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Volcano definitions

Source : Volcanoes (A Firefly Guide) isbn 1-55297-683-1

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Ash
Measurement of particle size applied to the finest pyroclastic material, fragments less than 0.08 inches (2mm) in diameter, blasted into the air by volcanic explosions.

Basalt
Volcanic rock poor in silica but rich in magnesium, iron, and calcium. The most common volcanic rock.Base surge
Turbulent low-density cloud of gas with suspended solid debris that expands radially outward from the base of an eruption column. Comparable to the ring that forms at the base of the cloud formed by a nuclear explosion.

Bomb
Fragment of magma varying in diameter from a few inches to several feet ejected into the air during a volcanic explosion (see tephra)

CalderaLarge depression produced following an eruption by the collapse of the roof of a magma chamber. Usually circular or horseshoe shaped when viewed from above.

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Cinder cone
Cone build up by the accumulation of loose bits of magma (scoria) that fall around a vent or crater after being expelled into the air during moderately explosive activity. If still sufficiently hot theymeld when they fall to the ground.

Compound volcano

Volcanic structure composed of two or more vents or lava domes or stratovolcanoes, often formed at different times.

Conduit (volcanic)
Passageway, more or less cylindrical in shape through which magma rises from the magma chamber to the surface during volcanic activity.

Crater (volcanic)
Bowl shaped depression or hollow,usually with steep sides at the summit of a volcano or on its flanks which is produced by volcanic activity.

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Dike
Tabular body of intrusive magma that cuts across layers of a volcanic structure. Volcano vocabulary Top

Eruption column
Vertical cloud of gas and pyroclastic fragments that forms during explosive eruptions and can reach stratospheric heights.

Falldeposit
Layer of fragmentary volcanic material created by fall from an eruption column or during an explosive eruption. Volcano vocabulary Top
Fissure volcano

Structure composed of the accumulation of volcanic material on the sides of an eruptive fissure, usually associated with a ridge or rift situation.

Fumarole chimney
Vertical structure with a vent through which volcanic gases aredischarged.

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Geyser
Intermittent vertical jet of water produced by the heating of underground water by geothermal activity. Volcano vocabulary Top

Hornito
Small cone or mound produced by the accumulation of spatter ejected by a vent. (see spatter cone)

Hot spot
Area on the planet where material from the mantle rises through a plume to reach a moving plate.Hummocks
Small hills that rise above deposits from a volcanic avalanche. Volcano vocabulary Top

Hyaloclastite
Fragmentary material of glassy composition produced by the rapid cooling of magma in contact with water.

Ignimbrite
Particular type of pyroclastic flow deposit containing glassy lenticular structures called flames. Ignimbrites can cover thousands of square miles of area.volcano vocabulary l-m
Lahar

Indonesian word for a volcanic mud flow usually formed when an eruption melts part of a glacier on a volcano. These flows involve large quantities of volcanic material and can move at high speeds.

Lapilli
Latin word meaning "small stone". Small fragments of lava (between 0.08 inches (2mm) and 2.5 inches (6.4 cm) across) shot into the air during eruptionswhen still molten.

Lava
Magma that has reached the surface of the Earth. Volcano vocabulary Top

Lava Dome

Accumulation of lava in the shape of a steep-sided dome over an eruptive vent.

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Lava lake
Lake of molten lava inside a crater tens or hundreds of feet in diameter. Such lakes can remain active for many years.

Lava Plateau
A wide, flat surface...