What is the driving force behind plate tectonics?

The driving force behind plate tectonics is best attributed to convection currents in the mantle. These currents arise from the Earth's internal heat, which causes the mantle rock to heat up and become less dense. As the heated rock rises towards the surface, it cools down and eventually sinks back down, creating a continuous cycle of movement. This process generates the forces necessary to move tectonic plates, which float on the semi-fluid asthenosphere beneath them.

Convection currents are critical because they not only cause the plates to shift but also play a significant role in various geological processes, such as earthquakes and volcanic activity. This mechanism explains how the plates can drift apart, collide, or grind past one another, leading to the dynamic nature of the Earth's surface.

While gravity does play a role in the movement of tectonic plates by influencing the slope of the ocean floor and causing subduction, it is the convection currents that are primarily responsible for the continuous motion and interactions of the plates. The Earth's magnetic field and subduction are related phenomena; however, they do not drive the tectonic movements in the same fundamental way that mantle convection does.