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Plate Tectonics

Plate Tectonics. Proposed by Alfred Wegener in 1912; the hypothesis that state that the continents once formed a single landmass ( Pangea ), broke up, and drifted to their current location. Theory of Continental Drift. Shape of the continents Fossil evidence on both sides of the Atlantic

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Plate Tectonics

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  1. Plate Tectonics

  2. Proposed by Alfred Wegener in 1912; the hypothesis that state that the continents once formed a single landmass (Pangea), broke up, and drifted to their current location Theory of Continental Drift

  3. Shape of the continents Fossil evidence on both sides of the Atlantic Rock formations on both sides of the Atlantic Climatic evidence (i.e. evidence of glaciers in Southern Africa) Wegener’s Evidence:

  4. Fossil Evidence

  5. He could not come up with the mechanisms or process that caused the continents to move Problems with his Theory

  6. a) Mid-Ocean Ridges – a long undersea mountain chain that has a steep, narrow valley at its center, that forms as magma rises from the mantle, and that creates new ocean floor as the tectonic plates move apart Missing Evidence:

  7. b) Sea Floor Spreading – the process by which new oceanic crust forms as magma rises to Earth’s surface and solidifies at a mid-ocean ridge, symmetry of rock layers show oldest layers are farther from the ridge Missing Evidence:

  8. c) Paleomagnetism – As magma solidifies, iron particles line up with the Earth’s magnetic field Rocks show reversals in the Earth’s Magnetism Rocks show symmetrical patterns on both side of the ridges, thus both plates formed at the same time Missing Evidence:

  9. Paleomagnetism

  10. The theory that explains how large pieces of the crust, called plates, move and change shape Plate Tectonics

  11. Lithosphere – solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle Asthenosphere – the solid, plastic layer of the mantle that flows slowly Plate Tectonics

  12. 15 Major Plates Identified: Tectonic Plates

  13. Convection– the movement of hot, less dense material up and cold, more dense material down Causes of Plate Motion:

  14. Interior of the Earth heats the mantle which rises to the surface at the Mid-Ocean Ridges Cools into rock and eventually sinks back into the mantle where it is melted and sinks This movement of the mantle drags the plates with it Mantle Convection

  15. Plate Boundaries

  16. The boundary between tectonic plates that are moving away from each other. Results in: magma rises to surface, forms mid-ocean ridges and rift valleys Divergent Boundaries

  17. The boundary between tectonic plates that are moving towards each other Convergent Boundaries

  18. One plate subducts under the other, forming a trench and melting the plate causing an island arc Oceanic-Oceanic

  19. The oceanic plate subducts under the less dense continental plate, the oceanic plate melts, causing volcanoes above Oceanic-Continental

  20. Neither plate is dense enough to subduct, thus mountains are built up Continental - Continental

  21. The boundary between two tectonic plates that are sliding past one another, like the San Andreas fault Transform Boundaries

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