Earth Sciences 1022A/B Lecture Notes - Lecture 6: Accretionary Wedge, Continental Crust, Volcanic Arc

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 1022A/B
• Professor: Stephen R Hicock

Document Summary

Earth sciences 1022a lecture brief 21 oct 14. Continents rise above oceans due to isostasy buoyant continental lithosphere floats on dense asthenosphere; thicker lithosphere, higher mountains with deeper roots . Andean-type: oceanic crust subducts beneath continental, developing accretionary wedge, continental volcanic arc, and plutons in core of 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 accreted terranes: foreign pieces of crust forcefully attached to continental margin. Wilson cycle oceans opened and closed, mountains built and rebuilt repeatedly; rarely pieces of oceanic crust got stuck onto continental margin during obduction. Origin and evolution of continental crust: originally by accretion of mantle material. As oceanic crust was subducted beneath continental crust, magma differentiated to produce andesitic and granitic volcanic arcs that coalesced to form earth"s earliest crude continents.