Erosion of hillslopes envolve processes that are primarily driven by gravity. They can be slow like creeping or extremely rapid like rock falls. One can distinguish two major processes :
Downhill creep is the slow downward progression of rock and soil down a low grade slope. Friction being the primary force to resist gravity is produced when one body of material slides past another offering a mechanical resistance between the two which acts on holding objects (or slopes) in place. As slope on a hill increases, the gravitational force that is perpendicular to the slope decreases and results in less friction between the material that could cause the slope to slide.
Landslides, rockfalls and avalanches design the sudden detachment of a portion of soil or rock and its fall downslope. A rich and complex classification of these "gravity flows" has been established in the litterature. It is generally based on the estimation of their size and rheology. Landslides are triggered by various phenomenons such as rainfalls and earthquakes.
© Patrick Meunier
