Answer: The Earth's continents are in constant motion. On at least three occasions, they have all collided to form one giant continent. If history is a guide, the current continents will coalesce once again to form another supercontinent. And a study in Nature now shows how that could come about.
You can think of continents as giant puzzle pieces shuffling around the Earth. When they drift apart, mighty oceans form. When they come together, oceans disappear. And it's all because continents sit on moving plates of the Earth's crust.
Then, Now And Future
A new model of continental drift predicts that the next supercontinent could form near the North Pole — in another 100 million years or so.
Two of the previous supercontinents, which formed 200 million years ago (Pangaea) and 800 million years ago (Rodinia).
Mitchell, et. al./Nature
The Americas and Asia may fuse together to form a new supercontinent, "Amasia."
Mitchell, et. al./Nature
"Continents on these plates typically move, I would say, at the rate your fingernails grow," says Ross Mitchell, a graduate student at Yale University. That may seem slow, but it adds up over hundreds of millions of years.
Look at an atlas and you can imagine how Africa and South America, for example, once nestled together.
"Rewind the tape and bring all the continents back into their jigsaw arrangement, you have this vast landmass of all the Earth's continental blocks together," Mitchell says.
Last time all the landmass clumped up, it formed a supercontinent called Pangaea. The dinosaurs walked there. But Pangaea wasn't the first.
"There had been three, possibly a debated fourth supercontinent through the billions of years," Mitchell says.
He has been studying that deep history by looking at tiny magnets buried in rock around the world. Those magnets pointed north when they were locked into the rock. Sample those magnets in layers of rock laid down over millions of years, and you can tell the story of how those continents have moved.
And naturally, that led Mitchell to wonder what the next supercontinent will look like.
There have been two leading ideas. One is that the continents will collapse together again at the site of the last supercontinent, centered on Africa. That would squeeze the Atlantic Ocean shut. The other idea is that the Atlantic would keep growing and growing.
