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Definition
A basaltic lava that has a rough, blocky surface. |
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Term
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Definition
| The petrographic boundary between basalts and undesites. It runs roughly around the Pacific basin margin. It also marks the boundary between continental (explosive) and oceanic (Hawaiian-type) volcanoes in the Pacific Ocean |
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Definition
| A “rain” of airborne volcanic ash. |
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Definition
| Large crater caused by explosive eruption and/or subsidence of the cone into the magma chamber, usually more than 1.5 km (1 mi) in diameter. |
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Definition
| Descriptive of magma or rock with abundant light-colored minerals and a high silica content. The term is derived from feldspar + silica +c. |
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Definition
| The process whereby granular solids (corn, wheat, volcanic ash and lapilli) under high gas pressures become fluid-like and flow downslope or can be pumped. |
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Definition
| A debris flow or mudflow consisting of volcanic material |
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Term
| lava dome (volcanic dome) |
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Definition
| Steep-sided protrusion of viscous, glassy lava, sometimes within the crater of a larger volcano (e.g., Mount St. Helens) and sometimes free-standing (e.g., Mono Craters). |
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Definition
| A broad elevated tableland, thousands of square kilometers in extent, underlain by a thick sequence of lava flows. |
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Definition
| A low-relief, broad volcanic crater formed by multiple shallow explosive eruptions. Maars commonly contain a lake and are surrounded by a low rampart or ring of ejected material. They typically form from phreatic eruptins. |
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Term
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Definition
| Descriptive of a magma or rock rich in iron and magnesium. The mnemonic term is derived from magnesium + ferric + ic. |
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Term
| nuée ardente (pyroclastic flow) |
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Definition
| ): French for “glowing cloud,” it is a highly heated, almost incandescent cloud of volcanic gases and pyroclastic material that travels with great velocity down the slopes of a volcano. Produced by the explosive disintegration of viscous lava in a vent. |
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Term
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Definition
| The release of gases and water vapor from molten rocks, leading to the formation of the earth’s atmosphere and oceans. |
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Term
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Definition
| Basaltic lava typified by smooth, billowy, or ropy surfaces. |
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Term
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Definition
| Volcanic eruption, mostly steam, caused by the interaction of hot magma with underground water, lakes, or seawater. Where significant amounts of new (magmatic) material are ejected in addition to steam, the eruptions are described as phreatomagmatic |
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Term
| Plinian eruption (volcanology) |
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Definition
| An explosive eruption in which a steady, turbulent, nearly vertical column of ash and steam is released from a vent at high velocity. |
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Term
| pyroclastic flow (“fire broken”) |
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Definition
| Descriptive of the fragmental material, ash, cinders, blocks, and bombs ejected from a volcano. (See also tephra.) |
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Term
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Definition
| The largest type of volcanoes, composed of piles of lava in a convex-upward slope. Found mainly in Hawaii and Iceland. |
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Term
| stratovolcano (composite cone) |
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Definition
| A large volcano that is shaped slightly concave upward and is composed of layers of ash and lava. |
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Term
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Definition
| A collective term for all pyroclastic material ejected from a volcano |
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Term
| Volcanic Explosivity Index (VEI) |
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Definition
| a scale for rating volcanic eruptions according to the volume of the ejecta, the height to which the ejecta rise, and the duration of the eruption. |
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Term
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Definition
| A glassy pyroclastic rock that has been made hard by the welding together of its particles under the action of retained heat. |
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