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Lecture 15 - GEOS 1004 SPOTILA/22/09 PLATE TECTONIC...

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GEOS 1004, SPOTILA Lecture 15, 10/22/09 PLATE TECTONIC BOUNDARIES D. Collisional plate boundaries, mountain belts Subduction ends when the oceanic plate is gone; what then? Continents don't subduct. -collision, between the continents or the continent and the volcanic arc that was above the subduction -creates mountain belts (also called orogenic belts; mountain building is orogeny ) Active continent collision? - India colliding with Asia (creating Himalayas) How is space made for 2 colliding continental plates? (they don’t subduct; they can’t occupy the same space) 1) fold and thrust belt (one mass of rock is stacking up on top of another) Thrust faults push one group of rock over another - this thickens the crust. Rocks are folded in between the thrust faults. Increasing the thickness of the crust increases elevation, grows mountains. Isostasy. -1 km gain in elevation for every 5 km extra thickness of crust. The 5 km Tibetan plateau is there because the crust is twice as thick (70 km) as usual.
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