The lost ocean that once separated the continents and built the supercontinent Pangaea

Nature · Published 3 October 2026 Swipe more like this →

In short: Before the Atlantic existed, the Rheic Ocean dominated the Paleozoic world. Stretching across the globe, its birth and eventual closure reshaped Earth's geography, triggered massive evolutionary shifts, and helped assemble the supercontinent Pangaea. Its legacy remains etched in mountain ranges spanning from Mexico to Turkey today.

The Rheic Ocean emerged during the Early Ordovician period, born from the rifting of the northern margin of the massive southern continent, Gondwana. As continental fragments like Avalonia and Carolina drifted northward, the ocean expanded, reaching a maximum width of 4,000 kilometers by the Silurian period. This process occurred as the older Iapetus Ocean closed, marking a significant transition in the planet's tectonic configuration.

The ocean's influence extended beyond mere geography. During the Silurian, the Prague Basin—a chain of volcanic islands on the Gondwanan shelf—served as a critical hotspot for biodiversity. These islands, characterized by rapid environmental shifts and high endemism, are thought to have accelerated the early diversification of vascular plants during the Silurian-Devonian Terrestrial Revolution. This period of geological activity highlights how the ocean's dynamic nature directly influenced the trajectory of terrestrial life.

The eventual closure of the Rheic Ocean, which began in the Early Devonian and concluded by the Mississippian, was a monumental tectonic event. The collision between Gondwana and Laurussia formed the supercontinent Pangaea and created the largest collisional orogen of the Paleozoic, including the Variscan, Alleghanian, and Ouachita mountain belts. This closure, combined with the onset of the Late Paleozoic Ice Age, is believed to have triggered the Carboniferous-Earliest Permian Biodiversification Event, a major radiation of marine life, particularly among brachiopods and fusulinids.

Today, the physical evidence of this ancient ocean is found in sutures stretching 10,000 kilometers across the globe. While the Rheic Ocean is long gone, its role in shaping the modern world—from the formation of vast mountain ranges to the evolutionary pressures that drove early plant and marine life—remains a cornerstone of our understanding of Earth's deep history.

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