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Continental Drift Theory

Continental Drift Theory

Continental Drift Theory was proposed by Alfred Wegner in 1912 after he found coal near polar region (a property of heated region) and glaciation evidence in equatorial region.

About 300 million years ago, Earth didn’t have seven continents, but instead one massive supercontinent called Pangaea, which was surrounded by a single ocean called Panthalassa.

In Carboniferous period around 200 million years ago, Pangaea began to split and gave rise to Laurasia and Gondwanaland which further broke into continents that the present world witness.

  • Breaking of Pangaea led to the formation of Tethys Sea (Present day Mediterranean Sea and some part of Himalayas as marine fossils have been found in Himalayas as well as it has rich Petroleum deposits.)

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Evidences to support the theory

  • Jigsaw fit along the coastline of the continents.

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  • Fossil analysis at different parts of the world. Example- Glossopetris Flora is found in Brazil, Africa, Peninsula India, Australia.
  • Rock analysis along the coastline shows rocks of same age and types are found across Atlantic.

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  • Glacial evidence in tropical land over some region. Example- Chotanagpur Plateau.

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  • Mountains like Appalachian and in Ireland and Scan Divian countries are similar.

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Limitations of the theory

  • Wegener failed to explain why the drift began in Mesozoic era.
  • Forces like buoyancy, tidal currents and gravity are too weak to be able to move continents which according to Wegner were the driving forces behind the movement of continents.
  • Modern theories (Plate Tectonics) accept the existence of Pangaea but the explanation rules out Wegner’s idea of drifting.
  • Continental crust made up of SIAL (Silica-Aluminum) is floating over Oceanic floor made up of SIMA (Silica-Magnesium) without resistance failed to satisfy his explanation about the formation of island arcs which according were created during the drifting of continents as a result of friction.
  • Later Plate Tectonic Theory showed that SIAL and SIMA as a whole landmass is floating over Asthenosphere.

Conclusion

Though Wegner could not explain the forces responsible for the drift, central idea of Drifting Theory was accepted and this central idea helped in the development of Plate Tectonic Theory.

 

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