What is the primary cause of plate movement?

The primary cause of plate movement is convection currents in the mantle. The Earth's mantle behaves like a viscous fluid over geological timescales, and the heat from the Earth's core creates convection currents as hotter, less dense material rises while cooler, denser material sinks. This movement of the mantle material drives the tectonic plates located on the rigid lithosphere above.

These convection currents form a cycle that leads to the continuous movement of tectonic plates, resulting in various geological processes such as earthquakes, volcanic activity, and the formation of mountain ranges. This mechanism has been a crucial factor in the dynamics of plate tectonics, highlighting the importance of thermal energy within the Earth.

The other options do not directly contribute to plate movement in the same way. Gravitational pull affects the orientation and stability of the plates, but it is not the driving force behind their movement. Magnetism primarily relates to the Earth's magnetic field and does not influence the tectonic processes. Changes in atmospheric pressure are unrelated to tectonic activity as they are atmospheric phenomena that do not affect the solid rocks of the Earth's crust and mantle.