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Plate Tectonics

Plate Tectonics. pg . 85 . Pangaea. Continental drift caused the supercontinent Pangaea to separate Pangaea -Greek word meaning ‘all the earth’ Evidence from similar rock formation and fossil remains found on two different continents

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Plate Tectonics

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  1. Plate Tectonics pg. 85

  2. Pangaea • Continental drift caused the supercontinent Pangaea to separate • Pangaea -Greek word meaning ‘all the earth’ • Evidence from similar rock formation and fossil remains found on two different continents • Coal deposits in Antarctica indicate the climate was once warm and temperate • Was initially rejected because there was no reason why the continents were moving

  3. Seafloor spreading • Seafloor was once thought to be flat and unchanging • Technology has proved otherwise • Sonar –uses reflecting sound waves • Magnetometer- detects changes in magnetic fields; measured strength of rocks magnetic field • Magma creeps up and creates new seafloor close to the ocean ridge • As new magma breaks through, older parts spread out

  4. Ocean Floor Topography • Maps were made containing ocean ridges • Volcanoes and earthquakes common near ridges • Also found trenches • Largest trench is the Mariana Trench in the Pacific Ocean (11 km deep)

  5. Ocean floor and magnetism • Scientists found the ages of rocks and thickness of rocks increased the further away from ocean ridges. • Used paleomagnetism to map the rocks and sediments • Basalt is commonly used to record magnetism • Revealed magnetic reversals • Using data from magnetic reversals, scientists were able to create an isochron

  6. Theory of plate tectonics • Earth’s crust and mantle are broken into enormous slabs called plates • Tectonic plates interact at plate boundaries • Some converge, others diverge, some move horizontally past one another

  7. Divergent Boundaries • Most are found on seafloor; form ocean ridges • Located in a rift, or fault bounded valley • Associated with high volcanic activity, earthquakes, and high heat • Divergent boundaries on continents create a rift valley • Long narrow depression

  8. Convergent boundary • 3 types • Oceanic crust converging w/ oceanic crust • One of the plates descends under another in a process called subduction • Can form islands • Oceanic converging w/ continental crust • Subduction occurs • Produces a trench and volcanic arc • Continental converging w/ continental • Mountain ridges form

  9. Transform Boundary • Place where 2 plates slide past one another • Crust is deformed and fractured • Characterized by long faults and small earthquakes

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