Theory of Plate Tectonics

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Learning Goals

• Describe the historical events that led to the
  Theory of Plate Tectonics.
• Explain the mechanism for the movement of the
  plates.

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Development of the TheoryAlfred Wegener (in
1924)

• He proposed the theory of continental drift,
  based on his observations of similar fossils
  found on different continents and of the shape of
  S. America and Africa. They appeared to fit like
  a puzzle.
• He believed that a super continent existed,
  called Pangaea, before they broke up.
• He lacked an explanation of a mechanism for that
  movement.

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Harry Hess (in the 1960s)

• contributed the idea of Sea Floor Spreading
• which explained how the plates could move
• and provided the mechanism for movement which
  supported Wegeners hypothesis.

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The Theory of Plate Tectonics was born

• Earths lithospheric plates rest and move on top
  of the asthenosphere.
• It explains the occurrence of volcanoes,
  earthquakes and mountain building.

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Lithosphere and Asthenosphere
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How do the Plates Move?

• Convection cells
• As hot molten material rises, it splits the
  crust.
• As the material cools, it sinks, pulling the
  crust with it. This is called the slab pull.

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Convection Cell Demo

• Fill out the worksheet as you watch and discuss
  the demonstration on convection cells.

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Proof in Science

• Imagine you are a scientist trying to prove or
  disprove life on other planet.
• Besides any actual sightings (people, cars,
  buildings, etc.), give 3 pieces of evidence that
  would PROOVE life exists on other planets.
• Give 3 pieces of evidence that would DISPROVE
  this theory.
• Do you believe there is life out there?