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Magma

Molten rock, underground.

Volcano

A weak spot in the crust where magma can escape.

Lava

Molten rock, above ground

Ring of Fire

A major volcanic belt, formed by the many volcanoes that rim the pacific ocean.

Pahoehoe

Fast moving, hot lava, low viscosity. Looks like a solid mass of rope-like coils.

Aa

Cooler, slower-moving lava, high viscosity. Rough, jagged surface.

Island Arc

A string of islands formed by the volcanoes along a deep-ocean trench.

Hot Spot

Volcano where magma from the mantle melts through the crust.

Viscosity

A liquids resistance to flowing.

Silica

A material found in magma. Causes explosive eruptions.

Magma Chamber

The pocket beneath a volcano where magma collects.

Pipe

A long tube through which magma moves from the magma chamber to the earth's surface.

Vent

Same as pipe.

Lava Flow

The area covered by lava as it pours out of a volcano's vent.

Crater

The top of a volcano.

Pyroclastic Flow

Expulsion of ash, cinders, bombs, gasses

Dormant

A volcano that is not active, but isn't dead yet

Extinct

The volcano will never erupt again supposedly

Shield Volcano

Wide, gently sloping, made of lava layers, quiet eruptions

Composite Volcano

Steep, alternates between quiet and explosive eruptions, made of lava and pyroclastic flow

Cinder Cone Volcano

Steep, explosive eruptions, made out of pyroclastic flow

Caldera

The large hole at the top of a volcano formed when the roof the magma chamber collapses.

Volcanic Neck

A deposit of hardened magma in a volcano's pipe.

Dike

Vertical pathways of magma

Sill

Horizontal pathways of magma

Batholith

A mass of rock formed when a large body of magma cools inside the crust.

Geyser

A fountain of water and steam that builds up pressure underground and erupts at regular intervals.

Cinders

Small rocks

Bombs

Huge rocks

Hot Springs

When there is a crack in the crust underwater, so that the water is heated

Mud Pots

Boiling pot of mud

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