Varnes classification of landslides

Mass movement is the downslope movement of rock, debris or soil under gravity. Varnes (1978) classified landslides by the type of movement and the type of material (rock, debris, earth/soil).

Types of movement

1. Fall: detachment and free fall, bouncing or rolling of material from a steep slope; rock fall, debris fall.
2. Topple: forward rotation of a rock mass about a point below its centre of gravity; common in columnar jointed rock.
3. Slide: movement of a mass along a surface of rupture.
   • Rotational slide (slump): curved slip surface, typically in homogeneous soil.
   • Translational (planar) slide: flat surface, along bedding, joints or foliation. Includes the wedge slide.
4. Spread (lateral spreading): lateral extension of a mass with shear or tension fractures; on gentle slopes.
5. Flow: the mass moves like a viscous fluid; debris flow, mud flow, earth flow, rock avalanche.
6. Complex: a combination of two or more types, e.g. slide-flow.

Classification table

Rate of movement: Varnes (1978) ranged it from extremely slow (below 0.06 m/year) to extremely rapid (above 3 m/s); the later revised scale (Cruden and Varnes, 1996) uses below 16 mm/year to above 5 m/s. Water content and speed distinguish slides from flows.