Plate tectonic forces:
Three plate tectonic forces:
Ever since plate tectonic theory took hold in the late 1960s, geoscientists have argued over what drives plates: mantle upwelling at ridges that pushes plates apart, mantle circulation that drags plates along, or slab pull have independently or in combination been proposed as driving forces for plate motion.
According to Don Anderson, a geophysicist at Caltech Seismological Laboratory, “... slabs drive tectonics. There is no need for other driving mechanisms such as plumes or mantle convection that are independent of plate tectonics.”
• Based on a simple model of lithosphere and mantle interactions, geophysicists have found that two major tectonic forces — slab suction and slab pull — can interact to explain most observed plate movements today. A slab can pull the rest of its plate behind it (the pull force). The slab can also drag against the viscous mantle and cause the sub-oceanic mantle to flow in toward the subduction zone. That flow sucks in the oceanic plate (the suction force).
The dynamic of plate motion is the result on the interplay between mantle flow and forces acting at plate level. The forces acting on plates are the Ridge Push (Frp), the Slab Pull (Fsp), and the continental Gravitational Forces (Fg). The ridge-push is the gravitational force acting between the high-standing mid-oceanic-ridge and the low-standing abyssal plain. The slab-pull is the pull exerced by the subducting slab on the rest of the oceanic lithosphere. The continental gravitational force is the gravitational force acting between the high-standing continental plate to the low-standing adjacent abysall plain. The interplay between these forces results in contrasted tectonic regimes:
Fg>Frp, Fsp Fg~Frp~Fsp Fsp<Frp, Fg