Geology 100 notes - C12 13 14 I sot opes Geology 100 Exam 1...

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C12, 13, 14 Isotopes Geology 100 9/20/10 Exam 1 next Monday Review Map of the ocean’s floor Some time in the past all the continents were joined into super contin, called Pangaea. Proposed by Alfred Wagner Due to WWII we discovered what was on the ocean floor, prior to, no knowledge. Divergent plate boundary, in certain areas of the earths interior, hot plastic athenosphere rises up and pushes lithosphere up, litho = brittle = breaks. As the athenso rises up, decompresses, there’s a lot of pressure, it begins to partially melt. Magma works up to surface and fills up cracks, as magma cools, it wants to sink down, but can’t. Instead of sinking down, lithosphere begins to move sideways = seafloor spreading. New ocean floor developed on axis, Red Sea opens up. At the other end, subduction: if ocean floor opens up in certain areas…if OC is being pushed into CC, cause OC = more dense then pushed down underneath CC and into the mantle. Deep Sea trenches are associated with subduction. The inclined zone of Equakes between OC and CC, Benioff zone. Also, melting going on, magma rises up towards surface volcanism = Andean Style Subduction. General case of subduction, but in rare circumstances, as the OC is pushed into the C what happens is OC may get pushed ontop of C “obduction” OC pushed ontop of C OC = less dense and very hot in obduction. Very young OC, more buoyant Ophiolites develop in obduction, sections of the ocean floor pushed on top of C, rare.
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2 pieces of OC being pushed into one another, situation in the Elution, Japan, Java and Sumatra. …mountains rise or one of them is pushed down, still have subduction, but what crust is pushed down? Older crust is pushed down. Older OC is colder and therefore more dense. Everything else is the same volcanism etc etc. Japan Style Subduction. 2 pieces of CC originally there is OC in between, have to have subduction. Closing off an ocean basin. Anytime there is collision with 2 CC, there is closing off of ocean basin. Ocean basin closure Lifeform introduction, ctrl of water circulation and weather. Significant event for geology. As 2 CC collide form mountains, no subduction, CC too buoyant to be subducted. Pushed up instead of down, results in very high mountains, Himalayan style convergence. Inverted mountain below, like iceberg mountain root: region when the mantle/lower crust has been displaced. Transform plate bounds Mid ocean ridge consists of numerous short offset segments. Crust does not like being pushed around so it simply breaks. One piece of litho slides past the other = transform faults: areas where litho slides past one another – Andreas Fault St Andreas extends from WA mid O.R. hugs coastline just south of San Fran, travels inland, cuts across state, hits LA, hangs turn and connects to Mid OR off of Baja. 1 piece of litho, sliding past the other. La and San fran moving closer to eachother.
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