VOLCANIC
LANDFORMS
VOLCANIC LANDFORMS
GEO 321 Lecture # 3
J. Steven Kite
West Virginia University
Cotopaxi Erupts in 1862
Painting by Frederic Church
Sources for Images:
http://volcanoes.usgs.gov/Products
/Pglossary/pglossary.html
http://vulcan.wr.usgs.gov/
Check out USGS Hawaii site
• http://hvo.wr.usgs.gov/kilauea/update/main.html
Most Important Igneous Rocks
Mineral Composition
Texture
Felsic
Intermediate Mafic
scoria
UltraMafic
Cellular, pumice
obsidian
Glassy
rare
Fine
rare
Mix
rhyolite andesite basalt
rhyolite andesite basalt
porphyry porphyry porphyry rare
Coarse granite diorite
gabbro
peridotite
1
Composition of Magma:
Important to Nature of
Volcanic Eruptions and
Resulting Landforms.
Tie Between Petrology
and Geomorphology.
Eruption Types:
• Exhalative or Phreatic : Few
Constructional Landforms
• Explosive: Viscous Magma Felsic - Pyroclastics, Tephra
(Ash, Bombs, etc.)
• Effusive: Fluid Magma - Mafic
- Lava
Exhalative Eruption:
• Gaseous: Few Landforms
2
Kelby Hicks, WVU
Phreatic Eruption:
Ukinrek Maars,
Alaska
Maar: Low-relief, Broad
Volcanic Crater Formed
by Shallow Explosive
Eruptions.
Explosions Are Usually
Caused by Boiling When
Magma Invades the
Groundwater Table.
Ukinrek Maars, Alaska
3
Eruption Types:
Exhalative -
Explosive Viscous Magma
- Felsic Bombs, Tephra,
Pyroclastics
Quito, Equador, 1999
Effusive
Eruption
Fluid Mafic
Lava Flow
Mauna Loa,
March 1983
2 Types of Eruption
Apertures:
• Fissures
• Vents
4
Fissure Eruptions
• Felsic (= Granitic):
Viscous Polymerized
Lava and Pyroclastics
–Welded Tuff = Huge
Sheet, 100s of ft thick
Felsic Eruptions
Rhyolitic (Granitic) Composition:
Viscous Lava or Tephra
Ignimbrite = Welded Tuff = Huge Sheet of
Tephra Includes Ash, Bombs, etc.
Mt. Mazama
“Ash” or
Tuff or
Tephra or
Pyroclastics
(Caldera Event)
Fissure Eruptions
• Mafic (Basaltic):
Fluid Lava
–Flood Basalts With
Many Feeder Dikes;
Basalt Plateaus, Lunar
Mare
5
Mare Humorum
Lunar Flood Basalt
European
Southern
Observatory
www.eso.org/outreach/press-rel/pr-1999/phot-02d-99-preview.jpg
Dry Falls, Washington
Nyriagongo Volcano, Dem. Rep. of Congo
Vent Eruptions =
True Volcanoes
6
Source of Next Images:
USGS Map
//vulcan.wr.usgs.gov/Volcanoes/Africa/Maps/
map_drcongo_volcanoes.html
Other Map: Global Volcanism Program Volcanic Activity Reports
www.volcano.si.edu/gvp/volcano/region02/
africa_c/nyamura/var.htm#2603
Map of eruption sites and lava flows at Nyiragongo and Nyamuragira's 1977
Murara vent. The location of the stippled flow on Nyiragongo was provided
by M. Krafft. Courtesy of Y. Pottier.
Y. Pottier
Nyriagongo Volcano
o
ng
go
ira ano
y
N o lc
V
ma
Go
Nyriagongo Volcano, Jan 2002
World’s fastest lava? 60 km/h
/www.cnn.com/2002/WORLD/africa/01/20/congo.eruption/index.html
7
Magma Composition:
Many Volcanoes (= Volcanos)
Change Character with Change
in Magma Composition
Typically, Magma Evolves from
Mafic (= Basic) and Fluid to
Felsic (= Acidic) and Viscous.
Mafic (Fluid) Eruptions
Exogenous Domes - Flows of
Lava - Low Gradient
Shield Volcano (Icelandic) - Single
Vent, Lava Lake in Crater.
