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Unformatted text preview: 1 Geological History I- Origin of the Sun & the Solar system I) Big Bang: 20 billion yrs ago II) The nebular hypothesis: T drops following the Big Bang 5 billion yrs ago: our own solar nebula collapses into a disk shaped Solar winds. Accretion: Planetesimals and protoplanets III) Earth evolution: Accretion causes an increase in the T Differentiation of the Earth into crust, mantle, and core. Earth acquires its magnetic field during the Early Precambrian. IV) Earths early atmosphere Outgassing Rich in H 2 O, CO 2 and N 2 Precipitation and the beginning of the hydrologic cycle. How did it evolve to the present composition? Cyanobacteria & plants. II- The Precambrian Era The Precambrian spans about 88% of Earth's history Between 4.5 billion years ago and ending approximately 540 million years ago Represented in the cores of the continents known as shields Important rock types: Greenstones and granitoids, Granulite facies metamorphic rocks....
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- Fall '08