GEOL 1001 Chapter : Chapter 2 Plate Tectonics
Document Summary
Chapter 2 plate tectonics: a scientific revolution unfolds. Alfred wegener (1915) the origin of continents and oceans. Hypothesis: 200 million years ago the supercontinent pangea began to break up, continents drifted to their present positions. 1950"s and 60"s technological strides (and the cold war) allowed for mapping of the ocean floor. Seafloor spreading hypothesis proposed by harry hess. Geomagnetic reversals: switching of the north and south poles, evidence found in stripes of oceanic crust, also in volcanos. Plate boundaries: divergent plate boundaries constructive margins, convergent plate boundaries destructive margins, transform plate boundaries conservative margins. Excess heat forms magma below the boundary which finds its way up to the crust spreading the crust apart. Lines of force exit and enter at the earth"s magnetic poles. Present day: normal polarity lines of force exit south and enter north. Rocks record magnetic field when they harden at the time of crystallization. Surveys of magnetic field over ridges revealed stripes parallel to ridge.
