The word slump is most commonly used as a colloquial description of a landslide with a markedly curved and concave-upward slip surface, which results in rotational movement of the mass above the slip surface. This stands in contrast to landslides with more nearly planar slip surfaces, above which the sliding motion is predominantly translational rather than rotational. Most landslides exhibit both kinds of motion, so the distinction is based on the predominant type of motion. Rotational slides tend to occur in slopes that are, at least mechanically speaking, relatively homogeneous whereas translational slides tend to occur in slopes that contain mechanical discontinuities such as steeply dipping bedding or soil-bedrock contacts that can evolve into slip surfaces.

Like the term mudslide, slump is frequently used but is not defined in the classification system used by most landslide specialists. Depending on the type of earth material involved, a slump can...