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31 Cards in this Set
- Front
- Back
The earth cools by
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convecting the mantle
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Viscosity rises as
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silica content in lava rises
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shield volcano
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broad, gentle dome
usually has basaltic lava flow with low viscosity |
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cinder cone
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cone-shaped, made of tephra, often as a rhyolitic dome
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stratovolcano
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alternates between basalt and andesite
large and cone-shaped terrestrial |
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Less viscous lava is . . .
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less silica
hotter gas-rich crystal-poor |
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Basalt melts at
Rhyolite melts at |
1200 degrees C
900 degrees C |
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lava tube
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insulated, tunnel like conduit within a flow
basaltic flow |
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pahoehoe
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flows with warm, pasty surfaces that wrinkles in to rope like ridges
basaltic flow |
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a'a'
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flows of sharp, angular fragments made up of broken up frozen lava from the surface layers of a flow
basaltic flow |
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When cooling, basalt . . .
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contracts and crystallizes
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columnar jointing
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hexagon shape
indicates cooled basalt |
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lava dome
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dome-like mass above a vent or in short and bulbous flows 1-2 km long
rhyolitic flow |
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lapilli
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pea to plum sized glass fragments, often made of pumice or scoria
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volcanic bomb
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pieces cool as they are flying through the air
apple to refrigerator sized fragments |
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pyroclastic flow
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fast-moving turbulent avalanches of hot ash and lapilli, full of blocks and bombs
400 degrees |
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Mid ocean ridge vulcanism is . . .
a. rhyolitic b. andesitic c. basaltic |
basaltic
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Island Arch volcanoes
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hot spots pushing up from the mantle
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andesitic magma tends to
it contains . . . it often causes a . . . after flow creates . . . |
explode!
lots of water medium vicousity H20 gets out by exploding pyroclastic flow toe of pumice blocks |
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lahar
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fast moving flow of ash-rich debris and water, volcanic mud flow
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basaltic lava flow
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low viscosity, usually but not always less than 10 km long
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andesitic lava flow
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intermediate silica content, first forms as a large mound above a vent and then advances about 1-5 meters per day in a lumpy flow that looks like a jumble of rubble
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rhyolitic flows
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most viscous, accumulates in a lava dome, rarely more than 1-2 km long
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hot-spot volcanoes form . . .
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above fingerlike plumes of hot mantle that rise from near the core-mantle boundary
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basaltic lava flow
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low viscosity, usually but not always less than 10 km long
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andesitic lava flow
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intermediate silica content, first forms as a large mound above a vent and then advances about 1-5 meters per day in a lumpy flow that looks like a jumble of rubble
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rhyolitic flows
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most viscous, accumulates in a lava dome, rarely more than 1-2 km long
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hot-spot volcanoes form . . .
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above fingerlike plumes of hot mantle that rise from near the core-mantle boundary
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Max depth of continental crust
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70 meters
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Why does Iceland have cool volcanoes?
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A mid-ocean ridge cuts through it
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Mt. Tambora
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Indonesia, 1816
ash filled and cooled the atmosphere Europe referred to 1816 as the "year w/o a summer" |