Volcanic Landforms

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Volcanic Landforms

• Processes and Hazards

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Volcanic Landforms

1. Intrusive Igneous Forms
2. Extrusive Basalt Landforms
3. Extrusive Composite volcanoes
4. Extrusive Rhyolite landforms

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1. Intrusive Igneous Forms

• Magma solidified at great depth (so mineral sizes
  are large)
• Plutons (individual magma chambers)
• Batholiths (merged magma chambers)

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Pluton seen because of glacial erosion, Chile
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Brandberg, Western Namibia

• Intrusive igneous rocks are often more resistant
  to erosion, so they are topographic highs

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Plutons (individual magma chambers) Batholiths
(merged magma chambers) Laccolith
(bubble up strata) Dikes vertical
magma cutting through Sill horizontal magma
inserted between
Large Small
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Dike, Spanish Peaks, Colorado more resistant than
surrounding sediment, so stand out
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Dike, Picture Gorge
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Volcanic Neck. Dike
Over time, the less resistant rock (i.e.,
pyroclasts and less consolidated lava flows)
comprising the flank of the volcano is eroded
away leaving the resistant neck exposed in
relief.
Shiprock (Tse bi Dahi, Rock With Wings), New
Mexico is the classic example of a volcanic neck
(base of composite volcano, so deep that is
intrusive rock)
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Classroom Resource

• Tse bi Dahi
• Rock With Wings
• Shiprock
• Volcanic
• Neck

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Viscosity Organization
Extrusive Basalt Landforms Extrusive
Composite volcanoes Extrusive Rhyolite landforms
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More Viscous More Explosive
Classroom Resource
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2. Extrusive Basalt Landforms

• Basalt Flow
• Flood Basalts
• Cinder Cone
• Shield Volcano

Shield Cinder Cone from basalt
eruptions Later Composite volcano
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Basalt flows will travel great distances and
slope angles will reflect low viscosity.
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Classroom Resources

• Recent Hawaii Eruptions (NPS)
• A year of pahoehoe Spatter Cone

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Low viscosity releases trapped gases easily, so
not explosive.
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Classroom Resources

• Etna Tourist Office
• No Lives Lost

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Different Textures, Same Basalt Rock

• Pahoehoe aa

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Lava Tubes so fluid that inside keeps moving
creates caves

• Classroom Resource
• Lava tube breakout

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• Lava Tube, Hawaii near Flagstaff, AZ

Mt St. Helens, OR
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Buries old topography
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Cinder Cones
SP Crater, AZ
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Cinder drops out (like hour glass)
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Cinder Cone Developing
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Largest drop out first
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Largest Clasts Volcanic Bombs

• Classroom Resource
• Cinder Cone Bombs

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Crater depression at top formed by force of
eruption
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Owens Valley, Calif
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Very common in Arizonaespecially S.F. Volcanic
Field
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Sunset Crater, AZ
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Shield Volcanoes
Isabela Island,Galapagos
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Hawaii built from Shield Volcanoes
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Weight of new lava has depressed the crust around
Hawaii

• Moat
• 5000 m
• Below
• Sea
• Level

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Mauna Loa note gentle profile from fluid basalt
flows
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Mauna Kea
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Often have Summit Caldera from collapse as lava
flows away
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3. Extrusive Composite Volcanoes

• Mt Ararat, Armenia

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Sit above Subduction Zones

• Fuji Egmont

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Extraordinarily Dangerous

• from Nova

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from Nova
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from Nova
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Future Disaster Popocatepetl, next to Mexico
City Puebla
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• Composite Volcano

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Online Animations

• Volcanic Hazards
• http//serc.carleton.edu/NAGTWorkshops/visualizati
  on/collections/volcano.html

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Classroom Resources

• Nuee Ardente (also called glowing avalanche,
  pyroclastic flow)

Set to music (www.mvo.ms) Soufriere, Montserrat
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Nuee Ardente (Glowing Avalanche or pyroclastic
flow)
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Mt. Vesuvius
Pompeii, Italy
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Volcanic Ash
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Debris Avalanche
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Mt St. Helens Before Eruption
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Classroom Resource

• Lahaar, Mt St. Helens Fly Over

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Mt Mazama (could be Rainier)
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Caldera from collapse after lava has
evacuated from magma chamber

• Crater Lake

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Mt Hood (my bet to go next)
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Mount Pinatubo
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Classroom Resources
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Arizona has San Francisco Peaks Mt Baldy
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Classroom Resource

• San Francisco Peaks (made by Simpkin, ASU)

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4. Extrusive Rhyolite Landforms

• Small Eruptions Rhyolite Domes, Mt Elden

Rhyolite so viscous has trouble flowing, so
piles up in dome shape
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Many Rhyolite Domes near Mono Lake, Calif
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Mammoth Lakes, still active evidence carbon
dioxide
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Classroom Resources

• After major eruption of composite volcano, will
  often start to rebuild with rhyolite domes

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Arizona has many rhyolite caldera super
eruptions (17-27 myr ago)

• Superstition Mtns

Chiricahua Mtns
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Toba almost did us in
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Imagery seen in this presentation is courtesy
of Ron Dorn and other ASU colleagues, students
and colleagues in other academic departments,
individual illustrations in scholarly journals
such as Science and Nature, scholarly societies
such as the Association of American Geographers,
city, state governments, other countries
government websites and U.S. government agencies
such as NASA, USGS, NRCS, Library of Congress,
U.S. Fish and Wildlife Service USAID and NOAA.c