Plate Tectonics- This is a theory that the Earth’s Crust cracked and we call the pieces or cracks, Plates. There is a lot of evidence that this occurred. First is the fact that the ocean floor seems to be getting bigger, while the continents seem to be moving farther and farther apart. Since we have already learned that the entire Earth’s crust is rock and the next layer down is the mantle, which is made up of molten magma, it does seem possible that the rock crust can move and shift over the molten magma.
Sea Floor Spreading- It seems that the cracks in the ocean floor have let magma come up and fill in, pushing the sea floor apart, making the continents move farther and farther away from each other.