Cave-in

A cave-in is a collapse of a geologic formation, mine or structure which typically occurs during mining or tunneling. Geologic structures prone to cave-ins include alvar, tsingy and other limestone formations, but can also include lava tubes and a variety of other subsurface rock formations.

In mining, the term roof fall is used to refer to a range of collapses, ranging from the fall of a single flake of shale to collapses that form sink holes that reach to the surface. Note that roof falls in mining are not all accidental. In longwall mining and retreat mining, miners systematically remove all support from under large areas of the mine roof, allowing it to settle just beyond the work area. The goal in such mining methods is not to prevent roof fall and the ensuing surface subsidence, but to control it.

From http://en.wikipedia.org/