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33 Cards in this Set
- Front
- Back
viscosity
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a measure of a fluid's resistance to flowing
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high viscosity means
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hard to flow
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viscosity due to
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polymerization of silicon and oxygen in magma
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high silica content =
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high viscosity
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mafic magmas have significantly lower _____ content than felsic magmas
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silica
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felsic magmas are (more/less) viscous than mafic minerals
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more (because more silica)
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high temperature =
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lower viscosity (flows easier)
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water dissolved in magmas =
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lower viscosity
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magmas rise from depth of Earth until: (3 things)
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1) density matches surrounding rock
2) no avenue to rise through 3) lost so much heat that viscosity is too high |
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lava
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magma that has erupted onto Earth's surface
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basaltic lava
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commonly flows over large distances, low viscosity
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rhyolitic lava
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very high viscosity, never travels far nor fast
(rhy = high) |
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felsic lava
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very viscous, commonly plugs up shallow plumbing of volcanoes
prevents gas from escaping lava domes |
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lava flow
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masses of molten rock that pour onto Earth's surface during an effusive eruption
moving lava |
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ash
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rock, mineral, volcanic glass fragments smaller than .2 mm in diameter
hard, does not dissolve in water shattering of rocks during violent eruption |
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pyroclastic flow
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ground-hugging avalanche of hot ash, pumice, rock fragments, volcanic gas
gushes down side of volcano very fast |
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Lahar
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volcanic mudflows or debris flows
rapidly flowing mixture of rock debris and water formed by rapid melting of snow and ice by PYROCLASTIC flows |
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tuff
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relatively soft, porous rock
compaction and cementation of volcanic ash |
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nuees ardente
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pyroclastic flows generated by dome collapse
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pillow lava
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when basalt erupts underwater
mounds of lava pillows form by repeated oozing and quenching of hot basalt |
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shield volcanoes
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broad, gentle slopes
built by eruption of fluid basalt lava enormous, low angle cones |
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cinder cone
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steep, conical hill of volcanic fragments that accumulate around and downwind from a vent
rock fragments are glassy with gas bubbles (magma exploded into air and cooled quickly) |
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composite (strato-) volcano
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steep, conical volcano
built by eruption of viscous lava flows and pyroclastic flows highly explosive many vents Mt. St. Helens |
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caldera
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large, usually circular depression at summit of volcano
formed when magma is withdrawn or erupted from a shallow underground magma reservoir removal of magma leads to loss of structural support, leading to collapse |
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dome
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rounded, steep sided mounds built by very viscous magma
too viscous to flow away |
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aa
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lava flows that have rough, rubbly surface composed of broken lava blocks called clinkers
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pahoehoe
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basaltic lava that has smooth surface
advances as small lobes and toes that continually break out from cooled crust |
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pumice
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light, porous volcanic rock
forms during explosive eruptions like a sponge, network of gas bubbles all types of magma make it |
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obsidian
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dense volcanic glass
rhyolitic in composition black in color cooled really fast |
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supervolcano
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capable of producing eruption with over 1000 square km of particles
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Hawaiin eruptions
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lava flows from a vent in a relatively gentle, low level eruption
basaltic magma of low viscosity and low content of gas very little volcanic ash |
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Plinian eruptions
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large explosive events that form enormous dark columns of gas high into stratosphere
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strombolian eruptions
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intermittent explosion or fountaining of basaltic lava from a single vent or crater
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