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Published bySabrina Cotham Modified over 9 years ago
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Early Earth …earliest phase of Earth heating… …near Moon… …first seas… …thin atmosphere of H, CO 2, H 2 O, N 2, CO, NH 3, CH 4 …early bombardment…
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Early Bombardment 2 phases? Relative dating
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Early Earth began to heat as the last extraterrestrial collisions subsided 1.Rock is a good insulator – stores heat 2.Collisions produced heat that was stored 3.Radioactivity 4.Gravitational contraction Early in Earth History the Planet Developed a Magma Sea 4.5-4.0 billion years ago What is the physical consequence of melting a homogeneous ball of rock?
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Temperature reached melting point of iron: Liquid iron flowed inward Friction raised temperature Liquid Silicon and Oxygen flowed outward (Ca/Na/Al/K) “Iron Catastrophe” Planet became chemically differentiated
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Lower lithosphere - Fe/Mg Crust – Si/O/Fe/Mg/Ca/Na/K/Al Oceanic crust – Fe/Mg/Ca Continental crust – Si/O/Na Inner core – Fe/Ni solid Inner core – Fe/Ni solid Outer core – Fe/Ni/Mg liquid Outer core – Fe/Ni/Mg liquid Mantle – Fe/Mg solid rock capable of flow Lithosphere – Fe/Mg/Si/O Increasing Fe/Mg toward core Increasing Si/O toward crust
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Effect of chemical differentiation
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Earth’s magnetic field emanates from the core complex and surrounds the planet. Magnetism gained from early nebula is magnified by turbulent iron, nickel fluid of outer core. Magnetic field envelops entire planet Polarity + - tends to reverse and fluctuate with time
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The “Bow Shock Effect”
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How does convection work? Another consequence of differentiation is convection. How will the lithosphere respond to a plume?
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The continental rifting process
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Mid-Ocean Ridge Spreading Center But if you keep making crust the Earth must be expanding! Right?
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Spreading center and subduction zone
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Global Tectonics Partial Melting Partial melting is responsible for evolving mantle rock… among other things this gives us continents.
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Oceanic lithosphere – general chemistry is Fe, Mg, Ca, Si, O in the form of a rock “Basalt” Continental lithosphere – general chemistry is Si, O, Al, Na, K…in the form of a rock “Granite”
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Plate Movement “Ridge Push” “Slab Pull” “Plate Drag”
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Main Types of Plate Motion Convergent Divergent Transform
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Five types of plate boundaries DivergentTransformConvergent Ocean-OceanOcean-Ocean Ocean-ContinentOcean-Continent Continent-ContinentContinent-Continent
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Five types of plate boundaries DivergentTransformConvergent Ocean-OceanOcean-Ocean Ocean-ContinentOcean-Continent Continent-ContinentContinent-Continent
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Divergent Boundary
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Convergent Boundary
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Transform Boundary
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Modern Earth Pangea 240 million
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Origin of India
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Hot Spot
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Paleomagnetism
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Igneous Rocks
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Sedimentary Rocks
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Metamorphic Rocks
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The Rock Cycle
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