What primarily drives tectonic plate movement across the Earth's crust?

Tectonic plate movement is primarily driven by convection currents in the Earth's mantle. These currents are caused by the heat from the Earth's core, which creates a process of uneven heating in the mantle. As material in the mantle heats up, it becomes less dense and rises toward the surface. Upon reaching the upper mantle and cooling down, this material then sinks back down, creating a continuous cycle.

This cycle of rising and sinking mantle material generates forces that can push and pull the tectonic plates floating on top of the mantle. As a result, the movement of these plates can lead to geological activities like earthquakes, volcanic eruptions, and mountain building. Understanding the role of convection currents is crucial for grasping how and why tectonic plates move, making it the correct answer for the question about what primarily drives this movement.