There's a continent called Pangaea?! Well, there once was. Hundreds of millions of years ago, Earth looked completely different from how it does today. All of the land was packed into a single supercontinent. Geologist Alfred Wegener theorized that this giant landmass split into chunks and slowly drifted apart. Rejected at first by the scientific community, Wegener's theory of continental drift eventually was proved correct: The earth's crust is split up into dozens of pieces called tectonic plates, which "float" on top of the mantle. Warmed by the blazing-hot core, the mantle churns in circular convection currents, dragging tectonic plates along for the ride. Today, plate tectonics is the unifying theory of the entire field of geology. It explains the rock cycle, the origin of Earth's surface features, and the cause of seismic activity, such as earthquakes and volcanoes. Get the drift? Watch this movie to learn more!