Mass wasting is a natural process, but it is influenced by roadway construction, removal of vegetation and the introduction of water to certain areas. Professor Stephen Nelson of Tulane University defines mass wasting as the down-slope movement of loose rock particles and soil.
Many natural events cause mass wasting, including earthquakes, ice wedging and animal activity. During an earthquake, seismic waves shake unstable slopes, causing loose rock particles and soil to move. Ice wedging refers to the formation of ice crystals in the tiny crevices between rocks. When the water freezes, it expands, putting additional force on the rocks. Some of the rocks may wedge apart and fall from canyons, mountains or other slopes. As animals move across a slope, their activity may cause loose rocks to fall.
Another natural cause of mass wasting is the presence of excess water on a slope. If snow melts quickly or heavy rains fall in a short amount of time, the mass of the slope increases. If the sediment is loose, the excess water will move it down the slope, causing mass wasting.
Humans are also partially responsible for mass wasting. If vegetation is removed from a slope, it will not have as much protection against the force of raindrops. When it rains, the rain will move loose rocks and soil.