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39 Cards in this Set
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intrusive igneous rock
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a rock that has forced its way into surrounding rock
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country rock
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rock surrounding intrusive igneous rocks.
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extrusive igneous rock
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rocks that form when lava or other material erupts from volcanoes. rapid cooling at earth's surface produces the finely grained texture or glassy appearance.
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pyroclasts
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volcanic rock fragment ejected into the air during an eruption.
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volcanic ash
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extremely small fragments, usually of glass, that form when escaping gases force a fine spray of magma from a volcano.
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tuff
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any volcanic rock lithified from pyroclasts.
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pumice
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frothy mass of volcanic glass with a great number of vesicles.
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obsidian
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glassy volcanic rock that contains only tiny vesicles and so is solid and dense.
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porphyry
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an igneous rock that has a mixed texture in which large crystals "float" in a predominantly fine crystalline matrix.
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granite
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a felsic, coarse-grained, intrusive igneous rock composed of quartz, orthoclase feldspar, sodium-rich plagioclase feldspar, and micas. Intrusive equivalent of rhyolite.
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rhyolite
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extrusive equivalent of granite. more finely grained than granite, though.
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intermediate igneous rocks
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midway between felsic and mafic. neither rich in silica nor poor in it.
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granodiorite
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light-colored felsic rock that looks something like granite.
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diorite
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contains less silica and is dominated by plagioclase feldspar, with little or no quartz.
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dacite
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volcanic equivalent of granodiorite
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andesite
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volcanic equivalent of diorite. derive name from andes mountains
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gabbro
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coarsely grained, dark grey intrusive igneous rock with even less silica than is found in intermediate igneous rocks.
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basalt
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dark gray to black and is the fine grained extrusive equivalent of gabbro. most abundant igneous rock of the crust, underlies virtually the entire seafloor.
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periodite
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dark greenish gray rock made up primarily of olivine with smaller amounts of pyroxene.
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viscosity
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the measure of a liquid's resistance to flow
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partial melting
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incomplete melting of a rock that occurs because the minerals that compose it melt at different temperatures.
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decompression melting
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melting that occurs when mantle material rises to an area of lower pressure at a mid-ocean ridge. as the mantle material rises and the pressure decreases below a critical point, solid rocks melt spontaneously, without the introduction of any additional heat.
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magma chambers
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magma-filled cavities in the lithosphere that form as rising drops of melted rock push aside surrounding solid rock.
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magmatic differentiation
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a process by which rocks of varying composition can arise from a uniform parent magma
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fractional crystallization
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process by which the crystals formed in a cooling magma are segregated from the remaining liquid.
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plutons
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large igneous bodies formed at depth in earth's crust.
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batholith
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largest plutons, are great irregular masses of coarse-grained igneous rock that by definition cover at lease 100 square kilometers.
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stocks
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an irregular mass of coarse-grained igneous rock less than 100 square km in area.
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discordant intrusions
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cut across the layers of the country rock that they intrude
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sill
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sheetlike body formed by the injection of magma between parallel layers of preexisting bedding rock
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concordant intrusion
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boundaries lie parallel to layers, whether or not the layers are horizontal.
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dikes
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major route of magma transport in the crust. cut across layers of bedding in country rock and so are discordant
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veins
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deposits of minerals found within a rock fracture that are foreign to the host rock.
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pegmatites
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veins of extremely coarse-grained granite cutting across a much finer grained country rock.
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hydrothermal veins
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vein filled with minerals that contain large amounts of chemically bound water and are known to crystallize from hot-water solutions.
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ophiolite suites
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consist of deep-sea sediments, submarine basaltic lavas, and mafic igneous intrusions.
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mafic rock
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a dark colored igneous rock containing minerals such as pyroxenes and olivines rich in iron and magnesium and relatively poor in silica.
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felsic rock
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light colored igneous rock that is poor in iron and magnesium and rich in high silica minerals such as quartz, orthoclase feldspar, and plagioclase feldspar.
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ultramafic rock
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igneous rock consisting primarily of mafic minerals and containing less than 10 percent feldspar.
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