CAS ES 105 Lecture 2: Notes
7 Oct 2015
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Asthenosphere: an alive planet, asthenosphere: greek for mobile , 5%melt, upper to deeper mantle. Lithosphere: greek for solid , crust and upper mantle, 14 plates. Continental drift: first proposed by alfred wegner in 1915, failed to be accepted as he could not provide a mechanism. Sea floor spreading: proposed by harold hess in 1960, a princeton geology professor. Observations: ocean ridges every ocean, all basalt, thin oceanic crust (7-10km, symmetrical ages to the ridge, young age (all < 220 m. y. ) Theory of plate tectonics was formulated as a unified explanation for origins of oceans, continents, earthquakes, and volcanoes. Average rate of sea floor spreading 6cm/yr in all oceans! East pacific rise: ridges rise and rift (iceland) Plate tectonics: a unifying theory, accounts for distribution of earthquakes and volcanoes how continents form, and why ocean basins are never to be long lived. Divergent: seafloor spreading, continental rifts (east africa rift lake victoria)
