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What you need to know about Pangaea, the ancient supercontinent on Earth 300 million years ago

Around 300 million years ago, before the first dinosaurs appeared, the Earth was not made up of seven continents. It had only one massive supercontinent called Pangaea, surrounded by just one ocean: the Panthalassa. But what do we actually know about these ancient lands?

The modern theory of tectonic plates stipulates that the external layer of the Earth is broken into several plates which slide over the rocky mantle of the Earth. Over the course of the last 3.5 billion years, several supercontinents have formed and broken apart, radically modifying the history of our planet. Over a century ago, scientist Alfred Wegener proposed the idea of an ancient supercontinent, which he called Pangaea. According to Wegener, several modern continents appear to fit perfectly together, and certain geological data also supported his theory. Coal deposits found in Pennsylvania for example have a similar composition to those from the same period found in Poland, Great Britain and Germany.

In fact, North America and Europe should once have been part of the same continental mass. In fossil archives, identical plants (some now extinct) can also be found in continents that are nowadays very far apart. The same goes for mountain ranges: the Appalachians in the United States and the Atlas Mountains in Morocco were once part of the mountain range in central Pangaea. They may have been formed by the collision of supercontinents Gondwana and Laurussia.

The presence of such a land mass would clearly have led to very different weather conditions from what we experience today. For example, it appears that the middle of the continent was completely dry, closed in by massive mountain ranges that blocked any humidity. But it wasn’t all dry. Coal deposits found in the United States and in Europe show that certain parts of the ancient supercontinent, near the equator, had luxuriant tropical forests, similar to the Amazon jungle. The coal in fact formed when dead plants and animals decayed in marshy water, and were then transformed into first peat and then coal by the water pressure.

Pangaea
Credits: Wikimedia Commons / Kieff

Furthermore, the coal deposits tell us that there was abundant life on Earth at this time. Weather modelling also confirms that central continental Pangaea had extreme climates, according to an article published in 2016 in Palaeogeography, Palaeoclimatology, Palaeoecology. The researchers based their work on biological and physical data gathered from the Moradi Formation, a region of stratified paleosols (fossil soils), in Northern Niger, in order to reconstruct the ecosystem and climate during the period in which Pangaea existed. Comparable to the African desert of Namibia and the Lake Eyre basin in Australia, it seems that Pangaea’s climate was generally arid with short recurrent periods of humidity, which sometimes included enormous floods.

In terms of fauna, it appears that several animal species flourished, including the Traversodontidae, a family of herbivores that includes the ancestors of mammals. During the Permian period, insects such as dragonflies and beetles also prospered. The high levels of oxygen released into the air by the forests (30% more oxygen than we have nowadays) in fact promoted gigantism in certain species. These insects were therefore enormous. Remember that Pangaea was next the scene of the worst mass extinction in history. Around 252 million years ago, the Permian Triassic extinction caused the disappearance of the majority of species on Earth. The early Triassic period saw the birth of the archosaurs, a group of animals which eventually evolved into crocodiles, birds and a plethora of reptiles. Finally, around 230 million years ago, the first dinosaurs emerged on Pangaea, including feather clad theropods.

And if the continents do not stop evolving, what does the future hold? The current configuration of the continents is unlikely to be the last. Supercontinents formed several times over the course of the Earth’s history, before dividing again into numerous continents. At present, for example, Australia is gradually moving towards Asia, and Eastern Africa is slowly separating from the rest of the continent. Geologists have also noticed an almost regular cycle in which supercontinents form and separate: they estimate that this occurs around every 300 to 400 million years.

Scientists have developed mathematical 3D simulations to attempt to better understand the mechanisms of continental movement over the coming 250 million years. Published in Geoscience Frontiers in 2017, Masaka Yoshida and M. Santosh’s works propose models suggesting that over the course of millions of years, the Pacific Ocean will gradually close, bringing Australia, North America, Africa and Eurasia together in the Northern hemisphere. Finally, these continents should fuse together, forming a supercontinent called “Amasia”. The two remaining continents, Antarctica and South America, should stay relatively immobile, separate from the new supercontinent.

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