EPSC 201 Lecture 2: earthquakes
29 Nov 2017
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Document Summary
Display variety of sizes and shapes - change size/shape throughout history. Rifting has progressed to mid ocean ridge formation. Forms a long, thin ocean basin with yound oceanic crust. New sea floor added at mid ocean ridge. Linear increase in age with distance from central ridge. Edge of ocean basin - -oldest, ridge proximal = youngest. New sea floor created only axis of the ridge. Sea floor spreading opens the axis rift valley. Pillow basalt - magma quenched at the sea floor. Water enteering fractured rock is heated by magma. Hot water dissolves minerals and cycles back out of rock. When water reaches the sea - minerals precipitate quickly. Continental crust cannot be subducted - too buoyant. Plate edge bends down and slips into mantle then leading edge sinks downward like an anchor rope. Descending plate partieally melts at 150 km depth. Forms between an island arc and a continent. Offshore subduction traps a piece of oceanic crust.
