7th grade Ch. 1 Sec. 4 Sea-Floor Spreading

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7th grade Ch. 1 Sec. 4 Sea-Floor Spreading

  1. 1. Ch. 1 Sec. 4 Sea-Floor Spreading
  2. 2. mid-ocean ridge <ul><li>longest mountain chain in world </li></ul><ul><li>curves along ocean floor </li></ul><ul><li>mapped using sonar = device that bounces sound waves off underwater objects & records echoes </li></ul>
  3. 3. The mid-ocean ridge (shown in red) winds its way between the continents much like the seam on a baseball.
  4. 5. Harry Hess’ idea Ocean floors move like conveyor belts- carrying continents w/ them Magma rises from mantle & erupts @ mid-ocean ridge Molten material spreads out- pushing older rock to both sides of mid ocean ridge
  5. 7. <ul><li>new material continually being added to ocean floor </li></ul>
  6. 9. evidence for sea-floor spreading 1. molten material 2. magnetic stripes 3. drilling samples
  7. 10. 1. Evidence from molten material The submersible Alvin photographed pillow lava along the mid-ocean ridge.
  8. 11. 2. Evidence from magnetic stripes
  9. 12. <ul><li>The Glomar Challenger was the first research vessel specifically designed in the late 1960s for the purpose of drilling into and taking core samples from the deep ocean floor. </li></ul>3. Evidence from drilling samples
  10. 13. subduction <ul><li>process where oceanic crust sinks down beneath trench into mantle </li></ul>
  11. 14. deep-ocean trench <ul><li>deep, underwater canyon </li></ul><ul><li>forms where oceanic crust bends </li></ul><ul><li>subduction takes place here </li></ul>
  12. 15. Oceanic crust is returned to the mantle through subduction
  13. 17. The Sea Floor is Spreading
  14. 18. REVIEW TIME
  15. 19. mid-ocean ridge <ul><li>winds beneath Earth’s oceans </li></ul><ul><li>mapped using sonar = device that bounces sound waves off underwater objects & records echoes </li></ul>
  16. 20. sea-floor spreading <ul><li>theory proposed by Harry Hess </li></ul><ul><li>new material is continually being added to ocean floor </li></ul>
  17. 21. deep-ocean trench <ul><li>deep, underwater canyon </li></ul><ul><li>forms where oceanic crust bends </li></ul><ul><li>subduction takes place here </li></ul>
  18. 22. Evidence for sea-floor spreading <ul><li>molten material </li></ul><ul><li>magnetic stripes </li></ul><ul><li>drilling samples </li></ul>
  19. 23. subduction <ul><li>process by which oceanic crust sinks down beneath trench  mantle </li></ul>
  20. 24. Harry Hess <ul><li>What scientist helped to discover the process of sea-floor spreading? </li></ul>
  21. 25. mid-ocean ridges <ul><li>Along what feature of the ocean floor does sea-floor spreading begin? </li></ul>
  22. 26. Evidence from The submersible Alvin photographed pillow lava along the mid-ocean ridge. molten material
  23. 27. <ul><li>The Glomar Challenger was the first research vessel specifically designed in the late 1960s for the purpose of drilling into and taking core samples from the deep ocean floor. </li></ul>Evidence from drilling samples
  24. 28. Evidence from magnetic stripes
  25. 29. Oceanic crust is returned to the mantle through subduction

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