Continental drift is the slow movement of the Earth's continents towards and away from each other.
continental drift in British English
noun
geology
the theory that the earth's continents move gradually over the surface of the planet on a substratum of magma. The present-day configuration of the continents is thought to be the result of the fragmentation of a single landmass, Pangaea, that existed 200 million years ago
See also plate tectonics
continental drift in American English
the theory that continents slowly shift their positions as a result of currents in the molten rocks of the earth's mantle, plate tectonics, etc.