What is a landslide?
A "Slope movement" (Varnes, 1978) or "landslide" (Sharpe, 1938) is understood as the movement of a rock mass or soil downward a slope (Cruden, 1991). This term includes all kinds of mass movements, except for erosion, subsidence, and karst collapse. Another definition, suggested by Corominas and García Yagüe (1997), defines landslides as movements of material on slopes and escarpments descending due to the force of gravity.
Figure 1. Evolution of a landslide in the Pampore Hills Regional Park, New Zealand (Link to full video: https://www.youtube.com/watch?v=Etm6c94eX-Y, source: Emma Kapu).
Figure 2. Gazost´s landslide, France (Red PyrMove, Regional analysis of the risk of landslides in the Pyrenees -2014 CTP 00051-).
Landslides classification depends on the criteria used for their differentiation and is mainly based on the failure mechanism and the propagation of movement. The PyrMove project distinguishes two types of potentially damaging landslides:
1. Great landslides
2. Multiple landslides caused by heavy rain episodes (MORLEs, Multiple Occurrence Regional Landslides Events)