ENVS 2250 Chapter : Unit 2 Notes.docx
2 Feb 2013
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Document Summary
The crust of the earth is divided into 8 major plates and several smaller ones. In some cases, a plate carries a continent on its back. Plates move about 2-3 cm per year at the mid-atlantic ridge to a max of about. 17 cm per year along the east pacific rise. Temperature gradients in the upper mantle cause convection cells and drags the overlying crust around with it. Slab pull older parts of oceanic crust sink down into the mantle when plates collide because they are colder then the warm mantle material underneath them. Ridge push as hot magma rises to the surface and forms new crust, it pushes the rest of the plate out of its way (far less significant than a slab pull in moving plates around) The life cycle of an ocean basin from its beginnings as a continental rift to its final death throes during a continent to continent collision.
