Earth Sciences 1022A/B Lecture Notes - Lecture 12: Subduction, Lithosphere
7 Dec 2015
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Earth sciences 1022a lecture 12 plate tectonics. Paleomagnetism: -magnetic minerals in basalt point to the existing magnetic pole at the time of rock crystallization; basalt is like a fossil compass to find paleo poles. Polar wandering: pole positions for n. america and europe over last 500 my show diverging paths; because poles migrate only slightly, continents must have drifted. Seafloor spreading: seafloor gradually moves from ocean ridges to ocean trenches. Rigid plates: canadian j. tuzo wilson discovered that earth"s lithosphere is divided into several plates that gradually move relative to one another. Their interactions cause earthquakes, volcanoes, and mountain building, mainly at plate boundaries. Divergent: where plates move apart (sea floor spreading) at oceanic ridges and new sea floor is created, or on continents at rift valleys located above magma plumes. Convergent: where plates move together at subduction zones and ocean trenches: denser oceanic crust goes under lighter continental crust, sea floor is consumed.
