Gravitational collapse in geology refers to the process where a mountain range or orogen undergoes extension and thinning due to the gravitational potential energy built up during tectonic compression. This process can lead to the formation of extensional faults, metamorphic core complexes, and the redistribution of crustal material.
Reference: Dewey, J. F. (1988). Extensional Collapse of Orogens. Tectonics.