The outer layer of the Earth, the solid crust on which we walk, is made up of broken parts, something similar to the shell made of pieces of an egg. These pieces, the tectonic plates, move around the planet at a speed of a few centimeters a year. Every so often, the plates come together and form a supercontinent that remains for more than 100 million years, until it disappears when the plates disperse. Subsequently, after a lapse of time between 400 and 600 million years, the process is repeated.
The last supercontinent, PangeaIt was formed about 310 million years ago and began to separate approximately 180 million years ago. It is believed that the next one will be formed in 200/250 million years, so that we are currently in the middle of the dispersion phase of the current training cycle. The question is, how and why will the future supercontinent be formed?
There are, fundamentally, four probable scenarios for said training: Novopangea, Pangea Last, Aurica and Amasia. How each one could be formed depends on different factors, but they are all related to the way in which Pangea separated and to the current movement of the continents.
The rupture of Pangea led to the formation of the Atlantic Ocean, which is still opening and expanding. As a result, the Pacific Ocean is narrowing. The Pacific houses a ring of subduction zones along its edges (the Pacific Ring of Fire), where the ocean floor is subducted under the continental plates towards the interior of the planet. In that way, the old ocean floor is recycled and can penetrate the volcanic columns. The Atlantic, on the other hand, has a large oceanic ridge that produces a new plate, but only houses two subduction zones: the Volcanic Arch of the Lesser Antilles, in the Caribbean, and the Arch of the Austral Antilles, located between South America and Antarctica.
If current conditions continue, that is, that the Atlantic continues to open and the Pacific closes, we would have a scenario in which the next supercontinent would form in the antipodes of Pangea. The American continent would collide with an Antarctic that would be sailing adrift to the north, to later collide with the already reunited Africa and Eurasia. This hypothetical supercontinent is called Novopangea or Novopangaea.
2. Pangea Last
The opening of the Atlantic, however, could slow down and even begin to close in the future. The two small subduction arcs of the Atlantic could extend along the east coast of all America, which would lead to a new formation of Pangea after the collision of America, Europe and Africa, producing a supercontinent called Pangea Last, which would be completely surrounded by a super Pacific ocean.
However, if the Atlantic develops new subduction areas, something that could be happening already, both the Pacific and the Atlantic could be closed. This means that a new ocean basin should be created to replace them.
In this scenario, the pan-Asian crack that crosses Asia from western India to the Arctic would open up to form a new ocean. The result would be the formation of supercontinent Aurica. Due to the current drift of Australia to the north, would be located in the center of the new continent, since the Far East and America would close the Pacific on each side. The European and African plates would thus meet with America for the closure of the Atlantic.
The fourth scenario predicts a completely different destination for the future Earth. Some of the tectonic plates are currently moving to the north, including Africa and Australia. It is believed that this drift is driven by anomalies in the interior of the Earth (in the mantle, concretely) inherited from Pangea. Due to this drift to the north, one can imagine a scenario in which all continents except Antarctica continue to travel north. This means that, in the end, they would meet around the North Pole in a supercontinent called Amasia. In this scenario, both the Atlantic and the Pacific would remain mostly open.
Of these four scenarios, we consider that Novopangea is the most likely. I would obey the logical progression of the current directions adopted by the continental plates adrift, while the other three scenarios would need additional processes to be performed.
For the Aurica formation, new subduction zones in the Atlantic would have to be created.
Pangea Ultima would only be formed with the investment of the Atlantic opening.
Finally, the birth of Amasia would depend on anomalies produced by Pangea inside the Earth.
Investigating the tectonic future of the Earth forces us to explore the limits of our knowledge and to think about the long processes that surround our planet. It also leads us to observe the terrestrial system as a whole, and it raises a series of questions: What will be the climate of the next supercontinent? How will the ocean circulation be adjusted? How will life evolve and adapt to its new environment? They are the kind of questions that test the limits of science because they do the same with the limits of our imagination.
Mattias Green, Reader in Physical Oceanography, Bangor University; Hannah Sophia Davies, PhD Researcher, University of Lisbon , and Joao C. Duarte, Researcher and Coordinator of the Marine Geology and Geophysics Group, University of Lisbon