earth sci - Plate Tectonics

earth sci - Plate Tectonics - kept in the rock) Convergent...

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Plate Tectonics Evidence - continental drift -geometric fit of continents -correlation of geologic features from continent to continent -polar wandering -Permian Glaciation another prime example -mountain belts as well (i.e. Appalachians on north America and Africa) Rigid Plates -seismically inactive (earthquakes not within, but at borders) -under same state of stress -have strength -plates move/float over the asthenosphere (weak part of upper mantle) -Earth’s diameter is constant THREE TYPES OF BOUNDARIES Divergent Boundaries -normal faults - divergent boundary: plates move apart -when they split, part of asthenosphere comes up (magma) and fills the gap, creating new crust -age of rock is older as you move away from the boundary
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a) rate = distance from ridge / age of crust b) direction perpendicular to ridge c) marked by: -submarine basaltic rift volcanism -shallow earthquakes -magnetic properties are stuck in rock (so when the poles of earth switch, that record is
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Unformatted text preview: kept in the rock) Convergent Boundary-reverse faults-plate consumed at convergent boundary-benioff zone marks trace of descending slab of ocean crust-island arc overlies descending slab-andesite volcanism-constructive-crust turned back into mantle plate creation = plate destruction spreading = subduction Continents-rest on plates-cannot be subducted (too light)-scrunch up together (mountains) Plate History-creation cooling subduction-200 million years (oldest ocean crust in place in active ocean)-african plate currently splitting Transform Boundary-divergent boundaries on a sphere are not stable (wide part and small parts); transform faults make them stable-all 3 boundaries put together make things stable and orderly-strike-slip faults J Tuzo Wilson-Canadian content in the formulation of plate tectonic ideas...
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This test prep was uploaded on 04/18/2008 for the course GEO EarthSci taught by Professor Graves during the Winter '07 term at Dalhousie.

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earth sci - Plate Tectonics - kept in the rock) Convergent...

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