landslide

Types of landslide. A mudflow is a tongue of mud that slides downhill. A slump is a fall of a large mass that stays together after the fall. A landslip occurs when beds of rock move along a lower bed.

Sudden downward movement (see mass movement) of a mass of soil or rocks from a cliff or steep slope. Landslides happen when a slope becomes unstable, usually because the base has been undercut or because materials within the mass have become wet and slippery.

A mudflow happens when soil or loose material is soaked so that it no longer adheres to the slope; it forms a tongue of mud that reaches downhill from a semicircular hollow. A slump occurs when the material stays together as a large mass, or several smaller masses, and these may form a tilted steplike structure as they slide. A landslip is formed when beds of rock dipping towards a cliff slide along a lower bed. Earthquakes may precipitate landslides.