Plate tectonics describes the large-scale movement of Earth’s lithosphere, which is broken into several major and minor rigid plates. These plates float and interact with the underlying, semi-fluid asthenosphere. The movement of these colossal segments drives many of the planet's most dramatic geological phenomena, including the formation of oceanic ridges, deep ocean trenches, and mountain ranges. Interactions between plates—such as convergent, divergent, and transform boundaries—are responsible for generating intense seismic activity, vulcanism, and significant changes in global topography and crustal composition over geological timescales.