GEOG 1290 Lecture Notes - Lecture 13: Ultramafic Rock, Continental Crust, Oceanic Crust
30 Oct 2017
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Layered structure: q earth has a radius of 6400 km. Temperatures range from 2800 c near the core to 1800 c near the crust. Outer layer of the mantle is brittle. Contact between crust and upper mantle = mohorvicic discontinuity (or. Moho) q marks a change in density q close to the surface below ocean floors (8 km) q deeper under land (40 km) Mundy upper mantle is cool + composed of brittle rock > thinnest under ocean. The solid upper part of the mantle plus the crust is often referred to as the lithosphere q discontinuous (i. e. , there are gaps) q 60 150 km thick. Beneath it lies the asthenosphere; the layer of soft, plastic rock in the mantle. The lithosphere is fragmented into lithospheric plates ( or tectonic plates) Precambrian (supereon - 87% of geologic time scale, encompases the following eons) 29% continental crust; 71% ocean infinite, caledonides formed during paleozoic (250-400ma) infinite, caledonides formed during paleozoic (250-400ma)
