Large-scale movements of continent s over the course of geologic time.
The first complete theory of continental drift was proposed in 1912 by Alfred Wegener , who postulated that a single supercontinent, which he called Pangaea , fragmented late in the Triassic Period (248206 million years ago) and the parts began to move away from one another. He pointed to the similarity of rock strata in the Americas and Africa as evidence to support his hypothesis. Wegener's ideas were widely rejected until they were combined with Harry H. Hess's seafloor spreading hypothesis in the 1960s. The modern theory states that the Americas were joined with Europe and Africa until 0441; 190 million years ago, when they split apart along what is now the Mid-Atlantic Ridge . Subsequent tectonic plate movements brought the continents to their present positions.