In summary, slopes in thin colluvium appear to be more stable than we would predict from laboratory measurements of residual strength of the colluvium. The puzzling question about thin landslides, then, is not why some slopes have failed, but rather why failure is not more extensive. Observations of episodes of movement of typical thin landslides (fig. 18) suggest that a type of stick-slip phenomenon may contribute to iarger-than-measured initial strength. We observed that a small displacement causes a large loss of resistance, and a thin landslide commonly accelerates out of the slide scar. The situation, shown schematically in figure 18, may be equivalent to the abrupt loss of strength in firsttime failures of slopes compared to reactivation of previously failed slopes. For thin colluvium, however, the slope has previously failed and yet retains greater resistance to sliding than predicted by laboratory measurements