The phenomenon that causes the Earth's tectonic plates to move is known as plate tectonics. This theory explains the movement of sections of the Earth's lithosphere on the more fluid asthenosphere beneath. Plate movement is driven by convection currents in the mantle, caused by the heat from the Earth's core. Interactions between these plates can lead to geological events, such as earthquakes, volcanoes, and the formation of mountain ranges. Understanding plate tectonics is crucial for geologists and helps explain the dynamic nature of Earth's surface.