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aa

a dry form of lava resembling clinkers

caldera

large, circular-shaped opening formed when the top of a volcano collapses

cinder cone

a steep, cone-shaped hill or small mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening.

crater

a bowl-shaped opening at the top of a volcano

felsic lava

silica-rich lava

fissure

an opening, a groove, a split

hot spot

a volcanically active area of Earth's surface far from a tectonic plate boundary

lapilli

Tephra particles between 2mm and 64mm in diameter

lava

magma that reaches Earth's surface

mafic lava

dark-colored lava rich in magnesium and iron

magama

liquid rock material that has not reahed the earth's surface

pahoehoe

Solidified basaltic lava flow on land that has formed with smooth, ropelike surfaces

pillow lava

lava that flows out of fissures on the ocean floor and cools rapidly in rounded shapes

pyroclastic material

The volcanic rock ejected during an eruption, including ash, bombs, and blocks

shield cone

volcanic mountain with a broad base and gently sloping sides

stratovolcano

A composite volcanic cone built of interlayered lava flows and pyroclastic materials

tephra

Rock fragments, classified by size, that are thrown into the air during a volcanic eruption and fall to the ground.

vent

a hole for the escape of gas or air

volcanic ash

rock particals more that 0.25mm but less than 5mm across that are blown into the air by a volcanic eruption

volcanic block

The largest tephra, formed from solid rock blasted from a fissure

volcanic bomb

large, spindle-shaped clot of lava thrown out of a volcano

volcanic dust

volcanic ash that is less than 0.25 mm in diameter

volcanism

any activity that includes the movement of magma toward or onto Earth's surface

volcano

a cone-shaped hill or mountain around this opening, built up of the material that is forced out

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