by overgrazing. (Bates and Jackson, 1995)
blowout dune [Eolian Landform] A general term for a small saucer-, cup-, or
trough-shaped hollow or depression formed by wind erosion on a pre-existing dune or
other sand deposit, esp. in an area of shifting sand or loose soil, or where protective
vegetation is disturbed or destroyed; the adjoining accumulation of sand derived from
the depression, where recognizable, is commonly included. Some blowouts may be
many kilometers in diameter. (Bates and Jackson, 1995)
bluff [Common Landform] A high bank or bold headland with a broad, precipitous,
sometimes rounded cliff face overlooking a plain or a body of water; esp. on the outside
of a stream meander; a river bluff. (Bates and Jackson, 1995)
bolson [Landscape Term and Fluvial Landform] (a) A term applied in the desert
regions of the southwest U.S. to an extensive flat alluvium-floored basin or depression,
into which drainage from the surrounding mountains flows centripetally with gentle
gradients toward a playa or central depression; an interior basin, or a basin with internal
drainage. (Bates and Jackson, 1995)
bottomlands [Landscape Term] (bottom) Low-lying, level land, usually highly fertile,
esp. in the Mississippi Valley region and farther west where the term signifies a grassy
lowland formed by deposition of alluvium along the margin of a watercourse; an alluvial
plain or a flood plain; the floor of a valley. (Bates and Jackson, 1995)
break [Landscape Term and Common Landform] A marked variation of topography, or
a tract of land distinct from adjacent land, or an irregular and rough piece of ground.
(Bates and Jackson, 1995)
A Geomorphic Classification System
82
butte [Fluvial Landform] A conspicuous, usually isolated, generally flat-topped hill or
small mountain with relatively steep slopes or precipitous cliffs, often capped with a
resistant layer of rock and bordered by talus, and representing an erosion remnant
carved from flat-lying rocks; the summit is smaller in extent than that of a mesa, and
many buttes in the arid and semiarid regions of the western U.S. result from the
wastage of mesas. (Bates and Jackson, 1995)
C
caldera [Volcanic Landform] A large, basin-shaped volcanic depression, more or less
circular or cirque like in form, the diameter of which is many times greater than that of
the included vent or vents, no matter what the steepness of the walls or form of the
floor. (Bates and Jackson, 1995)
canyon [Landscape Term] A long, deep, relatively narrow steep-sided valley confined
between lofty and precipitous walls in a plateau or mountainous area, often with a
stream at the bottom; similar to, but larger than, a gorge. It is characteristic of an arid or
semiarid area (such as western U.S.) where stream downcutting greatly exceeds
weathering; e.g. Grand Canyon. (Bates and Jackson, 1995)
canyonlands [Landscape Term] A general term for an area characterized by a series of
long, deep, relatively steep-sided valleys which generally occur within plateaus or
mountainous country in arid or semiarid climates.
carolina bay [Coastal Marine Landform] Any of various shallow, often oval or elliptical,
generally marshy, closed depressions in the Atlantic coastal plain (from southern New
Jersey to northeastern Florida, esp. developed in the Carolinas). They range from about
100 m to many kilometers in length, are rich in humus, and contain trees and shrubs
different from those of the surrounding areas. (Bates and Jackson, 1995)
channel [Fluvial Landform and Microfeature] The bed where a natural body of surface
water flows or may flow; a natural passageway or depression of perceptible extent
containing continuously or periodically flowing water, or forming a connecting link
between two bodies of water; a watercourse. (Bates and Jackson, 1995)
chemically denuding surface [Solution Landform] A portion of the Earth’s surface
which is predominantly undergoing solution weathering.
chenier [Coastal Marine Landform] A long narrow wooded beach ridge or sandy
hummock, 1 to 6 m high, forming roughly parallel to a prograding shoreline seaward of
marsh and mud-flat deposits (as along the coast of southwest Louisiana), enclosed on
the seaward side by fine-grained sediments, and resting on foreshore or mudflat
deposits. It is well drained and fertile, often supporting large evergreen oaks or pines on
higher areas; its width ranges from 45 to 450 m and its length may be several tens of
kilometers. (Bates and Jackson, 1995)
A Geomorphic Classification System
83
chenier plain [Coastal Marine Landform] A strand plain, occupied by cheniers and
intervening mud flats with marsh and swamp vegetation. Bight-coast chenier plains exist
in southwest Louisiana and in Guiana with a maximum length of 700 km. (Bates and
Jackson, 1995)
cinder cone [Volcanic Landform] A conical hill formed by the accumulation of
scoriaceous, basaltic, cinder-sized ejecta. Steepness of the slopes depends on
coarseness of the ejecta, height of eruption, wind velocity, and other factors, but is
normally greater than 10 degrees. (Bates and Jackson, 1995)
circle(s) [Microfeature (single), Periglacial Element Landform (groups)] A form of
patterned ground whose horizontal mesh is dominantly circular. (Bates and Jackson,
1995)
cirque [Glacial Element Landform] A deep steep-walled half-bowl-like recess or hollow,
variously described as horseshoe- or crescent-shaped or semicircular in plan, situated
high on the side of a mountain and commonly at the head of a glacial valley, and
produced by the erosive activity of a mountain glacier. It often contains a small round
lake, and it may or may not be occupied by ice or snow. (Bates and Jackson, 1995)
cirque floor [Glacial Element Landform] The nearly flat surface at the bottom of a
cirque. (Bates and Jackson, 1995)
cirque headwall [Glacial Element Landform] A steep slope at the head of a valley; esp.
the rock cliff at the back of a cirque. (Bates and Jackson, 1995)
cliff [Common Landform] Any high, very steep to perpendicular or overhanging face of
rock; a precipice. A cliff is usually produced by erosion, less commonly by faulting.
(Bates and Jackson, 1995)
coast [Landscape Term] (a) A strip of land of indefinite width (may be many kilometers)
that extends from the low-tide line inland to the first major change in landform features.
(b) The part of a country regarded as near the coast, often including the whole of the
coastal plain. (Bates and Jackson, 1995)
coastal marine [Geomorphic Process] The collection of geomorphic processes
occurring along or inland of, but related to, marine shorelines.
coastal plain [Landscape and Coastal Marine Landform] A low, generally broad plain
that has its margin on an oceanic shore and its strata either horizontal or very gently
sloping toward the water, and that generally represents a strip of recently prograded or
emerged sea floor; e.g. the coastal plain of the southeast U.S. extending for 3000 km
from New Jersey to Texas. (Bates and Jackson, 1995)
A Geomorphic Classification System
84
cockpits [Solution Landform] A group of steep-walled, star-shaped closed depressions
surrounded by conical hills in tropical karst areas, usually about ten times the size of a
temperate-karst sinkhole. Type area: Jamaica. (Bates and Jackson, 1995)
col [Glacial Element Landform] A high, narrow, sharp-edged pass or depression in a
mountain range, generally across a ridge or through a divide, or between two adjacent
peaks; esp. a deep pass formed by the headward erosion and intersection of two
cirques, as in the French Alps. (Bates and Jackson, 1995)
collapse caldera [Volcanic Landform] A type of caldera produced by collapse of the
roof of a magma chamber due to removal of magma by voluminous pyroclastic or lava
eruptions or by subterranean withdrawal of magma. Most calderas are of this type.
(Bates and Jackson, 1995)
collapse sinkhole [Solution Landform] (doline) A type of sinkhole that is formed by
collapse of an underlying cave. (Bates and Jackson, 1995)
colluvial shoulder [Mass Wasting Element Landform] The shoulder of a ridgetop
covered by an extensive blanket-like deposit of colluvium derived from an identifiable
source and deposited through creep processes.
colluvial slope [Mass Wasting Element Landform] A slope covered by an extensive
blanket-like deposit of colluvium derived from an identifiable source and deposited
through creep processes.
complex [Mass Wasting Subprocess] Movement is by a combination of one or more of
the five major types of mass wasting subprocesses, either within various parts of the
moving mass or at different stages in the development of the movements. (Modified
from Varnes, 1978)
composite cone [Volcanic Landform] (stratovolcano) A volcano that is constructed of
alternating layers of lava and pyroclastic deposits, along with abundant dikes and sills.
Viscous, acidic lava may flow from fissures radiating from a central vent, from which
pyroclastics are ejected. (Bates and Jackson, 1995)
compound fault scarp [Tectonic Landform] A fault that is expressed as a zone of
numerous small fractures or of breccia or fault gouge. A fault zone may be as wide as
hundreds of meters. (Bates and Jackson, 1995)
constructional [Volcanic Subprocess] Those volcanic processes which are acting to
build the landscape.
continental glaciation [Glacial Subprocess Modifier] A collection of processes and
landforms which occur or have occurred through glaciation by continental ice sheets.
(Bates and Jackson, 1995)
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85
coral pinnacle [Coastal Marine Landform] A small, isolated spire or column of rock or
coral, either slightly submerged or awash; specif. a small reef patch, consisting of coral
growing sharply upward (with slopes ranging from 45° to nearly vertical), usually within
an atoll lagoon, often rising close to the water surface. (Bates and Jackson, 1995)
coulee [Glacial Landform] A term applied in the northwest U.S. to a dry or intermittent
stream valley, gulch, or wash of considerable extent; esp. a long, steep-walled,
trench-like gorge or valley representing an abandoned overflow channel that temporarily
carried meltwater from an ice sheet, e.g. the Grand Coulee (formerly occupied by the
Columbia River) in Washington State. (Bates and Jackson, 1995)
crag and tail [Glacial Landform] An elongate hill or ridge resulting from glaciation,
having at the stoss end a steep, often precipitous, face or knob of ice-smoothed,
resistant bedrock (the ''crag'') obstructing the movement of the glacier, and at the lee
end a tapering, streamlined, gentle slope (the ''tail'') of intact weaker rock and/or drift
protected by the crag. (Bates and Jackson, 1995)
crater [Volcanic Landform] A basinlike, rimmed structure that is usually at the summit of
a volcanic cone. It may be formed by collapse, by an explosive eruption, or by the
gradual accumulation of pyroclastic material into a surrounding rim. (Bates and
Jackson, 1995)
crevasse [Glacial Element Landform] A deep, nearly vertical fissure, crack, or rift in a
glacier or other mass of land ice, or in a snowfield, caused by stresses resulting from
differential movement over an uneven surface. Crevasses may be concealed beneath
snowbridges, and some are as much as 100 m in depth. (Bates and Jackson, 1995)
cuesta [Fluvial Landform] A hill or ridge with a gentle slope on one side and a steep
slope on the other; specif. an asymmetric ridge with one face (dip slope) long and gentle
and conforming with the dip of the resistant bed or beds that form it, and the opposite
face (scarp slope) steep or even cliff-like and formed by the outcrop of the resistant
rocks, the formation of the ridge being controlled by the differential erosion of the gently
inclined strata. (Bates and Jackson, 1995)
D
debris avalanche [Mass Wasting Landform] The very rapid and usually sudden sliding
and flowage of incoherent, unsorted mixtures of soil and weathered bedrock. (Bates and
Jackson, 1995)
debris flow [Mass Wasting Landform] A moving mass of rock fragments, soil, and
mud, more than half of the particles being larger than sand size. Slow debris flows may
move less that 1 m per year; rapid ones reach 160 km per hour, as in the 1977
Huascaran flow in the Peruvian Andes. (Bates and Jackson, 1995)
A Geomorphic Classification System
86
debris slide basin [Mass Wasting Landform] A basin ranging in size from several tens
of acres to several hundred acres which appears to have formed through a series of
independent debris slide events. The sideslopes are generally steep and dissected.
debris slide-prone lateral scarp [Mass Wasting Element Landform] A steep surface
on the undisturbed ground at the side of a landslide, caused by movement of the slide
material away from the undisturbed ground, which remains subject or prone to debris
sliding.
debris slide-prone main scarp [Mass Wasting Element Landform] A steep surface on
the undisturbed ground at the edge of a landslide, caused by movement of the slide
material away from the undisturbed ground, which remains subject or prone to debris
sliding.
debris slide-prone secondary scarp [Mass Wasting Element Landform] A steep
surface on the displaced material of a landslide, produced by differential movements
within the sliding mass, which remains subject or prone to debris sliding.
deflation basin [Eolian Landform] A topographic basin excavated and maintained by
wind erosion which removes unconsolidated material and commonly leaves a rim of
resistant rock surrounding the depression. (Bates and Jackson, 1995)
delta [Fluvial Landform and Landscape Term] The low, nearly flat, alluvial tract of land
at or near the mouth of a river, commonly forming a triangular or fan-shaped plain of
considerable area, crossed by many distributaries of the main river, perhaps extending
beyond the general trend of the coast, and resulting from the accumulation of sediment
supplied by the river in such quantities that it is not removed by tides, waves, and
currents. Most deltas are partly subaerial and partly below water. (Bates and Jackson,
1995)
delta plain [Fluvial Element Landform] The level or nearly level surface composing the
landward part of a large delta; strictly, an alluvial plain characterized by repeated
channel bifurcation and divergence, multiple distributary channels, and interdistributary
flood basins. (Bates and Jackson, 1995)
deposit [Mass Wasting Element Landform] (talus) Earth material of any type, either
consolidated or unconsolidated, that has accumulated by various mass wasting
processes. (Bates and Jackson, 1995)
deposition [Fluvial Subprocess Modifier] A collection of slope processes where the
landforms are derived primarily from sediment deposition.
[Eolian Subprocess] A collection of eolian landforms derived from the transport and
deposition of airborne material.
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87
deposition stream channel system [Fluvial Process Modifier] A channel in which the
energy of a stream is less than that required to move the sediment available for
transport. This is meant to be a generalization, recognizing that all streams have
eroding, transporting and depositional reaches depending on flow regime and
morphology. These streams generally equate to Rosgen’s C, E and some F type
channels.
depositional stream terrace [Fluvial Landform] (Alluvial Terrace) A stream terrace
composed of unconsolidated alluvium (including gravel), produced by renewed
downcutting of the flood plain or valley floor by a rejuvenated stream or by the later
covering of a terrace with alluvium. (Bates and Jackson, 1995)
depression [Common Landform] Any relatively sunken part of the Earth's surface; esp.
a low-lying area surrounded by higher ground and having no natural outlet for surface
drainage, as an interior basin or a karstic sinkhole. (Bates and Jackson, 1995)
desert pavement [Eolian Element Landform] A natural residual concentration of
wind-polished, closely packed pebbles, boulders, and other rock fragments, mantling a
desert surface where wind action and sheetwash have removed all smaller particles,
and usually protecting the underlying finer-grained material from further deflation. The
fragments commonly are cemented by mineral matter. (Bates and Jackson, 1995)
destructional [Volcanic Subprocess] Those volcanic landforms that owe their origin or
general character to the removal of material by explosion or collapse.
diapir [Tectonic Landform] A dome or anticlinal fold in which the overlying rocks have
been ruptured by the squeezing-out of plastic core material. Diapirs in sedimentary
strata
usually contain cores of salt or shale; igneous intrusions may also show diapiric
structure. (Bates and Jackson, 1995)
differential fluvial erosion with complex structural control [Fluvial Subprocess
Modifier] Erosion which is concentrated due to layers of contrasting erodibility, due to
igneous intrusion, metamorphic differentiation, bedding or other structural properties.
