The Earth’s surface is actually in constant motion, driven by forces deep within the planet. This movement has repeatedly gathered the world’s landmasses into single, unified continents, known as supercontinents. The most recent of these assemblies was Pangea, which broke apart roughly 200 million years ago, scattering the pieces into the continents we recognize today. The current arrangement is merely a temporary stage in an ongoing geological drama, and the continents are already drifting toward their next great collision. The question is not if the continents will unite again, but when and how the new landmass will be configured.
The Engine of Continental Drift
The movement of continents is the surface expression of plate tectonics, powered by heat from the planet’s interior. The Earth’s rigid outer layer, the lithosphere, is broken into a series of large, interlocking pieces called tectonic plates. These plates, which carry both continental and oceanic crust, float upon the warmer, more pliable layer beneath them, the asthenosphere.
The primary mechanism driving this movement is mantle convection. Heat generated by the radioactive decay of elements deep within the Earth causes rock material in the mantle to warm, become less dense, and slowly rise toward the surface. As the material reaches the base of the lithosphere, it cools, spreads out, and eventually sinks back down, creating enormous, circular currents.
The flow drags the overlying tectonic plates along at rates of a few centimeters per year. Where convection currents rise, new oceanic crust is formed at mid-ocean ridges, pushing plates apart, such as in the Atlantic Ocean. Where currents descend, old, cold, and dense oceanic crust sinks back into the mantle at subduction zones, pulling plates together and consuming ocean basins, such as around the Pacific Ring of Fire.
The Recurring Supercontinent Cycle
The aggregation and dispersal of continental crust follows a quasi-periodic pattern known as the supercontinent cycle. This cycle typically spans a period of 300 to 500 million years, marking the time it takes for continents to assemble, stabilize, and then rift apart before gathering again.
The most recent example, Pangea, formed about 300 million years ago from the collision of smaller landmasses. Before Pangea, an earlier supercontinent named Rodinia assembled approximately 1.25 billion years ago before fragmenting.
The cycle profoundly influences global conditions, including sea level and climate. Sea levels are generally low when continents are joined because there are fewer mid-ocean ridges to displace water. Conversely, when a supercontinent breaks up, the increase in spreading centers causes sea level to rise as the new, hot, buoyant oceanic crust takes up more volume in the ocean basins.
Competing Models for the Next Assembly
The next supercontinent is predicted to form in approximately 200 to 350 million years, but scientists propose different scenarios for its final configuration based on the prevailing dynamics of the oceans. These models depend largely on whether the active Pacific Ocean or the growing Atlantic Ocean will eventually close. The two most prominent models are Amasia and Novopangea.
The Amasia model suggests that the continents will drift northward to converge around the North Pole. This scenario involves the continued subduction and closure of the Pacific Ocean, which is already shrinking. As the Pacific closes, the Americas and Asia will eventually collide, with the Atlantic Ocean continuing to widen and becoming the world’s largest ocean basin.
Conversely, the Novopangea model follows the Extroversion hypothesis, where the continents return to a configuration similar to the last one. This requires the current widening of the Atlantic Ocean to cease, and a new subduction zone to form, causing the Atlantic to begin closing. In this case, the Americas would collide with Africa and Eurasia, with the Pacific Ocean remaining large and the new supercontinent centered near the equator.
Geologic Timeline and Future Climate
The next supercontinent is expected to fully assemble between 250 and 350 million years from now. Continental collision will trigger immense environmental changes. One of the major consequences of continental collision will be a period of intense mountain building, forming mega-Himalayas and vast plateaus along the suture zones.
The assembly will also likely be accompanied by volcanism, which will release enormous quantities of carbon dioxide into the atmosphere. The combined effect of higher atmospheric carbon dioxide and a 2.5% increase in the Sun’s luminosity will cause global temperatures to soar. This heat will lead to extreme continental climates.
The interior regions of the new supercontinent will be far from any moderating ocean influence, leading to vast, hyper-arid deserts. Restricted ocean currents will prevent the efficient transfer of heat and moisture, intensifying these harsh conditions and making most of the landmass inhospitable. This environment will likely trigger a mass extinction event comparable in scale to those in deep geological history.