Mass movement of mancos shale crust near caineville, utah: a 30‐year record

Abstract

Rates of soil creep were studied periodically over a 30‐year period in southeastern Utah on Mancos Shale badland slopes averaging 35 degrees. More intensive studies were carried out over a 10‐year period on slopes averaging 40 degrees. On the 35 degree slope the average rate of movement was 2.71 cm yr−1.On the 40 degree slopes, rates varied from 3.14 to 5.94 cm yr−1.Individual rates of movement varied widely, but average movement of a given line was consistent. No statistical differences in rates of movement were found between north‐ and south‐facing slopes.About two‐thirds of the total movement occurred during the winter/spring period; episodes of rapid movement coincided with years in which storms deposited at least 0.6 cm of precipitation per day for at least two consecutive days. Downslope rotation of nails indicates that creep involves only the top few centimeters of soil.