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VOLCANIC LANDFORMSGEO 321 Lecture # 3

J. Steven KiteWest Virginia University

Cotopaxi Erupts in 1862 Painting by Frederic Church

VOLCANIC LANDFORMS

Sources for Many Images in this Lecture:

http://volcanoes.usgs.gov/Products/Pglossary/pglossary.html

http://hvulcan.wr.usgs.gov/ (dead link)Check out USGS Hawaii site

http://hvo.wr.usgs.gov/kilauea/update/main.html

Most Important Igneous Rocks

Mineral Composition

Text

ure

Felsic Mafic Ultra-Mafic

Inter-mediate

Cellular,GlassyFine

Coarse

Mix

rare

rare

rare

peridotite

basalt

gabbro

rhyolite

granite

andesite

diorite

scoriapumice

rhyoliteporphyry

andesiteporphyry

basaltporphyry

basalt

granite

andesiteporphyry

obsidian

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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

Kelby Hicks, WVU GEOL BS 2005, in Hawaii

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Sulphur Vent

Phreatic Eruption:Ukinrek Maars,

AlaskaMaar: 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

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Eruption Types:

Exhalative -Explosive -Viscous Magma - Felsic -Bombs, Tephra, Pyroclastics

Quito, Equador, 1999

Effusive Eruption

Fluid MaficLava FlowMauna Loa, March 1983

2 Types of Eruption Apertures:

•Fissures•Vents

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Fissure Eruptions

• Felsic (= Granitic): Viscous Polymerized Lava and Pyroclastics–Ignimbrite = Welded Tuff Huge sheets, 10s of m thick

Grand Canyon of the YellowstoneSulfur Creek rhyolite Tuff and Canyon rhyolite flow, erupted nearly

500,000 years ago, later altered by hydrothermal fluids. Photo by S.R. Brantley, 2001.

http://volcanoes.usgs.gov/yvo/images/20010520-122-srb large.jpg

New slide for 2008

Fissure Eruptions

•Mafic (Basaltic): Fluid Lava–Flood Basalts With Many Feeder Dikes; Basalt Plateaus, Lunar Mare

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Mare Humorum

Lunar Flood Basalt

European Southern

Observatory

www.eso.org/outreach/press-rel/pr-1999/phot-02d-99-preview.jpg

Dry Falls, Washington

New Slide for 2008Columnar Jointing, (photograph by Terry Tolan)

Frenchman Coulee, west-central Columbia Plateau, Washington from “Columbia River Basalt Stratigraphy in Oregon”

http://or.water.usgs.gov/projs_dir/crbg/photos/blocky_jointing.jpg

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Nyriagongo Volcano, Dem. Rep. of Congo

Vent Eruptions =True Volcanoes

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.

Source of Next Images:

Nyriagongo Volcano

Goma

Nyiragongo

Volcano

Y. Pottier

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Nyriagongo Volcano, Jan 2002World’s fastest lava? 60 km/h

/www.cnn.com/2002/WORLD/africa/01/20/congo.eruption/index.html

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

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Mt. Bachelor, Oregon:Icelandic-Type Shield Volcano

Mafic Shield Volcano, Hawaiian Type: Multiple VentsShield Volcano

Mafic Lava Flow

Shield Volcano: Mauna Loa, Hawaii

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Mauna Loa Central Vent, Mauna Kea in Distance

Kilauea Eruptions 1983-Date

1.8 km3 of Basalt100 km2 CoveredUp to 25 M Thick206 Hectares of New “Land”

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Kilauea Eruptions 1983-Date

181 Houses Destroyed13 km of Road Buried

Fissure Eruption 1983 Birth of Pu’u O’o

Pu’u O’o Cinder Cone 1983

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Pu’u O’o - Royal Gardens Aa Flow 1983

Pu’u O’o - Royal Gardens Aa Flow 1983

Pu’u O’o Cinder Cone 1986

255 m

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Pu’u O’o Cone and Flows 1986

Pu’u O’o Crater 1990

Pu’u O’o: Small Spatter Cone, 1992

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Pu’u O’o Cone Collapse 1995

Kupaianaha Pahoehoe Flow, 1988

Pahoehoe

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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

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Lava Tube Kelby Hicks,

WVU

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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 ConesCollapse of Magma Chamber &

Explosion (Pyroclastics).Possible Calderas

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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

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Tavurvur Volcano, Rabual, Papua New Guinea: Cinder Cone, Tephra

VulcanianEruption

Ashfall, Papua New Guinea, 1994

Mt. Etna, Italy

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Stromboli

Strombolian Eruption

Left offhere thislecture

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Vent Eruptions =True Volcanoes

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

Mesa Falls Ash-Flow Tuff & Underlying Fallout Ash,near Ashton, Idaho. Photo by Robert L. Christiansen, 1983

http://volcanoes.usgs.gov/yvo/images/198307-rc-010_large.jpg

New slide for 2008

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Popocatepetl, Mexico: 1994

Popocatepetl, Mexico: Dec 2000

Mayon Volcano, Philippines, Feb 2000

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Lava Flow onMayon Volcano,

Philippines,

Feb 2000

Pyro

clas

tics

May

on20

00

Soufriere Hills

VolcanoMontserrat

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Soufriere Hills VolcanoAndesite Lava Dome, 1997

Plymouth, Montserrat, July 1997

Bethel, Montserrat, July 1997

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Mt. St. Helens, Spirit Lake

Mt. St. Helens: The Day Before

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Mt. St. Helens, April 1980 Bulge

Plinian Eruption: Mt. St. Helens Tephra, 1980

Yellowstone Ash

Mt. MazamaAsh

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Blast Zone of Mt. St. Helens

Eruption Casualty

New Spirit Lake

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Felsic (= Granitic) Magmas:

Post-1980 Lava Dome

Mt. St. Helens

May Occur in Late Eruption Phases of Intermediate or Mafic Magma Chamber

Mt. St. Helens: 7 Years After

Mt. Rainier, WA

J.S. Kite Photo Nov ‘03

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Mount Rainier Hazard Zones

Lahars, Lava Flows, & Pyroclastic Flows

(Hoblitt et al., 1998; USGS OF 98-428).

U.S. Geological SurveyFact Sheet 034-02Online Version 1.0

Mount Rainier -- Learning to Live with Volcanic Risk

http://pubs.usgs.gov/fs/2002/fs034-02/images/fig3.jpg

NEW FOR 2008

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

Crater Lake: Caldera of Mt MazamaExplosive Eruption 7,700 B.P. Eruption Expelled About 50 Km3 of Magma.

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Crater Lake

pubs.usgs.gov/fs/crater-lake/index.html

Felsic EruptionsRhyolitic (Granitic) Composition:

Viscous Lava or TephraIgnimbrite = Welded Tuff = Huge Sheet of

Tephra Includes Ash, Bombs, etc.

Mt. Mazama“Ash” orTuff orTephra orPyroclastics(Caldera Event)

Wizard Island, Crater Lake,

J.S. Kite Photo July ‘03

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Aniakchak Caldera, Alaska

Yellowstone Caldera

http://vulcan.wr.usgs.gov/Imgs/Gif/Yellowstone/Maps/map_yellowstone_caldera.gif

Yellowstone Volcano Observatory Photo Gallery http://volcanoes.usgs.gov/yvo/images/2000-rbs-1.4ytspaceviewzoom_large2a.jpg

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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

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Shiprock, New Mexico