Active volcano

A volcano that is erupting or has erupted within historical time and is considered likely to do so in the future.

Ash

Fine particles of rock dust blown from an explosion vent.

Ashfall

Volcanic ash that has fallen through the air from an eruption cloud.

Vent

A vent is an opening at the Earth's surface of a volcanic conduit.

Composite Volcano

A steep volcanic cone built by both lava flows and pyroclastic eruptions.

Compound Volcano

A volcano that consists of a complex of two or more vents, or a volcano that has an associated volcanic dome, either in its crater or on its flanks. Examples are Vesuvius and Mont Pelee.

Conduit

A passage (pipe) followed by magma in a volcano.

Crater

A steep-sided, usually circular depression formed by either explosion or collapse at a volcanic vent.

Dormant volcano

A volcano which is presently inactive but which may erupt again.

Eruption

The process by which solid, liquid, and gaseous materials are ejected into the earth's atmosphere and onto the earth's surface by volcanic activity.

Fault

A crack or fracture in the earth's surface.

Fissures

Elongated fractures or cracks on the slopes of a volcano.

Geysers

Springs that throw boiling water high in the air. They are caused by volcanic heat warming trapped ground water.

Hot Spot

A volcanic center, 60 to 120 miles across and persistent for at least a few tens of million of years, that is thought to be the surface expression of a persistent rising plume of hot mantle material.

Lava

Magma which has reached the surface through a volcanic eruption. Streams of liquid rock that flow from a crater or fissure.

Lava Flow

An outpouring of lava onto the land surface from a vent or fissure.

Magma

Molten rock beneath the surface of the earth.

Magma chamber (Magna reservoir)

The subterranean cavity containing the gas-rich liquid magma which feeds a volcano.

Mantle

The zone of the earth below the crust and above the core.

Ring of Fire

The regions of mountain-building earthquakes and volcanoes which surround the Pacific Ocean.

Stratovolcano

A volcano composed of both lava flows and pyroclastic material.

Vent

The opening at the earth's surface through which volcanic materials issue forth.

Volcanic eruption

When hot rocks and lava burst from a volcano.

Volcano

A vent in the surface of the Earth through which magma and associated gases and ash erupt; also, the form or structure, usually conical, that is produced by the ejected material.

Vulcan

Roman god of fire and the forge, after whom volcanoes are named.