Craig Young

The continents rest on top of a layer of Earth called the "mantle".  The mantle is made of hot, compressed rock that is fluid - it flows.  Very slowly, but it does flow, like the lava that comes out of volcanoes.  As the mantle flows, it pushes on the continents on top, which causes earthquakes.  Over long periods of time, the movement in the mantle has pushed the continents around on Earth's surface.  Sometimes they move farther apart (like South America and Africa) and sometimes they move closer together (like India is pushing northward into Asia creating the Himalaya mountains).