The theory of plate tectonics explains Earth's geological activity by proposing that the Earth's lithosphere is divided into large, rigid plates that float on the semi-fluid asthenosphere beneath. These plates are constantly moving, driven by forces such as mantle convection, slab pull, and ridge push. As plates interact at their boundaries, they can diverge, converge, or slide past each other, leading to various geological phenomena. For example, divergent boundaries (where plates move apart) create mid-ocean ridges and volcanic activity, convergent boundaries (where plates collide) can form mountain ranges, deep ocean trenches, and trigger earthquakes, while transform boundaries (where plates slide past) can cause faulting and seismic activity. This dynamic movement is responsible for shaping Earth's surface over time.