We explain what Pangea was, when it existed, how it was formed and divided. Also, what is the theory of continental drift.
What was Pangea?
Pangea was the ancient supercontinent that existed between the end of the Paleozoic era and the beginning of the Mesozoic, that is, between 335 million years and 175 million years before our time. In it converged all continents current, forming a large land mass with the appearance of a letter C, distributed across the equator.
Pangea was surrounded by a single sea, called Panthalassa, and housed another one of smaller size in its concave part, called the Sea of Tethys. Its surface was so massive that the continental interior had very little contact with the humidity of ocean and therefore received very little rainfall, making it a gigantic desert.
Inside, the land animals they could migrate freely without being interrupted by water passages. There lived the first dinosaurs of the history.
Its name comes from the Greek bread, "everything and gea, "Earth". It was proposed by the German geophysicist Alfred Wegener (1880-1930), also author of the Theory of Continental drift , process the latter that accounts for both their formation and their separation.
Pangea formation
The formation of Pangea was just one stage in a long journey of formation and dismantling of numerous supercontinents. The formation of Rodinia can be taken as a starting point, about 1,100 million years ago, during the Proterozoic period.
Rodinia existed until 750 million years ago, when it fragmented and allowed the subsequent formation of Pannotia, 600 million years ago. This, in turn, fragmented about 540 million years ago, into two large fragments: Gondwana and Proto-Laurasia.
These fragments had a life of divisions and displacements. Approximately 359 million years ago, at the beginning of the Carboniferous period all the previous continents were unified Pangea. During this period of formation, numerous mountain ranges were born, such as the Atlases, the Appalachians, the Urals, Ouachita, among others.
Pangea Separation
Pangea began its decomposition in the middle of the Jurassic period (201-145 million years ago), when it suffered a crack that extended from its ocean interior (Tethys) to what would later become the eastern Pacific.
This is how present-day North America was separated from Africa, generating abundant faults that in turn gave rise to the Mississippi River, and a new ocean: the North Atlantic, which began an enlargement towards the south that took several million years. At the same time, Laurasia started a movement that closed the sea of Tethys and Africa suffered a series of cracks that later gave rise to the Indian Ocean.
Later, during the Cretaceous period (140-150 million years ago), the supercontinent Gondwana was divided into four new continents: Africa, South America, India and Antarctica / Australia. From the latter, New Zealand and New Caledonia soon began their independent life, as islands, during the late Cretaceous.
Finally, at the beginning of the Cenozoic Era (Paleocene and Oligocene periods), Eurasia separated from Greenland and North America, opening the Norwegian Sea about 60 million years ago. The expansion of the Indian and Atlantic oceans continued, Australia then separated from Antarctica and moved north, while it remained in its current place at the south pole.
This also gave rise to the circumpolar current, which runs through the free space between Antarctica, Africa and South America. About 35 million years ago, India collided with Asia and formed the Himalayas. The continents finally approached their current position, so it could be said that we are living in the final epoch of the separation from Pangea.
Theory of continental drift
This theory is the explanation that Alfred Wegener enunciated in 1912 to explain the formation and current location of the continents. It was properly demonstrated and explained thanks to the 1960 development of plate tectonics.
The formulation of this initial theory was based on the fact that the continents fit together like pieces of puzzle, and that the geological distribution and the fossil record show important similarities in the regions that were once in contact, such as the east coast of South America and the west coast of Africa, where the same type of plant and animal fossils could be found.
In his original thesis, Wegener assumed that the continents moved very slowly over a denser and more viscous layer of the Earth, the same that made up the ocean floors and extended under the continents. This concept involved enormous forces of friction that Wegener could not explain and this led to the rejection of his theories at the time.
Today, instead, we know that they are very close to the tectonic reality of the planet, and that the upper layers of the lithosphere move over the viscous layers of the mantle, thus allowing the constant reconfiguration of the land surface of our planet.