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42 Cards in this Set
- Front
- Back
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What is the opening of Earth's crust where magma and volcanic gases reach the surface?
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volcano
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What is molten rock underground that feeds a volcano?
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magma chamber
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What is a crack which magma may rise?
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vent
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How does the size of a vent affect the type of eruption?
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if vent is narrow and long, the eruption may be more explosive
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What 3 factors cause magma to erupt more explosively?
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-high water content
-more silica -longer, narrower vent |
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What is the thickness of lava calles?
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viscosity
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What's true of the viscosity the higher it is?
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the thicker it is
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What is Pahoehoe lava?
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-high viscosity
-flow like melted wax -hardens into wrinkled surface |
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What is Block lava?
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-high viscosity
-flows slowly; does not travel far -cools in big chunks |
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What is Aa lava?
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-lower viscosity
-flows faster -becomes brittle and jagged on surface |
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What is Pillow lava?
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-lower viscosity
-underwater -hardens into rounded lumps |
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How does pyroclastic material form?
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lava blasts into air
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Name the different types of pyroclastic material.
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-volcanic bombs
-volcanic blocks -ash -lapilli |
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What are volcanic bombs?
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large blobs of magma that hardens in the air
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What are volcanic blocks?
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solid rock that is blasted from volcano
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What is ash?
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tiny slivers of hardened magma
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What is lapilli?
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small pebbles of magma that harden in the air
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What are enormous amounts of gas, dust, and ash that are ejected and speed downhill?
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pyroclastic flow
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What are nonexplosive volcanic eruptions?
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-more common
-lava flows from this |
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What are explosive eruptions?
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-rarer and more destructive
-debris, ash, and gas shoot our |
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What is a funnel-shaped pit near the top of the central vent of a volcano?
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crater
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What are 2 reasons that a caldera may be formed?
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-magma chamber partially empties and chamber's roof collapses
-volcano top blown off |
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How are calderas and craters different from eachother?
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caldera larger and is a huge depression in the earth
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What are the 3 types of volcanic cones?
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-sheild
-cinder cone -composite |
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What is a sheild volcano?
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-gently sloping sides
-nonexplosive eruptions -mainly lava flow |
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What is a cinder cone volcano?
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-explosive eruptions
-steep slopes -pyroclastic eruptions |
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What is a composite volcano?
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-most common
-explosive and nonexplosive eruption -broad base -steeper slopes |
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What is a wide, flat landform that results from repeated nonexplosive eruptions of lava that spread over a large area?
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lava plateau
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Why does a volcanoes crater tend to get larger over time?
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-next eruption may blast away hardened lava
-after eruption the lava in a vent may sink causing the vent to collapse and form a larger crater |
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What are columns of rising magma?
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mantle plumes
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describe the difference among an extict, dormant, and active volcano.
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extict-hasn't erupted and never will
dormant-hasn't erupted for awhile , but probably will active-is erupting |
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How might a volcanic eruption affect the climate?
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-sun blocked
-darkness -temperature change -acid rain could change land and water |
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What is an area of deep cracks between tectonic plates?
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rift zone
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What are volcanoes far from the volcano boundary?
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hot spot
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What is 1 plate sinks under the other?
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subduction
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What happens if the temp. of rock remains constany but the pressure on the rock decreases?
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more rock will melt
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Explain how convergent and divergent plate boundaries cause magma formation.
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divergent-lava flows out and creates new crust (most underground)
convergent-subduction causes increase in temp. and pressure; rock melts |
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Why does an oceanic plate tend to subduct when it collides with a continental plate?
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oceanic plate is denser and thinner
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What causes an increase in the # and intensity of small earthquakes before an eruption?
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the movement of magma
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Describe 4 methods that scientists use to predict volcanic eruptions?
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-measure seismic activity to help track magma motion
-study volume nd composition of volcanic gas -measure slope cuz ground may swell or bulge -use sattellites like GPS yo detect changes in slope |
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What is the instrument that helps scientists detect small changes in the angle of a volcano's slope?
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tiltmeter
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What theory helps explain the causes of both earthquakes and volcanoes?
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theory of plate tectonics
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