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Plate Tectonics

Plate Tectonics. 1915- Wegener proposes his hypothesis of continental drift. Not widely accepted because he could not explain WHY? Died in 1930 still trying to figure it out. Alfred Wegener.

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Plate Tectonics

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  1. Plate Tectonics

  2. 1915- Wegener proposes his hypothesis of continental drift. • Not widely accepted because he could not explain WHY? • Died in 1930 still trying to figure it out. Alfred Wegener Continental Drift - 240 million years ago there was one supercontinent called Pangaea. Over time the continents have moved to their present locations and continue to move.

  3. South America and Africa fit together. Evidence-Jigsaw Puzzle Pieces

  4. Mesosaurus and Glossopteris - Matching fossils found in patterns across different continents Fossil Evidence

  5. Glaciers and Coal Deposits Signs of glaciers on multiple continents, some near equator. Found in cold areas but need tropical climate to form. Climatic Evidence

  6. Age, Type, and Alignment of Mountains • Appalachian Mtns. Same age and type as mtns. in Greenland and Europe Rock Evidence

  7. Move slowly about 5 cm or 2.5” per year • Plate movement causes EQs, volcanoes, & create mountains Plate Tectonics

  8. Lithosphere – plates • outer and rigid • Crust and upper mantle • Moves over the asthenosphere • Asthenosphere • below and plastic like • Lower mantle Earth’s Interior

  9. Transform • Plates slide past one another • Stress involved is shearing • Forms Eqs • Ex: San Andreas Fault Boundary Types

  10. Divergent • Plates move away from each other • Stress involved is tension • Forms mid ocean ridges and rift zones • Ex: Mid-Atlantic Ridge and Iceland Boundary Types

  11. Convergent • Plates move towards each other • Stress involved is compression • 3 different results!

  12. oceanic-continental crusts meet Subduction (denser plate [oceanic] dives below) Ocean trench forms offshore Continental volcanic arcs Ex: Cascades, Andes Boundary Types

  13. Oceanic-oceanic crusts meet • Subduction occurs and one plate dives down • Ocean trench forms • Volcanic island arcs • Ex: Japan, Aleutians Boundary Types

  14. C) Continental-continental crusts meet • No subduction • Collision boundary • Mountains form • Ex: Appalachians, Himalayas • Boundary Types

  15. 1. Paleomagnetism • Polar wandering & Polar reversals 2. Earthquake patterns • Earthquakes occur @ plate boundaries 3. Ocean Drilling • Glomar Challenger & Harry Hess • 180 million (oceanic) vs. 4 billion (continental) 4. Hot spots—example = Hawaii • Only one active volcano • Evidence of movement & direction • Islands further from hot spot are oldest Plate Tectonic Evidence

  16. Scientists generally agree that convection in the mantle is the basic driving force for plate movement. • The unequal heating within the earth causes this. • Read about slab-pull & ridge-push. • Read about mantle convection. Causes of Plate Motion

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