LANDSLIDE AND DEBRIS FLOWS
A landslide or landslip refers to a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. The action of gravity is the primary driving force though other contributing factors are rainfall, earthquakes, volcanic eruptions, groundwater pressure, erosion, destabilization of slopes as a result of deforestation, cultivation and construction, snow and glacial melt.
Debris flow or mudflow is a fast-moving mass of loose mud, sand, soil, rock, water and air that moves downhill due to gravity. Preconditions for debris flow are: very steep slopes, a lot of loose debris and water, and little vegetation. In very steep areas, debris flow can reach speeds of over 160 kilometres per hour (100 miles per hour). The speed and volume of flow make these very dangerous.