How are the theories of continental drift and plate tectonics related?

Continental drift is movement of the continents, the name 'drift' comes from the theory that the continents drift from one place to another. In other words, the continents have drifted across the ocean. Plate tectonics, however, could be know to be related, because of the collisions, movement, and change in the earth by the plates colliding together, resulting in change of the earth. Continental drift are similar to plate tectonics because of collisions, mostly movement.