Continental drift theory Upsc

Continental drift theory

It is a Hypothesis, theory regarding the formation of the continents. When we look at the shape coastline of the Atlantic Ocean, the symmetry of the coastlines on either side of the ocean creates a curiosity in us.

This made many scientists think that the Two American continents, Europe and Africa were once together. This idea was first proposed by Abraham Ortelius, a Dutch mapmaker in 1596.

Continental drift theory was proposed by?

Continental drift theory was proposed by Alfred Wegener.

Also, A guy named Antonio Pellegrini drew a map, illustrating that the three continents were once together. But the comprehensive argument to support this theory was put by a German Scientist, Alfred Wegener. This theory was known as the Continental Drift theory. This theory was proposed in the year 1912.

Continental Drift Theory
Continental Drift Theory by nationalgeographic.org/encyclopedia/continental-drift/

According to Wegener, all the continents were once together as a single continental mass and it is surrounded by a mega ocean. He called this Mega continent ‘PANGAEA‘ and this mega ocean ‘PANTHA-LASSA‘.

Wegner argued that Pangaea began to split around 200 million years ago. Also that the super continental split into two large continental masses, one is Laurasia and another one is Gondwanaland.

Laurasia formed the northern component and Gondwanaland formed the southern part. Subsequently, these two continental masses broke into many pieces that we see today.

The best evidence for continental drift theory

The following is the evidence that supports the Continental drift theory by Alfred Wegener.

  • Jig-Saw-Fit
  • Rocks of Same Time across the continent
    • Tillite
    • Placer Deposits
    • Distribution of Fossils
  • Placer Deposits
  • Distribution of Fossils
  • Force for Drifting
  • Post-Drift Studies

Jig Saw Fit

Africa and South America’s shorelines have a great and unmistakable match. In 1964, Bullard produced the best fit for Atlantic margin using computer drawings, and it proved to be a great match. The match was tried at 1000 Fathom, deep in the sea.

Fathom

a unit of Fathom is equal to six feet (1.8 metres), mainly used in reference to the depth of sea, lakes etc.

Rocks of the Same Age across the continent

The Age of rocks is determined by radiometric dating methods across the continents and oceans. By this method belt of ancient rocks from the Brazil coast which is of age 2000 million years match those from Western Africa.

And the rocks from the Jurassic age, are found along the coastline of South America and Africa. These were the earliest marine deposits. This also suggests that the ocean did not exist prior to this age.

Tillite

Gondawana sediments from India has its counterparts in 6 different places in southern Hemisphere
Tillite (Gondawana) found in India and Parts of Southern Hemisphere – CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=1320706

Tillite were the sedimentary rocks that are formed out of deposits of glaciers. A sedimentary rock that consists of consolidated masses of unweathered blocks such as large, angular, detached rock bodies and glacial till which are unsorted and unstratified rock material deposited by glacial ice in a rock flour.

Gondawana sediments from India and has their counterparts in six different landmasses of the Southern Hemisphere. At the base, the system has thick tillite indicating prolonged glaciation.

The Gondawana system of sediments from India was found in Africa, Falkland Island, Madagascar, Antarctica, and Australia.

The Glacial Tillite provides strong evidence of palaeoclimates and the drifting of continents.

Placer Deposits

Placer Deposits
Placer Deposits By © Hans Hillewaert, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=11750393

The presence of rich placer deposits of gold on the Ghana coast and the absolute absence of source rock in the region is an amazing thing.

The gold-bearing veins are in Brazil and are gold deposits of Ghana are derived from the Brazil plateau.

Distribution of Fossils

The same animal and plant fossils were found on different continents separated by thousands of Kilometres and the ocean between them is great evidence that the continents were once together.

Examples are Lemurs found in India, Madagascar and Africa linked to Lemuria landmass. These were separated by thousands of Kilometre and the ocean between them.

Also, Mesosaurus, an extinct marine reptile that has adapted to Brackish water, skeletons were found only in two places, are southern Cape province of South Africa and Iraver formation of brazil. The distance between these two locations is 4800 km and the ocean is in between them.

Force for Drifting

Alfred Wegners suggested that the movement of continents is due to tidal forces and polar-fleeing forces. Polar fleeing forces are forces created due to the rotation of the earth.

But the many scientists rejected this as these forces were very few.

Post-drift Studies

The post-World-II period and evolution of technology added new information to the studies. This includes information collected from the ocean floor mapping provided a new dimension for the study of the distribution of oceans and continents.

Conclusion

We discussed the Continental drift theory by Alfred Wegner and the evidence that supports this theory. This is useful for Upsc and other public service commission exams.

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* * All the Notes in this blog, are referred from Tamil Nadu State Board Books and Samacheer Kalvi Books. Kindly check with the original Tamil Nadu state board books and Ncert Books.
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