How does gravity cause plates to move?

Explain

The main driving force of plate tectonics is gravity. If a plate with oceanic lithosphere meets another plate, the dense oceanic lithosphere dives beneath the other plate and sinks into the mantle: this process is called subduction ... However, convection is also driving plate tectonics.

The main driving force of plate tectonics is gravity. If a plate with oceanic lithosphere meets another plate, the dense oceanic lithosphere dives beneath the other plate and sinks into the mantle. The sinking oceanic lithosphere drags the rest of the tectonic plate and this is the main cause of plate motion. This process is called subduction.