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 It was the ancient supercontinent that existed between the end of the Paleozoic Era and the beginning of the Mesozoic Era that is, between 335 million years and 175 million years before our time. All the current continents converged on it, 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 smaller one in its concave part, called the Tethys Sea. Its surface was so massive that the continental interior had very little contact with the humidity of the ocean and therefore received very little precipitation, making it a gigantic desert.
Inside, land animals could migrate freely without being interrupted by water passages. The first dinosaurs in history lived there.
Its name comes from Greek bread“everything”, and gea“land”. It was proposed by the German geophysicist Alfred Wegener (1880-1930), also author of the Theory of Continental Drift (1912), the latter process that accounts for both its formation and its separation.
Formation of Pangea
The formation of Pangea was just one stage in a long path of formation and dismantling of numerous supercontinents. The formation of Rodinia, about 1.1 billion years ago, during the Proterozoic period, can be taken as a starting point.
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 their own 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 created, such as the Atlas Mountains, the Appalachian Mountains, the Ural Mountains, and Ouachita Mountains, among others.
Pangea breakup
Pangea It began to decompose in the middle of the Jurassic period (201-145 million years ago), when it suffered a rift that extended from its interior ocean (Tethys) to what would later become the eastern Pacific.
This is how current 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 began a movement that closed the Tethys Sea 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 split 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 Antarctica remained in its current location 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 eventually approached their current position, so it could be said that We live in the final era of the separation of Pangea.
Continental drift theory
This theory It is the explanation that Alfred Wegener stated in 1912 to explain the formation and current location of the continents. It was properly demonstrated and explained thanks to the development of plate tectonics in 1960.
The formulation of this initial theory was based on the fact that the continents fit together like pieces of puzzleand 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 more viscous and dense layer of the Earth, the same one that made up the ocean floors and extended under the continents. This concept implied enormous friction forces that Wegener was unable to explain and this led to the rejection of his theories at the time.
Today, however, 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.
References
- “Pangea” on Wikipedia.
- “It all started in Pangea” in National Geographic.
- “The rise of Pangea” (video) by Michael Molina at TED en Español.
- “Pangea” in The Encyclopaedia Britannica.
