Continental drift, as a theory to explain changes in the positions of land masses on Earth, was proposed as a theory by Alfred Wegener in the early 1900's. He theorized that the continents had, and continue to, move on the Earth's surface over long periods of time, breaking apart from one original land mass and separating, then colliding in some cases to form the continents we see today. However, Wegener's theory did not explain what caused the continents to move.
With research in the 1950's and 1960's showing that cracks in the sea floor were spreading wider apart, the theory of plate tectonics was developed to explain the movement of the continents. The theory of plate tectonics supports the theory of continental drift by explaining why the continents move and how their interaction causes the resulting creation of different types of landforms.