(Bloom, 1991)
dike [Fluvial Landform] A tabular igneous intrusion that cuts across the bedding or
foliation of the country rock. (Bates and Jackson, 1995)
dip slope [Fluvial Element Landform] A slope of the land surface, roughly determined
by and approximately conforming with the direction and the angle of dip of the
underlying rocks; specif. the long, gently inclined face of a cuesta. (Bates and Jackson,
1995)
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88
disintegration moraine [Glacial Landform] Moraines formed by stagnant ice in the
marginal zone have local relief of up to 70 meters and develop from the release of
subglacial drift in the lower part of the ablation zone. (Ritter et al, 1995)
dome [Tectonic Landform] An uplift or anticlinal structure, either circular or elliptical in
outline, in which the rocks dip gently away in all directions. A dome may be small, e.g. a
Gulf Coast salt dome, or many kilometers in diameter. (Bates and Jackson, 1995)
drainage [Common Landform] A collective term for the streams, lakes, and other
bodies of surface water by which a region is drained; a drainage system. (Bates and
Jackson, 1995)
drainage channel (undifferentiated) [Glacial Element Landform] A channel or course
along which water moves in draining a glacier. (Bates and Jackson, 1995)
draw [Common Landform] (a) A small natural watercourse or gully, generally more
shallow or more open than a ravine or gorge; a shallow gulch; a valley or basin. (b) A
usually dry stream bed; a coulee whose water results from periodic rainfall. (c) A sag or
troughlike depression leading up from a valley to a gap between two hills. (Bates and
Jackson, 1995)
drumlin [Glacial Landform] A low, smoothly rounded, elongate oval hill, mound, or
ridge of compact glacial till or, less commonly, other kinds of drift (sandy till, varved
clay), built under the margin of the ice and shaped by its flow, or carved out of an older
moraine by readvancing ice; its longer axis is parallel to the direction of movement of
the ice. It usually has a blunt nose pointing in the direction from which the ice
approached, and a gentler slope tapering in the other direction. Height is 8-60 m,
average 30 m; length is 400-2000 m, average 1500 m. (Bates and Jackson, 1995)
drumlin field [Landscape Term] (basket-of-eggs topography) A landscape
characterized by swarms of closely spaced drumlins, distributed more or less en
echelon, and commonly separated by small marshy tracts. (Bates and Jackson, 1995)
dry sand flow [Mass Wasting Landform] A flow process involving dry sand which are
common along shores or embankments underlain by dry granular material. (Varnes,
1978)
dune (undifferentiated) [Eolian Element Landform] A low mound, ridge, bank, or hill of
loose, windblown granular material (generally sand, sometimes volcanic ash), either
bare or covered with vegetation, capable of movement from place to place but always
retaining its characteristic shape. (Bates and Jackson, 1995)
dune field [Eolian Landform and Landscape Term] An expanse covered by dunes.
(Bates and Jackson, 1995)
A Geomorphic Classification System
89
E
earth flow [Mass Wasting Landform] A mass wasting landform characterized by
downslope translation of soil and weathered rock over a discrete basal shear surface
within well defined lateral boundaries. The basal shear surface is more or less parallel
with the ground surface in the downslope portion of the flow, which terminates in
lobelike forms. Overall, little or no rotation of the slide mass occurs during displacement,
although, in the vicinity of the crown scarp, minor initial rotation is usually observed in a
series of slump blocks. (Bates and Jackson, 1995)
earth hummock [Microfeature] A low, dome-shaped frost mound, consisting of a
fine-textured earthen core covered by a tight mass of vegetation, esp. mosses, but also
humus, grasses, sedges, and scrubby plants, and produced by hydrostatic pressure of
ground water or by heaving from growth of ice lenses in arctic and alpine regions; the
general height is 10-20 cm and the diameter ranges from ½ to 1 m. Earth hummocks
form in groups to produce a nonsorted patterned ground. (Bates and Jackson, 1995)
earth lateral spread [Mass Wasting Landform] Movements which may involve
fracturing and extension of coherent soil material, owing to liquifaction or plastic flow of
the subjacent material. The coherent upper units may subside, translate, rotate or
disintegrate, or they may liquify and flow. The mechanism of failure can involve
elements not only of rotation and translation but also of flow. (Varnes, 1978)
earth pillar [Microfeature] A tall, conical column of unconsolidated to semiconsolidated
earth materials (e.g. clay, till, or landslide debris), produced by differential erosion in a
region of sporadic heavy rainfall (as in a badland or a high alpine valley), and usually
capped by a flat, hard boulder that shielded the underlying softer material from erosion;
it often measures 6-9 m in height, and its diameter is a function of the width of the
protective boulder. (Bates and Jackson, 1995)
emergence [Coastal Marine Subprocess] Landforms formed through coastal marine
processes which due to changes in sea level are exposed.
eolian [Geomorphic Process] Geomorphic processes and landforms pertaining to the
wind; esp. said of such deposits as loess and dune sand, of sedimentary structures
such as wind-formed ripple marks, or of erosion and deposition accomplished by the
wind. (Bates and Jackson, 1995) also
[Lacustrine Subprocess] Lakes formed by wind action such as basins dammed by
windblown sand, lakes between dunes or deflation basins formed by wind action.
(Hutchinson, 1957)
eroded bench [Mass Wasting Element Landform] A relatively level or gently inclined
strip or platform of land, earth, or rock, bounded by steeper slopes above and below,
and formed by past mass wasting, which is presently under the dominant influence of
surface erosion.
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90
eroding stream channel system [Fluvial Subprocess Modifier] A channel in which the
energy of a stream is greater than that required to move the sediment available for
transport. This is meant to be a generalization, recognizing that all streams have
eroding, transporting and depositional reaches depending on flow regime and
morphology. These streams generally equate to Rosgen’s A and G type channels.
erosion [Eolian Subprocess] Landforms developed from wind erosion through either
deflation or abrasion. (Bloom, 1991)
erosion fan remnant [Fluvial Landform] A landform that is the remaining part of various
older fan landforms that have been dissected. They have a flattish summit of relict fan
surface. (Peterson, 1981)
erosional stream terrace [Fluvial Landform] (strath terrace) A term used for an
extensive remnant of a strath (i.e. a flat valley bottom) that belonged to a former erosion
cycle and that has undergone dissection by a rejuvenated stream following uplift.
(Bates and Jackson, 1995)
escarpment [Common Landform] A long, more or less continuous cliff or relatively
steep slope facing in one general direction, breaking the continuity of the land by
separating two level or gently sloping surfaces, and produced by erosion or by faulting.
The term is often used synonymously with scarp, although escarpment is more often
applied to a cliff formed by differential erosion. (Bates and Jackson, 1995)
esker [Glacial Landform] A long, narrow, sinuous, steep-sided ridge composed of
irregularly stratified sand and gravel that was deposited by a subglacial or englacial
stream flowing between ice walls or in an ice tunnel of a stagnant or retreating glacier,
and was left behind when the ice melted. It may be branching and is often
discontinuous, and its course is usually at a high angle to the edge of the glacier.
Eskers range in length from less than 100 m to more than 500 km (if gaps are included),
and in height from 3 to more than 200 m. (Bates and Jackson, 1995)
estuary [Coastal Marine Landform] The seaward end or the widened funnel-shaped
tidal mouth of a river valley where fresh water comes into contact with seawater and
where tidal effects are evident; e.g. a tidal river, or a partially enclosed coastal body of
water where the tide meets the current of a stream. (Bates and Jackson, 1995)
exogenous dome [Volcanic Landform] Domes that form by repeated overflows of very
viscous lava from a vent in their summit. (McDonald, 1972)
explosion caldera [Volcanic Landform] A type of caldera that is formed by explosive
removal of the upper part of a volcanic cone. It is extremely rare, and is small in size.
(Bates and Jackson, 1995)
A Geomorphic Classification System
91
F
faceted spur [Common Landform] A spur or ridge with an inverted-V face that was
produced by faulting or by the trimming, beveling, or truncating action of streams,
waves, or glaciers. (Bates and Jackson, 1995)
fall [Mass Wasting Subprocess] A very rapid downward movement of a mass of rock or
earth that travels mostly through the air by free fall, leaping, bounding, or rolling, with
little or no interaction between one moving unit and another; e.g. rockfall; debris fall.
(Bates and Jackson, 1995)
fall-prone slope [Mass Wasting Landform] A near vertical slope which has the
characteristics to undergo fall type mass wasting processes.
fan apron [Fluvial Element Landform] A sheet-like mantle of relatively young alluvium
covering part of an older fan piedmont or occasionally, an older alluvial fan. It
somewhere buries a pedogenic soil which can be traced to the edge of the fan apron
where the buried soil emerges as the land-surface or relict soil. (Peterson, 1990)
fan-head collar [Fluvial Landform Element] A landform comprised of a thin, short,
relatively young mantle of alluvium along the very upper margin of a major alluvial fan at
a mountain front. The mantle somewhere buries a pedogenic soil that can be traced to
the edge of the fan collar where it emerges as the land surface, or relict soil. (Peterson,
1981)
fan piedmont [Landscape Term and Fluvial Landform] The most extensive landform of
most piedmont slopes, formed by the lateral coalescence of mountain-front alluvial fans
downslope into one generally smooth slope without the transverse undulations of the
semi-conical alluvial fans and by accretion of fan aprons. Fan piedmonts commonly are
complexes of many landforms. (Peterson, 1981)
fan remnant [Fluvial Landform] A generic term for landforms which are the remaining
parts of various older fan landforms that have either been dissected or partially buried.
(Peterson, 1981)
fan skirt [Fluvial Element Landform] A landform comprised of laterally coalescing,
small alluvial fans that issue from gullies, cut into, or are extensions of inset fans of the
fan piedmont and that merge along their toe slopes with the basin floor. Fan skirts are
smooth or only slightly dissected. (Peterson, 1981)
fan-head trench [Fluvial Element Landform] A relatively deep drainage way originating
in a mountain valley and cut into the apex of, and commonly across an alluvial fan. It
may empty into an interfan-valley drainage way, debouch onto the fan piedmont, or
cross the fan piedmont. (Peterson, 1981)
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92
faros [Coastal Marine Landform] A small, atoll-shaped or oblong reef with a lagoon up
to 30 m deep, forming part of the rim of a barrier reef or of an atoll. (Bates and Jackson,
1995)
fault scarp [Tectonic Landform] A steep slope or cliff formed directly by movement
along a fault and representing the exposed surface of the fault before modification by
erosion and weathering. (Bates and Jackson, 1995)
fault terrace [Tectonic Landform] (fault bench) An irregular, terrace-like tract between
two fault scarps, produced on a hillside by step faulting in which the downthrow is
systematically on the same side of two approximately parallel faults. (Bates and
Jackson, 1995)
fault trace [Tectonic Landform] (fault line) The trace of a fault plane on the ground
surface or on a reference plane. (Bates and Jackson, 1995)
faulting [Tectonic Subprocess] The process of fracturing and displacement that
produces a fault. (Bates and Jackson, 1995)
fissure [Tectonic Landform] A surface of fracture or a crack in rock along which there
is a distinct separation. (Bates and Jackson, 1995)
fissure vent [Volcanic Landform] The opening at the Earth's surface of a volcanic
conduit having the form of a crack or fissure. (Bates and Jackson, 1995)
flat [Common Landform] A general term for a level or nearly level surface or small area
of land marked by little or no relief, as a plain; specif: mud flat; valley flat. Also, a nearly
level region that visibly displays lower relief than its surroundings. (Bates and Jackson,
1995)
flatland [Landscape Term] A region, or tract of land, characterized by predominant
levelness or by no significant variation in elevation, as along a river or a coast. (Bates
and Jackson, 1995)
floating block [Mass Wasting Element Landform] A large block of bedrock which is
translating downslope within a complex slump-earth flow mass wasting landform.
flood plain [Fluvial Landform] The surface or strip of relatively smooth land adjacent to
a river channel, constructed by the present river in its existing regimen and covered with
water when the river overflows its banks. It is built of alluvium carried by the river during
floods and deposited in the sluggish water beyond the influence of the swiftest current.
A river has one flood plain and may have one or more terraces representing abandoned
flood plains. (Bates and Jackson, 1995)
floor [Common Landform] (a) The bed of any body of water; esp. the continuous and
gently curved or essentially horizontal surface of the ground beneath the water of a
A Geomorphic Classification System
93
stream, lake, or ocean. (b) valley floor. (c) The bottom of a depression, such as the floor
of a crater. (Modified from Bates and Jackson, 1995)
flow [Mass Wasting Subprocess] A mass wasting process where the movement of
unconsolidated material exhibits a continuity of motion and a plastic or semifluid
behavior resembling that of a viscous fluid. (Bates and Jackson, 1995)
flute [Glacial Element Landform] Lineations or streamline grooves and ridges parallel to
the direction of ice movement, formed in newly deposited till or older drift. They range in
height from a few centimeters to 25 m, and in length from a few meters to more than 20
km. (Bates and Jackson, 1995)
fluted moraine surface [Glacial Landform] Moraine surface in front of a glacier
containing parallel ridges that have a more or less constant height over distances of the
order of tens or hundreds of meters. The ridge axes are parallel to the flow direction of
the glacier. (Bates and Jackson, 1995)
fluve [Common Landform] A linear depression (topographic low) of any size, along
which water flows at some time. (Peterson, 1981)
fluvial [Geomorphic Process] Geomorphic processes pertaining to a river or rivers;
produced by river action. (Bates and Jackson, 1995)
fluvial slope processes [Fluvial Subprocess] Fluvial erosional and depositional
processes resulting from overland flow or unchannelized flow on slopes.
fluviatile [Lacustrine Subprocess] Lakes formed due to fluvial action, including fluvial
erosion and fluvial deposition. (Hutchinson, 1957)
fold [Tectonic Landform] A curve or bend of a planar structure such as rock strata,
bedding planes, foliation, or cleavage. A fold is usually a product of deformation,
although its definition is descriptive and not genetic and may include primary structures.
