A small amount of molten rock located under tectonic plates encourages them to move. This is what scientists have recently discovered. Their new model takes into account not only the velocity of seismic waves but also the way in which they are attenuated by the medium they pass through. The velocity of tectonic plates near the surface is thus directly correlated with the quantity of magma present.
Click here for original story, Deep magma facilitates the movement of tectonic plates
Source: ScienceDaily