Plate Tectonic Map of the Earth

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The Theory of Continental Drift
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• Continental drift was proposed by Alfred Wegener
• He used the following ideas to support his
  theory
• 1. The fit of the continents
• 2. The distribution of fossils
• 3. Similar sequence of rocks
• 4. Ancient climates
• 5. The wandering of the Earth's polar regions
• Wegener used his observations to hypothesize that
  all of the present-day continents were once part
  of a single supercontinent called Pangaea

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The Fit of the Continents
animation
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• Fossils of the same species were found on several
  different continents.
• For example, Glossopteris, a fern, was found on
  the continents of South America, Africa, India,
  and Australia. If the continents are reassembled
  into Pangaea, the distribution of Glossopteris
  can be accounted for over a much smaller area.

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Distribution of Similar Fossils
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Continental Drift - Rock Sequences
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Continental Drift - Glaciation
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Sea-Floor Spreading

• In 1962, Harry Hess proposed that new ocean floor
  is formed at the mid-ocean ridges. The ocean
  floor is produced by magma that rises from the
  Earths interior.
• Hess suggested that the ocean floor moved away
  from the ridge and plunged into an oceanic trench
  along the continentals.

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