 A crust formed when the molten outer layer of Earth cooled to form a solid as the accumulated water vapor began to act in the atmosphere . The two models that explain land mass propose either a steady growth to the present @-@ day forms or , more likely , a rapid growth early in Earth history followed by a long @-@ term steady continental area . Continents formed by plate tectonics , a process ultimately driven by the continuous loss of heat from Earth 's interior . On time scales lasting hundreds of millions of years , the supercontinents have formed and broken up three times . Roughly 750 mya ( million years ago ) , one of the earliest known supercontinents , Rodinia , began to break apart . The continents later recombined to form <unk> , 600 – 540 mya , then finally Pangaea , which also broke apart 180 mya . 
