ABSTRACT
Mass movement is a common hazard in moun - tainous areas. It results from the displacement of surface materials down-slope under the force of gravity and exists in most environments where slopes are present. The movements vary greatly in size (ranging from a few cubic metres to over 100 cubic kilometres) and in speed (ranging from millimetres per year to hundreds of metres per second). Rapid mass movements generally cause the greatest loss of life, whilst slower down-slope movements create significant economic costs. It is convenient to classify mass movements according to the material forming most of their mass. Landslides consist mostly of rock and/or soil; snow avalanches are formed predominantly from snow and/or ice. Mass movements are usually triggered by natural processes, notably earthquakes, intense and/or prolonged rainfall and snowmelt, but some damaging landslides occur in materials deposited by humans. These include mining waste, landfill or garbage and, overall, people play an increasing role in the causation of this hazard.
