A form of mass movement in which material slides in a relatively straight plane, generally breaking into many blocks as it moves. Slides usually have a length far greater than the depth of the moving material, and are triggered by high water pressure (Dai et al. (1999) Eng. Geol. 53, 3–4), but the competence of the rock is also significant; see Warburton et al. (2003) ESPL 28, 5.