Collapse of cave passages results in piles of fallen rock fragments known as breakdown. Breakdown occurs as blocks, slabs, and chips, as isolated rock fragments, and as massive piles of fallen rock. Models for the formation of breakdown include brittle fracture under gravitational loading of fixed or cantilever beams and also by microfracturing with inelastic creep. Geological mechanisms that trigger breakdown include loss of buoyant support, dissolutional action of vadose waters, frost pry, and mineral replacement. Breakdown plays an important role in the final stages of the truncation and decay of caves as surface erosion destroys the system.