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Download Plate Tectonics – study of crustal movement, and the
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Plate Tectonics – study of crustal movement, and the results of that movement. Lithosphere – outer layer of the earth (60 – 150 miles deep over continents, 3 – 50 miles deep over oceans), consisting of the crust and outer mantle. Exhibits rigid behavior. Asthenosphere – partially melted rock that is soft, and can flow, not rigid. The lithosphere floats on the asthenosphere like an iceberg floats on water. The thicker the crust, the higher the elevation of the crust. Continental Crust consists predominantly of feldspar and quartz, with density of 3.0 g/cm3. Averages 20 miles thick Oceanic Crust consists mainly of FeMags, with a density of 3.2 g/cm3. Averages 3 miles thick. Lower density of continental crust causes it to float higher on the asthenosphere than oceanic crust. Through nuclear reactions occurring in the core, heat is generated, and causes the asthenosphere to convect. This causes the lithosphere to move like it were on a conveyer belt. The Earths crust is composed of 7 large, rigid plates, and many smaller plates. Between each plate is 1 of 6 types of boundaries: Diverging Plate Boundaries: 1) Diverging Ocean : Ocean mid-Atlantic is a good example. As plates move away from the mid-ocean ridge, fractures are filled with molten rock from the mantle. Cooling then creates brand new crust. The further you move away from the ridge, the older the ocean crust. 2) Diverging Continent : Continent Example: Africa and Saudi Arabia This is what started the separation of Europe from North America. Ocean crust is more dense than continental crust, therefore subducts (goes under) continental crust, Converging Plate Boundaries: and is then melted back into the mantle, to be recycled as new ocean crust later in time. Creates 3) Continental : Oceanic mountain ranges above subduction zone. Example: Cascades (Washington to California) and Andes (South America) 4) Converging Ocean : Ocean - Creates a chain of islands, (called an island arc) as one ocean plate subducts below the other. Japan is a chain of islands formed by subducting ocean plates. 5) Converging Continental : Continental Examples: India and Asia collision forms the Himalaya Mountains 6) Transform Boundary, where 2 plates don’t collide, but rather, slip past each other. A stationary “hot spot” of upwelling magma rises under the Pacific Ocean, and as the Pacific crust passes over the hot spot, volcanoes form. Features along plate boundaries: 1) Faults and Earthquakes 2) Volcanoes 3) Mountains 4) Trenches 5) Ridges