Igneous Rocks a Intrusive magma crystallizes deep in the crust Coarse grained

Igneous rocks a intrusive magma crystallizes deep in

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Igneous Rocksa)Intrusive- magma crystallizes deep in the crust. Coarse grained, interlocking crystals. b)Extrusive- rapidly cooled magma at earth’s surface. Fine-grained, interlocking crystals. Common minerals. Silicatesmainly and few oxides (Table 3.5) Sedimentary RocksFormed from sediments- particles formed as preexisting rocks undergo weathering (breakdown) at/near earth’s surface. (Fig. 3.24) Sediments are soft, altered by lithification into hard sedimentary rock.Involves1.Compaction- grains squeezed together by overlying material 2.Cementation- minerals precipitate binding grains together. Two Types of Sediments
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a)Clastic- physically broken/altered particles from preexisting rock. Laid down by running water/ice/wind. Minerals – all silicates. b)(Bio) chemical- new chemical substances (made from some of preexisting rocks components dissolved during weathering precipitated from sea water. Minerals- Carbonates/Sulfates/Chlorides(Table 3.5) Sediments and sedimentary rocks show bedding- parallel layers as particles settle. Since these rocks form by surface processes, they dominate at/near earth’s surface (~75%). Igneous rocks dominate in the earth’s crust as a whole (~95%) Metamorphic RocksFormed by subjecting preexisting (IG/SY/MC) rocks to high temperature and pressure deep within the earth. Rocks remain solid (are not melted) but change mineralogy/texture/chemical composition. Tamp> ~250 degree C but <~800 degree CCommon miners- silicates and carbonates. (table 3.5) for all rocks quartz and feldspar most common/important. Subdivisions. 1.regional metamorphism- large regions affected by high. Temp and pr. For long periods of time. Often associated with regions where plates collide such rocks often show texture called foliation- wavy/flat planes produced by rock deformation. 2.contact metamorphism- small volumes of rock affected, such as near igneous intrusions. Where we see rocks. Mostly at outcrops – where underlying (bed) rock is exposed. Sea cliffs/mountains/canyons etc. Some of out knowledge comes from rocks recovered by drilling into continents and ocean bottom. Rock Cycle- results from plate tectonics and climate. Change igneous-sedimentary-metamorphic into each other (Fig. 3.26) Process may involve one of more steps, and can take millions of years to complete.
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January 31, 2007Written notesFebruary 2, 2007In going from Felsic to ultramafic1.Si02 content decreases 2.(Mg+Fe) content increases3.Melting point rises4.Viscosity decreases Table 4.2Viscosity measures liquid’s resistance to flow. High viscosity- “clumpy” like tarLow viscosity- runny like waterViscosity increases with a)Decreasing temperature of magma (cf. engine oil.) b)“Felsic content” of magma. Derivation of magma- melting of rocks, Melting of Rocks Aided by:1.Raising the temperature 2.Addition of water to rocks 3.Raising the pressure hinders melting (Table 4.3) oGenerally when rocks melt, on a small fraction melts-partialmelting (some minerals/fractions melts) oFelsic minerals melt more readily (at lower temps.) than mafic ones.
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