776
PHOTOGRAMMETRIC ENGINBERING
field and in the office. The profession is developing collections of photographs
for teaching and research purposes.
The success of such a program is hampered by the fact that geographers,
generally, are not in a position to broaden their experience in the development
of techniques by using photographs which are made specifically for geographic
purposes to geographers' specifications. Photographs, in almost limitless numbers, are available for geographic use and their contribution to the development
of field techniques and interpretation procedures is unquestioned and obvious.
The geographer, however, has special needs which are not commonly met and
it is not unreasonable to assume that he can best develop methods which are
geographically effective if he be afforded the opportunity of experimenting with
photography that is designed to serve his particular purposes.
A KEY FOR THE PHOTO-IDENTIFICATION OF
GLACIAL LANDFORMS
William E. Powers (Northwestern University)
SUMMARY is presented herein of a key for the photo-identification of
A
glacial landforms developed by the writer and Dr. Clyde F. Kohn as part of
Research Project N -7-onr-45-005, under a contract between the Office of Naval
Research and Northwestern University. Field work was completed during the
summer of 1950.
The objective of this part of the project was to produce a key or study procedure by which a photo-interpreter untrained in glaciation or geomorphology
can identify correctly the landscape features in a region formerly occupied by
continental glaciers. Such' glaciated regions form a large part of the northern
United States and Canada, portions of Alaska, and areas of unknown, but almost
certainly vast extent, in northern and northeastern Asia. The photo-interpreter
is expected to have vertical stereopairs of aerial photographs, and should also
make use of all available information on the climate, vegetation, geology, and
human occupancy of the region considered. For field studies, five areas were
selected in the glaciated region adjacent to Lake Michigan, and their landforms
were studied and mapped in detail. In addition, ground photographs of all
landform types .studied were taken in stereopairs, so as to show the photointerpreter the ground appearance of the features which he identifies on aerial
photos.
FORM OF KEY
Analysis of the landforms in the five areas selected disclosed eleven types
of direct glacial origin and four types of non-glacial origin but likely to be associated with or adjacent to the glacial types. A form of key was adopted in
which, by a series of questions pertaining to specific features apparent on vertical
stereopairs of photos, the photo-interpreter is able to separate the landform types
into smaller and smaller groups until only two remain; a final question then
identifies the form. The first question selected is whether the fOfm is of glacial
or non-glacial origin; it was considered necessary to examine not one but
several contrasting characteristics to make this decision. Subsequent questions
deal, for simplicity, with only one element in the appearance of the feature to be
identified.
A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS
777
CLASSIFICATION OF LANDFORMS
Fifteen types of landforms were recognized in this study. Of these, types 1
to 4 are non-glacial but may be closely associated with glacial types, while
types 5 to 15 are directly glacial in origin:
1. Lacustrine Plains
9. Till knobs other than drumlins
2. Valley plains of streams
10. Kames
3. Stream-dissected plains or hill lands
11. Eskers
4. Dunes
12. Valley train terraces
5. Glaciated bedrock-controlled plains
13. Kame terraces
6. Rough and moraine
14. Outwash plains
7. Undulating till plain
15. Filled basins
8. Drumlins
INTERROGATION PROCEDURE
The following fourteen questions form a guide for differentiating and identifying the 15 landform types:
IS LANDFORM TYPE GLACIATED OR NON-GLACIATED?
1. a. Location:
b. Drainage:
Glaciated
(a) In region believed to
have been glaciated.
(a) Many lakes and swamps;
. poor drainage.
c. Stream pat- (a) Aimless; incomplete pattern (if pretern.
sent) :
d. Landform
types and
patterns:
(a) Many small
diverse
landforms.
(b) Many landforms appear
unrelated to any stream
pattern.
(c) Rounded, isolated hills
and ridges are common.
(d) Low,
narrow
ridges
winding with crests of'
varying altitude.
(e) Closed deep basins common.
(£) Oriented
or
parallel
forms may be present.
e. Soil
terns:
(g) Forms
of
crescentic
ground plan very rare.
(h) Hilly belts higher than
surrounding
country
may be present.
pat- (a) Irregular, unorganized
pattern of dark soils on
low ground. Soil pattern
unrelated to stream pattern.
Non-Glaciated
Generally found in non-glaciated
region.
Few or no lakes and swamps;
drainage may be good. Exception:
flat lacustrine plains or valley plain
may be swampy and poorly
drained.
Branching or rectangular; integrated and complete pattern; or
regularly meandering. (Applies
only if stream pattern is present.)
Estensive areas of similar landforms.
Some but not all landforms may be
related directly to stream erosion
pattern, if present.
Irregular but connected ridges
with angular or branching pattern
may be present.
Low ridges tend to be straight with
uniform crests. (Dunes are crescentic in plan.)
Closed deep basins rare save in
dunes.
Oriented forms rare save beach
ridges, sand bars, or crescentic
dunes.
Crescentic ground plan common in
dunes.
Hilly belts if present are not higher
than surrounding country, save
dunes.
Darker soils commonly organized
into branching or fish bone patterns. Flat lake plains may have
irregular soil patterns. Dunes may
have crescentic patterns of light
soils.
778
PHOTOGRAMMETRIC ENGINEERING
NON-GLACIATED FORMS
II. Is area mainly flat plain, or is it hilly or deeply cut by valleys?
a. Lacustrine plains (1) and valley plains of streams (2) are mainly flat.
b. Dissected plains or hill lands (3) and dune areas (4) are dominantly hilly.
