Lec 3 Ch 2 Spr 08

Lec 3 Ch 2 Spr 08 - Lecture Outline CHAPTER 2 Plate...

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1. Continental drift, seafloor spreading, subduction and plate tectonics (continued). 2. Measurements of plate motion by geodesy. 3. Reconstructing plate tectonic movements. 4. Types of plate tectonic boundaries (continued). 5. Paleogeography. Lecture Outline CHAPTER 2 Plate Tectonics: The Unifying Theory
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1.   Continental drift, seafloor spreading, subduction and plate tectonics (continued). DIVERGENT PLATE BOUNDARY (Plates moving apart) CONVERGENT PLATE BOUNDARY (Plates moving together) TRANSFORM-FAULT PLATE BOUNDARY Plates moving past one another horizontally
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Rates and History of Plate Motions 2. Measurements of Plate Motion by Geodesy Geodesy : measuring the shape of the Earth and determining your position on it. 1 mm (millimeter) = 0.04 inches Astronomical Positioning Global Positioning System (GPS)
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3. Reconstructing plate tectonic movements Magnetic epochs : Assigning ages to chrons Isotopic dating of minerals in lava flows on dry land (above) and dating of fossil assemblages in marine sediment over oceanic crust (below, right) allows ages to be determined for magnetic epochs. YOUNGER FOSSILS OLDER FOSSILS Direction of plate movement Sediment accumulates at a constant rate on oceanic crust. Older crust has thicker sediment, older fossils USGS (2005) International Ocean Drilling Program (ODP) drill ship Resolution
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The Seafloor as a Magnetic Tape Recorder Changes in the Earth’s GEODYNAMO system periodically make the earth’s magnetic field reverse polarity. These changes leave a record in the orientation of magnetic minerals formed in oceanic crust during seafloor spreading. “Normal” “Reversed” Ship-towed magnetometer 3. Reconstructing plate tectonic movements
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3. Reconstructing plate tectonic movements Chrons : Magnetic anomaly pattern in the oceanic crust
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