Landslide is a general term used to describe a variety of geologic processes involving the movement of fine-grained earth, coarse-grained debris, or rock down a slope under the influence of gravity. This broad definition of downslope movements includes falling, toppling, sliding, spreading, and flowing. Landslides can also occur under water (submarine landslides) and trigger tsunamis.

Commonly used landslide classification systems rely on separate terms to describe the type of movement (falling, toppling, sliding, spreading, or flowing) and the type of material involved. Unlithified material is classified as debris if it is predominantly coarse-grained (sand, gravel, cobbles, or boulders) and earth if it is primarily fine-grained (silt or clay). Thus, a debris flow would involve the down slope flow of predominantly coarse-grained material, whereas a debris slide would involve the sliding of the same kind of material along a well-defined slip surface. Additional detail can be included by specifying...