Ch 4 (Volcanoes & Other Igneous Activity) Vocab
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Created by:
naomifelicia on December 15, 2010
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41 terms
Terms | Definitions |
|---|---|
 aa flow | a type of lava flow that has a jagged, blocky surface |
| batholith | a large mass of igneous rock that formed when magma was emplaced at depth, crystallized, and was subsequently exposed by erosion |
| block lavas | lava having a surface of angular blocks associated with material having andesitic and rhyolitic compositions |
| caldera | a large depression typically caused by collapse of the summit area of a volcano following a violent eruption |
| cinder cone | a rather small volcano built primarily of pyroclastics ejected from a single vent |
| columnar joints | a pattern of cracks that forms during cooling of molten rock to generate columns |
| composite cone | a volcano composed of both lava flows and pyroclastic material |
| concordant | a term used to describe intrustive igneous masses that form parallel to the bedding of the surrounding rock |
| conduit | a piplike opening through which magma moves toward Earth's surface; terminates at a surface opening called a vent |
| continental volcanic arc | mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent; examples: Andes & Cascades |
| crater | the depression at the summit of a volcano, or that which is produced by a meteorite impact |
| dike | a tabular-shaped intrustive igneous feature that cuts through the surrounding rock |
| discordant | a term used to describe plutons that cut across existing rock structures, such as bedding planes |
| eruption column | buoyant plumes of hot ash-laden gases that can extend thousands of meters into the atmosphere |
| fissure | a crack in rock along which there is a distinct separation |
| fissure eruption | an eruption in which lava is extruded from narrow fractures or cracks in the crust |
| flood basalt | flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters |
| fumarole | a vent in a volcanic area from which fumes or gases escape |
| hot spot | a proposed concentration of heat in the mantle capable of introducing magma that in turn extrudes onto Earth's surface; the intraplate volcanism that produced the Hawaiian Islands is one example |
| intraplate volcanism | igneous activity that occurs within a tectonic plate away from plate boundaries |
| laccolith | a massive, concordant igneous body intruded between preexisting strata |
| lahar | mudflows on the slopes of volcanoes that result when unstable layers of ash and debris become saturated and flow downslope, usually following stream channels |
| lava dome | a bulbous mass associated with an old-age volcano, produced when thick lava is slowly squeezed from the vent; lava domes may act as plugs to deflect subsequent gaseous eruptions |
| lava tube | tunnel in hardened lava that acts as a horizontal conduit for lava flowing from a volcanic vent; lava tubes allow fluid lavas to advance great distances |
| mantle plume | a mass of hotter-than-normal mantle material that ascends toward the surface, where it may lead to igneous activity; these plumes of solid yet mobile material may originate as deep as the core-mantle boundary |
| nuee ardente | incandescent volcanic debris that is buoyed up by hot gases and moves downslope in an avalanche fashion |
| pahoehoe flow | a lava flow with a smooth-to-ropy surface |
| parasitic cone | a volcanic cone that forms on the flank of a larger volcano |
| pillow lava | basaltic lava that solidifies in an underwater environment and develops a structure that resembles a pile of pillows |
| pipe | a vertical conduit through which magmatic materials have passed |
| pluton | a structure that results from the emplacement and crystallization of magma beneath Earth's surface |
| pyroclastic flow | a highly heated mixture, largely of ash and pumice fragments, traveling down the flanks of a volcano or along the surface of the ground |
| pyroclastic material | the volcanic rock ejected during an eruption; include ash, bombs, and blocks |
| shield volcano | a broad, gently sloping volcano built from fluid basaltic lavas |
| sill | a tabular igneous body that was intruded parallel to the layering of preexisting rock |
| tabular | describing a feature such as an igneous pluton having two dimensions that are much larger than the third |
| viscosity | a measure of a fluid's resistance to flow |
| volcanic island arc | a chain of volcanic islands generally located a few n kilometers from a trench where there is active subduction of one oceanic plate beneath each other |
| volcanic neck | an isolated, steep-sided, erosional remnant consisting of lava that once occupied the vent of a volcano |
| volcano | a mountain formed from lava and/or pyroclastics |
| volatiles | gaseous components of magma dissolved in the melt; will readily vaporized (form a gas) at surface pressures |
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