In science, the word “theory” doesn’t mean guesswork. It means the idea is accepted as fact by the scientific community. See also “theory of relativity,” “quantum theory,” and “theory of evolution.” Specifically, the theory you are referring to is called the theory of plate tectonics. Plate tectonics does not involve the rapid or devastating or crashing movement of continents. It is extremely slow, over millions of years. Pangaea was simply an ancient arrangement of the continental plates. To get into a little more detail, here is what plate tectonics says. Over long periods of time, the earth’s mantle—that’s the layer right below the crust—actually acts like a liquid. The continental plates, again over long time periods, slide and drift over the mantle like ice cubes floating in water. But this process is extremely slow!