V. Mechanism

Convection in the Mantle

• Convection is the term used to describe the heat transfer that occurs when magma moves. It is thought that the Earth's radioactive element decay serves as the convection's heat source. 

Ridge Push

• It is essential to the movement of plates. Magma rises and forces the plates apart at mid-ocean ridges, where new crust is forming. New oceanic crust is created when plates are pushed away from the ridge by ridge-push forces.

Slab Pull

• Slab-pull forces are the result of subduction, or the sinking of ancient oceanic crust at trenches. The motion downward is a part of the plate motion. The remainder of the plate is pulled down as one plate falls beneath another.  

Slab Suction

• Slab suction is the weakest of the three major forces involved in plate motion, the others being slab pull, the strongest, and ridge push.

Access the PhET simulation on Tectonic Plates to fully understand the mechanism by clicking the picture.