III. If area is mainly flat plain, is it extensive and non-linear, or is it narrow and linear?
a. If area is extensive, non-linear, and unoriented with respect to a stream, it is
lacustrine plain (1).
b. If area is linear with bounding bluffs and is related to a present or former
stream, it is a valley plain (2).
IV. If area is hilly or deeply cut by valleys, does it contain connected ridges integrated to a
drainage pattern, or small individual hills with depressions but with few streams?
a. If area has an integrated, orderly drainage pattern separating organized, integrated dividing ridges of branching or rectangular pattern, the area is dissected
.
plain or hill land (3).
b. If there are many small hills, some of crescentic pattern, associated with depressions but having few streams and no' organized drainage pattern, area is
dunes (4).
GLACIATED FORMS
V. Is area one of thick glacial drift, or is drift thin w,ith topography dominated by bedrock?
a. Angular cliffs, very steep or vertical slopes, bare rock outcrops with few or no
plants, and stone quarries indicate bedrock-controlled plain (5).
b. The absence of angular ciiffs, of very steep or vertical slopes unless associated
with undercutting by a stream or wave action, of bare rock exposures without
plants, and of stone quarries-indicates that landforms are of glacial drift deposited by glacier (6 to 15).
•
VI. Are all landform summits rounded or rolling, or are there flat-topped forms of accordant level?
a. Rounded glacial landforms include rough end moraine (6), undulating till
plain (7), drumlins (8), other till knobs (9), kames (10), and eskers (11).
b. Flat-topped glacial landforms include valley trains (12), kame terraces (13),
outwash plains (14), and filled basins (15).
If forms are rounded:
VII. Is area extensive including many elevations and depressions, or does area consist of an
individual hill br ridge?
a. Rough end moraine (6), and undulating till plains (7) are extensive.
b. Drumlins (8), other till knobs (9), kames (10), and eskers (11), are individual
hills or ridges.
VIII. If area is extensive, do the rounded elevations form a belt of hilly topography with
moderate to strong relief. or is distribution pattern non-linear and relief low?
a. Hilly belts of strong to moderate relief are end or terminal moraine (6).
b. Low relief and lack of arrangement among the swells and basins indicate
undulating till plain (7).
If landform is individual hill or ridge:
IX. Are the sides steeply or gently sloping?
a. Drumlins (8) and othe'r till knobs (9) have gently sloping sides.
b. Kames (10) and eskers (11) have relatively steeply sloping sides.
X. If side slopes are gentle, does form have oval, oriented ground plan with one end
steeper than other, or is plan non-oval with no spefial relation of side slopes to ground
plan?
a. Oval, oriented till hills with one end steeper than other are drumlins (8).
b. Non-oval hills with slope angle unrelated to form are till knobs (9).
779
A KEY FOR PHOTO-IDENTIFICATION OF GLACIAL LANDFORMS
XI. If slopes are steep, is the landform a sharp, roughly circular hill or is it an enlongated
ridge?
a. Sharp, steep, roughly circular hills are kames (10).
b. Elongate, steep-sided ridges are eskers (11).
If glacial landforms are flat or contain flat-topped forms:
XII. In its broad aspects, is the form terrace-like, with higher ground on one side and lower
on the other, or is it a non-terrace?
a. Valley trains (12) and, kame terraces (13) are terrace-like.
b. Outwash plains (14) and filled basins (15) are non-terrace forms.
XIII. If terrace-like, does the outer edge of the terrace form show irregular knobs and pits
due to ice-contact when form was being deposited, or does outer edge appear smooth
or scalloped as if eroded by a stream?
,
'
a. Valley train terraces (12) have smooth, stream-eroded edges or margins.
b. Kame terraces (13) have irregular, ice-contact margins. (Where such ice-contact
margins have been eroded to smooth slopes, the kame terrace looks like a valley
train terrace.)
XIV. If flat form is not a terrace, is it a poorly-drained basin-like form with a very flat
floor, or is it dominantly a well-drained plain?
a. A well-drained plain with or without pits or channels is an outwash plain (14).
b. A poorly-drained flat-floored basin is a filled basin (15).
Typical examples of each of these 15 landform types are shown in vertical
stereogiams and also in stereopairs of ground photographs. After each form is
identified, the photo-interpreter is directed to verify his identification by comparing its observed characteristics with a list of all possible characteristics that
such a feature may possess. Agreemen~ in several respects, and few or no contradictions, are considered to constitute verification.
It is believed that this identification procedure, if faithfully' followed, will
quickly train the photo-interpreter to recognize landform types due to or associated with glaciation. Experience will speed the identification process, and will
indicate associations of landform types that permit rapid generalizations and
the quick recognition of individual forms. A procedure of this type is particularly
well adapted to the study of areas where all or most features are due to a single
process (here glaciation) and hence all elements of the landscape may be considered to be related in origin.
'
ABC's OF PHOTOGRAMMETRY
PART I
FUNDAMENTALS
PART II'
TILT AND CONTROL
GOMER T. McNEIL
RALPH O. ANDERSON
Photo measurements for the photo
interpreter. 2nd printing. $3.00 per copy.
An OPERATIONAL book placing emphasis on
HOW. $3.00 per copy.
ABC's OF PHOTOGRAMMETRY ~:s~~n5g~on
13, D.C.