EAS205 Lecture Notes - Plate Tectonics, Continental Crust, Subduction
8 May 2014
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Document Summary
Age back calculation of the rate of expansion of the universe. Spinning cloud of dust and gas formed the sun and planets. Accounts for the almost co-planar orbits of the planets. Addition of solid matter through collisions (cold accretion) A function of the distance from the sun(s) Gravitational contraction elevates the internal temperature (>1000 c) At time zero earth likely produced 5x more heat than today. Fe and ni sink to the core. Lighter elements in the crust, heavier ones in the mantle. Gravitational pull prevented some primordial gases from escaping into space. Primordial atmosphere likely contained h2o, h2, hcl, co, co2 and. Photosynthetic organisms (around 3. 5 ga) produced o2, but all of it was fixed. Around 2 ga, enough o2 remained free to become part of the created. Sedimentary rocks dated 4 ga (possibly older?) Partial melting in the crust and mantle. Preferentially destroys mafic material (fe and mg) Enhances the felsic (sio2) component of the continental crust.
