MEA 200 Lecture Notes - Lecture 1: Continental Crust, Oceanic Crust, Asthenosphere
30 Mar 2017
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Document Summary
Earth formed from the accumulation of dust and gas, and collisions of smaller planetary bodies. Driven by gravity, earth"s dense metallic core formed as iron sank to the center of the planet. Less dense rocks slowly cooled to form outer layers of earth"s crust and mantle. Earth interior is still losing heat from the formation process but most of the heat is generated by radioactive decay of elements. This heat flows through earth"s interior largely by convection. Convection in the mantle drives earth"s internal motion : Lithosphere = crust + uppermost mantle = tectonic plate. Asthenosphere = layer in upper mantle (hot and weak; mostly solid) Lithosphere tectonic plates that float on ductile asthenosphere. Large-scale geologic features occur at plate boundaries. The plates are composed of continental crust, oceanic crust, or both. Tectonic plates - the crust (where we live) Because of this the less dense continents ride on the denser oceanic plates.
