A landslide is a form of mass wastage that includes a wide range of earth movements, such as rock falls, steep slope faults, and surface waste streams. Landslides can occur underwater, called a submarine landslide, coastal and coastal environments. Although the action of gravity is the main driving force for a collapse, there are other factors that contribute to the stability of the original slope. Typically, pre-conditional factors accumulate specific sub-surface conditions that make slope area prone to failure, while actual slip often requires a trigger before being released. The landslides should not be confused with mud flows, a form of mass waste involving an extremely rapid flow of debris that has been partially or totally liquefied by the addition of significant amounts of water to the source material.