Chapter 10 ii


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Chapter 10 ii

  1. 1. Chapter 10 – Section I
  2. 2. The continental drift hypothesis – continents have moved slowly to their current locations
  3. 3. All continents were once connected as one large landmass now called Pangaea
  4. 4. The land mass broke apart, and the continents drifted to their present positions.
  5. 5. Evidence for continental drift
  6. 6. Puzzle-like fit of the continents
  7. 7. Similar fossils have been found on different continents
  8. 8. Remains of warm-weather plants in Arctic areas and glacial deposits in tropical areas suggest that continents have moved
  9. 9. Similar rock structures are found on different continents.
  10. 10. At first, continental drift was not accepted because no one could explain how or why continents had moved
  11. 11. Chapter 10 Section II Seafloor Spreading
  12. 12. <ul><li>Using sound waves, scientists discovered a system of underwater mountain ranges called the mid-ocean ridges in many oceans. </li></ul>
  13. 13. In the 1960s, Harry Hess suggested the theory of seafloor spreading to explain the ridges
  14. 14. 1) Hot, less dense material below Earth’s crust rises towards the surface at the mid-ocean ridges.
  15. 15. 2) Then, it flows sideways, carrying the seafloor away from the ridge.
  16. 16. 3) As the seafloor spreads apart, magma moves up and flows from the cracks, cools, and forms new seafloor
  17. 18. Evidence for seafloor spreading <ul><li>Youngest rocks are located at mid-ocean ridges. </li></ul><ul><li>Reversals of Earth’s </li></ul><ul><li>magnetic field are </li></ul><ul><li>recorded by rocks </li></ul><ul><li>in strips parallel to ridges. </li></ul>
  18. 19. Section III – Theory of Plate Tectonics <ul><li>Plate movements </li></ul>
  19. 20. 1) Earth’s crust and upper mantle are broken into sections
  20. 21. 2). The sections, called plates, move on a plasticlike layer of the mantle
  21. 22. 3) The plates and upper mantle form the lithosphere.
  22. 23. 4. The plasticlike layer below the lithosphere is called the asthenosphere
  23. 24. Plate Boundaries <ul><li>1. Plates moving apart – divergent boundaries </li></ul>
  24. 25. Movie
  25. 26. <ul><li>2. Plates moving together – convergent boundaries </li></ul>
  26. 27. <ul><li>Denser plates sink under less dense plates. </li></ul>
  27. 28. <ul><li>Newly formed hot magma forced upward forms volcanic mountains. </li></ul>
  28. 30. Plates Collide <ul><li>Plates crumple up to form mountain ranges </li></ul>
  29. 31. <ul><li>Earthquakes are common. </li></ul>
  30. 32. <ul><li>Plates slide past – called transform boundaries, sudden movement can cause earthquakes. </li></ul>
  31. 34. <ul><li>Convection inside Earth – The cycle of heating, rising, cooling, and sinking of material inside Earth is thought to be the force behind plate tectonics. </li></ul>
  32. 35. Features caused by plate tectonics <ul><li>1) Fault and rift valleys. </li></ul>
  33. 36. <ul><li>2) Mountains and Volcanoes </li></ul>
  34. 37. <ul><li>Strike-slip faults – cause of earthquakes </li></ul>
  35. 38. Testing for plate tectonics – scientists can measure movements as little as 1 cm per year