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Essay: Alfred Wegner – the theory of continental drift

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  • Alfred Wegner - the theory of continental drift
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The solar system was created with a cloud of dust and gas, which is also known as the Solar Nebula. The Solar Nebula was created approximately 4.6 billion years ago (Redd, 2016) and after it was created, the gravity collapsed on itself as it began to spin and created the sun in the center of the nebula (Redd, 2016). As the atoms in the nebula continued to spin, it created several different planets and Earth was one of the few planets scientists know of today. Before Earth had several different continents, Earth started out with having only one gigantic landmass. This landmass was known as the Supercontinent or its other name was Pangea. The name Pangea came from the Greek Pangaia, meaning “all the Earth” (Britannica, 2018).

Continental Drift After 250 Million Years is a photograph by Mikkel Juul Jensen which was uploaded on May 1st, 2013

Before Pangea, there were other supercontinents. The first supercontinent was Vaalbara which was created 3.6 billion years ago but broke apart 2.8 billion years ago. The second supercontinent was Kenorland which was formed about 2.7 billion years ago but broke apart 2.4 billion years ago. The third supercontinent was created 2.5 billion years ago and was called Columbia and existed until 1.6 billion years ago. After Columbia came Rodinia. Rodinia existed 1.2 billion years ago but broke apart about 700 million years ago. Then after Rodinia finally came Pangea, which Pangea broke apart 200 million years ago. Pangea was a huge landmass formed by the convergence of multiple continents (King, 2018).

In 1912, a German scientist and an adventurer named Alfred Wegner developed the theory of continental drift (Higgins, 2015). Wegner published a book in 1912 called The Origin of Continents and Oceans, which he talked about the theories of the shifting plates, he named the theory plate tectonics and the continental drift (Weisstein, 1996). Wegner believed that the supercontinent existed and broke up 200 million years ago. After Pangea broke up, Wegner stated that the parts of Pangea “drifted” to their present positions (Weisstein, 1996). When Wegner first proposed this theory of the continental drift, nobody believed him because he could not explain how the continents drifted apart. Some of the problems with Wegner’s theory was that he could not explain what forces caused the continents to shift or that what happens to the ocean’s floor as the continents continued to move. Wegner thought that the answer to his theory was the forces arising from Earth’s rotation and the oceans tide which was influenced by the moon. But with these accusation, physicists were able to prove Wegner’s theory was wrong. Physicists showed that the rotation of the Earth and the tidal forces caused from the moon were too weak to cause such a huge impact as moving continent. But with others proving Wegner wrong, this did not stop him from continuing his research.

As Wegner continued to search for more evidence to support this theory, he found large scales of geological features matching one another on different continents such as South America and Africa (Waggoner, 1996). When he looked closely at the Appalachian Mountains of eastern North America, it matched the Scottish Highlands. They had similar rocks and structures which matched each other’s coasts. If one were to piece it together, the coasts would fit just like a puzzle. With this information, Wegner suggested the two had once been connected, but now they are separated by the Atlantic Ocean. But how they became separated, Wegner had no answer.

Pangea was known to be just one large landmass of plate tectonic, but it was not just one instead it was made out of nine plates combined. The nine major plates were named after the landforms that were found on. These nine major plates are North American, Pacific, Eurasian, Africa, Indo-Australian, Australian, Indian, South American and Antarctic (Oskin, 2017). The way plate tectonics moved had to do with the Earth’s mantle. The hot material which consist of very hot lava moves towards the surface and the colder mantle rocks would sink. This caused what is known as seafloor spreading which this answers Wegner’s question of how plate tectonics moved. When seafloor spreading occurs, it causes two tectonic plates to meet and with one plate sliding beneath one another, usually the cold plate moves below the hot plate pulling the crust behind it downwards (Oskin, 2017), this is also known as subduction zones. The Earth’s plates move a few centimeters per year, which helps push the continents apart and sometimes even pull them together. When these plates slides, a series of movements are caused which is known as Earthquakes.
One of Wegner’s theory was continental drift which consisted of plate tectonics sliding over one another. Plate tectonics is the theory that the Earth’s outer shell is divided into several plates that glide over the mantle (Oskin, 2017). This theory generally explains the movement of the lithosphere and the asthenosphere. From the bottom of the ocean to the tip of the mountains, plate tectonics explains how each part of the land got to where they are today. The plates that line the Earth’s crust is called lithosphere. The Earth’s crust consists of low density, easily melted rocks which were also granitic while the mantle consisted of basalt and gabbro. Lithosphere consists of the Earth’s crust and is part of the mantle, which allows the plates to move and slide which causes what is known as the continental drift. Where the lithosphere lies, it consists of rigid, strong outer layer of the earth with an averaging 100 km thick. The lithosphere includes both the uppermost mantle and the overlying crust. Below the lithosphere is the asthenosphere. This layer lies an averaging 100 to 300 km below the surface which also consists of soft, weak and somewhat fluidity, causing fluids to flow very easily. Asthenosphere allows slow moving fluids to move above it thus causing continents to slowly drift. With this, this allows mountains chains to form and this also causes continental drift. Not only does this allow continents to move, but the pressure in the mantle is great enough to stop melting from taking place even in high temperature, but this may be capable of very slow flow over hundreds of millions of years.

