A form of mass movement (also called a single rotational slide) where rock and soil rotate backwards with movement down a concave face: ‘a more or less rotational movement, about an axis that is parallel to the slope contours, involving shear displacement along a concavely upward facing failure surface’ (D. Varnes 1978). Slumps are most common in thick regoliths (Nwadije (1998) Nat. Hazards 1, 2) and large mudstone rock units (Plint (1986) Sedimentol. 33, 3).