Continental Drift Theory
Abraham Ortelius first put forward the speculation that the continent might have ‘drifted’ in 1596.
The first comprehensive and fully developed Continental Drift Theory proposed by a German meteorologist, Alfred Wegener in 1912. Alfred Wegener was the first person who used the phrase ‘continental drift’.
- According to his hypothesis, all the continents were once been joined into a single landmass, called Pangaea, and a Mega Ocean surrounded this supercontinent. The name of mega ocean ‘Panthalassa’, before breaking apart and drifting to their recent location.
- A sea named Tethys divides the Pangea into Laurasia to the north and Gondwanaland to the south Tethys.
- In his speculation the Pangaea started splitting during the Carboniferous period (before 200 million years ago) and broken into two large continental masses – Laurasia and Gondwanaland by which northern and southern components formed respectively.
- Laurasia and Gondwanaland continued to break into various smaller continents that are existing today.
Evidences supporting the Continental Drift Theory:
The Matching of Continents (Jig- Saw- Fit) or Apparent affinity of Physical Feature:
- The coastline of Africa and South America Facing each other having a remarkable match.
- Africa, Madagascar, and the western coastline of India Seems had joined.
Rocks of the same age across the Ocean:
- The methods of radiometric dating have correlated the rock formation in different continents across the oceans.
- The Caledonian and Hercynian mountains of Europe and the Appalachians of the USA seem to be of the same and continuous series.
- The rock belts around the coast of Brazil match with the rock belt found in Western Africa.
- These are sedimentary rocks formed by the deposit of glaciers.
- The tillite in the Gondwana system of sediments in India also found in six different landmasses in the southern hemisphere. It is found in the Gondwana system in India, Africa, Falkland, Madagascar, Antarctica, and Australia. These all were previously a part of Gondwana as it gives clear evidence for paleoclimates and the drifting of continents.
- The plentiful placer deposits of gold are found at Ghana coast (in west Africa) do not have source rock in the region but the sources are in Brazil. So the gold deposits of Ghana are derived from The Brazil Plateau when the two continents lay side by side.
Distribution of Fossils
- Identical species of flora and fauna (plant and animals) adapted to live on land or in Aquatic habitat – Freshwater, are found on either side of the marine barriers. e.g. The remains of Mesosauraus a freshwater reptile (- 286 to 258 million years ago) are found in southern Africa and Eastern South America (Travers formation of Brazil).
- The lemurs occur in India, Madagascar and Africa led to consider the contiguous landmass ‘Lemuria’ which connecting these three landmasses.
- The fossil of seed fern Glossopteris was also found on the continent side by side.
Force for Drifting
- According to Wagener, the Drift was in two directions due to centrifugal force and tidal currents.
- The drifting was towards the equator due to the centrifugal effect.
- The Westward movement of continents was due to the tidal force of the moon and the sun. So the forces of the moon to less extent but the forces of the sun played a major role. Although most of the Scholars found these forces to be insufficient.
- According to Wegener, Earth’s Gravity, the buoyancy of seas, and tidal currents were the main factors that causing the drift.
Drawbacks and criticism of the Theory:
- Alfred Wegener considered drifting only in the Mesozoic era, he failed to explain why drifting did not begin before.
- It only considers continents but not oceans.
- He took proofs mostly based on assumptions that are generalist
- The tidal currents, Buoyancy, and gravity are weak forces and these are not able to move continents.
- Plate Tectonics accepts the existence of Pangaea and related landmasses, but it gives a different explanation to the causes for drifting.
Conclusion: On various grounds, it was criticized but the Wegener’s theory is a significant milestone, the theory was incorporated into the theory of Plate Tectonics.