Pangea, the most recent supercontinent, fully assembled during the Carboniferous period, approximately 335 million years ago, and began to break apart around 200 million years ago. Before this familiar configuration, the planet’s continents were in constant motion, driven by forces deep within the Earth. The geological record reveals a vast history of continents coming together and splitting apart in a recurring cycle that long preceded Pangea. Understanding Earth before Pangea requires looking back hundreds of millions of years to earlier colossal landmasses.
The Supercontinent Cycle
The continuous assembly and breakup of the world’s continents follow the Supercontinent Cycle. This cycle is fundamentally driven by plate tectonics, the theory that Earth’s outer layer is divided into large plates moving relative to one another. The movement is often described by the Wilson Cycle, which details the repeated opening and closing of ocean basins.
The Wilson Cycle involves a sequence of stages, beginning with continental rifting that forms a new ocean basin, such as the Red Sea today. The ocean grows through seafloor spreading and continental drift, and eventually, the basin closes as one oceanic plate subducts beneath another. The process culminates in the collision of the two continents, creating immense mountain ranges and ultimately forming a supercontinent. This entire cycle, from one supercontinent’s formation to the next, is estimated to take between 300 and 500 million years.
The cycle is fueled by the Earth’s internal heat, which generates convection currents in the mantle. When continents gather into a single mass, they act as an insulating blanket, reflecting heat back into the mantle. This causes more vigorous currents that eventually fracture the overlying crust, initiating the next phase of rifting. The primary force pulling the plates apart during the cycle appears to be “slab-pull,” where the dense, subducting oceanic plate drags the rest of the plate along behind it.
Rodinia: The Predecessor Continent
Long before Pangea, the supercontinent Rodinia existed. Rodinia assembled approximately 1.1 billion years ago and remained largely intact for about 450 million years, existing throughout the Mesoproterozoic and Neoproterozoic Eras. Its formation resulted from multiple continental blocks colliding during mountain-building events, most notably the Grenville Orogeny.
Reconstructions suggest that Rodinia’s structure was centered around Laurentia, the ancient continental core of modern-day North America. Other major cratons, like the East European, Amazonian, and West African blocks, were grouped around this core. This immense landmass was likely situated mostly south of the equator, extending into the southern polar regions.
The physical arrangement meant that Rodinia’s vast interior was far from the moderating influence of the sea, leading to an extremely cold and arid climate. The rifting that signaled Rodinia’s demise began around 750 million years ago, driven by the accumulation of heat beneath the supercontinent and the rise of volcanic plumes. This fragmentation was a prolonged process that saw the supercontinent tear into at least eight major continental fragments.
Fragmentation and Reassembly
The rifting created a number of massive pieces, including proto-Laurasia, which was composed of what would become North America, Siberia, and Baltica, and a vast southern landmass known as proto-Gondwana. The breakup also led to the formation of new ocean basins, such as the Iapetus Ocean, which opened between Laurentia and the fragments of Gondwana and Baltica.
Over the next few hundred million years, these fragments began to move and collide again, closing the newly formed oceans. A major step toward Pangea was the collision of Laurentia, Baltica, and a smaller terrane called Avalonia, which occurred during the late Ordovician period. This collision, known as the Caledonian Orogeny, closed the Iapetus Ocean and fused the landmasses together to form the continent of Euramerica, also called Laurussia.
Meanwhile, the southern continent of Gondwana—comprising modern South America, Africa, India, Australia, and Antarctica—drifted slowly toward the South Pole. The final stages of Pangea’s formation involved the collision of Gondwana with Euramerica during the Carboniferous period, closing the remaining seaways. This immense continental collision created the Central Pangean Mountains, which were comparable in scale to the modern Himalayas.
Ancient Oceans and Environments
Rodinia was surrounded by a single, global ocean called Mirovia. As Rodinia began to fragment, new oceans were born; the Iapetus Ocean separated the northern and southern continental blocks, and the vast Panthalassa Ocean surrounded all the newly dispersed landmasses.
The Neoproterozoic era, which coincided with the breakup of Rodinia, was marked by the “Snowball Earth” events. During the Cryogenian period, major glaciations covered much of the planet, with ice potentially reaching the equator. This global freeze is thought to have been influenced by the continental configuration, which allowed for increased weathering and a reduction of atmospheric carbon dioxide, leading to a runaway cooling effect.
Despite the environmental severity, the period immediately following the Cryogenian glaciations saw the rise of the earliest complex, multicellular life forms. The Ediacaran biota represents the first large, soft-bodied organisms to appear in the fossil record. The breakup of Rodinia and the subsequent environmental upheaval created evolutionary pressure and new ecological niches that spurred the diversification of life leading into the Cambrian explosion.