Mass wasting: as we already know, mass wasting is the movement of material under the influence of gravity.

In a purely technical sense, material being carried downstream in a creek might be called mass wasting, but mass wasting how we are going to use the term usually implies that wind, water, or ice did not act as a transport medium.

Landslides move along surfaces of separation by the various combinations of falling, sliding, and/or flowing. Several distinct landforms develop as a result of landslide transport. Landslides may be classified on the basis of the nature of the slope-forming materials and the type of movement. Four basic kinds of landslides are common. These move at different speeds and include:

1. Debris slides: internally disrupted and broken landslides that move downslope along basal slip surfaces.
2. Earthflows: composed of unconsolidated material which move downslope like a viscous fluid. Individual slip surfaces are absent. Flow can occur simultaneously along different fronts, and involve several lobes moving at different speeds. Earthflows most often occur during or following heavy rainfall when the internal cohesiveness of soil is reduced. Earthflows can move along relatively gentle slopes and cover large distances.
3. Slumps: relatively coherent and internally intact landslides. These move downslope by rotation and sliding along slip surfaces both within and along the base of the slide unit. Adjacent slumps can coalesce to form a compound slump.
4. Rock falls: move by free-fall or downslope bouncing of rock fragments. Debris that accumulates along the base of a rock fall is called talus.

Natural slope stability is controlled by a complex interaction of several factors. These include:

1. Physical characteristics of the soil and/or bedrock; unconsolidated soil moves more easily downslope than consolidated bedrock.
2. Structural characteristics of the soil and/or bedrock; these include joints and fractures (number and orientation relative to the slope) and the attitude of bedding or foliation.
3. Slope angle; landslides are more likely to occur along steep slopes.
4. Degree of water saturation; slope instability increases with the degree of internal water saturation which increase weight, reduces internal cohesion, and lubricates potential movement surfaces.
5. Characteristics of vegetation; variations in type, amount, and seasonal status of vegetative cover can markedly affect slope stability because of internal binding afford by root systems.
6. Proximity to areas of active erosion; areas of active erosional undercutting are susceptible to landsliding (shore and watercourses).
7. Seismic ground shaking; ground shaking during an earthquake can loosen slope-forming material and greatly reduce stability.

Risk from landslide across the United States varies.  Risk factors include soil type, bedrock depth and type, seasonal and instantaneous moisture contents, slope angle, and human disturbances.  Even something such as slope aspect (orientation) can have a major impact on risk.