EARTH 222 Lecture 3: Plate Tectonics
11 Jun 2016
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Document Summary
Structure of the earth lithosphere: rigid outer layer, crust + uppermost mantle asthenosphere: deformable layer of upper mantle lower mantle: denser and less deformable outer core: dense, viscous liquid inner core: solid, very dense. Continents and ocean basins differ in composition, elevation and physiographic features granite. Continental crust is mainly composed of granite, a light colored, lower density (2. 7 gm/cm3) igneous rock rich in aluminum, silicon, and oxygen. Oceanic crust is composed of basalt, a dark colored, higherdensity (2. 9 gm/cm3) volcanic rock rich in silicon, oxygen, and magnesium. Continental crust is thick (ave 40 km), has low density, and rises high above the supporting mantle rocks. Oceanic crust is thin (ave 7 km), has greater density, and does not rise as high above the mantle. Alfred wegener and the theory of continental drift: in 1912 wegener proposed that continents are not stationary, but drift around.