(Bates and Jackson, 1995)
folding [Tectonic Subprocess] The formation of folds in rocks.
1995)
(Bates and Jackson,
foothills [Landscape Term] A region of relatively low, rounded hills at the base of or
fringing a mountain range; e.g. the low, undulating region along the western base of the
Sierra Nevada in California. (Bates and Jackson, 1995)
foredune [Eolian Landform] A coastal dune or dune ridge oriented parallel to the
shoreline, occurring at the landward margin of the beach, along the shoreward face of a
beach ridge, or at the landward limit of the highest tide, and more or less completely
stabilized by vegetation. (Bates and Jackson, 1995)
A Geomorphic Classification System
94
fosse [Glacial Element Landform] A long, narrow depression or troughlike hollow
between the edge of a retreating glacier and the wall of its valley, or between the front
of a moraine and its outwash plain. It may result from local acceleration of melting due
to absorbed or reflected heat from the valley sides. (Bates and Jackson, 1995)
free face [Common Landform] The part of a hillside surface consisting of an outcrop of
bare rock (such as a scarp or cliff) that stands more steeply than the angle of repose of
the constant slope immediately below. (Bates and Jackson, 1995)
fringing reef [Coastal Marine Landform] An organic reef that is directly attached to or
borders the shore of an island or continent, having a rough, tablelike surface that is
exposed at low tide; it may be more than 1 km wide, and its seaward edge slopes
sharply down to the sea floor. There may be a shallow channel or lagoon between the
reef and the adjacent mainland. (Bates and Jackson, 1995)
front [Landscape Term] The more or less linear outer slope of a mountain range that
rises above a plain or plateau. (Bates and Jackson, 1995)
frost action [Periglacial Subprocess] A subprocess where the driving force is the
growth of ice within a soil or rock. (Ritter et al, 1995)
frost creep slope [Mass Wasting Landform] The downslope movement of particles in
response to expansion and contraction due to freezing and thawing and under the
influence of gravity. (Ritter et al, 1995)
frost boil [Microfeature] (a) An accumulation of excess water and mud liberated from
ground ice by accelerated spring thawing, commonly softening the soil and causing a
quagmire. (b) A low mound developed by local differential frost heaving at a place most
favorable for the formation of segregated ice and accompanied by an absence of an
insulating cover of vegetation. (c) A break in a surface pavement due to swelling frost
action; as the ice melts, soupy subgrade materials issue from the break. (Bates and
Jackson, 1995)
frost mound [Microfeature] A general term for a knoll, hummock, or conical mound in a
permafrost region, containing a core of ice, and representing a generally seasonal and
localized upwarp of the land surface, caused by frost heaving and/or hydrostatic
pressure of ground water. (Bates and Jackson, 1995)
fumarole field [Volcanic Landform] A group of vents, usually volcanic, from which
gases and vapors are emitted; it is characteristic of a late stage of volcanic activity. It is
sometimes described by the composition of its gases, e.g. chlorine fumarole. (Bates
and Jackson, 1995)
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95
G
gap [Common Landform] A term used for a sharp break or opening in a mountain
ridge, or for a short pass through a mountain range; e.g. a wind gap. (Bates and
Jackson, 1995)
general chemical weathering [Solution Subprocess] The process of weathering by
which chemical reactions (hydrolysis, hydration, oxidation, carbonation, ion exchange,
and solution) transform rocks and minerals into new chemical combinations that are
stable under conditions prevailing at or near the Earth's surface; e.g. the alteration of
orthoclase to kaolinite. (Bates and Jackson, 1995)
giant ripples [Glacial Element Landform] A ripple that is more than 30 m in length; it
usually shows superimposed megaripples (Bates and Jackson, 1995)
gilgai [Microfeature] The microrelief of heavy clay soils with high coefficients of
expansion and contraction according to changes in moisture. Gilgai is typical of
Vertisols. (Bates and Jackson, 1995)
glacial [Geomorphic Process] Pertaining to distinctive processes and features
produced by or derived from glaciers and ice sheets. (Modified from Bates and
Jackson, 1995)
[Lacustrine Subprocess] Lakes formed by glacial activity including lakes held by ice,
lakes in glacial rock basins, lakes held by glacial deposits, drift basins and pingo lakes.
(Hutchinson, 1957)
glacial quarry [Glacial Element Landform] An area where the process of glacial erosion
by which sizable rock fragments, such as blocks, are loosened, detached, and borne
away from bedrock by the freezing of water along joints and stratification surfaces with
resulting removal of rock as the ice advances. (Bates and Jackson, 1995)
glaciated uplands [Landscape Term] Said of a formerly glacier-covered upland
surface, esp. one that has been modified by the action of a glacier or an ice sheet.
(Bates and Jackson, 1995)
glacier [Glacial Landform] A large mass of ice formed, at least in part, on land by the
compaction and recrystallization of snow, moving slowly by creep downslope or outward
in all directions due to the stress of its own weight, and surviving from year to year.
Included are small mountain glaciers as well as ice sheets continental in size, and ice
shelves which float on the ocean but are fed in part by ice formed on land. (Bates and
Jackson, 1995)
gorge [Common Landform] A narrow, deep valley with nearly vertical rocky walls,
enclosed by mountains, smaller than a canyon, and more steep-sided than a ravine;
esp. a restricted, steep-walled part of a canyon. (Bates and Jackson, 1995)
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96
graben [Landscape Term and Tectonic Landform] An elongate, relatively depressed
crustal unit or block that is bounded by faults on its long sides. (Bates and Jackson,
1995)
ground moraine [Glacial Landform] An accumulation of till after it has been deposited
or released from the ice during ablation, to form an extensive area of low relief devoid of
transverse linear elements. (Bates and Jackson, 1995)
gulch [Common Landform] A term used esp. in the western U.S. for a narrow, deep
ravine with steep sides, larger than a gully. (Bates and Jackson, 1995)
gully [Common Landform] (a) A very small valley, such as a small ravine in a cliff face,
or a long, narrow hollow or channel worn in earth or unconsolidated material (as on a
hillside) by running water and through which water runs only after a rain or the melting
of ice or snow; it is smaller than a gulch. (b) Any erosion channel so deep that it cannot
be crossed by a wheeled vehicle or eliminated by plowing, esp. one excavated in soil on
a bare slope. (c) A small, steep-sided wooded hollow. (Bates and Jackson, 1995)
H
hanging valley [Glacial Landform] A glacial valley whose mouth is at a relatively high
level on the steep side of a larger glacial valley. The larger valley was eroded by a trunk
glacier and the smaller one by a tributary glacier, and the discordance of level of their
floors, as well as their difference in size, is due to the greater erosive power of the trunk
glacier. (Bates and Jackson, 1995)
headland [Coastal Marine Landform] An irregularity of land, esp. of considerable height
with a steep cliff face, jutting out from the coast into a large body of water (usually the
sea or a lake); a bold promontory or a high cape. (Bates and Jackson, 1995)
highland [Landscape Term] A general term for a relatively large area of elevated or
mountainous land standing prominently above adjacent low areas; a mountainous
region. The term is often used in the plural in a proper name; e.g. the Highlands of
Scotland. (Bates and Jackson, 1995)
hills [Landscape Term] A natural elevation of the land surface, rising rather prominently
above the surrounding land, usually of limited extent and having a well-defined outline
(rounded rather than peaked or rugged), and generally considered to be less than 300
m from base to summit; the distinction between a hill and a mountain is arbitrary and
dependent on local usage. (Bates and Jackson, 1995)
hillslope bedrock outcrop [Mass Wasting Element Landform] The source zone on the
hillslope for downslope colluvium.
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hogback [Fluvial Landform] Any ridge with a sharp summit and steep slopes of nearly
equal inclination on both flanks, and resembling in outline the back of a hog; specif. a
sharp-crested ridge formed by the outcropping edges of steeply inclined resistant
rocks, and produced by differential erosion. The term is usually restricted to ridges
carved from beds dipping at angles greater than 20° . (Bates and Jackson, 1995)
homocline [Tectonic Landform] A general term for a series of rock strata having the
same dip, e.g. one limb of a fold, a tilted fault block, or an isocline. (Bates and Jackson,
1995)
hoodoo [Fluvial Landform] A fantastic column, pinnacle, or pillar of rock produced in a
region of sporadic heavy rainfall by differential weathering or erosion of horizontal
strata, facilitated by joints and by layers of varying hardness, and occurring in varied
and often eccentric or grotesque forms. (Bates and Jackson, 1995)
horn [Glacial Element Landform] A high rocky sharp-pointed mountain peak with
prominent faces and ridges, bounded by the intersecting walls of three or more cirques
that have been cut back into the mountain by headward erosion of glaciers. (Bates and
Jackson, 1995)
horst [Tectonic Landform and Landscape Term] An elongate, relatively uplifted crustal
unit or block that is bounded by faults on its long sides. (Bates and Jackson, 1995)
hummock [Common Landform] A rounded or conical knoll, mound, hillock, or other
small elevation. Also, a slight rise of ground above a level surface. (Bates and Jackson,
1995)
I
ice apron [Glacial Element Landform] The thin mass of snow and ice attached to the
headwall of a cirque above the bergschrund. (Bates and Jackson, 1995)
ice contact deposition [Glacial Subprocess] The environment where the edge of the
glacier interacts with the landscape, where moraines, eskers and drumlins form. (Ritter
et al, 1995)
ice erosion [Glacial Subprocess] Landforms created from the direct influence of glacial
erosion.
ice margin channel [Glacial Landform] (ice-marginal drainage) Stream drainage along
the side or front of a glacier. (Bates and Jackson, 1995)
ice wedge [Microfeature] Wedge-shaped, foliated ground ice produced in permafrost,
occurring as a vertical or inclined sheet, dike, or vein tapering downward, and
measuring from a few millimeters to as much as 6 m wide and from 1 m to as much as
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98
30 m high. It originates by the growth of hoar frost or by the freezing of water in a
narrow crack or fissure produced by thermal contraction of the permafrost. (Bates and
Jackson, 1995)
inselberg [Fluvial Landform] A prominent isolated residual knob, hill, or small mountain
of circumdenudation, usually smoothed and rounded, rising abruptly from and
surrounded by an extensive lowland erosion surface in a hot, dry region (as in the
deserts of southern Africa or Arabia), generally bare and rocky although partly buried by
the debris derived from and overlapping its slopes; it is characteristic of an arid or
semiarid landscape in a late stage of the erosion cycle. (Bates and Jackson, 1995)
inset fan [Fluvial Element Landform] A special case of the floodplain of a commonly
ephemeral stream that is confined between fan remnants, basin-floor remnants,
ballenas, or closely opposed fan toeslopes. Its transversely-level cross section is
evidence of alluviation of a fluve. It must be wide enough that raw channels cover only
a fraction of this component landform’s surface. (Peterson, 1981)
interdune flat [Eolian Landform] (interdune) Pertaining to the relatively flat surface,
whether sand-free or sand-covered, between dunes; e.g. said of the long, troughlike,
wind-swept passage between parallel longitudinal dunes. (Bates and Jackson, 1995)
interfluve [Common Landform] The area between rivers; esp. the relatively
undissected upland or ridge between two adjacent valleys containing streams flowing in
the same general direction. (Bates and Jackson, 1995)
interlobate moraine [Glacial Landform] A lateral or end moraine formed along the line
of junction and roughly parallel to the axes of two adjacent glacial lobes that have
pushed their margins together. (Bates and Jackson, 1995)
intermontane basin [Landscape Term] (Intermontane) Situated between or surrounded
by mountains, mountain ranges, or mountainous regions; e.g. the Great Basin of
western U.S., between the Sierra Nevada and the Wasatch Mountains. (Bates and
Jackson, 1995)
internested rotational-translational slides
[Mass Wasting Landform] A complex mass wasting landform where numerous
translational and rotational landslides occur adjacent to and on top of one another on a
slope. Often the toe zone of one slide is the head scarp of a slide lower on the slope.
intrusive dome
[Volcanic Landform] A volcanic dome formed mainly by intrusion at shallow depths.
(Williams and McBirney, 1979)
island [Coastal Marine, Fluvial and Lacustrine Landform and Landscape Term] A tract
of land smaller than a continent, surrounded by the water of an ocean, sea, lake, or
stream. The term has been loosely applied to land-tied and submerged areas, and to
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99
land cut off on two or more sides by water, such as a peninsula. (Bates and Jackson,
1995)
K
kame[Glacial Landform] A low mound, knob, hummock, or short irregular ridge,
composed of stratified sand and gravel deposited by a subglacial stream as a fan or
delta at the margin of a melting glacier; by a superglacial stream in a low place or hole
on the surface of the glacier; or as a ponded deposit on the surface or at the margin of
stagnant ice. (Bates and Jackson, 1995)
kame moraine [Glacial Landform] An end moraine that contains numerous kames.
