10.3.4 Creeps are defined as very slow, usually continuous movement of regolith down slope. Creep occurs on almost all slopes, but the rates vary. Evidence for creep is often seen in bent trees, offsets in roads and fences, and inclined utility poles (figure 12). The combination of small movements of soil or rock in different directions over time are directed by gravity gradually downslope. The steeper the slope, the faster the creep. Creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. This happens at a rate that is not noticeable to the naked eye.


There are generally three types of creep: (a) seasonal, where movement is within the depth of soil affected by seasonal changes in soil moisture and soil temperature; (b) continuous, where shear stress continuously exceeds the strength of the material; and (c) progressive, where slopes are reaching the point of failure as other types of mass movements.





    Figure 12: Example of creep occurs in road slope and forest slope.