EOSC 114 Lecture Notes - Lecture 3: Lithosphere, Mid-Ocean Ridge, Volcanism
12 Sep 2016
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Document Summary
Most important factor in volcano distribution is plate tectonics. Crust composition and melt origin will strongly influence type of volcanism. Continental & oceanic crust can be on the same lithospheric plate. General plate boundaries: divergent, convergent, transform (slide past; no collision) Divergent: oceanic < > oceanic plate spreading, continental < > continental plate spreading. Transform: oceanic-oceanic plates, oceanic-continental plates, continental-continental plates. Two plates spread apart across rift zone (a long, linear volcano) Divergent margins becomes a spreading centre (mid ocean ridge) New oceanic crust is created as the older crust is pulled away. Becomes intermediate to felsic (explosive type eruption) as it rises. Processes at the boundary: plates locked = stress + deformation, plates release = earthquake + tsunami. *continental crust cannot be subducted because it"s less dense than mantle rock (oceanic crust). Oceanic crust is very close to mantle composition. Cold oceanic lithosphere is denser than asthenospheric mantle rock. If oceanic plate and oceanic plate converge, the oldest subducts.
