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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 Images:

http://volcanoes.usgs.gov/Products/Pglossary/pglossary.htmlhttp://vulcan.wr.usgs.gov/

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

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Kelby Hicks, WVU

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–Welded Tuff = Huge Sheet, 100s of ft thick

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)

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

Nyriagongo Volcano, Dem. Rep. of Congo

Vent Eruptions =True Volcanoes

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USGS Map

//vulcan.wr.usgs.gov/Volcanoes/Africa/Maps/map_drcongo_volcanoes.htmlOther 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

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

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

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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

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Mafic Shield Volcano, Hawaiian Type: Multiple VentsShield Volcano

Mafic Lava Flow

Shield Volcano: Mauna Loa, Hawaii

Mauna Loa Central Vent, Mauna Kea in Distance

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Kilauea Eruptions 1983-Date

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

Kilauea Eruptions 1983-Date

181 Houses Destroyed13 km of Road Buried

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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

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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

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Pu’u O’o Crater 1990

Pu’u O’o: Cinder Cone, Small Shield w/ Tiny Spatter Cone, 1992

Spatter Cone

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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

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

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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

SoufriereHills

VolcanoMontserrat

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Soufriere Hills VolcanoAndesite Lava Dome, 1997

Plymouth, Montserrat, July 1997

Bethel, Montserrat, July 1997

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Mt. Rainier, WA

J.S. Kite Photo Nov ‘03

Mt. St. Helens, Spirit Lake

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Mt. St. Helens: The Day Before

Mt. St. Helens, April 1980 Bulge

Plinian Eruption: Mt. St. Helens Tephra, 1980

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Yellowstone Ash

Mt. MazamaAsh

Blast Zone of Mt. St. Helens

Eruption Casualty

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Vent Eruptions =True Volcanoes

New Spirit Lake

Felsic (= Granitic) Magmas:

Post-1980 Lava Dome

Mt. St. Helens

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

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Mt. St. Helens: 7 Years After

Left offhere thislecture

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

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Long Valley Caldera

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

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

LANDSAT False Color image of Yellowstone National Park, 1999

• http://www.lpi.usra.edu/education/EPO/yellowstone2002/workshop/y_caldera_extra/y_calderaextra_imgs/l7tm_13jul99_432_m.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