Mass Wasting

Mass wasting is the movement of rock and soil at a slope downward due to the force of gravity. Some forms of mass wasting include landslides, rock falls and slides. Mass wasting occurs when the gravitational force exceeds the forces holding the slope together.

Some factors which influence mass wasting include weathering and slope gradient. Slope gradient refers to the steepness of the slope, the steeper the slope, the higher the shear forces of gravity experienced by the rock. Streams, and man made excavations are usually the culprits in steepening of the slope gradient. Weathering refers to the erosion of rock into unconsolidated soil. Mass wasting is more likely to occur in unconsolidated material as opposed to solid rock.

The effect of climate on mass wasting can be inferred by thinking about its effect on weathering. Colder climates can influence weathering through frost action. Since water expands when it freezes, water which gets inside of rocks will tend to break the rock apart when wintertime comes. This yearly cycle of expansion and contraction will contribute to weakening of the slope.

While this loosening of the soil through freezing is not present in arid climates, that doesn’t mean that weathering does not occur in these areas. Sudden large amounts of rainfall can drop a large amount of liquid water on the slope at a short period of time and the lack of vegetation to hold the slope together as well as to absorb the water can trigger landslides and mudflows. As a whole though, I would have to say that the activities of frost action in colder climates would make mass wasting in these areas much more prevalent compared to those in dry and hot areas.

Bibliography

Thompson, G.. & Turk, J. (2007) Earth Science and the Environment 4^th edition. New York: Thomson Brooks Cole