In Geography class 11: Continental Drift Theory, we shall learn more about this topic, the reason for the force of drifting, and post drift studies. The scientists think of the possibility that once upon a time, the two Americas, Europe, and Africa were all a part of one continent.
How did it all start?
- Abraham Ortelius –
This possibility of one single continent was first predicted by the famous Dutch mapmaker Abraham Ortelius in 1596.
- Antonio Pellegrini –
Then, Antonio Pellegrini drew a map and showed all the three continents together.
- Alfred Wegener
In 1912, a breakthrough came in this argument. Alfred Wegener, a German meteorologist, made a profuse argument known as the continental drift theory.
As per the continental drift theory, there was a single massive continent floating on a mega ocean. This supercontinent was called Pangaea, and the mega-ocean was named Panthalassa. Then, around 200 million years ago, the supercontinent began to drift apart. This drifting caused the formation of two new continent masses- Laurasia (the northern component) and Gondwana land (the southern component). Then as time went by, they also started to tear up which led to the formation of seven smaller continents.
Evidence in support of Continental Drift Theory:
The numerous facts that support the continental drift theory are:
1. Pieces of Puzzles –
The continents look like pieces of a massive puzzle. The shorelines of the continents of Africa and South America are somewhat similar if you take a closer look at the map.
2. Same age of Rocks –
The process of radioactive dating helped in finding the relation between the rocks of two different continents. The rocks from the Brazilian coast formed around 2000 million years ago were an exact match to those in Western Africa.
Researchers also found out that the first marine deposits along the coastline of the South American and African continents date to the Jurassic period. It means that there were no ocean bodies between the continents before the dinosaurs.
3. Tillite –
The sedimentary rocks that are made from the deposits of glaciers are called Tillite. The sediments from the Gondwana part of India had counterparts that belonged to six different landmasses of the Southern Hemisphere. The rest of this succession was detected in the parts of Africa, Falkland Island, Madagascar, Antarctica, and Australia respectively.
At the base, the system has a thick glacial tillite indicating extensive glaciation.
4. Location of Placer Deposits-
The most astonishing fact is that there are gold mines on the coast of Ghana; however, no clue of the source rock of the mine is present there. It is because there are gold mines in Brazil that have the same properties as the mines present in Ghana. Thus, one can say that the gold deposits of Ghana are derived from these Brazilian gold mines!
5. Distribution of Fossils-
Lemurs are a kind of animal that is native to Madagascar, however new research reveals that their fossils were also found in India and Africa. This directly indicates that these three places were once located together on a single mass land called Lemuria.
Also to support this theory, Mesosaurus belonged to the lizard family from the early Permian times and they lived in shallow saline water bodies. However, most of their fossils were found in South America. But, later their skeletons were also found in the parts of South Africa and Brazil! The Continental Drift Theory is the only possible reason for this.
Force for Drifting
The continental Drift Theory suggested that the force of drifting apart of continents could be possible because of two reasons:
- It may be because of the polar-fleeing force. It also causes the rotation of the earth.
- The second reason for this drifting could be the tidal force. The tidal force is caused due to the attraction of the sun and moon, which then cause tides in the ocean.
After World War II, numerous discoveries changed the face of geological literature. These discoveries and revelations added more details to the picture, making it clearer, and are called post drift studies.
Arthur Holmes proposed the conventional current theory in the 1930s. It discussed the possibility of convection current generated in the mantle portion of the earth. The currents are because of differences in the thermal energy of radioactive elements.