(Bates and Jackson, 1995)
kame terrace [Glacial Landform] A terracelike ridge consisting of stratified sand and
gravel formed as a glaciofluvial or glaciolacustrine deposit between a melting glacier or
a stagnant ice lobe and a higher valley wall or lateral moraine, and left standing after the
disappearance of the ice; a filling of a fosse. A kame terrace terminates a short distance
downstream from the terminal moraine; it is commonly pitted with kettles and has an
irregular ice-contact slope. (Bates and Jackson, 1995)
karst [Landscape Term] A type of topography that is formed on limestone, gypsum,
and other rocks by dissolution, and that is characterized by sinkholes, caves, and
underground drainage. (Bates and Jackson, 1995)
karstification [Solution Subprocess] The formation of karst features by the solutional,
and sometimes mechanical, action of water in a region of limestone, gypsum, or other
bedrock. (Bates and Jackson, 1995)
karst tower [Solution Landform] An isolated hill in a karst region surrounded by a plain
that is commonly alluviated. (Bates and Jackson, 1995)
karst window [Solution Landform] An unroofed cave, at the bottom of which can be
seen a subterranean stream. (Bates and Jackson, 1995)
kegel karst [Solution Landform] (cockpit karst) A typical karst of the tropics, in which
cockpits are separated by steep-walled rounded hills, forming a pattern that resembles
a molded egg box. (Bates and Jackson, 1995)
kettle [Glacial Element Landform] A steep-sided, usually basin- or bowl-shaped hole or
depression, commonly without surface drainage, in glacial-drift deposits (esp. outwash
and kame fields), often containing a lake or swamp; formed by the melting of a large,
detached block of stagnant ice (left behind by a retreating glacier) that had been wholly
or partly buried in the glacial drift. Kettles range in depth from about a meter to tens of
meters, and in diameter to as much as 13 km. (Bates and Jackson, 1995)
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100
kettled outwash plain [Glacial Landform] (kettled sandur or pitted outwash plain) An
outwash plain marked by many irregular depressions such as kettles, shallow pits, and
potholes; many are found in Wisconsin and Minnesota. (Bates and Jackson, 1995)
knob [Common Landform] (a) A rounded eminence, as a knoll, hillock, or small hill or
mountain; esp. a prominent or isolated hill with steep sides, commonly found in the
southern U.S. (b) A peak or other projection from the top of a hill or mountain. Also, a
boulder or group of boulders or an area of resistant rocks protruding from the side of a
hill or mountain. (Bates and Jackson, 1995)
knoll [Common Landform] (a) A small, low, rounded hill; a hillock or mound. (b) The
rounded top of a hill or mountain. Bates and Jackson, 1995)
L
laccolith [Tectonic Landform] A concordant igneous intrusion with a known or assumed
flat floor and a postulated dikelike feeder commonly thought to be beneath its thickest
point. It is generally plano-convex in form and roughly circular in plan, less than ten km.
in diameter, and from a meter to nearly one hundred meters in thickness. (Bates and
Jackson, 1995)
lacustrine [Geomorphic Process] Pertaining to, produced by, or formed in a lake or
lakes. (Bates and Jackson, 1995)
lacustrine (undifferentiated) [Lacustrine Subprocess] A Subprocess where the origin of
a particular lake is not known.
lagoon [Coastal Marine Landform] A shallow stretch of seawater, such as a sound,
channel, bay, or saltwater lake, near or communicating with the sea and partly or
completely separated from it by a low, narrow, elongate strip of land, such as a reef,
barrier island, sandbank, or spit; esp. the sheet of water between an offshore coral reef
and the mainland. It often extends roughly parallel to the coast, and it is little affected by
tides. (Bates and Jackson, 1995)
lahar [Volcanic Landform] A mudflow composed chiefly of volcaniclastic materials on
the flank of a volcano. The debris carried in the flow includes pyroclasts, blocks from
primary lava flows, and epiclastic material. Lahars occur in response to or shortly after
volcanic eruptions. (Modified from Bates and Jackson, 1995)
lake [Lacustrine Landform] Any inland body of standing water occupying a depression
in the Earth's surface, generally of appreciable size (larger than a pond) and too deep to
permit vegetation (excluding subaqueous vegetation) to take root completely across the
expanse of water; the water may be fresh or saline. The term includes an expanded part
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101
of a river, a reservoir behind a dam, or a lake basin intermittently or formerly covered by
water. (Bates and Jackson, 1995)
lake bed [Lacustrine Landform] The flat to gently undulating ground underlain by
fine-grained sediments deposited in a former or intermittent lake. (Bates and Jackson,
1995)
lake plain [Lacustrine Landform] (a) The nearly level surface marking the floor of an
extinct lake, filled in by well-sorted deposits from inflowing streams. (b) A flat lowland or
a former lake bed bordering an existing lake. (Bates and Jackson, 1995)
lake terrace [Lacustrine Landform] A narrow shelf, partly cut and partly built, produced
along a lake shore in front of a nip or line of low cliffs, and later exposed when the water
level falls. (Bates and Jackson, 1995)
landslide [Lacustrine Subprocess] Lakes formed by landslides including those formed
through damming as well as those formed on the surface of slides. (Hutchinson, 1957)
lateral moraine [Glacial Landform] A low ridge like moraine carried on, or deposited at
or near, the side margin of a mountain glacier. It is composed chiefly of rock fragments
loosened from the valley walls by glacial abrasion and plucking, or fallen onto the ice
from the bordering slopes. (Bates and Jackson, 1995)
lateral scarp (undifferentiated) [Mass Wasting Element Landform] A steep surface on
the undisturbed ground at the side of a landslide, caused by movement of the slide
material away from the undisturbed ground. (Bates and Jackson, 1995)
lateral spread [Mass Wasting Subprocess] Lateral movements in a fractured mass of
rock or soil, which result from liquefaction or plastic flow of subjacent materials. (Bates
and Jackson, 1995)
lava blister [Microfeature] A surficial swelling of the crust of a lava flow formed by the
puffing-up of gas or vapor beneath the flow. A blister is usually about one m. in
diameter, and is hollow. (Bates and Jackson, 1995)
lava flow (undifferentiated) [Volcanic Landform] A lateral, surficial outpouring of molten
lava from a vent or a fissure; also, the solidified body of rock that is so formed. (Bates
and Jackson, 1995)
lava plain [Landscape Term] A broad stretch of level or nearly level land, usually many
hundreds of square kilometers in extent, underlain by a relatively thin succession of lava
flows, most of which are basaltic and the product of fissure eruptions. (Bates and
Jackson, 1995)
lava plateau [Landscape Term] A broad, elevated tableland or flat-topped highland,
usually many hundreds or thousands of square kilometers in extent, underlain by a thick
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102
succession of lava flows, most of which are tholeiitic basalts and the product of fissure
eruption. (Bates and Jackson, 1995)
ledge [Common Landform] (a) A narrow shelf or projection of rock, much longer than
wide, formed on a rock wall or cliff face, as along a coast by differential wave erosion of
softer rocks. (b) A rocky outcrop; solid rock. (c) An underwater ridge of rocks, esp. near
the shore; also, a nearshore reef. (d) A quarry exposure or natural outcrop of a mineral
deposit. (Bates and Jackson, 1995)
levee [Fluvial Element Landform] (natural levee) A long broad low ridge or
embankment of sand and coarse silt, built by a stream on its flood plain and along both
banks of its channel, esp. in time of flood when water overflowing the normal banks is
forced to deposit the coarsest part of its load. It has a gentle slope (about 60 cm/km)
away from the river and toward the surrounding flood plain, and its highest elevation
(about 4 m above the flood plain) is closest to the river bank, at or near normal flood
level. (Bates and Jackson, 1995)
loess deposit (undifferentiated) [Eolian Landform] A deposit of a widespread,
homogeneous, commonly nonstratified, porous, friable, slightly coherent, usually highly
calcareous, fine-grained blanket deposit (generally less than 30 m thick), consisting
predominantly of silt with subordinate grain sizes ranging from clay to fine sand. (Bates
and Jackson, 1995)
loess flow Mass Wasting Landform] A fluid suspension of dry porous silt in air, moving
downslope, such as occurred following the 1920 earthquake in Kansu Province, China.
(Bates and Jackson, 1995)
longitudinal bar [Fluvial Element Landform] A depositional stream channel feature
which is primarily comprised of bed load temporarily at rest; part may be preserved in
more durable channel fills or later accretions. (Bloom, 1991)
longshore bar [Coastal Marine Landform] A low, elongate sand ridge, built chiefly by
wave action, occurring at some distance from, and extending generally parallel with, the
shoreline, being submerged at least by high tides, and typically separated from the
beach by an intervening trough. (Bates and Jackson, 1995)
louderback [Fluvial Landform] A remnant of a lava flow appearing in a tilted fault block
and bounded by a dip slope. (Bates and Jackson, 1995)
lowland [Common Landform and Landscape Term] (a) A general term for low-lying land
or an extensive region of low land, esp. near the coast and including the extended
plains or country lying not far above tide level. (b) The low and relatively level ground of
a region, in contrast with the adjacent, higher country; e.g. a vale between two cuestas.
(c) A low or level tract of land along a watercourse; a bottom. (Bates and Jackson,
1995)
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103
M
maar [Volcanic Landform] A low-relief, broad volcanic crater formed by multiple shallow
explosive eruptions. It is surrounded by a crater ring, and may be filled by water.
(Bates and Jackson, 1995)
main scarp (undifferentiated) [Mass Wasting Landform] A steep surface on the
undisturbed ground at the edge of a landslide, caused by movement of the slide
material away from the undisturbed ground. (Bates and Jackson, 1995)
marine terrace (undifferentiated) [Coastal Marine and Lacustrine Landform] (a) A
narrow, gently sloping constructional coastal strip extending seaward or lakeward, and
veneered by a sedimentary deposit; esp. a wave-built terrace. (b) Loosely, a stripped
wave-cut platform that has been exposed by uplift or by lowering of the water level; an
elevated wave-cut bench. (Bates and Jackson, 1995)
mass wasting [Geomorphic Process] A general term for the dislodgement and
downslope transport of soil and rock material under the direct application of gravitational
body stresses. In contrast to other erosion processes, the debris removed by mass
wasting is not carried within, on, or under another medium. The mass properties of the
material being transported depend on the interaction of the soil and rock particles and
on the moisture content. Mass wasting includes slow displacements, such as creep and
solifluction, and rapid movements such as rockfalls, rockslides, and debris flows. (Bates
and Jackson, 1995)
meander belt [Landscape Term] The zone along a valley floor across which a
meandering stream shifts its channel from time to time; specif. the area of the flood
plain included between two lines drawn tangentially to the extreme limits of all fully
developed meanders. It may be from 15 to 18 times the width of the stream. (Bates and
Jackson, 1995)
meander scar [Fluvial Element Landform] A crescentic, concave mark on the face of a
bluff or valley wall, produced by the lateral planation of a meandering stream which
undercut the bluff, and indicating the abandoned route of the stream.(Bates and
Jackson, 1995)
meander scroll [Fluvial Element Landform] One of a series of long, parallel, closely
fitting, arcuate ridges and troughs formed along the inner bank of a stream meander as
the channel migrated laterally down-valley and toward the outer bank. (Bates and
Jackson, 1995)
medial moraine [Glacial Landform] An elongate moraine carried in or upon the middle
of a glacier and parallel to its sides, usually formed by the merging of adjacent and inner
lateral moraines below the junction of two coalescing valley glaciers. (Bates and
Jackson, 1995)
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104
meltwater erosion
[Glacial Subprocess] Erosion resulting from water derived from the melting of snow or
ice, esp. the stream flowing in, under, or from melting glacier ice. (Bates and Jackson,
1995)
mesa [Fluvial Landform] An isolated, nearly level landmass standing distinctly above
the surrounding country, bounded by abrupt or steeply sloping erosion scarps on all
sides, and capped by layers of resistant, nearly horizontal rock (often lava). Less strictly,
a very broad, flat-topped, usually isolated hill or mountain of moderate height bounded
on at least one side by a steep cliff or slope and representing an erosion remnant. A
mesa is similar to, but has a more extensive summit area than, a butte, and is a
common topographic feature in the arid and semiarid regions of the U.S. (Bates and
Jackson, 1995)
meteoric [Lacustrine Subprocess] Lakes formed by meteoric impact. (Hutchinson,
1957)
mima mound [Microfeature] A term used in the northwest U.S. for one of numerous
low, circular or oval domes composed of loose, unstratified, gravelly silt and soil
material, built upon glacial outwash on a hog-wallow landscape; the basal diameter
varies from 3 m to more than 30 m, and the height from 30 cm to about 2 m. (Bates and
Jackson, 1995)
monadnock [Fluvial Landform] An upstanding rock, hill, or mountain of
circumdenudation rising conspicuously above the general level of a peneplain in a
temperate climate, representing an isolated remnant of a former erosion cycle in a
mountain region that has been largely beveled to its base level. Type locality: Mount
Monadnock in New Hampshire. (Bates and Jackson, 1995)
monocline [Tectonic Landform] A local steepening in an otherwise uniform gentle dip.
(Bates and Jackson, 1995)
moraine (undifferentiated) [Glacial Landform] A mound, ridge, or other distinct
accumulation of unsorted, unstratified glacial drift, predominantly till, deposited chiefly
by direct action of glacier ice, in a variety of topographic landforms that are independent
of control by the surface on which the drift lies. (Bates and Jackson, 1995)
moulin [Glacial Element Landform] A roughly cylindrical, nearly vertical, well-like
opening, hole, or shaft in the ice of a glacier, scoured out by swirling meltwater as it
pours down from the surface. (Bates and Jackson, 1995)
mound [Common Landform] (a) A low rounded natural hill, generally of earth; a knoll.
(b) A small man-made hill, composed either of debris accumulated during successive
occupations of the site or of earth heaped up to mark a burial site. (Bates and Jackson,
1995)
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105
mountain(s) [Common Landform (singular), Landscape Term (plural)] (a) Any part of
the Earth's crust higher than a hill, sufficiently elevated above the surrounding land
surface of which it forms a part to be considered worthy of a distinctive name,
characterized by a restricted summit area (as distinguished from a plateau), and
generally having comparatively steep sides and considerable bare-rock surface; it can
occur as a single, isolated eminence, or in a group forming a long chain or range, and it
may form by earth movements, erosion, or volcanic action. Generally, a mountain is
considered to project at least 300 m above the surrounding land. (b) Any conspicuous
or prominent elevation in an area of low relief, esp. one rising abruptly from the
surrounding land and having a rounded base. (c) A region characterized by mountains;
term usually used in the plural. (Bates and Jackson, 1995)
mountain valley [Common Landform] Any low-lying land bordered by higher ground;
especially an elongate, relatively large, gently sloping depression of the Earth's surface,
commonly situated between two mountains or between ranges mountains, and often
containing a stream with an outlet. It is usually developed by stream erosion, but may
be formed by faulting. (Bates and Jackson, 1995)
mountain-valley fan [Fluvial Landform] A landform created by alluvial filling of a
mountain valley or intramontane basin by coalescent valley-sideslope fans whose
toeslopes meet from either side of the valley along an axial drainageway. It is an
extension of the upper piedmont slope into mountain valleys. Most mountain-valley
fans have been dissected. (Peterson, 1981)
mud flat [Coastal Marine Landform] A relatively level area of fine silt along a shore (as
in a sheltered estuary) or around an island, alternately covered and uncovered by the
tide, or covered by shallow water; a muddy tidal flat barren of vegetation. (Bates and
Jackson, 1995)
mud pot field [Volcanic Landform] A type of hot spring containing boiling mud, usually
sulfurous and often multicolored, as in a paint pot. Mud pots are commonly associated
with geysers and other hot springs in volcanic areas. (Bates and Jackson, 1995)
mud volcano [Volcanic Landform] An accumulation, usually conical, of mud and rock
ejected by volcanic activities. (Bates and Jackson, 1995)
N
nested bench [Mass Wasting Element Landform] A long, narrow, relatively level or
gently inclined strip or platform of land, earth, or rock, bounded by steeper slopes above
and below, and formed by displacement of material through mass wasting processes,
which is hummocky in appearance and comprised of subsidiary rotational and
translational mass wasting features.
