How long before the continents collide

Lewis Ashwal at the University of the Witwatersrand in Johannesburg, South Africa, and his colleagues think the crystals once belonged to a drowned landmass and were dragged up to the surface during the formation of Mauritius.

In other words: They came from an ancient continent hidden deep beneath the Indian Ocean. The continent, dubbed Mauritia, is likely as large as Japan and dates back to the time of the dinosaurs. The world looked much different then: The continents were joined together in a single enormous landmass called Pangea. Over time, the dinosaurs went extinct and that mighty supercontinent fractured, causing Mauritia to drown beneath the waves.

But the newly discovered continent is more than just collateral damage. That rhythm will continue to bring the next supercontinent into view hundreds of millions of years from now in a world that will look almost alien to our own. Consider fossils of the lizard-like animal Lystrosaurus , which have been found in South Africa, India, and Antarctica. Or the extinct seed fern Glossopteris , which once thrived in the polar circle and the tropics.

Such oddities made sense only if the continents were once nuzzled up next to each other as parts of Pangea. Look at an atlas and it might be tempting to slide the Americas eastward, hooking them into Africa like three puzzle pieces. Scientists now know the c-shaped supercontinent consisted of two smaller continents that collided at the equator: Laurasia in the Northern Hemisphere, which encompassed North America, Greenland, Europe and much of Asia, and Gondwanaland in the Southern Hemisphere, which was composed of South America, Africa, India, Australia and Antarctica.

During the Triassic period some million years ago, earthquakes began to rock the spot where New Jersey nestled against Morocco.

Volcanic eruptions spewed huge amounts of lava and gas. As a result, the region literally began to pull itself apart. Just as the toffee might droop, the continental crust formed valleys so deep that ocean water rushed in. The region continued to spread and the Atlantic Ocean was formed.

That ocean continues to grow today. However, if the Atlantic was to develop new subduction zones — something that may already be happening — both the Pacific and Atlantic oceans may be fated to close. This means that a a new ocean basin would have to form to replace them.

In this scenario the Pan-Asian rift currently cutting through Asia from west of India up to the Arctic opens to form the new ocean. The result is the formation of the supercontinent Aurica. Because of Australia's current northwards drift it would be at the centre of the new continent as East Asia and the Americas close the Pacific from either side. The fourth scenario predicts a completely different fate for future Earth. Several of the tectonic plates are currently moving north, including both Africa and Australia.

This drift is believed to be driven by anomalies left by Pangea, deep in the Earth's interior, in the part called the mantle. Because of this northern drift, one can envisage a scenario where the continents, except Antarctica, keep drifting north. This means that they would eventually gather around the North Pole in a supercontinent called Amasia. It is a logical progression of present day continental plate drift directions, while the other three assume that another process comes into play.

There would need to be new Atlantic subduction zones for Aurica, the reversal of the Atlantic opening for Pangea Ultima, or anomalies in the Earth's interior left by Pangea for Amasia. Investigating the Earth's tectonic future forces us to push the boundaries of our knowledge, and to think about the processes that shape our planet over long time scales. In about million years a new supercontinent, Pangaea Proxima, will form. All rights reserved. This story appears in the June issue of National Geographic magazine.

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