It acts as an accessory pigment! Hope this helps! Also sorry that it took 11 hrs. for people to answer! =)
Answer:
"Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones."
Explanation:
Does this help?