09F_i_Volcanoes2 - • East edge of Sierra Nevada •...

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Types of volcanoes (1) Shield volcanoes - broad gentle slopes  - succession of low viscosity basalt flows - long lava flows, lava fountains,  non-explosive (2) Cinder cones  Cerro Negro, Nicaragua (1968) - built from ejected lava fragments - slopes of 30-40° (angle of repose) - typically <~300 m high - short life span (3) Stratovolcanoes or composite cones - built from alternating lava flows and pyroclastic flow deposits - intermediate in size highly explosive Mauna Loa, Hawaii ~9 km high
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Calderas large, steep walled depression formed from collapse of the volcanic structure after underlying  magma chamber is emptied during an eruption Long Valley caldera
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Unformatted text preview: • East edge of Sierra Nevada • Eruptive history of Long Valley caldera • 3.2 - 2.6 Ma - lava flows and domes • 2.1 - 0.8 Ma - felsic (rhyolite) domes - Glass Mtn • 0.73 Ma - caldera formation - Bishop tuff • 0.73 - 0.65 - increased magma pressure - resurgent dome • 0.5, 0.3, 0.1 - “moat” rhyolites • ~40,000 - 500 years ago - Mono/Inyo craters • Rhyolite domes, flows, and craters along north-south fissure Active magma chamber beneath the Long Valley caldera Fissure eruptions- lava flows out of crack- basaltic- mid-ocean ridges- flood basalts - huge volumes of lava poured onto continents Laki fissure, Iceland...
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This note was uploaded on 10/26/2009 for the course GLY 1232 taught by Professor Vagnl during the Spring '09 term at University of Florida.

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09F_i_Volcanoes2 - • East edge of Sierra Nevada •...

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