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Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 1
Volcano
How and Where Formed
Magma and Erupted Materials
Volcanic Landforms
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 2
Where Volcanoes Form • Subduction Boundaries
– Cascade Mtns– Mariana Islands
• Divergent Boundaries– Iceland
• Hot Spots– Hawaiian Islands
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 3
Magma Types• Basaltic Magma
– rifts, ocean hot spots• Kilauea
• Andesitic Magma– subduction boundaries
• Mount St. Helens
• Rhyolitic Magma– continental hot spots
• Yellowstone Caldera
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 4
Lava Flows• Basaltic Lava Flows
– (low silica)• very fluid, fast moving
– pahoehoe flow – twisted ropes• viscous, slow moving
– aa flow – sharp edges/projections
• Underwater Lava Flows– cools more quickly
• pillow lava
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 5
Materials From Eruption• Gases
– concentration varies• can effect “eruption explosions”
– composition varies• carbon dioxide – odorless• sulfur compound – pungent odor
“burn”
• Pyroclastic Materials– gases and solid fragments
released by a volcano
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 6
Pyroclastic Materials• pyroclastics
– particles ejected by expanding gases in magma
• vary by size– ash– welded tuff– pumice– lapilli– blocks– bombs
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 7
Volcanic Landforms• Shield Volcano
– lava builds up in layers– broad base, gentle slope
• Mauna Loa
• Cinder Cone Volcano– molten lava thrown from vent
• Capulin
• Composite Volcano– layers formed from eruptions
• Mount St. Helens• Mount Shasta
Updated 4/16/2009 Created by C. IppolitoApril 2009
Slide 8
Volcanic Landforms (con’t)
• Caldera– Large crater shaped basin
formed when top of volcano collapses
• Crater Lake– http://earthsci.org/education/teacher/basicgeol/igneous/igneo
us.html