Pangaea

For about 160 million years, almost all the land on Earth was joined in one piece. Pangaea came together around 335 million years ago, when the great southern continent of Gondwana collided with the northern lands of Europe and North America, and Siberia was the last large piece to join, around 250 million years ago. It stretched from the far north to the far south in the shape of a C, wrapped around a warm sea called the Tethys. The rest of the planet was a single ocean, Panthalassa.

A world of extremes

With so much land in one place, much of the interior lay far from the sea. It was dry and fiercely seasonal, and it held one of the most extensive deserts in the history of the planet. Some of its dunes are still there, turned to stone: the Navajo Sandstone of the American Southwest, up to about 700 m thick, is a sea of sand that once lay on Pangaea’s western side.

Through the middle ran the Central Pangean Mountains, raised by the collision of the continents and, in the early Permian, comparable in size to the Himalayas today. Their worn-down roots survive as the Appalachians, the Ouachitas and the Atlas Mountains.

Around the coasts, a gigantic seasonal monsoon brought rain. A 2023 study ran 26 climate simulations across 250 million years and found that in the Triassic this “megamonsoon” covered an enormous area but delivered only weak rainfall. It was the size and position of the land, not the global temperature, that set its pattern.

Matching coasts, rocks and fossils

The idea that the continents had once been joined is old, but the German scientist Wegener was the first to argue it in detail, in three articles in 1912 and a book in 1915. He used the name Pangaea in the 1920 edition. The evidence he and later researchers gathered is still the core of the case. The coasts on either side of the Atlantic fit together closely when they are matched at the edge of the continental shelf. Mountain belts and deposits left by glaciers continue from one continent to another. Fossils of the small reptile Mesosaurus, about 275 million years old, are found in South Africa, Uruguay and Brazil, which are now separated by the South Atlantic. Magnetism frozen into old lava records where each continent lay.

Breaking apart

The first rifts opened about 230 million years ago, and the main breakup followed about 175 million years ago. As North America pulled away from Africa, an enormous outpouring of lava, the Central Atlantic Magmatic Province, erupted about 201 million years ago and spread over roughly 11 million square kilometres.

How the breakup started is still being worked out. A study published in 2026 used oceanic crust along the edges of the Atlantic and Indian oceans to estimate the temperature of the mantle beneath Pangaea, and found it was only slightly warmer than normal. That argues against the idea that a heat build-up under the supercontinent forced it apart. Another 2026 study, using seismic surveys off the east coast of the United States, found that the volcanic activity that finally split the crust there came around 15 million years after the great lava outpouring, weakening the idea that the eruption itself opened the Atlantic.

The breakup has not stopped. The Red Sea and the East African Rift are places where continents are still tearing apart today.