Pangaea Proxima

Supercontinents describe the merger of all or nearly all of Earth's landmass into a single contiguous continent. In the Pangaea Proxima scenario, subduction at the western Atlantic, east of the Americas, leads to the subduction of the Atlantic mid-ocean ridge, followed by subduction destroying the Atlantic and Indian basin, causing the Atlantic and the Indian Oceans to close, and bringing the Americas back together with Africa and Europe. As with most other supercontinents, the interior areas of Pangaea Proxima are presumed to become semi-arid or desert regions, which will be prone to extreme temperatures up to 131°F. Most land mammals, including the descendants of humans, may be driven to extinction (as were many orders of terrestrial vertebrates during the Permian–Triassic extinction event) because of these environments.

Formation

According to the Pangaea Proxima hypothesis, the Atlantic and the Indian Oceans will continue to get wider until new subduction zones bring the continents back together and form a future Pangaea. Most continents and microcontinents are predicted to collide with Eurasia, just as when most continents collided with Laurentia.

In the next 50 million years (assuming no new subduction zones come into being before then), North America is predicted to shift west and Eurasia east and possibly even to the south and bring Great Britain closer to the North Pole and Siberia southward towards warm, subtropical latitudes. Africa is predicted to collide with Europe and Arabia, closing the Mediterranean Sea (thus completely closing the Tethys Ocean (or Neotethys)) and the Red Sea between Sudan and Saudi Arabia, and the Persian Gulf will be closed off resulting in Iran to become a landlocked country. A long mountain range (the Mediterranean Mountain Range) would then extend from Iberia, across Southern Europe and into Asia. Some are even predicted to have peaks higher than Mount Everest between Spain, Greece, Italy, and Egypt. Similarly, Australia is predicted to beach itself past the doorstep of Southeast Asia, causing islands such as the Philippines and Indonesia to be compressed inland, forming another potential mountain range while Japan will collide with China, Korea, and Russia. Meanwhile, Southern and Baja California are predicted to have already collided with Alaska, with new mountain ranges formed between the United States and Canada.

About 125 million years from now, the Atlantic Ocean is predicted to stop widening and to begin to shrink, as the Mid-Atlantic Ridge seafloor spreading gives way to subduction. In this scenario, the mid-ocean ridge between South America and Africa will probably be subducted first; the Atlantic Ocean is predicted to narrow as a result of subduction beneath the Americas. The Indian Ocean is also predicted to be smaller due to northward subduction of oceanic crust into the Central Indian trench. Antarctica is expected to split into two and shift northwards, colliding with Madagascar and Australia, enclosing a remnant of the Indian Ocean, which Scotese calls the "Medi-Pangaean Sea."

When the last of the Mid-Atlantic Ridge is subducted beneath the Americas, the Atlantic Ocean is predicted to close rapidly. Research by Duarte et al in 2024 is consistent with this by noting that the Gibraltar Arc may evolve into a subduction zone entering the Atlantic Ocean and forming an Atlantic analogue to the current Ring of Fire, which would lead to the closure of the Atlantic Ocean.

At 250 million years in the future, the Atlantic is predicted to have closed, with only small vestiges of the former ocean remaining. North America will have collided with Africa but be in a more southerly position than where it rifted away. South America is predicted to be wrapped around the southern tip of Africa and Antarctica and to completely enclose the Medi-Pangaean Sea. The supercontinent will be encircled by a global ocean, the Neopanthalassan Ocean (meaning "new" Panthalassan Ocean), which encircles half the Earth. The Earth is expected to have a hothouse climate with an average global temperature of 28 °C (82 °F). The only areas likely to be habitable for land mammals are those closest to the poles.