EESA06H3 Lecture Notes - Lecture 4: Continental Crust, Toffee, Supercontinent Cycle
3 Sep 2015
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Document Summary
Sea and east african rift) condense again (atlantic ocean: dying: an ocean that is condensing and is being pushed over (subduction) by the other continent (pacific ocean, the border of the pacific ocean is all surrounded by subduction zones, that is the ocean floor is being pushed under the continents, the supercontinent cycle (wilson cycle): continents are spreading apart and they reach a point where they will retreat back to the shape of pangaea, asthenosphere: weak sphere. Not fluid, more like plastic, the toffee layer. ": lithosphere: the rigid plates that float over the asthenosphere, differing densities of oceanic and continental crust, oceanic crust is basalt which is being subducted in the pacific ocean, mafic, sits low, less than mantle density, thinner, usually less than 10km thick, basaltic composition. Average density: 2. 9g/cm3: continental crust: less density therefore rides higher, decompression melting of dry mantle rock to produce basaltic magma (slide, when dry mantle rock come out of the surface it undergoes.
