| Abstract | Soil creep is an important component of mass wasting in the Rocky Mountains of southern Alberta. Near the Continental Divide, the movement takes place principally in summer when the soil contains 40% moisture by volume. Movement may range up to 323 mm and the trees move with the soil. In the Front Range, soil creep may amount to 210 mm per year at a site, but occurs mainly in late summer and fall when soil moisture contents are minimal. It is independent of freeze-thaw cycles. Some movement (20 mm) also occurs in winter when the ground is frozen. Continuous recording apparatus demonstrates diurnal fluctuations on bare ground. Insolation correlates with downslope movement, and similar fluctuations occur in a vertical direction. Heaving correlates with increased humidity of the air at night or in early morning. The combined result is that a given soil particle tends to follow an orbital path elongated in a horizontal direction, unlike the diurnal movement proposed in many current theoretical studies. Retrograde creep also occurs in colder weather. The logarithm of the sine of the angle of slope correlates with the amount of movement on a south-facing slope, movement apparently ceasing at angles below 2°. Movement usually decreases with depth except on screes or in shallow soils over bedrock. In the latter, water abstraction by plants or a perched water table produce increased soil creep with depth. |
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