Plate tectonic theory explains that Earth's outer shell, the lithosphere, is divided into several large and small rigid plates that float on a softer, partially molten layer called the asthenosphere beneath them. These tectonic plates move slowly, typically at rates of 5 to 10 cm per year, and interact at their boundaries in three main ways: converging (pushing together), diverging (pulling apart), or sliding past each other. These interactions cause most of Earth's seismic and volcanic activity, mountain building, ocean formation, and continental drift
. The theory integrates earlier ideas of continental drift and seafloor spreading, providing a comprehensive framework to explain the past and present geography of continents and oceans, and the processes shaping Earth's surface. It also helps explain the distribution of earthquakes, volcanoes, and mountain ranges, which mostly occur along plate boundaries
. Plate movements are driven mainly by mantle convection currents-where heat causes magma to rise and sink in circular motions-and by slab pull, where denser oceanic plates sink into the mantle at subduction zones, dragging the rest of the plate along. This dynamic process recycles Earth's crust and influences long-term climate, atmospheric composition, and the environment in which life evolves
. In summary, plate tectonic theory tells us that:
- Earth's lithosphere is broken into moving plates.
- Plates interact at boundaries causing earthquakes, volcanoes, and mountain formation.
- Continents drift as part of these plates, reshaping Earth's surface over millions of years.
- Mantle convection and slab pull drive plate motions.
- The theory unifies many geological phenomena and explains Earth's evolving landscape
