volcanic landforms processes and hazards. volcanic landforms 1.intrusive igneous forms 2.extrusive...
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Volcanic Landforms
Processes and Hazards
Volcanic Landforms
1. Intrusive Igneous Forms
2. Extrusive – Basalt Landforms
3. Extrusive – Composite volcanoes
4. Extrusive – Rhyolite landforms
1. Intrusive Igneous FormsMagma solidified at great depth (so mineral
sizes are large)
Plutons (individual magma chambers)
Batholiths (merged magma chambers)
Pluton seen because of glacial erosion, Chile
Brandberg, Western NamibiaIntrusive igneous rocks are often more
resistant to erosion, so they are topographic highs
Plutons (individual magma chambers)
Batholiths (merged magma chambers)
Laccolith (bubble up strata)
Dikes – vertical magma cutting through
Sill – horizontal magma inserted between
Large
Small
Dike, Spanish Peaks, Colorado
more resistant than surrounding sediment,
so stand out
Dike, Picture Gorge
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)
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.
Volcanic Neck.
Dike
Classroom Resource
Tse bi Dahi
Rock With Wings
Shiprock
Volcanic
Neck
Viscosity Organization
Extrusive – Basalt Landforms
Extrusive – Composite volcanoes
Extrusive – Rhyolite landforms
More Viscous = More Explosive
Classroom Resource
2. Extrusive – Basalt Landforms
• Basalt Flow
• Flood Basalts
• Cinder Cone
• Shield Volcano
Shield & Cinder Cone – from basalt eruptions
Later: Composite volcano
Basalt flows will travel great distances and slope angles will reflect low viscosity.
Classroom ResourcesRecent Hawaii Eruptions (NPS)
A year of pahoehoe Spatter Cone
Low viscosity releases trapped gases easily, so not explosive.
Classroom Resources
Etna Tourist Office
No Lives Lost
Different Textures, Same Basalt Rock
Pahoehoe a’a
Lava Tubes – so fluid that inside keeps moving & creates caves
Classroom Resource
Lava tube breakout
Lava Tube, Hawaii near Flagstaff, AZ
Mt St. Helens, OR
Buries old topography
Cinder Cones
SP Crater, AZ
Cinder drops out (like hour glass)
Cinder Cone Developing
Largest drop out first
Largest Clasts: Volcanic Bombs
Classroom Resource
Cinder Cone Bombs
Crater: depression at top formed by force of eruption
Owens Valley, Calif
Very common in Arizona:especially S.F. Volcanic Field
Sunset Crater, AZ
Shield Volcanoes
Isabela Island,Galapagos
Hawaii built from Shield Volcanoes
Weight of new lava has depressed the crust around Hawai’i
Moat
~ 5000 m
Below
Sea
Level
Mauna Loa: note gentle profile from fluid basalt flows
Mauna Kea
Often have Summit Caldera – from collapse as lava flows away
3. Extrusive – Composite Volcanoes
Mt Ararat, Armenia
Sit above Subduction ZonesFuji Egmont
Extraordinarily Dangerous
from Nova
from Nova
from Nova
Future Disaster: Popocatepetl, next to Mexico City & Puebla
Composite Volcano
Online Animations
Volcanic Hazards
http://serc.carleton.edu/NAGTWorkshops/visualization/collections/volcano.html
Classroom ResourcesNuee Ardente (also called glowing
avalanche, pyroclastic flow)
Set to music (www.mvo.ms)
Soufriere, Montserrat
Nuee Ardente (Glowing Avalanche or pyroclastic flow)
Pompeii, Italy
Mt. Vesuvius
Volcanic Ash
Debris Avalanche
Mt St. Helens Before Eruption
Classroom ResourceLahaar, Mt St. Helens Fly Over
Mt Mazama (could be Rainier)
Caldera – from collapse after lava has “evacuated” from magma chamber
Crater Lake
Mt Hood (my bet to go next)
Mount Pinatubo
Classroom Resources
Arizona has San
Francisco Peaks & Mt Baldy
Classroom Resource
San Francisco Peaks (made by Simpkin, ASU)
4. Extrusive – Rhyolite LandformsSmall Eruptions: Rhyolite Domes, Mt Elden
Rhyolite so
viscous
has trouble
flowing, so
piles up in
dome
shape
Many Rhyolite Domes near Mono Lake, Calif
Mammoth Lakes, still active evidence: carbon dioxide
Classroom ResourcesAfter major eruption of composite volcano,
will often start to rebuild with rhyolite domes
Arizona has many rhyolite caldera super eruptions (17-27 myr ago)
Superstition Mtns
Chiricahua Mtns
Toba – almost did us in
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