continental drift

The North American continent is growing in the west as a result of collision with the Pacific plate. On the east of the wide area of the Ozark Plateau shield lie the Appalachian Mountains, showing where the continent once collided with another continent. The eastern coastal rifting formed when the continents broke apart. On the western edge, new impact mountains have formed.

The continents are slowly shifting their positions, driven by fluid motion beneath the Earth's crust. Over 200 million years ago, there was a single large continent called Pangaea. By 200 million years ago, the continents had started to move apart. By 50 million years ago, the continents were approaching their present positions.

The changing positions of the Earth's continents. Millions of years ago, there was a single large continent, Pangaea. This split 200 million years ago: the continents had started to move apart, to form Gondwanaland in the south and Laurasia in the north. By 50 million years ago the continents were almost in their present positions.

In geology, the theory that, about 250–200 million years ago, the Earth consisted of a single large continent (Pangaea), which subsequently broke apart to form the continents known today. The theory was first proposed in 1912 by German meteorologist Alfred Wegener, but such vast continental movements could not be satisfactorily explained or even accepted by geologists until the 1960s.

The theory of continental drift gave way to the theory of plate tectonics. Whereas Wegener proposed that continents pushed their way through underlying mantle and ocean floor, plate tectonics states that continents are just part of larger lithospheric plates (which include ocean crust as well) that move laterally over the Earth's surface.