Why is water considered a major factor in mass wasting?

Water is considered a major factor in mass wasting primarily because it decreases friction on the slope. When water saturates the soil and rock materials on a slope, it increases the pore water pressure within those materials. This increased pressure can effectively reduce the frictional resistance that holds these materials in place, making it easier for gravity to initiate movement.

As water accumulates, it can also lead to additional processes such as lubrication between particles, further destabilizing the slope. This is particularly important during heavy rainfall or rapid snowmelt scenarios, where excess water can trigger landslides and other forms of mass wasting. Thus, the presence of water is a critical factor in determining the stability of slopes and the likelihood of mass movement events.