The Iapetus Ocean was a vast body of water that existed between roughly 600 and 425 million years ago, during the late Neoproterozoic and early Paleozoic eras. It lay in the Southern Hemisphere, separating the ancient continents of Laurentia, Baltica and Avalonia before these landmasses collided to form Euramerica.
The ocean closed through a series of mountain-building events — the Caledonian, Taconic and Acadian orogenies — as the surrounding continents gradually converged. Its southern portion may have disappeared earlier through the Famatinian orogeny, involving a collision between western Gondwana and Laurentia. The Iapetus Ocean occupies a curious place in Earth history: because it once separated landmasses that would eventually become the opposing shores of the Atlantic, it can be understood as a precursor to that modern ocean. The opening mechanism of the Iapetus shares notable similarities with the Atlantic’s own rifting in the Jurassic period. Fittingly, it takes its name from Iapetus, the Greek titan who fathered Atlas — the figure for whom the Atlantic itself is named.
