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46 Cards in this Set
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Andesite |
An intermediate igneous rock with a composition between that of dacite and that of basalt |
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Basalt |
A dark, fine-grained, mafic igneous rock composed largely of plagioclase feldspar and pyroxene |
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Batholith |
A great irregular mass of intrusive igneous rock that covers at least 100 km2 that largest of pluton |
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Bomb |
A pyroclast 2mm or larger, usually consists of blobs of lava that cools in flight and becomes rounded or a chunk torn loose from previously solidified volcanic rock |
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Breccia |
A volcanic rock formed by the lithification of large pyroclasts |
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Caldera |
A large, steep-walled, basin-shaped depression formed by a violent volcanic eruption in which large volumes of magma are discharged rapidly form a large magma chamber, causing the overlying volcanic structure to collapse catastrophically through the roof of the emptied chamber |
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Country Rock |
The rock surrounding an igneous intrusion |
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Crater |
A bowl- shaped it found at summit of most volcanoes centered on the vent, or caused by meteorite |
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Dacite |
A light-colored, fine-grained, intermediate igneous rock with a composition between that of rhyolite and andesite |
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Decompression Melting |
The spontaneous melting of rising mantle material as it reaches a level where pressure decreases below a critical point, without the introduction of any additional heat |
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Dike |
A sheetlike discordant igneous intrusion that cuts across layers of bedded country rock |
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Diorite |
A coarse-grained intermediate igneous rock with a composition between that of grandiorite and gabbro |
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Felsic Rock |
Light-colored igneous rock that is poor in iron and magnesium and rich in silica minerals such as quartz or orthoclase, feldspar |
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Fluid-Induced Melting |
Melting of rock induced by the presence of water, which lowers its melting point |
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Fractional Cyrstallization |
The process by which the crystals formed in cooling magma are segregated from the remaining liquid rock, usually by settling to the floor of the magma chamber |
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Gabbro |
A dark gray, coarse-grained igneous rock containing an abundance of mafic minerals, proxene |
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Granite |
A felsic, coarse-grained igneous rock composed of quartz, orthoclase feldspar, micas |
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Granodiorite |
A light-colored, coarse-grained intermediate igneous rock that is similar to granite in containing a lot of quartz but is mostly feldspar that is plagioclase |
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Hot Spot |
A region of intense, localized volcanism found far from a plate boundary, hypothesized to be the surface expression of a mantle plume |
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Intermediate Igneous Rock |
An igneous rock midway in composition between mafic and felsic, neither rich in silica nor as poor as mafic |
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Lahar |
A torrential mudflow of wet volcanic debris |
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Lava |
Magma that flows out onto Earth's surface |
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Mafic Rock |
Dark-Colored, igneous rock containing minerals such as pyroxenes and olivines that are rich in iron and magnesium and relatively poor in silica |
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Magma Chamber |
A large pool of magma that forms in the lithosphere as rising magmas melt and push aside surrounding solid rock |
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Magmatic Differentiation |
A process by which rocks of varying composition arise from a uniform parent magma as various minerals are withdrawn from it by fractional crystallization as it cools, changes its compostion |
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Mantle Plume |
A narrow, cynlindrical jet of hot, solid material rising from deep within the mantle, thought to be responsible for intraplate volcanism |
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Obisidian |
A dense, glassy volcanic rock, usually felsic composition |
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Partial Melting |
Incomplete melting of a rock that occurs because the minerals that compose it melt at different temperatures |
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Pegmatite |
A vein of extremely coarse-grained granite, crystallization from a water-rich magma in the late stages of solidification, that cuts across much finer grained country rock and may contain rich concentrations of rare minerals |
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Peridiotite |
A coarse-grained, dark greenish gray, ultramafic igneous rock, intrusive, composed primarily of olivine with smaller amounts of pyroxene and other minerals such as spinel or garnet, the dominant rock in Earths Mantle and the source rock of Basaltic magmas |
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Pluton |
A large igneous intrusion, ranging in size from a cubic kilometer to hundreds of cubic kilometers, formed deep in the crust |
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Porphyry |
An igneous rock of mixed texture in which large crystals " float" in a predominantly fine-grained matrix. |
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Pumice |
A volcanic rock, usually rhyolitic in composition, containing numerous cavities ( vesicles) that remain after trapped gas has escaped from solidifying lava |
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Pyroclast |
A rock fragment ejected into the air by a volcanic eruption |
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Pyroclastic Flow |
A glowing could of ash ash, dust, and gases ejected by a volcanic eruption that rolls downhill at high speeds |
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Rhyolite |
A light brown to gray, fine- grained felsic igneous rock |
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Shield Volcano |
A broad, shield -shaped volcano many tens of kilometers in circumference and more than 2 km high, built by successive flows of basaltic lava from a central vent |
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Sill |
A sheetlike concordant igneous intrusion formed by the injection of magma between parallel layers of bedded country rock |
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Stock |
A pluton less than 100 km2 in area |
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Stratovolcano |
A concave-shaped volcano formed from alternating layers of lava flows and beds of pyroclasts |
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Tuff |
A volcanic rock formed by the lithification of small pyroclasts |
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Ultramafic Rock |
An igneous rock consisting primarily of mafic minerals and containing less than 10 percent feldspar |
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Vein |
A sheetlike deposit of minerals precipitated in fractures or joints in country rock often by hydrothermal solution |
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Viscosity |
A measure of a fluids resistance to flow |
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Volcanic Ash |
Pyroclasts less than 2mm in diameter, usually glass, that form when escaping gases force a fine spray of magma from a volcano |
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Volcano |
A hill or mountain constructed from the accumulation of erupted lava and pyroclasts |