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

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

  • Ch. 1 Sec. 4 Sea-Floor Spreading
  • mid-ocean ridge
    • longest mountain chain in world
    • curves along ocean floor
    • mapped using sonar = device that bounces sound waves off underwater objects & records echoes
  • The mid-ocean ridge (shown in red) winds its way between the continents much like the seam on a baseball.
  •  
  • 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
  •  
    • new material continually being added to ocean floor
  •  
  • evidence for sea-floor spreading 1. molten material 2. magnetic stripes 3. drilling samples
  • 1. Evidence from molten material The submersible Alvin photographed pillow lava along the mid-ocean ridge.
  • 2. Evidence from magnetic stripes
    • 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.
    3. Evidence from drilling samples
  • subduction
    • process where oceanic crust sinks down beneath trench into mantle
  • deep-ocean trench
    • deep, underwater canyon
    • forms where oceanic crust bends
    • subduction takes place here
  • Oceanic crust is returned to the mantle through subduction
  •  
  • The Sea Floor is Spreading
  • REVIEW TIME
  • mid-ocean ridge
    • winds beneath Earth’s oceans
    • mapped using sonar = device that bounces sound waves off underwater objects & records echoes
  • sea-floor spreading
    • theory proposed by Harry Hess
    • new material is continually being added to ocean floor
  • deep-ocean trench
    • deep, underwater canyon
    • forms where oceanic crust bends
    • subduction takes place here
  • Evidence for sea-floor spreading
    • molten material
    • magnetic stripes
    • drilling samples
  • subduction
    • process by which oceanic crust sinks down beneath trench  mantle
  • Harry Hess
    • What scientist helped to discover the process of sea-floor spreading?
  • mid-ocean ridges
    • Along what feature of the ocean floor does sea-floor spreading begin?
  • Evidence from The submersible Alvin photographed pillow lava along the mid-ocean ridge. molten material
    • 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.
    Evidence from drilling samples
  • Evidence from magnetic stripes
  • Oceanic crust is returned to the mantle through subduction