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Continental Drift Theory by Alfred Wegener
Alfred Wegener proposed the Continental Drift Theory in 1912. It was first suggested by Abraham Ortelius in 1596, and Alfred Wegener completed its development. The hypothesis addresses how the continents and oceans are distributed. According to Wegener’s hypothesis of continental drift, Pangaea, a Mega Ocean surrounding a supercontinent that consisted of all the continents as a single continental mass known as a Super Continent. Panthalassa is another name for the Mega Ocean.
Although until Arthur Holmes subsequently proposed the theory, Wegener’s original theory could not account for mantle convection. The mega-ocean was known as Panthalassa, and the supercontinent was known as Pangaea (Pangea). This idea states that the supercontinent Pangaea started to divide about 200 million years ago. The southern and northern modules were formed when Pangaea originally separated into two large continental masses known as Gondwanaland and Laurasia. Later, Gondwanaland and Laurasia began to fragment into other smaller modern-day continents.
Continental Drift Theory for UPSC: Various Stages
A mega-ocean called Panthalassa ringed the supercontinent Pangea during the Carboniferous period’s first stage.
The supercontinent Pangaea started to separate in the second stage of the Jurassic epoch about 200 million years ago. Pangaea initially split into two massive continental masses, with the northern and southern components being created by Laurasia and Gondwanaland, respectively.
During the Mesozoic era’s third stage, the Tethys Sea steadily widened and filled the space between Laurasia and Gondwanaland.
The Atlantic Ocean first appeared in the fourth stage, some 100 million years ago, when North and South America moved westward. The westward movement of North and South America resulted in the formation of the Rockies and Andes.
The fifth stage is the Orogenetic Stage, during which mountain-building activity occurred.
Forces Responsible for Continental Drift
- Because the earth is not perfectly spherical and has a bulge at the equator, the continental drift was equatorward due to the combined action of gravity forces, pole-fleeing forces, and buoyancy factors.
- The tidal currents brought on by the earth’s rotation forced the continental drift to move westward.
- However, it was later found that these two variables were insufficient explanations for continent drift, which is viewed as a criticism of Wegener’s theory.
Objective about Continental Drift Theory
In 1912, German scientist Alfred Wegener introduced the idea of continental drift. In a book titled “Die Entstehung de Kontinente und Ozeane,” published in 1922 and then translated into English in 1924, he expanded on his theory.
Wegener’s primary motivation for formulating his drift hypothesis was to provide an explanation for significant climatic shifts that have happened in Earth’s previous geological history, such as the Carboniferous Glaciation.
The climate changes that occurred may have two different causes:
- If the climatic zones fluctuated from one region to another while the continents remained stationary in their positions,
- If the continents migrated while the climate zones remained constant. Wegener favoured the second option.
Other Theories related to Formation of Continents
According to the most widely accepted view, the movement of tectonic plates is what causes continents to form. The fact that Earth’s surface is separated into solid slabs, which Wegener in his theory referred to as tectonic plates, makes it unique among the planets and distinguishes it from our moon. Despite the recent deformation visible on their surfaces, neither planet’s surface is separated into plates.
The hypotheses of continental drift and seafloor spreading received solid scientific evidence as technology developed, enabling deeper research. The contemporary plate tectonic hypothesis was created by combining the two theories.
Evidences Supporting Continental Drift Theory
The Matching of Continents (Jig-Saw-Fit)
The shorelines of South America and Africa resemble one another when they are faced with one another. Africa, Madagascar, and India’s east coast all fit together when matched in a similar way.
Rocks of Same Age across the Oceans
Rock development on different continents has been correlated using radiometric dating methods. It implies that the mountain ranges of Western Africa correspond to the 2,000 million-year-old band of ancient rocks off the coast of Brazil. There are parallels between the Caledonian and Appalachian mountain ranges as well. It also implies that the Jurassic period is when the early marine deposits along the shores of Africa and South America were formed, suggesting that the ocean did not exist before to that time.
The sedimentary rock known as tillite was produced by glacial deposits. Six separate landmasses in the Southern Hemisphere, including Africa, the Falkland Islands, Madagascar, Antarctica, Australia, and India, have been found to have analogies to the Gondwana system of deposits from India. It demonstrates that these land masses had a remarkably similar history in antiquity.
Along Ghana’s coast, there are gold placer deposits that can be found (West Africa). On the other hand, there is no source rock nearby. It’s remarkable that gold-bearing veins could exist in Brazil. Ghana’s gold deposits appear to come from the Brazil plateau when the two continents are placed side by side.
Distribution of Fossils
On each side of the sea barrier, the same kinds of species and animals may be found. For instance, only Southern Africa and Eastern South America are home to Mesosaurus, a freshwater crocodile-like reptile that lived between 286 and 258 million years ago.
Limitations of Continental Drift Theory
Wegener was unable to clarify why the drift started during the Mesozoic epoch. According to Wegner, the forces that propelled the movement of continents were buoyancy, tidal currents, and gravity, but these forces are too weak to move continents. Pangaea is acknowledged by contemporary ideas (Plate Tectonics), although the explanation disproves Wegner’s theory of drifting.
His explanation of how the SIAL (Silica-Aluminum)-based continental crust, which is floating over the SIMA (Silica-Magnesium)-based ocean floor, formed island arcs that, according to him, were formed during the drifting of continents as a result of friction, fell short. Later Plate Tectonic Theory demonstrated that the entirety of SIAL and SIMA is floating over the asthenosphere.
Continental Drift Theory FAQs
Q What is continental drift theory it explain?
Ans. The theory of continental drift describes how the Earth’s continents move in relation to one another, giving the impression that they are drifting across the ocean floor together.
Q What are the 4 evidences of continental drift?
Ans. The proponents of continental drift based their theory on a number of pieces of evidence, including how well the continents fit together, pale climate indicators, truncated geologic structures, and fossils.
Q What is the importance of continental drift theory?
Ans. Large-scale horizontal movements of continents in relation to one another and to ocean basins over the course of one or more geologic epochs are referred to as continental drift. This idea served as a crucial building block for the theory of plate tectonics, which includes it.
Q Who proposed continental drift theory?
Ans. Alfred Wegener, a German geophysicist and meteorologist, developed the Continental Drift theory in the early 20th century, which partially described how continents and ocean basins are arranged now on Earth.
Q What was the first evidence of continental drift?
Ans. The fact that some continents’ coasts fit together like jigsaw puzzle pieces was Wegener’s first piece of supporting information. On the first world maps, South America and Africa’s coastlines were compared, and some people speculated that the continents had been torn apart.
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