The mass movement of a minimum volume of 500 000 m3 of rock (Scheidegger (1973) Rock Mechanics 5) derived from the collapse of competent masses of coarse-grained, hard bedrock. Hewitt (2006) PPG 30, 3 examines rockslide-rock avalanches in mountain landscapes, and the landforms associated with them, backed up with useful pictures and really clear explanations.