 | Term | Definition |
| |
andesitic composition [ intermediate composition ] |
a compositional group of igneous rocks, in which the rock contains at least 25% dark silicate minerals; the other dominant mineral is plagioclase feldspar |
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basaltic composition [ mafic ] |
a compositional group of igneous rocks in which the rock contains substantial dark silicate minerals and calcium-rich plagioclase feldspar |
| |
bowens reaction series |
a concept proposed by N.L. Bowen that illustrates the relationships between magma and the minerals crystalizing from it during the formation of igneous rocks |
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chemical sedimentary rock |
sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means |
| |
chemical weathering |
alters the internal structure of minerals by removing and/or adding elements |
| |
coarse grained texture |
an igneous rock texture in which the crystals are roughly equal in size and large enough so that individual minerals can be identified with the unaided eye |
| |
contact metamorphism [ thermal metamorphism ] |
changes in rock caused by the head from a nearby magma body |
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crystallization |
the formation and growth of a crystalline solid from a liquid or gas |
| |
crystal settling |
during the crystallization of magma, the earlier formed minerals are denser than the liquid portion and settle to the bottom of the magma chamber |
| |
detrital sedimentary rock |
rock formed from the accumulation of material that originated and was transported in the form of solid particles derived from both mechanical and chemical weathering |
| |
evaporite deposite |
a sedimentary rock formed of material deposited from solution by evaporation of the water |
| |
extrusive (volcanic) |
igneous activity that occurs outside the crust |
| |
felsic [ granic composition ] |
a compositional group of igneous rocks in which the rock is composed of almost entirely of light-colored silicates |
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fine-grained texture |
a texture of igneous rocks in which the crystals are too small for individual minerals to be distinguished with the unaided eye |
| |
foliated texture |
a texture of metamorphic rocks that gives the rock a layered apperance |
| |
fossil |
the traces or remains of prehistoric life, are perhaps the most important inclusions found in some sedimentary rock |
| |
glassy texture |
a term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals |
| |
igneous rock |
a rock formed by the crystallization of molten magma |
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intrusive (plutonic) |
igneous rock that formed below the earths surface |
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lava |
magma that reaches earths surface |
| |
lithification |
the process, generally cementation and/or compaction, of converting sediments to solid rock |
| |
magma |
a body of molten rock found at depth, including any dissolved gases and crystals |
| |
magmatic differentiation |
the formation of one or more secondary magmas from a single parent magma |
| |
mechanical weathering |
when a rock is broken into smaller and smaller pieces; each piece retains the characteristics of the original material |
| |
metamorphic rock |
rocks formed by the alteration of preexisting rock deep within earth ( but still in the solid state ) by heat, pressure, and/or chemically active fluids |
| |
metamorphism |
the changes in mineral composition and texture of a rock subjected to high temperatures and presures within earth |
| |
nonfoliated texture |
metamorphic rocks that do not exhibit foliation |
| |
porphyritic texture |
an igneous texture consisting of large crystals embedded in a matrix of much smaller crystals |
| |
regional metamorphism |
metamorphism associated with the large-scale mountain-building processes |
| |
rock cycle |
a model that illustrates the orgin of the three basic rock types and the interrelatedness of earth materials and processes |
| |
sediment |
unconsolidated particles created by the weathering and erosion of rock, by chemical precipitation from solution in water, or from the secretions of organisms and transported water, wind, or glaciers |
| |
sedimentary rock |
rock formed from the weathered products of preexisting rocks that have been transported, deposited, and lithified |
| |
strata |
parallel layers of sedimentary rock |
| |
texture |
the size, shape, and distribution of the particles that collectively constitute a rock |
| |
ultramafic composition |
a composition group of igneous rocks in which the rock contains mostly olivine and pyroxene |
| |
weathering |
the disintegration and decomposition of rock at or near the surface of earth |
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