East African Rift Zone is a good example of a continental rift zone. (Cross section by José F. Vigil from This Dynamic Planet — a wall map produced jointly by the U.S. Geological Survey, the Smithsonian Institution, and the U.S. Naval Research Laboratory.)

After Wegner found out about moving plate tectonics and how they moved, he was able to understand how the continents got to where they were. Wegner studied and looked at the map and realized that it was not only the coastal lines of the continents that matched one another, but that there were also fossils which he used as evidence of continental drift. One particular fossil Wegner found was of an extinct reptile called the Mesosaurus (Society, 2012). The Mesosaurus was thought to be a large crocodile- like reptile that lived in the rivers and lakes. They lived during the early Permian (between 286 to 258 million years ago). During this period of the Permian, insects like dragonflies and beetles also already existed. Another type of fossil found to help claim that these huge land masses used to be connected was the fossils of the Cyognathus. Cynognathus is an extinct mammal-like reptile which literally translates to ‘dog jaw’ (Society, 2012). These mammal-like reptiles were as large as modern wolves and lived during the Triassic time period (250 to 240 million years ago). During this period of the Triassic, it give more life to the archosaurs. Archosaurs were a group of animals that would later on develop into animals such as crocodiles and birds and even reptiles. These fossils were found in Southern Africa and South America thus helping scientists to believe that millions of years ago, Pangea did in fact exist.

Not only did fossil remains support the theory of Pangea, but there were also geological fits as well. While Wegner was researching, he also found other geological features that matched one another but were from separate coasts. An example of this would be from South America and West Africa. When Wegner mapped the continents together, it revealed that ancient rock that existed over 2,000 million years old were continuous from one continent to another (Society, 2012). Being a meteorologist, Wegner knew that if the continents were once connected together, their climates in the past would have been the same as their present climate. With this knowledge, Wegner found evidence of glacial deposits. Since glaciers are very large and very icy, when they move, they erode rock and sediments. While moving they commonly expose bare ricks beneath the ice, commonly stripping off all soil cover as it slowly moves. When glaciers move, they can also transport sediment of any size from place to place. Glacial deposits that formed during the Permo-Carboniferous glaciation (about 300 million years ago) are found in Antarctica, Africa, South America, India and Australia (Society, 2012). When glaciers move, they create what is known as glacial erosion. Glacial erosion causes the surfaces of rocks to be polished with scratches and grooves. The glacial grooves in the polished rocks help give more support and provided further evidence that a huge landmass once existed.

Not only were animal fossils found, but coal deposits were found as well in the United States and Europe which helped scientists understand that part of the ancient supercontinent near the equator would have been very rich in tropical rain forests very much like the Amazonian jungle. Coal deposits occur when dead plants and animals sink into swampy water, where pressure and water then transform the material into peat, then to coal (Ghose, 2018).

These were some of the reasons how Pangea broke part, but before Pangea broke apart, Pangea consisted of two halves. The top half of Pangea was known as Laurasia, which is now known as Eurasia and North America. The bottom half of Pangea was known as Gondwana, which is now Africa, South America, Antarctica, India and Australia (Ghose, 2018). The supercontinent, Pangea began to slowly break apart approximately 200 million years ago. Gondwana first split from Laurasia 150 million years ago (Ghose, 2018). North America began to split away from Eurasia 60 million years ago (Ghose, 2018).

Before Pangea broke apart, there had to have been life and there was evidence to prove it. As stated above with the fossils of reptiles that were found, that meant there must have been some sort of climate to help support life itself. Having one massive landmass would have made for very different climatic cycles (Ghose, 2018). This being said, the further inland into Pangea, the dryer it became. It is thought to be dryer inland because all the mountains would have blocked all moisture and or rainfall from reaching the inland.
About 4.6 billion years ago the earth was created and 270 million years after, Pangea was created. Pangea was known to be the supercontinent coined by a German scientist named Alfred Wegner.

At first when Wegner came out with this theory, no one believed him because he could not explain how the continents were able to move to be where they are today. With many years of research, Wegner found that there was evidence to help support his theory. He saw that the coasts of the continents fitted together like a jig saw puzzle if one were to connect them together. Not only did he realize the coasts fitted together, but that there was also fossil evidence. Fossils were found on coasts of continents such as South America and Africa. Wegner concluded that it would be impossible for the animals to swim across the Atlantic Ocean to mate with one another and for them to die there. Not only that, there were also geological such as glaciers and coal deposits. So, with all these information Wegner concluded that all the continents did in fact used to be all connected with one another.

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