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Transcript
Structure of the Earth and the Rock Cycle Lithosphere composed of minerals Definition of “Mineral” ? Silicate minerals 92% of crust silicon and oxygen A rock is a natural solid substance made up of minerals rocks classified by origin : 3 types Types of Rocks 1. IGNEOUS molten rock that has cooled and solidified molten rock is magma or lava a) INTRUSIVE cools below surface; big crystals; coarse b) EXTRUSIVE cools at surface; fine Fine-textured extrusive Coarse-textured intrusive Glassy; rapid cooling Basalt with vesicles extrusive intrusive Mafic and felsic igneous rock Felsic: mostly felsic minerals Mafic: mostly mafic minerals High in feldspar and silicate minerals Lighter Less dense High in magnesium and iron Darker Denser Ultramafic: all mafic minerals 2. SEDIMENTARY made up of sediments that have been compacted and cemented. sediments: all solid particles transported by water, ice, wind, gravity mud, sand, shells, debris, dust, rock fragments mudstone, sandstone, limestone, conglomerate, shale accumulate in strata (layers) mudstone sandstone limestone conglomerate strata 3. METAMORPHIC altered from original rock by heat, pressure or chemical activity began as igneous, sedimentary, or metamorphic rock shale --> slate slate --> schist granite --> gneiss limestone --> marble gneiss schist slate Rock Cycle Structure of Earth Core Mantle Crust Core Inner 5150 – 6370 km (below surface) Solid iron 5400 – 9000 degrees F Outer 2900 – 5150 km Molten iron Core Mantle Crust Lower mantle Upper Uppermost Lower mantle Upper mantle very dense; iron and magnesium 670 – 2900 km rigid at lower end “plastic” toward crust: asthenosphere 250 -670 km Uppermost mantle Rigid “Moho” to 70 km “Moho” Mohorovičić discontinuity Boundary between crust and mantle Change in seismic waves here Core Mantle Crust Crust continental : 25 miles thick oceanic: 5-6 miles thick Lower mafic; upper felsic (granite) Less dense Mafic (basalt) More dense Lithosphere = uppermost mantle and crust Rigid ultramafic Lithosphere is divided into large plates rigid plates “float” on the plastic asthenosphere, just deep enough to support their own weight: Isostasy Isostatic adjustment of crust: add weight (sediment, glacial ice): crust will sink remove weight (erosion, glacial ice melts): crust will rebound ice Duluth Crust sank Northeast “drowned “ St. Louis River