How do tectonic plates primarily move within the Earth?

Tectonic plates primarily move within the Earth due to convection currents in the mantle. These convection currents are created by the heat from the Earth’s core, which causes the mantle material to become less dense and rise. As it reaches the upper mantle and cools, it then becomes denser and sinks back down. This circular movement creates a dynamic system that drives the plates on the Earth’s surface. The interaction between these moving mantle currents and the plates allows for various tectonic processes, including plate separation, collision, and sliding against each other.

The other options do not accurately describe the primary driving mechanism of plate movement. While gravitational forces do play a role in the overall dynamics of the Earth, they are not the primary reason for plate motion. Sliding over each other describes a consequence of plate movement rather than the initial cause. Magnetic forces in the crust are relevant to certain geological phenomena but are not responsible for the tectonic movement of plates.