EARTH 222 Lecture Notes - Lecture 4: Divergent Boundary, Seafloor Spreading, Subduction
9 Oct 2018
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Last lecture: continental motion, sea floor spreading, earth"s interior, 3 types of plate boundaries. Ex. of divergent boundary - east african rift valley. Ex. of divergent plate boundary on land = red sea / east african rift zone. If initial depth is 2. 5 km: easy mistake to make: just put in 100 under age, not 100,000,000. Ex. of volcanism that comes from subduction zone: pacific northwest, because of all the water content in the crust that"s subducting you have a lot of volatiles and explosive volcanism, eruption of mount st. helens - huge explosion. Earth"s internal structure: what causes the two modes, step back and think about what lies below surface crusts. Inner core, outer core, mantle, crust: rocks that flow and float, asthenosphere is upper mantle material close to its melting point that behaves like glacial ice, lithosphere is outermost layer of the earth composed of rigid plates. Isostasy: continental crust is both less dense and thicker.
