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Plate Tectonics

Plate Tectonics. Continental Drift Seafloor Spreading Theory of Plate Tectonics Causes of Plate Motion. Chap. 17. Continental Drift. The End. Seafloor Spreading – 17.2. Objectives. Summarize the evidence that led to the discovery of seafloor spreading.

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Plate Tectonics

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  1. Plate Tectonics Continental Drift Seafloor Spreading Theory of Plate Tectonics Causes of Plate Motion Chap. 17

  2. Continental Drift

  3. The End

  4. Seafloor Spreading – 17.2 Objectives • Summarize the evidence that led to the discovery of seafloor spreading. • Explain the significance of magnetic patterns on the seafloor. • Explain the process of seafloor spreading.

  5. Seeing the ocean floor

  6. Seeing the ocean floor • Sonar

  7. Seeing the ocean floor • Sonar • Magnetometer

  8. Topography of Ocean Floor *See map on p. 912

  9. Topography of Ocean Floor • Mountain ranges (oceanic ridges) These are associated with earthquakes and volcanos

  10. Topography of Ocean Floor • Mountain ranges (oceanic ridges) • Canyons (deep-sea trenches) *See map on p. 912

  11. Rock Studies • Youngest rocks near ridges

  12. Rock Studies • Old rocks (over 180 million years) cannot be found on seafloor. Continental rocks have been dates up to 3.8 billion years old.

  13. Rock Studies • Thin layer of sediment present (thickness increases further away from ridge).

  14. Rock Studies • Magnetism Paleomagnetism is the study of the Earth’s magnetic record.

  15. Rock Studies • Magnetism • Magnetic reversals have occurred. A change in the Earth’s magnetic field

  16. Rock Studies • Magnetism • Magnetic reversals have occurred. • Basaltic rocks show these reversed fields.

  17. Rock Studies • Magnetism • Reversals are records in the seafloor.

  18. Rock Studies • Magnetism • Scientists created isochrons. A line on a map that connects points of equal .

  19. Rock Studies • Magnetism • Scientists created isochrons. A line on a map that connects points of equal age.

  20. Seafloor Spreading

  21. Seafloor Spreading • Theory developed by Harry Hess

  22. Seafloor Spreading • Theory developed by Harry Hess • Magma surfaces at ocean ridges, forming new crust.

  23. Seafloor Spreading • Theory developed by Harry Hess • Magma surfaces at ocean ridges, forming new crust. • Crust is destroyed at deep-sea trenches

  24. The End

  25. Theory of Plate Tectonics

  26. Plates and Boundaries

  27. Plates and Boundaries • Tectonic plates are named (*diagram) • Pacific plate • North American Plate • Eurasian Plate • African Plate • South American Plate • Indian-Australian Plate • Antarctic Plate • Arabian Plate • Philipine Plate • Caribbean Plate • Nazca Plate • Cocos Plate

  28. Plates and Boundaries • Tectonic plates are named (*diagram) • Boundaries Location where tectonic plates interact

  29. Plates and Boundaries • Tectonic plates are named (*diagram) • Boundaries • Divergent

  30. Divergent Boundaries

  31. Divergent Boundaries • Plates are moving apart

  32. Divergent Boundaries • Plates are moving apart • Causes thinning of the lithosphere

  33. Divergent Boundaries • Plates are moving apart • Causes thinning of the lithosphere • Often form on ocean floor

  34. Divergent Boundaries • Plates are moving apart • Causes thinning of the lithosphere • Often form on ocean floor • Ex. Rift Valley in East Africa

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