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106
nested lateral scarp [Mass Wasting Element Landform] A steep surface on the
undisturbed ground at the side of a landslide, caused by movement of the slide material
away from the undisturbed ground. The surface of the scarp is hummocky due to the
presence of subsidiary internested translational and rotational slides.
nested main scarp
[Mass Wasting Element Landform] (nested crown scarp) The outward-facing scarp,
bordering the upper portion of a landslide. It is almost always concave in a downslope
direction. The surface of the scarp is hummocky due to the presence of subsidiary
internested translational and rotational slides.
nested secondary scarp
[Mass Wasting Landform Element] (nested minor scarp) A steep surface on the
displaced material of a landslide, produced by differential movements within the sliding
mass. The surface of the scarp is hummocky due to the presence of subsidiary
internested translational and rotational slides.
nested toe zone [Mass Wasting Element Landform] The lower, usually curved, margin
of the disturbed material of a landslide pushed over onto the undisturbed slope; it is
most distant from the place of origin. The surface of the area is hummocky due to the
presence of subsidiary internested translational and rotational slides.
net(s) [Microfeature (single) ,Periglacial Element Landform (groups)] A form of
horizontal patterned ground whose mesh is intermediate between a circle and a
polygon. (Bates and Jackson, 1995)
nivation hollow [Glacial Element Landform] A shallow depression or hollow in a
mountainside, permanently or intermittently occupied by a snowbank or snow patch and
produced by nivation. If the snow completely melts each summer the hollow is
deepened; otherwise not. (Bates and Jackson, 1995)
nivation ridge [Glacial Element Landform] A low convex accumulation of fine sediment
downslope from a nivation hollow, consisting of fine material carried by sheetwash and
rivulet flow from beneath the melting edge of a snow patch or snowbank. (Bates and
Jackson, 1995)
non-buried fan remnant [Fluvial Landform] A generic term for component landforms
that are the remaining parts of various older fan landforms that have been partially
buried. Non-buried fan remnants are all relict fan surfaces. (Peterson, 1981)
non-sorted circle [Microfeature] A form of patterned ground whose mesh is dominantly
circular and has a nonsorted appearance due to the absence of a border of stones;
developed singly or in groups. Vegetation characteristically outlines the pattern by
forming a bordering ridge. When well-developed, it has a distinctly domed central area.
Diameter: commonly 0.5 to 3 m. (Bates and Jackson, 1995)
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107
noseslope [Common Landform] (nose) The projecting end of a hill, spur, ridge, or
mountain. (Bates and Jackson, 1995)
nunatak [Glacial Landform] An isolated hill, knob, ridge, or peak of bedrock that
projects prominently above the surface of a glacier and is completely surrounded by
glacier ice. (Bates and Jackson, 1995)
O
oceanic atoll [Coastal Marine Landform] A coral reef appearing in plan view as roughly
circular (though sometimes elliptical or horseshoe-shaped), and surmounted by a chain
or ring of closely spaced low coral islets that encircle or nearly encircle a shallow lagoon
in which there is no pre-existing land or islands of noncoral origin; the reef is surrounded
by deep water of the open sea, either oceanic or continental-shelf. Atolls range in
diameter from 1 km to more than 130 km, and are esp. common today in the western
and central Pacific Ocean. (Bates and Jackson, 1995)
organic [Lacustrine Subprocess] Lakes formed by the accumulation of organic matter.
(Hutchinson, 1957)
organic reef (undifferentiated) [Coastal Marine Landform] A bioherm of sufficient size to
develop associated facies. It is erected by, and composed mostly of the remains of,
sedentary or colonial and sediment-binding organisms, generally marine: chiefly corals
and algae, less commonly crinoids, bryozoans, sponges, mollusks, and other forms that
live their mature lives near but below the surface of the water (although they may have
some exposure at low tide). Their exoskeletal hard parts remain in place after death,
and the deposit is firm enough to resist wave erosion. An organic reef may also contain
still-living organisms. (Bates and Jackson, 1995)
outburst floodplain [Glacial Landform] A floodplain resulting from a sudden, often
annual, release of meltwater from a glacier or glacier-dammed lake, sometimes
resulting in a catastrophic flood, formed by melting of a drainage channel or buoyant
lifting of ice by water or by subglacial volcanic activity. (Bates and Jackson, 1995)
outwash fan [Glacial Landform] A fan-shaped accumulation of outwash deposited by
meltwater streams in front of the end moraine of a glacier. Coalescing outwash fans
form an outwash plain. (Bates and Jackson, 1995)
outwash plain [Glacial Landform] (plain sandur ) A broad, gently sloping sheet of
outwash deposited by meltwater streams flowing in front of or beyond a glacier, and
formed by coalescing outwash fans; the surface of a broad body of outwash. (Bates
and Jackson, 1995)
outwash terrace [Glacial Landform] A dissected and incised valley train or benchlike
deposit extending along a valley downstream from an outwash plain or terminal
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108
moraine; a flat-topped bank of outwash with an abrupt outer face. (Bates and Jackson,
1995)
oxbow [Fluvial Element Landform] The abandoned, bow- or horseshoe-shaped channel
of a former meander, left when the stream formed a cutoff across a narrow meander
neck. (Bates and Jackson, 1995)
P
paha [Eolian Landform] A low, elongated, rounded glacial ridge or hill consisting mainly
of drift, rock, or windblown sand, silt, or clay but capped with a thick cover of loess;
found esp. in northeastern Iowa. Height varies between 10 and 30 m. (Bates and
Jackson, 1995)
pahoehoe flow [Volcanic Landform] A Hawaiian term for a type of basaltic lava flow
typified by a smooth, billowy, or ropy surface. Varieties include corded, elephant-hide,
entrail, festooned, filamented, sharkskin, shelly, and slab pahoehoe. (Bates and
Jackson, 1995)
palsa [Periglacial Landform] An elliptical domelike frost mound containing ice lenses in
peat, commonly 3-6 m high and 2-25 m long, occurring in subarctic bogs of the tundra,
esp. in Scandinavia, and often surrounded by shallow open water. (Bates and Jackson,
1995)
parabolic dune [Eolian Landform] A sand dune with a long, scoop-shaped form,
convex in the downwind direction so that its horns point upwind, whose ground plan,
when perfectly developed, approximates the form of a parabola. It is characteristically
covered with sparse vegetation, and is often found along the coast where strong
onshore winds are supplied with abundant sand. (Bates and Jackson, 1995)
parasitic cone [Volcanic Landform] Said of a volcanic cone, that occurs on the side of
a larger cone; it is a subsidiary. (Bates and Jackson, 1995)
parna dune [Eolian Landform] An eolian dune built of sand size aggregates of clayey
material that commonly occurs leeward of a playa. (Peterson, 1981)
partial ballena [Fluvial Landform] A erosional landform with a fully rounded crest, that is
connected to an erosional fan remnant large enough that some relict fan surfaces in
preserved on the remnant summit. (Peterson, 1981)
patch reef [Coastal Marine Landform] A moundlike or flat-topped organic reef,
generally less than a kilometer across, less extensive than a platform reef, and
frequently forming a part of a larger reef complex. (Bates and Jackson, 1995)
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109
paternoster lakes [Lacustrine Landform] One of a chain or series of small circular lakes
occupying rock basins, usually at different levels, in a glacial valley, separated by
morainal dams or riegels, but connected by streams, rapids, or waterfalls, to resemble
a rosary or a string of beads. (Bates and Jackson, 1995)
patterned ground (undifferentiated) [Microfeature (single), Periglacial Landform
(groups)] A group term for certain well-defined, more or less symmetrical forms, such as
circles, polygons, nets, steps, and stripes, that are characteristic of, but not necessarily
confined to, surficial material subject to intensive frost action. It is classified according to
type of pattern and presence or absence of sorting. (Bates and Jackson, 1995)
pediment [Fluvial Landform] An erosion surface that lies at the foot of a receded slope,
with underlying rocks or sediments that also underlie the upland, which is barren or
mantled with sediment, and which normally has a concave upward profile. (Peterson,
1981)
pedestal [Microfeature] A tall, conical column of unconsolidated to semiconsolidated
earth materials (e.g. clay, till, or landslide debris), produced by differential erosion in a
region of sporadic heavy rainfall (as in a badland or a high alpine valley) or an area with
highly erodible soils, and usually capped by a flat impervious particle such as a pebble,
stick, bark fragment or leaves that shielded the underlying softer material from erosion;
it is similar to an earth pillar in form, but is much smaller in size, generally less than 5
cm. in height and several centimeters across. (Modified from Bates and Jackson, 1995)
pelean dome [Volcanic Landform] A volcanic dome which has a diameter much larger
than its feeding pipes. They are characterized by blocky fractured tops and by large
aprons of blocky talus. (Williams and McBirney, 1979)
peninsula [Landscape Term] An elongated body or stretch of land nearly surrounded
by water and connected with a larger land area, usually by a neck or an isthmus.
(Bates and Jackson, 1995)
periglacial [Geomorphic Process] Said of the processes, conditions, areas, climates,
and topographic features at the immediate margins of former and existing glaciers and
ice sheets, and influenced by the cold temperature of the ice. (Bates and Jackson,
1995)
periglacial flows (undifferentiated) [Mass Wasting Landform] Undifferentiated flows
which occur in the periglacial environment, including solifluction, frost creep, rock
glaciers and block flows.
permafrost [Periglacial Subprocess] Any soil, subsoil, or other surficial deposit, or even
bedrock, occurring in arctic, subarctic, and alpine regions at a variable depth beneath
the Earth's surface in which a temperature below freezing has existed continuously for a
long time (from two years to tens of thousands of years). This definition is based
exclusively on temperature, and disregards the texture, degree of compaction, water
A Geomorphic Classification System
110
content, and lithologic character of the material. The thickness of permafrost ranges
from over 1000 m in the north to 30 cm in the south. (Bates and Jackson, 1995)
piedmont [Landscape Term] Lying or formed at the base of a mountain or mountain
range; e.g. a piedmont terrace or a piedmont pediment. An area, plain, slope, glacier,
or other feature at the base of a mountain; e.g. a foothill or a bajada. In the U.S., the
Piedmont is a plateau extending from New Jersey to Alabama, lying east of the
Appalachian Mountains. (Bates and Jackson, 1995)
pimple mounds
[Microfeature] A term used along the Gulf Coast of eastern Texas and southwestern
Louisiana for one of hundreds of thousands of low, flattened, rudely circular or elliptical
domes composed of sandy loam that is coarser than, and distinct from, the surrounding
soil; the basal diameter ranges from 3 m to more than 30 m, and the height from 30 cm
to more than 2 m. (Bates and Jackson, 1995)
pingo [Periglacial Landform] A large frost mound, esp. a relatively large conical mound
of soil-covered ice (commonly 30-50 m high and up to 400 m in diameter), raised in part
by hydrostatic pressure of water within or below the permafrost of Arctic regions (esp.
Canada), and of more than one year's duration; an intrapermafrost ice-cored hill or
mound. Its crest is sometimes ruptured or collapsed due to melting of the ice, thus
forming a star-shaped crater; the term has also been applied to such a depression.
(Bates and Jackson, 1995)
pinnacle [Common Landform] (a) A tall slender tapering tower or spire-shaped pillar of
rock, either isolated or at the summit of a mountain or hill; esp. a lofty peak. (b) A hill or
mountain with a pointed summit. (Bates and Jackson, 1995)
plain [Landscape Term] A general term referring to an extensive, lowland area that
ranges from level to gently sloping or undulating. A plain has few or no prominent hills
or valleys, and usually occurs at low elevation relative to surrounding areas. (Bates and
Jackson, 1980)
plateau [Landscape Term] Any comparatively flat area of great extent and elevation;
specif. an extensive land region considerably elevated (more than 150-300 m in
altitude) above the adjacent country or above sea level; it is commonly limited on at
least one side by an abrupt descent, has a flat or nearly smooth surface but is often
dissected by deep valleys and surmounted by high hills or mountains, and has a large
part of its total surface at or near the summit level. A plateau is usually higher and has
more noticeable relief than a plain (it often represents an elevated plain), and is usually
higher and more extensive than a mesa; it may be tectonic, residual, or volcanic in
origin. (Bates and Jackson, 1995)
platform reef [Coastal Marine Landform] An organic reef, more extensive than a patch
reef (i.e., several km across), with a flat upper surface, and sometimes forming an
island. (Bates and Jackson, 1995)
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111
playa [Fluvial Element Landform] A term used in the southwest U.S. for a dry,
vegetation-free, flat area at the lowest part of an undrained desert basin, underlain by
stratified clay, silt, or sand, and commonly by soluble salts. The term is also applied to
the basin containing an expanse of playa, which may be marked by ephemeral lakes.
(Bates and Jackson, 1995)
plug dome [Volcanic Landform] (upheaved plug dome) A volcanic dome characterized
by an upheaved, consolidated conduit filling not much wider than its feeding pipe.
(Williams and McBirney, 1979)
point bar [Fluvial Element Landform] One of a series of low, arcuate ridges of sand
and gravel developed on the inside of a growing meander by the slow addition of
individual accretions accompanying migration of the channel toward the outer bank.
(Bates and Jackson, 1995)
polje [Solution Landform] (interior valley) A large flat-floored closed depression in a
karst area. Its drainage is subsurface, its size is measured in kilometers or tens of
kilometers, and its floor is commonly covered by alluvium. Interior valleys may become
intermittent lakes during periods of heavy rainfall, when the sinking streams that drain
them cannot manage the runoff. (Bates and Jackson, 1995)
polygon [Microfeature (single), Periglacial Element Landform (groups)] A form of
horizontal patterned ground whose mesh is tetragonal, pentagonal, or hexagonal. Its
formation is favored by intensive frost action. (Bates and Jackson, 1995)
pothole [Common Landform] (a) A generic, imprecise term for any pot-shaped pit or
hole; (b) A term applied to a small pit depression (1 to 15 meters deep, generally
circular or eliptical, occurring in an outwash plain, a recessional moraine or till plain; (c)
A small, rounded, steep-sided depression or pit in a coastal marsh, containing water at
or below low-tide level; (d) A shallow depression, generally less than 10 acres in area,
occurring between dunes on a prairie (as in Minnesota and the Dakotas), often
containing an intermittent pond or marsh and serving as a nesting place for waterfowl.
