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Plate Tectonics

Plate Tectonics. lithosphere. asthenosphere. mesosphere. Lithosphere (hard). Asthenosphere (soft). Mesosphere. Earth formed 4.6 bya. Inner Core- 4300 o C mostly iron core inner part is so compressed that it is solid Outer Core- 3700 o C iron and sulfur liquid. Crust

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Plate Tectonics

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  1. Plate Tectonics

  2. lithosphere asthenosphere mesosphere

  3. Lithosphere (hard) Asthenosphere (soft) Mesosphere

  4. Earth formed 4.6 bya • Inner Core- 4300oC • mostly iron core • inner part is so compressed that it is solid • Outer Core- 3700oC • iron and sulfur • liquid • Crust • floats on top of lithosphere • continental crust (granite) • 20 to 70 km thick • oceanic crust (basalt) • ~ 8 km thick • Mantle- 1000oC • mesosphere • Solid • ~ 2300 km thick • asthenosphere • Soft • ~3000 km thick • lithosphere • hard • ~100 km thick

  5. Principles of plate tectonics • The Earth is composed of a mosaic of thin rigid plates (pieces of lithosphere) that move horizontally with respect to one another • Plates interact with each other along their plate boundaries • Plate boundaries associated with tectonic activity (mountain building, earthquakes, active volcanoes)

  6. Continental Drift Theory Alfred Wegener • Proposed Theory of Continental Drift (1915) • Failed to provide a mechanism

  7. Evidence for Continental Drift • continental shape • similar geology • fossil evidence (animal and plant) • volcano and earthquake zone • paleomagnetism

  8. Objections to the continental drift model • Wegener envisioned continents plowing through ocean basins • Wegener did not provide a plausible mechanism to explain how the continents could have drifted apart • Most Earth scientists rejected continental drift because it was • Too far-fetched • Contrary to the laws of physics Lacked technology

  9. Jigsaw Puzzle Evidence for continental drift • Matching coastlines on different continents

  10. Similar Geology Evidence for continental drift • Matching mountain ranges across oceans Today 300 million years ago

  11. Evidence for continental drift • Glacial ages and climate evidence

  12. Fossil Evidence

  13. Fossil Evidence Distribution of fossils such as Mesosaurus Mesosaurus

  14. Permian 225 mya Triassic 200 mya Jurassic 135 mya Cretaceous 65 mya Present Day

  15. Marie Tharp

  16. Marie Tharp's "World Ocean Floor Map” 1977

  17. Evidence for plate tectonics • Pattern of worldwide earthquakes (left) matches plate boundaries (right)

  18. Plate Tectonics &

  19. Hess- Convection Cell Theory

  20. The 3 types of plate boundaries • Divergent • Convergent • Transform

  21. Divergent plate boundaries • The Mid-Atlantic Ridge is a divergent plate boundary where sea floor spreading occurs

  22. Divergent plate boundaries • Iceland sits atop a divergent plate boundary where continental rifting occurs

  23. Divergent plate boundaries • Formation of an ocean basin by rifting and sea floor spreading

  24. Convergent plate boundaries a. Ocean-continent • Convergent plate boundaries vary depending on the type of crust c. Continent-continent b. Ocean-ocean

  25. Convergent plate boundaries • An ocean-continent convergent plate boundary produces the Cascadia subduction zone and Cascade Mountains

  26. Convergent plate boundaries • A continent-continent convergent plate boundary produces the Himalaya Mountains

  27. Transform plate boundaries • Transform plate boundaries occur between segments of the mid-ocean ridge • Can also occur on land (ex: San Andreas Fault)

  28. The world as it may look 50 million years in the future

  29. Glomar Challenger (1960’s) Deep sea ocean drilling

  30. N S Earth's Magnetic Field

  31. Mid-Ocean Ridge (Atlantic Ocean) + - + - + - + - + - + - There have been 170 reversal in the last 76 million years. The earth’s present orientation has existed for the past 60,000 years.

  32. Age of the Atlantic

  33. Inquiry • What layer of the mantle do the plates move on? • What is the convection cell theory? • Wegeners evidence for continental drift includes: ______. • Why was his theory disregarded? • What did Marie Tharp discover? • How are trenches formed?

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