The Theory Of Continental Drift
In the past, continents were thought to be solid for millions of years. Nothing was known that the earth’s crust was made up of plates moving thanks to the convection currents of the mantle. However, scientist Alfred Wegener proposed the theory of continental drift. This theory states that the continents have migrated for millions of years and are still doing so.
By all accounts, this theory was quite a revolution for the world of science and geology. Do you want to learn everything about continental drift and discover its mysteries?
Continental Drift Theory
This theory relates to the current movement of the plates that support the continents and move over millions of years. Throughout Earth’s geological history, the continents have not always been in the same position. There is a body of evidence that will later help Wegener disprove his theory.
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If you look closely at the shape of all the continents, it seems like America and Africa are united. This was the attention of philosopher Francis Bacon in 1620. However, he did not propose a theory that these continents had stayed together in the past.
This was mentioned by Antonio Snider, an American living in Paris. In 1858 he raised the possibility that the continents might be moving.
It was already 1915 when the German meteorologist Alfred Wegener published his book entitled “The Origin of Continents and Oceans”. In it he revealed the entire theory of continental drift. Wegener is therefore considered the author of the theory.
In the book, he explained how our planet had hosted a kind of supercontinent. That is, all the continents we have today once together formed one. He named the supercontinent Pangea . Due to the internal forces of the earth, Pangea would break and move away bit by bit. After millions of years, the continents would take the position they are in today.
Evidence and Evidence
According to this theory, in the future, the continents will meet again in millions of years. What made it important to demonstrate this theory with proof and evidence?
Paleomagnetic TestsThe first piece of evidence that made them believe him was the explanation of paleomagnetism. The earth’s magnetic field was not always in the same orientation. Again and again, the magnetic field has reversed . What is now the south magnetic pole used to be north and vice versa. This is known because many rocks with high metal content are given an orientation to the current magnetic pole. Magnetic rocks have been found with the north pole pointing towards the south pole. So in antiquity it must have been the other way around.
This paleomagnetism could not be measured until the 1950s. Although it was possible to measure, very poor results were obtained. However, analysis of these measurements managed to determine where the continents were located. You can tell this by the orientation and age of the rocks. In this way it could be shown that all continents were once united.
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Biological Testing
Another test that confused more than one were the biological ones. Both animal and plant species are found on different continents. It is unthinkable that non-migratory species could move from one continent to another. Which suggests they were once on the same continent. The species dispersed over time as the continents moved
Also in western Africa and eastern South America rock formations of the same type and age are found.
A discovery that led to these tests was the discovery of fossils of the same broadleaf fern in South America, South Africa, Antarctica, India and Australia. How can the same species of fern come from different places? It was concluded that they lived together in Pangea. Lystrosaurus reptile fossils have also been found in South Africa, India and Antarctica, and Mesosaurus fossils in Brazil and South Africa.
Both flora and fauna belonged to the same common areas, which grew apart over time. When the distance between the continents was too great, each species adapted to the new situation.
Geological Tests
It has already been mentioned that the edges of the African and American continental shelves fit together perfectly. And they were once one. In addition, they have in common not only the puzzle shape, but also the continuity of the mountain ranges of the South American continent and Africa. Today, the Atlantic Ocean is responsible for separating these mountain ranges.
Paleoclimatic Tests
The weather also helped interpret this theory. Evidence of the same erosion pattern has been found on different continents. Currently, each continent has its own regime of precipitation, winds, temperatures, etc. However, when all the continents formed one, there was a unified climate.
In addition, the same moraine deposits have been found in South Africa, South America, India and Australia.
Stages Of Continental Drift
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We will analyze what are the main stages of continental drift:
About 1100 billion years ago: The formation of the first supercontinent took place on the planet Rodinia. Contrary to popular belief, Pangea was not the first. Despite this, the possibility that other earlier continents may have existed is not excluded, although there is insufficient evidence.
About 600 billion years ago: Rodinia took about 150 million years to fragment and a second supercontinent called Pannotia took shape. It had a shorter duration of only 60 million years.
About 540 million years ago Pannotia fragmented into Gondwana and Proto-Laurasia.
About 500 billion years ago: Proto-Laurasia was divided into three new continents: Laurentia, Siberia and the Baltic Sea. In this way, this division created two new oceans known as Iapetus and Khanty.
About 485 billion years ago: Avalonia separated from Gondwana (the land corresponding to the United States, Nova Scotia and England. The Baltic Sea, Laurentia and Avalonia collided and formed Euramérica.
About 300 billion years ago: There were only 2 big continents. On the one hand we have Pangea. it existed about 225 million years ago. Pangea was the existence of a single supercontinent on which all living things spread. If we look at the geologic timescale, we see that this supercontinent existed during the Permian Period. On the other hand we have Siberia. Both continents were surrounded by the Panthalassa Ocean, the only existing ocean.
Laurasia and Gondwana : As a result of the breakup of Pangea, Laurasia and Gondwana formed. Antarctica also began to form during the Triassic. It happened 200 million years ago and differentiation of species of living beings began.
Current Distribution Of Living Beings
Although after the continents separated, each species acquired a new branch in evolution, there are species with the same characteristics on different continents. These analyzes show a genetic similarity to species from other continents. The difference between them is that they have evolved over time by being in new environments. An example of this is the garden snail found in both North America and Eurasia.
With all this evidence, Wegener tried to defend his theory. All these arguments convinced the scientific community. He really had discovered a great discovery that would make a breakthrough in science.
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This post was last modified on February 4, 2023 10:05 am