(e) A term used in Death Valley, Calif., for a circular opening, about a meter in diameter,
filled with brine and lined with halite crystals; (f) vertical cave; (g) A smooth,
bowl-shaped or cylindrical hollow, generally deeper than wide, formed in the rocky bed
of a stream by the grinding action of a stone or stones, or of coarse sediment (sand,
gravel, pebbles, boulders), whirled around and kept in motion by eddies or the force of
the stream current in a given spot, as at a strong rapid or the foot of a waterfall. (Bates
and Jackson, 1995)
pressure ridge [Volcanic Element Landform] An elongate uplift of the congealing crust
of a lava flow, probably due to the pressure of underlying still-flowing lava. (Bates and
Jackson, 1995)
[Glacial Landform Element] A ridge of glacier ice, produced by horizontal pressure
associated with glacier flow. (Bates and Jackson, 1995)
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112
proglacial deposition [Glacial Subprocess] Deposition which occurs in front of or just
beyond the outer limits of a glacier or ice sheet, generally at or near its lower end.
(Bates and Jackson, 1995)
pumice cone [Volcanic Landform] A conical hill formed by the accumulation of
scoriaceous, light-colored siliceous pumice-sized ejecta, such as rhyolite, dacite,
trachyte or phonolite. Steepness of the slopes depends on coarseness of the ejecta,
height of eruption, wind velocity, and other factors, but is normally greater than 10
degrees. (Bates and Jackson, 1995, Williams and McBirney, 1979)
pyroclastic cone (undifferentiated) [Volcanic Landform] A conical hill formed by the
accumulation of pyroclasts, normally of basaltic or andesitic composition. Steepness of
the slopes depends on coarseness of the ejecta, height of eruption, wind velocity, and
other factors, but is normally greater than 10 degrees. (Williams and McBirney, 1979)
pyroclastic flow [Volcanic Element Landform] (ash flow) A density current, generally a
highly heated mixture of volcanic gases, ash and blocks, traveling down the flanks of a
volcano or along the surface of the ground; produced by the explosive disintegration of
viscous lava in a volcanic summit crater, by the explosive emission of gas-charged ash
from a fissure or group of fissures, or related to domes or crumbling fronts of lava flows.
Ash flows of the type described at Mt. Pelée are considered to represent the feeblest
type of the nuée ardente. The solid materials contained in a typical ash flow are
generally unsorted and ordinarily include volcanic dust, pumice, scoria, and blocks in
addition to ash. (Bates and Jackson, 1995, Williams and McBirney, 1979)
R
raised beach [Coastal Marine Landform] A beach occurring above the present
shoreline and separated from the present beach, having been elevated above the
high-water mark either by local crustal movements (uplift) or by lowering of sea level,
and often bounded by inland cliffs. (Modified from Bates and Jackson, 1995)
raised beach ridge [Coastal Marine Element Landform] A beach ridge occurring above
the present shoreline and separated from the present beach, having been elevated
above the high-water mark either by local crustal movements (uplift) or by lowering of
sea level, and often bounded by inland cliffs. (Modified from Bates and Jackson, 1995)
raised inner beach [Coastal Marine Element Landform] An inner beach occurring
above the present shoreline and separated from the present beach, having been
elevated above the high-water mark either by local crustal movements (uplift) or by
lowering of sea level, and often bounded by inland cliffs. (Modified from Bates and
Jackson, 1995)
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113
raised estuary [Coastal Marine Landform] An ancient estuary occurring above the
present shoreline and separated from the present estuary, having been elevated above
the high-water mark either by local crustal movements (uplift) or by lowering of sea
level, and often bounded by inland cliffs. (Bates and Jackson, 1995)
raised mudflat [Coastal Marine Landform] An ancient mudflat occurring above the
present shoreline and separated from the present mudflat, having been elevated above
the high-water mark either by local crustal movements (uplift) or by lowering of sea
level, and often bounded by inland cliffs. (Bates and Jackson, 1995)
raised tidal flat [Coastal Marine Landform] An ancient tidal flat occurring above the
present shoreline and separated from the present tidal flat, having been elevated above
the high-water mark either by local crustal movements (uplift) or by lowering of sea
level, and often bounded by inland cliffs. (Bates and Jackson, 1995)
range [Landscape Term] (mountain range) A single, large mass consisting of a
succession of mountains or narrowly spaced mountain ridges, with or without peaks,
closely related in position, direction, formation, and age; a component part of a
mountain system or of a mountain chain. (Bates and Jackson, 1995)
ravel cone [Mass Wasting Landform] A conical shaped deposit of dry sand and gravel
which is deposited at the foot of a slope by dry flow processes.
ravine [Common Landform] A small narrow deep depression, smaller than a gorge or
a canyon but larger than a gully, usually carved by running water; esp. the narrow
excavated channel of a mountain stream. (Bates and Jackson, 1995)
recessional moraine [Glacial Landform] An end or lateral moraine built during a
temporary but significant pause in the final retreat of a glacier. Also, a moraine built
during a slight or minor readvance of the ice front during a period of general recession.
(Bates and Jackson, 1995)
relict coastline [Coastal Marine Landform] Said of a coastline that remains after other
parts of the coastline have been removed or have disappeared.
reversing dune[Eolian Landform] A dune that tends to develop unusual height but
migrates only a limited distance because seasonal shifts in direction of dominant wind
cause it to move alternately in nearly opposite directions. Its general shape may
resemble that of a barchan or a transverse dune, but it differs in the complexity of its
internal structural orientation due to reversals in direction of the slip face. (Bates and
Jackson, 1995)
ridge [Common Landform] (a) A general term for a long, narrow elevation of the Earth's
surface, usually sharp-crested with steep sides, occurring either independently or as
part of a larger mountain or hill; e.g. an extended upland between valleys. A ridge is
generally less than 8 km long. (b) A term occasionally applied to a range of hills or
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114
mountains. (c) The top or upper part of a hill; a narrow, elongated crest of a hill or
mountain. (Bates and Jackson, 1995)
ridge and valley [Landscape Term] A land surface characterized by a close
succession of parallel or nearly parallel ridges and valleys, and resulting from the
differential erosion of highly folded strata of varying resistances. Type region: Ridge and
Valley region in the Appalachian Mountains, lying to the west of the Blue Ridge. (Bates
and Jackson, 1995)
ridgetop bedrock outcrop [Mass Wasting Element Landform] The ridgetop source
zone for downslope colluvium.
riegel [Glacial Element Landform] A low, transverse ridge or barrier of bedrock on the
floor of a glacial valley, esp. common in the Alps; it separates a rock basin from the
gently sloping valley bottom farther downstream. (Bates and Jackson, 1995)
rift valley [Landscape Term] A valley that has developed along a rift, which is a long,
narrow continental trough that is bounded by normal faults; a graben of regional extent.
It marks a zone along which the entire thickness of the lithosphere has ruptured under
extension. (Bates and Jackson, 1995)
rill [Microfeature] One of the first and smallest channels formed by runoff, such as a
shoestring rill. (Bates and Jackson, 1995)
rim [Common Landform] The border, margin, edge, or face of a landform, such as the
curved brim surrounding the top part of a crater or caldera; specif. the rimrock of a
plateau or canyon. (Bates and Jackson, 1995)
ripple mark [Microfeature] An undulatory surface or surface sculpture consisting of
alternating subparallel small-scale ridges and hollows formed at the interface between a
fluid and incoherent sedimentary material (esp. loose sand). It is produced on land by
wind action and subaqueously by currents or by the agitation of water in wave action,
and generally trends at right angles or obliquely to the direction of flow of the moving
fluid. (Bates and Jackson, 1995)
riser [Common Landform] The vertical or steeply sloping surface of one of a series of
natural steplike landforms, such as those of a glacial stairway or of successive stream
terraces. (Bates and Jackson, 1995)
roche mountonnee [Glacial Landform] A small elongate protruding knob or hillock of
bedrock, so sculptured by a large glacier as to have its long axis oriented in the
direction of ice movement, an upstream (stoss or scour) side that is gently inclined,
smoothly rounded, and striated, and a downstream (lee or pluck) side that is steep,
rough, and hackly. It is usually a few meters in height, length, and breadth. (Bates and
Jackson, 1995)
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115
rock fall avalanche [Mass Wasting Landform] A complex mass wasting landform
comprised of an area where a rock fall occurred which downslope transitioned into a
rock avalanche. The very rapid downslope flowage of rock fragments, during which the
fragments may become further broken or pulverized. Rock avalanches typically result
from large rockfalls and rockslides, and their patterns of displacement have led to the
term rock-fragment flow. Characteristic features include chaotic distribution of large
blocks, flow morphology and internal structure, relative thinness in comparison to large
areal extent, high porosity, angularity of fragments, and lobate form. (Bates and
Jackson, 1995)
rock glacier [Mass Wasting Landform] A mass of poorly sorted angular boulders and
fine material, with interstitial ice a meter or so below the surface (ice-cemented) or
containing a buried ice glacier (ice-cored). It occurs in high mountains in a permafrost
area, and is derived from a cirque wall or other steep cliff. Rock glaciers have the
general appearance and slow movement of small valley glaciers, ranging from a few
hundred meters to several kilometers in length, and having a distal area marked by a
series of transverse arcuate ridges. When active, they may be 50 m thick with a surface
movement (resulting from the flow of interstitial ice) of 0.5-2 m/yr. (Bates and Jackson,
1995)
rock slide-rock fall [Mass Wasting Landform] A complex mass wasting landform which
originates through a combination of rock sliding and falling. (Varnes, 1978)
rock spread [Mass Wasting Landform] Movements which may involve fracturing and
extension of coherent rock material, owing to liquifaction or plastic flow of the subjacent
material. The coherent upper units may subside, translate, rotate or disintegrate, or
they may liquify and flow. The mechanism of failure can involve elements not only of
rotation and translation but also of flow. (Varnes, 1978)
rock stream [Mass Wasting Landform] Masses of angular rock rubble which flow down
mountainsides in a periglacial environment. (Bloom, 1991)
rotational slide [Mass Wasting Landform] A slide in which shearing takes place on a
well defined, curved shear surface, concave upward, producing a backward rotation in
the displaced mass. It may be single, successive (repeated up- and down-slope), or
multiple (as the number of slide components increases). (Bates and Jackson, 1995)
rotational-translational slide [Mass Wasting Landform] Movement of a mass of
material through slide processes along a failure plane which varies from planar to
curving. Movement can range from gradual to rapid depending on material and local
conditions.
runout zone [Mass Wasting Element Landform] The area where snow avalanches
generally slow and deposit due to a change in slope or obstacles.
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116
S
saddle [Common Landform] (a) A low point in the crest line of a ridge, commonly on a
divide between the heads of streams flowing in opposite directions. (b) A broad, flat gap
or pass, sloping gently on both sides, and resembling a saddle in shape. (Bates and
Jackson, 1995)
sag pond [Lacustrine Landform] A small body of water occupying an enclosed
depression or sag formed where active or recent fault movement has impounded
drainage; specif. one of many ponds and small lakes along the San Andreas Fault in
California. (Bates and Jackson, 1995)
sand boil [Microfeature] (a) A spring that bubbles through a river levee, with an
ejection of sand and water, as a result of water in the river being forced through
permeable sands and silts below the levee during flood stage. (Bates and Jackson,
1995) (b) a sand deposit ranging from one to several meters across, which is the result
of liquifaction and surface extrusion from underlying unconsolidated sand deposits due
to seismic activity.
sandhills [Landscape Term] A region comprised predominantly of unconsolidated sand
hills, which are individually a ridge of sand; esp. a sand dune in a desert region.
Example as in north-central Nebraska. (Modified from Bates and Jackson, 1995)
sand ramp [Eolian Landform] A sand sheet blown up onto the lower slopes of a
bedrock hill or mountain, sometimes filling small mountain-side valleys and even
crossing low passes. (Peterson, 1990)
sand sea [Eolian Landform] An extensive assemblage of sand dunes of several types in
an area where a great supply of sand is present, characterized by an absence of travel
lines or other directional indicators, and by a wavelike appearance of dunes separated
by troughs, much as though storm sea waves were frozen into place. (Bates and
Jackson, 1995)
sand sheet [Eolian Landform] A broad area of eolian sand, commonly on a bolson or
semi-bolson floor, but also sometimes extending onto or across the piedmont slope and
joining sand ramps against mountain slopes. The surface is commonly smooth, but
may have numerous sand-copice-dunes across it. (Peterson, 1990)
scablands [Landscape Term] An elevated area, underlain by flat-lying basalt flows,
with a thin soil cover and sparse vegetation, and usually with deep, dry channels
scoured into the surface. An example is the Columbia lava plateau of eastern
Washington, which was widely and deeply eroded by glacial meltwaters. (Bates and
Jackson, 1995)
scarp [Common Landform] (a) A line of cliffs produced by faulting or by erosion. The
term is an abbreviated form of escarpment, and the two terms commonly have the
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117
same meaning, although ''scarp'' is more often applied to cliffs formed by faulting. See
also: fault scarp; erosion scarp. (b) A relatively straight, clifflike face or slope of
considerable linear extent, breaking the general continuity of the land by separating
surfaces lying at different levels, as along the margin of a plateau or mesa. A scarp may
be of any height. The term should not be used for a slope of highly irregular outline. See
also: scarp slope. (c) beach scarp. (d) The main scarp or minor scarp of a landslide.
