» This article's about a geology phenomenon. For the rock band, see Cave In. A cave-in's 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. Geological formations Alvar structures such as occur on the Stora Alvaret, Oland, Sweden Tsingy limestone such as occur in the M… (More on Cave-in)