The term mass wasting (sometimes called mass movement) encompasses a broad array of processes whereby earth material is transported down a slope by the force of gravity. It is related closely to weathering, which is the breakdown of minerals or rocks at or near Earth's surface through physical, chemical, or biological processes, and to erosion, the transport of material through a variety of agents, most of them flowing media, such as air or water. Varieties of mass wasting are classified according to the speed and force of the process, from extremely slow creep to very rapid, dramatic slide or fall. Examples of rapid mass wasting include landslides and avalanches, which can be the cause of widespread death and destruction when they occur in populated areas.