What causes plate tectonics?

Plate tectonics is primarily driven by convection currents in the upper mantle. These convection currents occur due to the heat generated from the Earth's core and the decay of radioactive materials within the mantle. As the mantle heats up, the less dense material rises towards the surface, while cooler, denser material sinks, creating a continuous flow. This movement in the mantle exerts forces on the overlying tectonic plates, causing them to move, collide, pull apart, or slide against each other.

The interaction of these plates leads to various geological phenomena, including earthquakes, volcanic activity, and the formation of mountain ranges. The reliance of plate tectonics on convection currents highlights the importance of thermal dynamics within the Earth rather than external atmospheric conditions or celestial gravitational effects. This fundamental understanding of fluid dynamics in the semi-fluid upper mantle is essential to grasp the mechanisms behind plate movements and their implications on Earth's geological processes.