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Transcript
Earth’s Systems Movement of the Earth’s Crust Earth’s Layers There are three main layers of Earth. The Earth’s outermost layer is the crust. The layer directly beneath the crust is the mantle. The innermost layer is the core. Layer Descriptions The Inner core: Mainly iron, solid, extremely hot, high pressure. The Outer Core:Extremely hot liquid metals, mainly iron and nickel. Mantle:High temperatures only partially melt metal here because of high pressure. Layer Description Asthenosphere: Part of the upper mantle that is partial melted rock. Lithosphere: Upper mantle and lower crust, floats on the asthenosphere, cool and solid. Crust: Thinnest layer of Earth. Mainly granite but under oceans mainly basalt. Earth’s Plates The lithosphere has seven major plates (see map on pg..D8-D9). These plates can flow (plasticity) in the asthenosphere. Heat in the center of the Earth causes currents and hot mantle is pushed up by cooler rock. The rock spreads, cools and sinks again. These plates are constantly moving and changing shape. Plates sometimes split or combine with another plate. Sometimes plates slide under another plate to become mantle rock again. The boundaries where plates meet are usually the sites of earthquakes and volcanoes. Plate Tectonics Plate tectonics is the theory scientist use to explain plate movements. Major plates are named for the continents or oceans they carry. Ocean crust is newer and thinner then that of the continents. See page D8-D9. Changes to the Earth’s Surface Plate movement causes the Earth’s surface to change. They form mountains, cause earthquakes and volcanic eruptions. Meteors, glaciers, wind and water are other factors that can change the Earth’s surface. Summary Earth is composed of core, mantle and crust. The crust makes up the lithosphere where Earth’s land and oceans are found. Plate tectonics explains how the plates move around causing changes to the Earth’s surface. Other changes in the Earth’s surface come from glaciers, wind, water and meteors.