Earth Sciences 1022A/B Lecture Notes - Lecture 13: Oceanic Crust, Supercontinent Cycle, Isostasy
10 Jan 2017
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Document Summary
Chapter 13 mountain building and continental framework. Continents rise above ocean due to isostasy buoyant continental lithosphere floats on dense asthenosphere; thicker lithosphere, higher mountains with deeper. Mountain building processes are collectively called orogenesis. Mountain (orogenic) belts parallel plate boundaries in three main settings of continental margins: Divergent mantle plume rises, uplifts, and splits continental lithosphere from rift valley with blocks dropped along normal faults, and volcanoes along valley sides. Passive rift widens, seawater invades, and a new ocean basin forms whose sides experience no seismic activity but gradually subside under weight of sediment load. Convergent as mountains grow, undergo isostatic adjustments to balance weight (types: andean, aleutian, continental collision, accreted terrines) Andean type ocean crust subducts beneath continental, developing accretionary wedge, continental volcanic arc, and plutons in core deformed mountain belt. Aleutian type oceanic crust subducts under oceanic, to form volcanic island arc. Continental collision ocean basin closes, subduction stops, highest mountains form.