(Bates and Jackson, 1995)
scarp slope [Fluvial Element Landform] The relatively steeper face of a cuesta, facing
in a direction opposite to the dip of the strata. (Bates and Jackson, 1995)
[Tectonic Landform] A relatively straight, clifflike face or slope of some linear extent,
which formed through faulting, which breaks the general continuity of the land by
separating surfaces lying at different levels. (Modified from Bates and Jackson, 1995)
scour [Common Landform and Microfeature] (a) The powerful and concentrated
clearing and digging action of flowing air, water, or ice, esp. the downward erosion by
stream water in sweeping away mud and silt on the outside curve of a bend, or during
time of flood. (b) A place in a stream bed swept (scoured) by running water, generally
leaving a gravel bottom. (Bates and Jackson, 1995)
scoured basin [Glacial Landform] (glacial basin) A rock basin caused by erosion of the
floor of a glacial valley. (Bates and Jackson, 1995)
sea cliff [Coastal Marine Landform] A cliff or slope produced by wave erosion, situated
at the seaward edge of the coast or the landward side of the wave-cut platform, and
marking the inner limit of beach erosion. It may vary from an inconspicuous slope to a
high, steep escarpment. (Bates and Jackson, 1995)
secondary scarp (undifferentiated) [Mass Wasting Element Landform] (minor scarp) A
steep surface on the displaced material of a landslide, produced by differential
movements within the sliding mass. (Bates and Jackson, 1995)
seep
[Common Landform] An area, generally small, where water or oil percolates slowly to
the land surface. For water, it may be considered as a syn. of seepage spring, but it is
used by some for flows too small to be considered as springs. (Bates and Jackson,
1995)
seif dune
[Eolian Landform] A very large, sharp-crested, tapering longitudinal dune or chain of
sand dunes, commonly found in the Sahara Desert; its crest in profile consists of a
succession of peaks and cols, and it bears on one side a succession of curved slip
faces produced by strong but infrequent cross winds that tend to increase its height and
width. A seif dune may be as much as 200 m high, and from 400 m to more than 100
km long (300 km in Egypt). (Bates and Jackson, 1995)
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semi-bolson [Landscape Term and Fluvial Landform] A wide desert basin or valley
that is drained by an intermittent stream flowing through canyons at each end and
reaching a surface outlet (such as another stream, a lower basin, or the sea); its central
playa is absent or poorly developed. It may represent a bolson where the alluvial fill
reached a level sufficient to permit occasional overflow across the lowest divide. (Bates
and Jackson, 1995)
serac [Glacial Element Landform] A jagged pinnacle, sharp ridge, needlelike tower, or
irregularly shaped block of ice on the surface of a glacier (commonly among intersecting
crevasses, as on an icefall), formed where the glacier is periodically broken as it passes
over a steep slope. (Bates and Jackson, 1995)
shelf atoll [Coastal Marine Landform] (pseudoatoll) An atoll that rises from the outer
margin of a rimless shoal; a reef platform encircling a shallow pool of water, rising to
low-tide level from the continental shelf. (Bates and Jackson, 1995)
shield volcano [Volcanic Landform] A volcano in the shape of a flattened dome, broad
and low, built by flows of very fluid basaltic lava and/or pyroclasitic flows. (Modified from
Bates and Jackson, 1995)
shoal [Common Landform] (a) A relatively shallow place in a stream, lake, sea, or
other body of water; a shallows. (b) A submerged ridge, bank, or bar consisting of or
covered by sand or other unconsolidated material, rising from the bed of a body of water
to near the surface so as to constitute a danger to navigation; specif. an elevation, or an
area of such elevations, at a depth of 10 fathoms (formerly 6) or less, composed of
material other than rock or coral. It may be exposed at low water. Cf: reef. (c) A rocky
area on the sea floor within soundings. (d) A growth of vegetation on the bottom of a
deep lake, occurring at any depth. (Bates and Jackson, 1995)
shoreline [Coastal Marine Landform] The intersection of a specified plane of water with
the shore or beach; it migrates with changes of the tide or of the water level. The term is
frequently used in the sense of ''high-water shoreline'' or the intersection of the plane of
mean high water with the shore or beach, or the landward limit of the intermittently
exposed shore. (Bates and Jackson, 1995)
[Lacustrine Subprocess] Lakes associated with shorelines. Lakes are often formed
behind bars, spits and tombolos. Their formation is favored by the rise in sea level,
causing the drowning of estuaries, followed by a fall in sea level, thus stabilizing the
bars. (Hutchinson, 1957)
shoreline processes [Coastal Marine Subprocess] Processes which occur at the
intersection of the plane of mean high water with the shore or beach, or the landward
limit of the intermittently exposed shore. (Bates and Jackson, 1995)
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119
shrub-coppice dune [Microfeature] A small, streamlined dune that forms to the lee of
bush-and-clump vegetation on a generally smooth surface. Buildup can be comprised
of not only sand, but other sized earth material as well as plant litter. (Modified from
Bates and Jackson, 1995)
shutter ridge [Tectonic Landform] A ridge formed by vertical, lateral, or oblique
displacement on a fault traversing a ridge-and-valley topography, with the displaced part
of a ridge ''shutting in'' the adjacent ravine or canyon. (Bates and Jackson, 1995)
sidewall [Glacial Element Landform] The steep, U-shaped sideslope of a glacial valley.
(Bates and Jackson, 1995)
sinkhole (undifferentiated) [Solution Landform] (doline) A circular depression in a karst
area. Its drainage is subterranean, its size is measured in meters or tens of meters, and
it is commonly funnel-shaped. (Bates and Jackson, 1995)
slide [Mass Wasting Subprocess] A mass wasting process resulting from failure of
earth, snow, or rock under shear stress along one or several surfaces that are either
visible or may reasonably be inferred; e.g. landslide; snowslide; rockslide. The moving
mass may or may not be greatly deformed, and movement may be rotational or planar.
A slide can result from lateral erosion, lateral pressure, weight of overlying material,
accumulation of moisture, earthquakes, expansion owing to freeze-thaw of water in
cracks, regional tilting, undermining, and human agencies. (Modified from Bates and
Jackson, 1995)
slip face [Common Landform] The steeply sloping surface on the lee side of a dune,
standing at or near the angle of repose of loose sand, and advancing downwind by a
succession of slides wherever that angle is exceeded. (Bates and Jackson, 1995)
slough [Common Landform] (a) A small marsh; esp. a marshy tract lying in a swale or
other local shallow undrained depression on a piece of dry land, as on the prairies of the
Midwest U.S. Also, a dry depression that becomes marshy or filled with water. Syn:
slew; slue; sleugh. (b) A large wetland, as a swamp; e.g. in the Everglades of Florida.
(c) A term used esp. in the Mississippi Valley for a creek or sluggish body of water in a
tidal flat, bottomland, or coastal marshland. (d) A sluggish channel of water, such as a
side channel of a river, in which water flows slowly through low, swampy ground, as
along the Columbia River, or a section of an abandoned river channel, containing
stagnant water and occurring in a flood plain or delta. Also, an indefinite term indicating
a small lake, a marshy or reedy pool or inlet, a bayou, a pond, or a small and narrow
backwater. Syn: slew; slue. (e) A small bay in eastern England. (f) A piece of soft, miry,
muddy, or waterlogged ground; a place of deep mud, as a mudhole. (Bates and
Jackson, 1995)
slump and topple prone slope [Mass Wasting Landform] A complex mass wasting
landform formed through a combination of slumping and toppling.
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slump earth flow [Mass Wasting Landform] A complex mass wasting landform formed
through a combination of flowing and slumping, having many element landforms.
slump pond [Lacustrine Landform] A pond on the surface of an active or recently active
mass wasting feature formed in a depression caused by differential movement within
the slide mass.
snow avalanche slope [Mass Wasting Landform] A slope where there is historic
evidence of a large mass of snow, ice, soil, or rock, or mixtures of these materials,
falling, sliding, or flowing very rapidly under the force of gravity. (Bates and Jackson,
1995)
snowfield [Glacial Landform] A broad expanse of terrain covered with snow, relatively
smooth and uniform in appearance, occurring usually at high latitudes or in
mountainous regions above the snowline, and persisting throughout the year. (Bates
and Jackson, 1995)
soil creep slope [Mass Wasting Landform] A slope undergoing the slow, more or less
continuous downslope movement of mineral, rock, and soil particles under gravitational
stresses. Many types of creep have been described, on the basis of material properties,
stress level, stage and rate of deformation, fundamental mechanics of failure, geometric
patterns, and cause of deformation. However, the term should not be limited by a
presumption of mechanism, depth, velocity profile, thickness of creep zone, or lateral
extent. (Bates and Jackson, 1995)
solifluction lobe [Mass Wasting Landform] An isolated, tongue-shaped feature, up to
25 m wide and 150 m long, formed by more rapid solifluction on certain sections of a
slope showing variations in gradient. It commonly has a steep front (15°-25°) and a
relatively smooth upper surface. (Bates and Jackson, 1995)
solifluction sheet [Mass Wasting Landform] A broad deposit of solifluction mantle
which is the unsorted, water-saturated, locally derived material moved downslope by
solifluction, occurring evenly across a wide slope. (Bates and Jackson, 1995)
solifluction terrace [Mass Wasting Landform] A low terrace or bench formed by
solifluction at the foot of a slope; it may have a lobate margin reflecting uneven
movement. (Bates and Jackson, 1995)
solution [Geomorphic Process] A process of chemical weathering by which mineral
and rock material passes into solution; e.g. removal of the calcium carbonate in
limestone or chalk by carbonic acid derived from rainwater containing carbon dioxide
acquired during its passage through the atmosphere. (Bates and Jackson, 1995)
[Lacustrine Subprocess] Lakes formed by the solution of limestone which forms roughly
circular depressions, or lakes formed by solution in tectonically determined basins, or
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lakes formed by subsidence after natural solution underground of soluble salts.
(Hutchinson, 1957)
solution sinkhole [Solution Landform] (solution doline) The most common type of
sinkhole, which grows when closely spaced fissures underneath it enlarge and
coalesce. (Bates and Jackson, 1995)
sorted circle [Microfeature] A form of patterned ground whose mesh is dominantly
circular and has a sorted appearance commonly due to a border of stones surrounding
finer material; developed singly or in groups. Diameter: a few centimeters to more than
10 m; the stone border may be 35 cm high and 8-12 cm wide. (Bates and Jackson,
1995)
source area [Mass Wasting Element Landform] For various mass wasting processes,
the area from which the material moved.
spatter cone [Volcanic Element Landform] A low, steep-sided cone of spatter built up
on a fissure or vent; it is usually of basaltic material. (Bates and Jackson, 1995)
spillway [Glacial Landform] (overflow channel) A channel or notch cut by the overflow
waters of a lake, esp. the channel draining meltwater from a glacially dammed lake; an
outlet of a proglacial lake. (Bates and Jackson, 1995)
spit [Coastal Marine Landform] A small point or low tongue or narrow embankment of
land, commonly consisting of sand or gravel deposited by longshore drifting and having
one end attached to the mainland and the other terminating in open water, usually the
sea; a fingerlike extension of the beach. (Bates and Jackson, 1995)
splay [Common Landform] (flood-plain splay) A small alluvial fan or other outspread
deposit formed where an overloaded stream breaks through a levee (artificial or natural)
and deposits its material (often coarse-grained) on the flood plain. (Bates and Jackson,
1995)
stack [Coastal Marine Landform] An isolated pillar-like rocky island or mass near a cliffy
shore, detached from a headland by wave erosion assisted by weathering; esp. one
showing columnar structure and roughly horizontal stratification. (Bates and Jackson,
1995)
star dune [Eolian Landform] An isolated hill of sand, its base resembling in plan a star,
and its sharp-crested ridges converging from the basal points to a central peak that may
be as high as 100 m above the surrounding plain; it tends to remain fixed in place for
centuries in an area where the wind blows from all directions. (Bates and Jackson,
1995)
step [Common Landform] (a) A canyon bench greatly broadened by erosion, such as
those characteristic of the high plateaus of the western U.S.; a steplike landform on a
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hillside or valley slope that is otherwise smoothly rising. (b) rock step. (Bates and
Jackson, 1995)
step(s) [Microfeature (single), Periglacial Element Landform (groups)] A form of
patterned ground characteristic of moderate slopes, and having a steplike form; it is
transitional between a polygon (upslope) and a stripe (downslope). A step typically
develops as a obate solifluction terrace with the lower border convex downslope.
(Bates and Jackson, 1995)
steptoe [Volcanic Landform] An isolated hill or mountain of older rock surrounded by a
lava flow. (Bates and Jackson, 1995)
stock [Tectonic Landform] An igneous intrusion that is less than 100 sq km in surface
exposure, is usually but not always discordant, and resembles a batholith except in size.
(Bates and Jackson, 1995)
stone stripe [Microfeature] A sorted stripe consisting of coarse rock debris, and
occurring between wider stripes of finer material. (Bates and Jackson, 1995)
storm berm [Coastal Marine Landform] A low ridge along a beach, marking the limit of
wave action during storms. (Bates and Jackson, 1995)
strand plain [Coastal Marine Landform] A prograded shore built seaward by waves
and currents, and continuous for some distance along the coast. It is characterized by
subparallel beach ridges and swales, in places with associated dunes; some date back
to about 6000 B.C. A glacio-isostatically uplifted or tilted strand plain may date back to
the late Pleistocene (about 13,000 B.C.). (Bates and Jackson, 1995)
stream processes [Fluvial Subprocess] The collection of fluvial processes which occur
or are directly related to streams.
stream terrace (undifferentiated) [Fluvial Landform] One of a series of level surfaces in
a stream valley, flanking and more or less parallel to the stream channel, originally
occurring at or below, but now above, the level of the stream, and representing the
dissected remnants of an abandoned flood plain, stream bed, or valley floor produced
during a former stage of erosion or deposition. (Bates and Jackson, 1995)
stripe(s) [Microfeature (single), Periglacial Element Landform (groups)] One of the
alternating bands of fine and coarse surficial material, or of rock or soil and
vegetation-covered ground, comprising a form of patterned ground characteristic of
slopes steeper than those of steps. It is usually straight, but may be sinuous or
branching, and is probably the result of solifluction acting in conjunction with other
processes, such as rillwork. (Bates and Jackson, 1995)
structural [Tectonic Subprocess] A feature produced by deformation of rocks.
(Modified Bates and Jackson, 1995)
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structural basin [Tectonic Landform] (Basin) A low area in the Earth's crust, of tectonic
origin, in which sediments have accumulated, e.g. a circular centrocline such as the
Michigan Basin, a fault-bordered intermontane feature such as the Bighorn Basin of
Wyoming, or a linear crustal downwarp such as the Appalachian Basin. Such features
were drainage basins at the time of sedimentation but are not necessarily so today.
(Bates and Jackson, 1995)
structural dome [Tectonic Landform] (Dome) An uplift or anticlinal structure, either
circular or elliptical in outline, in which the rocks dip gently away in all directions. A
dome may be small, e.g. a Gulf Coast salt dome, or many kilometers in diameter.
Domes include diapirs, volcanic domes, and cratonic uplifts. Type structure: Nashville
Dome, Tennessee. (Bates and Jackson, 1995)
subjacent karst collapse sinkhole [Solution Landform] A sinkhole which forms at
depth below a resistant nonsoluble rock. (Bates and Jackson, 1995)
subsidence sinkhole [Solution Landform] (subsidence doline) A sinkhole which in
nonsoluble rock caused by the solution of a buried karst. (Bloom, 1991)
surface eroding slope [Fluvial Landform] A slope which is being eroded predominantly
by unchannelized sheetflow and rilling. These slopes generally are underlain by
relatively erodible soils and characteristically have high stream channel densities.
syncline [Tectonic Landform] A fold of which the core contains the stratigraphically
younger rocks; it is generally concave upward. (Bates and Jackson, 1995)
swale [Commom Landform] (a) A slight depression, sometimes swampy, in the midst
of generally level land. (b) A shallow depression in an undulating ground moraine due to
uneven glacial deposition. (c) A long, narrow, generally shallow, trough-like depression
between two beach ridges, and aligned roughly parallel to the coastline. (d) A slight
depression on a hillslope, which lies upslope from an organized stream channel.
