Oceanic Trench - Trench Rollback

Trench Rollback

Although trenches would seem to be positionally stable over time, it is hypothesized that some trenches, particularly those associated with subduction zones where two oceanic plates converge, retrograde, that is, they move backward into the plate which is subducting, akin to a backward-moving wave. This has been termed trench rollback (also hinge rollback). This is one explanation for the existence of back-arc basins.