Editing Oceanic trench (section)

===Processes involved===

Several forces are involved in the process of slab rollback. Two forces acting against each other at the interface of the two subducting plates exert forces against one another. The subducting plate exerts a bending force (FPB) that supplies pressure during subduction, while the overriding plate exerts a force against the subducting plate (FTS). The slab pull force (FSP) is caused by the negative buoyancy of the plate driving the plate to greater depths. The resisting force from the surrounding mantle opposes the slab pull forces. Interactions with the 660-km discontinuity cause a deflection due to the buoyancy at the [[phase transition]] (F660).{{sfn|Nakakuki|Mura|2013}}  The unique interplay of these forces is what generates slab rollback. When the deep slab section obstructs the down-going motion of the shallow slab section, slab rollback occurs. The subducting slab undergoes backward sinking due to the negative buoyancy forces causing a retrogradation of the trench hinge along the surface. Upwelling of the mantle around the slab can create favorable conditions for the formation of a back-arc basin.{{sfn|Flower|Dilek|2003}}

[[Seismic tomography]] provides evidence for slab rollback. Results demonstrate high temperature anomalies within the mantle suggesting subducted material is present in the mantle.{{sfn|Hall|Spakman|2002}} Ophiolites are viewed as evidence for such mechanisms as high pressure and temperature rocks are rapidly brought to the surface through the processes of slab rollback, which provides space for the exhumation of [[ophiolites]].

Slab rollback is not always a continuous process suggesting an episodic nature.{{sfn|Schellart|Lister|Toy|2006}} The episodic nature of the rollback is explained by a change in the density of the subducting plate, such as the arrival of buoyant lithosphere (a continent, arc, ridge, or plateau), a change in the subduction dynamics, or a change in the plate kinematics. The age of the subducting plates does not have any effect on slab rollback.{{sfn|Nakakuki|Mura|2013}} Nearby continental collisions have an effect on slab rollback. Continental collisions induce mantle flow and extrusion of mantle material, which causes stretching and arc-trench rollback.{{sfn|Flower|Dilek|2003}} In the area of the Southeast Pacific, there have been several rollback events resulting in the formation of numerous back-arc basins.{{sfn|Schellart|Lister|Toy|2006}}