(Modified from Bates and Jackson, 1995)
T
tableland [Landscape Term] (a) A general term for a broad, elevated region with a
nearly level or undulating surface of considerable extent. (b) A plateau bordered by
abrupt clifflike edges rising sharply from the surrounding lowland; a mesa. (Bates and
Jackson, 1995)
talus [Common Landform] Rock fragments of any size or shape (usually coarse and
angular) derived from and lying at the base of a cliff or very steep, rocky slope. Also, the
outward sloping and accumulated heap or mass of such loose broken rock, considered
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as a unit, and formed chiefly by gravitational falling, toppling, rolling, or sliding. (Bates
and Jackson, 1995)
tarn [Lacustrine Landform] A relatively small and deep, steep-banked lake or pool amid
high mountains, esp. one occupying an ice-gouged rock basin (cirque) amid glaciated
mountains. (Bates and Jackson, 1995)
tectonic [Lacustrine Subprocess] Lakes formed by gentle crustal movements, lakes
formed by uplift of peneplains during orogenic movements, lakes in basins formed by
folding and lake basins formed by faulting. (Hutchinson, 1957)
[Geomorphic Process] A general term for all processes which have contibuted to the
formation of landforms through movement of the crust. (Bates and Jackson, 1995)
terminal deposition [Fluvial Subprocess Modifier] Referring to deposition in a delta
environment.
terminal moraine [Glacial Landform] The end moraine, extending across a glacial
valley as an arcuate or crescentic ridge, that marks the farthest advance or maximum
extent of a glacier; the outermost end moraine of a glacier or ice sheet. It is formed at or
near a more-or-less stationary edge, or at a place marking the cessation of an important
glacial advance. (Bates and Jackson, 1995)
terracette(s) [Microfeature (single),Common Landform (groups)] A small ledge, bench,
or steplike form, or a series of such forms, produced on the surface of a slumped soil
mass along a steep grassy slope or hillside, ranging from several centimeters to 1.5 m
in height and averaging a meter in width, and developed as a result of small landslides
and subsequent backward tilting of the soil surface. (Bates and Jackson, 1995)
thalweg [Fluvial Landform] The line connecting the lowest or deepest points along a
stream bed or valley, whether under water or not; the longitudinal profile of a stream or
valley; the line of maximum depth. (Bates and Jackson, 1995)
thermokarst [Landscape Term and Periglacial Landform] Karstlike topographic
features produced in a permafrost region by the local melting of ground ice and the
subsequent settling of the ground. (Bates and Jackson, 1995)
tidal flat [Coastal Marine Landform] An extensive, nearly horizontal, marshy or barren
tract of land that is alternately covered and uncovered by the tide, and consisting of
unconsolidated sediment (mostly mud and sand). It may form the top surface of a
deltaic deposit. (Bates and Jackson, 1995)
till plain [Landscape Term] An extensive area, with a flat to undulating surface,
underlain by till with subordinate end moraines; such plains occupy parts of Indiana,
Illinois, and Iowa. (Bates and Jackson, 1995)
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tilt block [Tectonic Landform] A fault block that has become tilted, perhaps by rotation
on a hinge line. (Bates and Jackson, 1995)
toe zone (undifferentiated) [Mass Wasting Element Landform] (a) The lower, usually
curved, margin of the disturbed material of a landslide pushed over onto the undisturbed
slope; it is most distant from the place of origin. (b) The intersection (sometimes buried)
between the lower part of the surface of rupture of a landslide and the original ground
surface. (Varnes, 1978)
tombolo [Coastal Marine Landform] A sand or gravel bar or barrier that connects an
island with the mainland or with another island. (Bates and Jackson, 1995)
topple [Mass Wasting Subprocess] A mass movement that consists of the forward
rotation of a unit or units about some pivot point, below or low in the unit, under the
action of gravity and forces exerted by adjacent units or by fluids in cracks. It is tilting
without collapse. (Varnes, 1978)
topple prone slope [Mass Wasting Landform] A slope which is likely to undergo mass
movement through
forward rotation of a rock unit under the action of gravity and forces exerted by adjacent
units.
tor [Periglacial Landform] A high, isolated crag, pinnacle, or rocky peak; a pile of rocks,
much-jointed and usually granitic, exposed to intense weathering, and often assuming
peculiar or fantastic shapes. (Bates and Jackson, 1995)
tower karst [Solution Landform] An area which is comprised of a type of tropical karst
that is characterized by isolated, steep-sided limestone hills that may be flat-topped and
that are surrounded by a flat plain usually underlain by alluvium. (Bates and Jackson,
1995)
translational block slide [Mass Wasting Landform] (block glide) A translational
landslide in which the slide mass remains essentially intact, moving outward and
downward as a unit, most often along a pre-existing plane of weakness, such as
bedding, foliation, joints, or faults. In contrast to rotational slides, the various points
within a displaced block-glide slide have predominantly maintained the same mutual
difference in elevation in relation to points outside the slide mass. (Bates and Jackson,
1995)
translational-debris slide [Mass Wasting Landform] (debris slide) A slide involving a
slow to rapid downslope movement of comparatively dry and predominantly
unconsolidated and incoherent earth, soil, and rock debris in which the mass does not
show backward rotation (as in a slump) but slides or rolls forward, forming an irregular
hummocky deposit resembling a moraine. (Bates and Jackson, 1995)
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transport zone [Mass Wasting Element Landform] (a) An area through which
movement by gravity of loose material occurs, as solid particles. (b) (avalanche track)
The central channel-like corridor along which an avalanche has moved; it may take the
form of an open path in a forest, with bent and broken trees, or an eroded surface
marked by pits, scratches, and grooves. (Bates and Jackson, 1995)
transporting stream channel system [Fluvial Subprocess Modifier] A channel in
which the energy of a stream is generally equal to that required to move the sediment
available for transport. This is meant to be a generalization, recognizing that all streams
have eroding, transporting and depositional reaches depending on flow regime and
morphology. These streams generally equate to some of Rosgen’s B and F type
channels.
transverse dune [Eolian Landform] A strongly asymmetrical sand dune elongated
perpendicularly to the direction of the prevailing winds, having a gentle windward slope
and a steep leeward slope standing at or near the angle of repose of sand; it generally
forms in areas of sparse vegetation. (Bates and Jackson, 1995)
tread [Common Landform] (a) The flat or gently sloping surface of one of a series of
natural steplike landforms, such as those of a glacial stairway or of successive stream
terraces; a bench level. Cf: riser. (b) A small flat. (Bates and Jackson, 1995)
tree-tip mound [Microfeature] The small mound of debris sloughed from the root plate
(ball) of a tipped-over tree. (USDA, NRCS, 1993b)
tree-tip pit [Microfeature] The small pit or depression resulting from an area vacated by
the root plate (ball) arising from the tree tip. Such pits are commonly adjacent to small
mounds composed of the displaced material. (USDA, NRCS, 1993b)
trench [Volcanic Element Landform] A long and generally straight depression on lava
flows formed through the collapse of an underlying lava tube system.
[Common Landform] (a) A long, straight, commonly U-shaped valley or depression
between two mountain ranges, often occupied by two streams that drain in opposite
directions. (b) A narrow, steep-sided canyon, gully, or other depression eroded by a
stream. (c) Any long, narrow cut or excavation produced naturally in the Earth's surface
by erosion or tectonic movements. Also, a similar feature produced artificially, such as a
ditch. (Bates and Jackson, 1995)
trough [Glacial Landform] (glacial valley) A deep, steep-sided U-shaped valley leading
down from a cirque, and excavated by an alpine glacier that has widened, deepened
and straightened a preglacial river valley. (Bates and Jackson, 1995)
tunnel valley [Glacial Landform] A shallow trench cut in drift and other loose material,
or in bedrock, by a subglacial stream not loaded with coarse sediment. (Bates and
Jackson, 1995)
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turf hummock [Microfeature] A low, dome-shaped frost mound, consisting of a turf
core covered by a tight mass of vegetation, esp. mosses, but also humus, grasses,
sedges and scrubby plants, and produced by hydrostatic pressure of ground water or by
heaving from growth of ice lenses in arctic and alpine regions; the general height is
10-20 cm and the diameter ranges from 1/2 to 1 m. Turf hummocks form in groups to
produce a nonsorted patterned ground. (Bates and Jackson, 1995)
U
undifferentiated stream channel system [Fluvial Subprocess Modifier] A channel in
which the general transport mechanism is unclear.
uniform fluvial erosion without structural control [Fluvial Subprocess Modifier]
Slopes which are eroding with little or no influence by geologic structural features.
upheaved dome [Volcanic Landform] A volcanic dome which has risen above the rim
of the crater from which it emerged. (Williams and McBirney, 1979)
upland [Landscape Term] (a) A general term for high land or an extensive region of
high land, esp. far from the coast or in the interior of a country. Sometimes used
synonymously with fastland. (b) The higher ground of a region, in contrast with a valley,
plain, or other low-lying land; a plateau. (Bates and Jackson, 1995)
uvala [Solution Landform] A closed depression formed by the coalescence of several
sinkholes. Its drainage is subsurface, its size is measured in hundreds of meters to a
few kilometers, and it usually has an irregular floor and a scalloped margin inherited
from the sinkholes. (Bates and Jackson, 1995)
V
valle [Landscape Term] (a) Any low-lying land bordered by higher ground; esp. an
elongate, relatively large, gently sloping depression of the Earth's surface, commonly
situated between two mountains or between ranges of hills or mountains, and often
containing a stream with an outlet. It is usually developed by stream erosion, but may
be formed by faulting. (b) A broad area of generally flat land extending inland for a
considerable distance, drained or watered by a large river and its tributaries; a river
basin. Example: the Mississippi. (Bates and Jackson, 1995)
valley floor [Fluvial Element Landform] (basin floor) The comparatively broad, flat
bottom of a valley; it may be excavated and represent the level of a former erosion
cycle, or it may be buried under a thin cover of alluvium. (Bates and Jackson, 1995)
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valley flat [Fluvial Element Landform] (alluvial flat) (a) A nearly level, graded, alluvial
surface between the piedmont slope and playa of a bolson or the axial-stream floodplain
of a semi-bolson. This landform may include both recent and relict components. (b) The
low or nearly level ground lying between valley walls and bordering a stream channel;
esp. the small plain at the bottom of a narrow, steep-sided valley. The term can be
applied noncommittally to a flat surface that cannot be identified with certainty as a flood
plain or terrace. (Peterson, 1981 and Bates and Jackson, 1995)
valley inner gorge [Mass Wasting Landform] A complex mass wasting feature which
develops on the lowermost slopes adjacent to stream channels. This landform
generally has slope gradients in excess of 65 percent, and is separated from the
upslope area by a distinct break in slope. The valley inner gorge is formed primarily
through mass wasting triggered by channel downcutting, lateral cutting, oversteepening
and/or undercutting of the slope.
valley train [Glacial Landform] (valley sandur) A long, narrow body of outwash,
deposited by meltwater streams far beyond the terminal moraine or the margin of an
active glacier and confined within the walls of a valley below the glacier; it may or may
not emerge from the mouth of the valley to join an outwash plain. (Bates and Jackson,
1995)
v-notch [Common Landform] A small valley having a pronounced cross profile
suggesting the form of the letter “V”, characterized by steep sides, resulting from
downcutting by a stream. (Modified from Bates and Jackson, 1995)
volcanic [Geomorphic Process] The processes by which magma and its associated
gases rise into the crust and are extruded onto the Earth's surface and into the
atmosphere. (Bates and Jackson, 1995)
[Lacustrine Subprocess] Lakes associated with volcanic activity including lakes in
modified or partially modified craters, lakes in calderas, lakes in modified calderas
where pre-existing faults are important, lakes in collapsed lava flows and lakes formed
by barriers of lava, volcanic mud or volcanoes. (Hutchinson, 1957)
volcanic cone (undifferentiated) [Volcanic Landform] A conical hill of lava and/or
pyroclastics that is built up around a volcanic vent. (Bates and Jackson, 1995)
volcanic dome (undifferentiated) [Volcanic Landform] A steep-sided, rounded
extrusion of highly viscous lava squeezed out from a volcano, and forming a
dome-shaped or bulbous mass of congealed lava above and around the volcanic vent.
Portions of older lavas may be elevated by the pressure of the new lava rising from
below. The structure generally develops inside a volcanic crater or on the flank of a
large volcano, and is usually much fissured and brecciated. (Bates and Jackson, 1995)
volcanic mountains [Landscape Term] A landscape term for a region characterized by
mountains of volcanic origin, which are any part of the Earth's crust higher than a hill,
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sufficiently elevated above the surrounding land surface of which it forms a part to be
considered worthy of a distinctive name, characterized by a restricted summit area (as
distinguished from a plateau), and generally having comparatively steep sides and
considerable bare-rock surface of volcanic origin. (Bates and Jackson, 1995)
W
wash [Common Landform] (a) A term applied in the western U.S. (esp. in the arid and
semiarid regions of the southwest) to the broad, gravelly, normally dry bed of an
intermittent stream, often situated at the bottom of a canyon; it is occasionally filled by a
torrent of water. (b) A shallow body of water; esp. a shallow creek. (Bates and
Jackson, 1995)
washover fan [Coastal Marine Landform] A fan-like deposit consisting of sand washed
over a barrier island during a storm. (Bates and Jackson, 1995)
water deposition in close proximity to ice [Glacial Subprocess] Landforms formed in
the environment close to the terminus of the glacier through fluvial processes. (Bloom,
1991)
wave-built terrace [Coastal Marine Landform] A gently sloping coastal feature at the
seaward or lakeward edge of a wave-cut platform, constructed by sediment brought by
rivers or drifted along the shore or across the platform and deposited in the deeper
water beyond. (Bates and Jackson, 1995)
wave-cut platform [Coastal Marine Landform] A gently sloping surface produced by
wave erosion, extending far into the sea or lake from the base of the wave-cut cliff. It
represents both the wave-cut bench and the abrasion platform. (Bates and Jackson,
1995)
Y
yardang [Eolian Landform] A long, irregular, sharp-crested, undercut ridge between two
round-bottomed troughs, carved on a plateau or unsheltered plain in a desert region by
wind erosion, and consisting of soft but coherent deposits (such as clayey sand); it lies
in the direction of the dominant wind, and may be up to 6 m high and 40 m wide. (Bates
and Jackson, 1995)
yardang trough [Eolian Landform] A long, shallow, round-bottomed groove, furrow,
trough, or corridor excavated in the desert floor by wind abrasion, and separating two
yardangs. (Bates and Jackson, 1995)
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