Pangaea was a colossal supercontinent that incorporated nearly all of Earth’s landmasses into a single entity. Fully assembled by the Early Permian period, approximately 300 million years ago, this immense landmass dominated the globe for roughly 100 million years. Its dissolution, beginning around 200 million years ago in the Mesozoic Era, marked the start of the modern continental configuration. The fragmentation occurred in distinct phases, with the opening of a single ocean basin signifying the starting point of the breakup.
Pangaea’s Precursor Waters: Panthalassa and Tethys
Before the continents began to separate, the world’s oceans were fundamentally different from today’s geography. The entire supercontinent of Pangaea was surrounded by a single, massive global ocean known as Panthalassa, a name derived from the Greek meaning “all sea”. This immense body of water covered approximately 70% of the Earth’s surface, and its floor has largely been subducted and recycled into the mantle over geological time. The modern Pacific Ocean is considered the direct continuation of this ancient superocean.
Pangaea was C-shaped, and its eastern edge framed a significant inlet called the Tethys Ocean. This water body acted as a large bay, separating the northern landmass of Laurasia from the southern landmass of Gondwana. The Tethys Ocean was a warm-water system that influenced Pangaea’s climate by bringing humid, tropical air over the supercontinent’s interior. These two precursor oceans, Panthalassa and Tethys, existed before the newly forming rifts began to open.
The Direct Result: Formation of the Central Atlantic Ocean
The ocean that formed as the direct result of Pangaea’s initial rifting is the Central Atlantic Ocean. This first major phase of breakup began in the Late Triassic and Early Jurassic periods, with oceanic crust forming around 180 million years ago. The separation was initiated by a massive fissure that grew between North America and the combined landmass of Africa and South America. This split effectively separated the northern continent of Laurasia from the southern continent of Gondwana.
Continental rifting is the geological mechanism where the Earth’s crust stretches and thins under extensional forces. As the crust pulled apart, magma welled up from the mantle, creating a volcanic rift zone and forming the first narrow ocean basin. The continuous divergence of these land blocks allowed seawater to flood the depressed rift valley, leading to the birth of the Central Atlantic. This basin gradually widened as sea-floor spreading commenced along the Mid-Atlantic Ridge.
The Mid-Atlantic Ridge is a divergent plate boundary where new oceanic lithosphere is continuously generated, pushing the continental plates further apart. The rate of plate movement is slow, about four centimeters per year, explaining why the Atlantic’s opening took millions of years. The formation of this oceanic ridge and the creation of true oceanic crust between North America and Africa marks the Central Atlantic as the first modern ocean basin to emerge from Pangaea’s fragmentation. This foundational event set the stage for the rest of the supercontinent’s dissolution.
The Subsequent Formation of the Indian and Southern Oceans
The Central Atlantic’s opening was followed by a second major phase of rifting during the Early Cretaceous period, approximately 150 to 140 million years ago. This phase focused on the fragmentation of the southern supercontinent, Gondwana, which included Africa, South America, Antarctica, India, and Australia. As Africa and South America began to rift, the South Atlantic Ocean started to open, extending the break southward and reshaping the southern hemisphere’s geography.
Concurrently, the eastern portion of Gondwana began to break apart, leading to the formation of the Indian Ocean. India separated from Antarctica and Australia, beginning its rapid northward journey toward Asia. This movement created the central Indian Ocean basin, which expanded as the Indian plate moved, eventually colliding with Eurasia to form the Himalayas.
The Southern Ocean, which encircles Antarctica, was the last of the major oceans to fully develop, forming during the Paleogene period. Its creation was tied to the final separation of Antarctica from Australia and South America. The rifting that created the Drake and Tasmanian passages allowed for the initiation of the Antarctic Circumpolar Current. This powerful, cold-water current isolated the continent and established the Southern Ocean as a distinct body of water.