subduction zones, places where the earth's surface dips down toward the lower layers.
What makes this important is the enormous water content of weathered rock sediments. Water carried down into the mantle would soften the mantle, increasing the overall churn. In computer simulations, an increase churn of mantle rocks leads to increased continental movement and breakage.
So, if life has sufficiently changed (or is still changing) which rocks get weathered, and how fast, these changes would alter the entire face of the planet-- encouraging more tectonic plates and motions.