- The age of earth is about 4.5 billion years. About 70% of total earth surface is covered by the oceans (Hydrosphere). whereas remaining 29.2% is represented by continents, (Lithosphere).
- More than 75% of the total land area of the globe is situated to the north of equator, therefore northern hemisphere is also known as the ‘Land Hemisphere‘ and the Southern hemisphere as the ‘Water Hemisphere’. It is believed that the continents are moving away from each other, Several theories have been propounded to explain this phenomenon. One such theory is continental drift theory.
Continental Drift Theory:
- Continental drift theory was proposed by famous German Geographer, According to this theory, Before 200 million years ago, there was a single land mass surrounded by water which was named as Pangea.
- About 200 million years ago, pangena got cracked into two parts i.e. (a) Angara land (or Laurasia) (b) Gondwana land, and ocean land filled in it. As a result, a narrow sea was created, known as Thethy’s Sea.
- During further course of time, Angaland was cracked into:
- Northern American Plate
- Eurasian Plate
Whereas Gondwana land was cracked into 5 plates:
- American Plate
- Southern American Plate
- Indian Plate
- Australian Plate
- Antartic Plate
After that, about 40 years ago, Indian plate started drifting towards North East direction where it collided with Eurasian plate and as a result of collision, folding occurs over Tethy’s sea which resulted into upliftment is still going on.