Vocab Cards

Front 1

volcano

Back 1

is a weak spot in the crust wheremolten material, or magma, comes to the surface.

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magma

Back 2

is amolten mixture of rock-forming substances, gases, and waterfrom the mantle.

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lava

Back 3

When magma reaches the surface,

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ring of fire

Back 4

One major volcanic belt formed by the many volcanoes that rim thePacific Ocean

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island arc

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The resulting volcanoes create a string of islands

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hot spot

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an area where material from deep within the mantlerises and then melts, forming magma. A volcano forms abovea hot spot when magma erupts through the crust and reachesthe surface.

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element

Back 7

a substance that cannot bebroken down into other substances.

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compound

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a substancemade of two or more elements that have been chemically combined.

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physical properties

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any characteristicof a substance that can be observed or measured withoutchanging the composition of the substance.

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chemical properties

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any propertythat produces a change in the composition of matter.

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viscosity

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is the resistance of a liquid to flowing.

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silica

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made up of particles of the elements oxygenand silicon. Silica is one of the most abundant materialsin Earth’s crust.The amount of silica in magma helps to determineits viscosity. The more silica magma contains,the higher its viscosity.

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pahoehoe

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is fast-moving, hot lava that has low viscosity.

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aa

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Lava that is cooler and slower-moving

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magma chamber

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Beneath a volcano, magma collects in apocket

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pipe

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The magma moves upwardthrough a, a long tube in the ground that connects themagma chamber to Earth’s surface.

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vent

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Molten rock and gas leave the volcano through an opening

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lava flow

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the area covered bylava as it pours out of a vent.

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crater

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a bowl-shaped areathat may form at the top of a volcano around the central vent.

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pyroclastic flow

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occurs when an explosive eruption hurls out a mixture of hotgases, ash, cinders, and bombs.

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dormant

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when a volcano is sleeping and can erupt again

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extinct

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when a volcano is dead and will never erupt

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shield volcano

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Such lava flows gradually build a wide, gently slopingmountain

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cinder cone

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These materialsbuild up around the vent in a steep, cone-shaped hill or smallmountain

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Composite volcanoes

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tall, cone shapedmountains in which layers of lava alternate with layersof ash.

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caldera

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huge hole left by the collapse of a volcanicmountain.

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volcanic neck

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forms when magma hardensin a volcano’s pipe.

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dike

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Magma that forces itself across rock layershardens .

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sill

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magma squeezes between horizontal layers of rock, itforms

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batholith

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a massof rock formed when a large body of magma cools inside thecrust.

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geothermal activity

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magma a few kilometers beneath Earth’s surface heats undergroundwater.

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geyser

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a fountain of water and steam that erupts from theground.

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explosive eruption

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A volcano erupts explosively if its magma is high in silica. High-silica magma has high viscosity,making it thick and sticky. The high-viscosity magma does notalways flow out of the crater. Instead, it builds up in the volcano’spipe, plugging it like a cork in a bottle. The erupting gases and steam push the magma out of the volcano with incredible force

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quite eruption

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A volcano erupts quietly if its magma is low in silica. Low-silica magma has low viscosity and flows easily. Quiet eruptions can produce both pahoehoe and aa.