Image courtesy of USGS
A rapid downslope movement of rock or soil as a more or less coherent mass. Landslides are characterized by a slippage plane that is clearly defined. A landslide may turn into a flow at the bottom as the blocks become tumbled over. Usually the material moves as a large block known as a slump block. The scar above a landslide is easily visible. Steep slopes of shale are susceptible to landslide activity. But landslides occur everywhere on large or small scales. They can occur after earthquakes or removal of part of the slope due to construction, particularly in the construction of roads.