Plate Tectonic Theory

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  • Created by: tenk
  • Created on: 27-03-16 13:09

Alfred Wegener

  • 1620 - Francis Bacon noted the jigsaw like fit of the E.coast of S.America and the W.coast of Africa.
  • 1912 - Wegener published his theory that a single continent existed about 300 million years ago => 'Pangaea'.
  • He maintained that it had somehow later split into two giant continents => 'Laurasia' to the north and 'Gondwanaland' to the south. 
  • These two land masses split further and drifted apart. 
  • Ideas were rejected in his day as he could not offer an explanation as to how continental movement had occurred. 
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Evidence

Geological

  • Areas of South America and Africa have rocks of the same age and composition - if you fit these continents together, the distribution of rocks matches up.
  • Rock sequences in northern scotland closely agree with those found in eastern Canada, indicating that they were laid down under the same conditions in one location - this would only be possible if the continents were once joined. 
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Evidence (2)

Fossil Records

  • By fitting land masses together you can match up the distribution of some fossils, e.g. fossils of Lystrosaurus, Cynognathus, Mesosaurus (all reptiles) and Glossopteris (a plant).
  • It's very unlikely that these species migrated across thousands of miles of water, or that they evolved in different places. 
  • So fossil records suggest that these places were once joined together when these organisms were alive - hundreds of millions of years ago. 
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Evidence (3)

Living Species

  • The same living organisms can be found on different continents - again, it's unlikely that some of them migrated across the oceans, or evolved in different places. 
  • For example, earthworms of the family Megascolecidae, are found in New Zealand, parts of Asia and North America. This suggests the continents were once joined, aloowing earthworms to travel between them. 
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Evidence (4)

Climatology

  • There's evidence that the past climates of some continents were similar, despite being thousands of miles apart now. This suggests that they were located together and in a different place on Earth to where they are now. 
  • There is evidence of glaciation of the late carboniferous period (290 million years ago), deposits from which are found in South America, Antarctica and India. The formation of these deposits cannot be explained by their present position, they must have been formed togther and then moved. There are also striations on rocks in Brazil and West Africa which point to a similar situation.
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