Do supercontinents like Pangaea assemble and break apart in a repeating cycle?

It really looks that way. A supercontinent is what you get when most of Earth's land, at least about 75 percent of the continental crust, is welded into one mass, by one common definition. That has happened several times. The latest, Pangaea, held together from about 336 to 175 million years ago. Then it split into the continents we know. Right now there is no supercontinent. Africa and Eurasia together come closest, with about 57 percent of all land.

The engine is slow convection in the mantle. Old ocean plates sink at subduction zones. They pile up about 660 kilometres down. Every so often, the pile avalanches into the lower mantle. Hot rock then rises somewhere else as a plume. Continents get pushed away from the plumes and toward the low spots where slabs sank. Over time, they crowd together into a supercontinent. Later, heat builds up under the giant landmass and splits it apart again.

Geologists separate this global rhythm from a smaller one, the Wilson cycle. It is the opening and closing of a single ocean. Canadian geophysicist J. Tuzo Wilson described it in 1967, using the Atlantic as his example. Both cycles helped build Pangaea. As oceans closed, continents collided. When Gondwana met Laurasia, they raised a mountain belt about 6,000 kilometres long. The Appalachians are what's left of its western part.

And the cycle isn't over. Some geologists think a new supercontinent, nicknamed Pangaea Proxima, could form within the next 250 million years. The same slow dance of crashing and splitting would start again.