Can anyone explain the difference between plate tectonics theory and the ridge push/slab pull theory? I don't get how the last one is a different theory and not just an explanation of the theory..?!
Thanks so much in advance!
Plate tectonics theory is when convection currents driven by heat from the mantle re raised up into the asthenosphere and then is pulled along the underside of the plate and then sinks again. At constructive plate boundaries, the currents pull the plates apart (divergence). At destructive plate boundaries, the currents pull the plates towards each other (convergence). One major flaw in the theory is that the forces Wegener stated were needed to move the plates are wholly insufficient.
Ridge push is when magma that is extruded through a gap in the plates heats the rocks around it. These rise up, and then when they have solidified and cooled into rocks, gravity acts on it and the rocks are pulled down a slope. This explains sea-floor spreading.
Slab pull theory explains the movement of plates at destructive boundaries, and specifically explains subduction and ocean trenches. When one plate descends under another into the mantle, the plate has enough weight to pull the rest of the plate with it.
It has been suggested ridge push "is not a significant control on the motion of most plates", in particularly plates "affected by slab pull from a subducting plate margin". It is said that slab pull (and slab suction; you don't need to know about this) account for "almost all of the force driving plate tectonics". Ridge push rifts only contributes 5-10%.