Shield Volcano (Hawaiian) - Flank
(Lateral) Eruptions
Mt. Bachelor, Oregon:
Icelandic-Type Shield Volcano
8
Mafic Shield Volcano,
Hawaiian Type: Multiple Vents
Shield Volcano
Mafic Lava Flow
Shield Volcano: Mauna Loa, Hawaii
Mauna Loa Central Vent,
Mauna Kea in Distance
9
Kilauea Eruptions 1983-Date
1.8 km3 of Basalt
100 km2 Covered
Up to 25 M Thick
206 Hectares of New “Land”
Kilauea Eruptions 1983-Date
181 Houses Destroyed
13 km of Road Buried
10
Fissure Eruption 1983 Birth of Pu’u O’o
Pu’u O’o Cinder Cone 1983
Pu’u O’o - Royal Gardens Aa Flow 1983
11
Pu’u O’o - Royal Gardens Aa Flow 1983
Pu’u O’o Cinder Cone 1986
255 m
Pu’u O’o Cone and Flows 1986
12
Pu’u O’o Crater 1990
Pu’u O’o: Cinder Cone, Small Shield
w/ Tiny Spatter Cone, 1992
Spatter Cone
13
Pu’u O’o Cone Collapse 1995
Kupaianaha Pahoehoe Flow, 1988
Pahoehoe
14
Aa Flow Buries Pahoehoe
Pu’u O’o Lava Delta 1993
Pillow Basalts, So. Pacific Sea Floor
http://www.geology.sdsu.edu/how_volcanoes_work/
Images/Noaa/pillow_basalt_crop_l.jpg
15
Lava Tube
Kelby Hicks,
WVU
16
Lava Tube,
Hawaiian
Volcanoes
National Park
Mauna Kea Cinder Cone
Felsic (= Granitic) Eruptions:
Viscous Magma
Lava Domes (= Endogenous Domes)
w/ Minor Viscous Lava Flows
Cinder Cones, Spatter Cones
Collapse of Magma Chamber &
Explosion (Pyroclastics).
Possible Calderas
17
Newberry Cone Obsidian Flow
Newberry Cone Obsidian Flow
Lava Dome (Plug Dome), Valley of
10,000 Smokes, Katmai NP, Alaska
Novarupta Vent Blew 15 km3 in 1912
18
Tavurvur Volcano, Rabual, Papua New
Guinea: Cinder Cone, Tephra
Vulcanian
Eruption
Ashfall, Papua New Guinea, 1994
Mt. Etna, Italy
19
Stromboli
Strombolian Eruption
Intermediate (Andesitic) Magma:
• Composition Varies - Viscous to
Fluid
• Small Cinder Cones or Spatter
Cones & Flows Grow into....
• Composite Cones
(=Stratovolcanos)
–Composite of Flows and
Pyroclastics
20
Popocatepetl, Mexico: 1994
Popocatepetl, Mexico: Dec 2000
Mayon Volcano, Philippines, Feb 2000
21
Lava Flow on
Mayon Volcano,
Philippines,
Pyroclastics Mayon 2000
Feb 2000
Soufriere
Hills
Volcano
Montserrat
22
Soufriere Hills Volcano
Andesite Lava Dome, 1997
Plymouth, Montserrat, July 1997
Bethel, Montserrat, July 1997
23
Mt. Rainier, WA
J.S. Kite Photo
Nov ‘03
Mt. St. Helens, Spirit Lake
24
Mt. St. Helens: The Day Before
Mt. St. Helens, April 1980 Bulge
Plinian Eruption:
Mt. St. Helens
Tephra, 1980
25
Yellowstone
Ash
Mt. Mazama
Ash
Blast Zone of Mt. St. Helens
Eruption Casualty
26
Vent Eruptions =
True Volcanoes
New Spirit Lake
Felsic (= Granitic) Magmas:
May Occur in Late Eruption Phases of
Intermediate or Mafic Magma Chamber
Post-1980
Lava Dome
Mt. St. Helens
27
Mt. St. Helens: 7 Years After
Left off
here this
lecture
Caldera: Collapse of Magma
Chamber:
• Krakatoa, 1880s
• Mt. St. Helens 1980 (Landslide)
• Pinitubo,1991
– Positive Feed Back System; Low
Pressure = Eruption; Increase
Eruption = Lower Pressure
28
Long Valley Caldera
Crater Lake: Caldera of Mt Mazama
Explosive Eruption 7,700 B.P.
Eruption Expelled About 50 Km3 of Magma.
Wizard Island,
Crater Lake,
J.S. Kite Photo July ‘03
29
Aniakchak Caldera, Alaska
Yellowstone
Caldera
http://vulcan.wr.usgs.gov/Im
gs/Gif/Yellowstone/Maps/m
ap_yellowstone_caldera.gif
LANDSAT False Color image of
Yellowstone National Park, 1999
• http://www.lpi.usra.edu/education/EPO/yell
owstone2002/workshop/y_caldera_extra/y_
calderaextra_imgs/l7tm_13jul99_432_m.jpg
30
Areas of the United States that
once were covered by volcanic ash
from Yellowstone's giant eruptions
• See "Windows into the Earth, The Geologic
Story of Yellowstone and Grand Teton
National Park", Robert B. Smith and Lee J.
Siegel, Oxford University Press, 2000.
Erosion • Volcanic Neck Usually More
Resistant To Erosion
• Erosion often Simultaneous
with Eruption –Complex Forms
Mt. Washington, OR:
Eroded Remnant of Composite Cone
31
Shiprock, New Mexico
32