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

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