Chapter 9: Volcanoes
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Created by:
jacobbigham on January 16, 2012
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28 terms
Terms | Definitions |
|---|---|
 a'a' | A lava flow with a rubbly surface. |
| active volcano | A volcano that has erupted within the past few centuries and will likely erupt again. |
| aerosols | Tiny solid particles or liquid droplets that remain suspended in the atmosphere for a long time. |
| caldera | A large circular depression with steep walls and a fairly flat floor, formed after an eruption as the center of the volcano collapses into the drained magma chamber below. |
| cinder cone | A subaerial volcano consisting of a cone-shaped pile of tephra whose slope approaches the angle of repose for tephra. |
| columnar jointing | A type of fracturing that yields roughly hexagonal columns of basalt; columnar joints form when a dike, sill, or lava flow cools. |
| crater | (1) A circular depression at the top of a volcanic mound; (2) a depression formed by the impact of a meteorite. |
| dormant volcano | A volcano that has not erupted for hundreds to thousands of years but does have the potential to erupt again in the future. |
| effusive eruption | An eruption that yields mostly lava, not ash. |
| explosive eruptions | Violent volcanic eruptions that produce clouds and avalanches of pyroclastic debris. |
| extinct volcano | A volcano that was active in the past but has now shut off entirely and will not erupt in the future. |
| fissure | A conduit in a magma chamber in the shape of a long crack through which magma rises and erupts at the surface. |
| ignimbrite | Rock formed when deposits of pyroclactic flows solidify. |
| lahar | A thick slurry formed when volcanic ash and debris mix with water, either in rivers or from rain or melting snow and ice on the flank of a volcano. |
| lapilli | Marble-to-plum-sized fragments of pyroclastic debris. |
| lava dome | A dome-like mass of rhyolitic lava that accumulates above the eruption vent. |
| lava flow | Sheets or mounds of lava that flow onto the ground surface or sea floor in molten form and then solidify. |
| lava tube | The empty space left when a lava tunnel drains; this happens when the surface of a lava flow solidifies while the inner part of the flow continues to stream downslope. |
| mare | The broad darker areas on the Moon's surface, which consist of flood basalts that erupted over 3 billion years ago and spread out across the Moon's lowlands. |
| pahoehoe | A lava flow with a surface texture of smooth, glassy, rope-like ridges. |
| phreatomagmatic eruption | An explosive eruption that occurs when water enters the magma chamber and turns into steam. |
| pyroclastic flow | A fast-moving avalanche that occurs when hot volcanic ash and debris mix with air and flow down the side of a volcano. |
| recurrence interval | The average time between successive geologic events. |
| shield volcano | A subaerial volcano with a broad, gentle dome, formed either from low-viscosity basaltic lava or from large pyroclastic sheets. |
| stratovolcano | A large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra. |
| tephra | Unconsolidated accumulations of pyroclastic grains. |
| volcanic ash | Tiny glass shards formed when a fine spray of exploded lava freezes instantly upon contact with the atmosphere. |
| volcanic-danger-assessment map | A map delineating areas that lie in the path of potential lava flows, lahars, debris flows, or pyroclastic flows of an active volcano. |
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