EARTH221 Lecture Notes - Lecture 12: Plate Tectonics, Asthenosphere, Lithosphere
26 Aug 2016
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Compositional layering: chemical subdivisions (atmosphere, oceans)crust, mantle, core. Lithosphere crust + uppermost part of mantle (most brittle: rocks respond to deformation by breaking, faulting or folding. Asthenosphere part of upper mantle (most ductile: top of this layer few % of partial melt, capable of flowing. Plate tectonics: * the small bump in the graph (fig 1. 3) is due to the waves coming into contact with the asthenosphere causing a change in velocity. Lithosphere rides passively on top of flowing asthenosphere. Mesosphere middle/lower mantle also ductile, but not as much as the asthenosphere because of increasing pressure: rocks respond to deformation by flowing, earth"s bulk composition. Fe, o, mg, si are the four most abundant elements in earth. The earth is mostly enriched in these elements because: *task 9 answer: goldschmidt"s classification of elements. Lithophile: follow the silicates/oxides (these elements like to go into rocks) *informal category: biophile: elements that are concentrated in organisms.
