Gravitational force & the formation of continental plateaux:

• Depending on its sign, GPE may oppose or enhance thickening.
In this example (Vanderhaeghe et al., 2003) a mountain belt develops due to the subduction of the continental lithospheric mantle.

a) A localised mountain belt has formed. Crustal thickening produces an extensional gravitational force (Fg) that opposes the tectonic driving force (Fd).

b) and c) When Fg balances Fd, thickening migrates into adjacent areas: the mountain belt grows laterally and a plateau develops.
The mountain belt is supported by the basal traction exerced by the subduction at the base of the overriding plate. Should the subduction stop, there would be no force to oppose Fg, which will then drive extensional collapse.