Seafloor spreading and continental drift are believed to be caused by plate tectonics. Plate tectonics is the scientific theory that explains how the Earth's lithosphere is divided into a number of plates that move and interact with each other due to the underlying convective flow in the mantle. The movement of these plates can cause a variety of geological phenomena such as earthquakes, volcanic eruptions, and the creation of mountain ranges. Seafloor spreading is a process in which new oceanic crust is formed through volcanic activity at mid-ocean ridges, and continental drift is the movement of continental plates across the Earth's surface.