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Unformatted text preview: The theory of plate tectonics: what is it, and why it cannot be applied to continents the Earth's surface is composed of rigid plates that move relative to one another. The plates are rigid and consequently, deformation/mountain building, and seismicity (earthquakes) occur only at plate boundaries. Volcanism, except for hot spots, occurs only at plate boundaries. plate tectonic theory adequately explains the tectonics of oceanic lithosphere, but in many cases, continental lithospheres does not follow the rules of plate tectonics What happens first when continents are broken up by passive rifting? Plate motions cause extension within a continental plate. Extension within a continental plate proceeds until the entire continental lithosphere is thinned to zero thickness. Upwelling asthenosphere partially melts as it rises to fill the space, and yields mafic composition magma, which erupts as basalt/sea floor crust Signature of passive rifting: volcanism first, then uplift (reflected in rock record as an unconformity above...
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This note was uploaded on 01/06/2012 for the course GEOL 102 taught by Professor Antoniogarcia during the Fall '11 term at Cal Poly.
- Fall '11