Recent studies of scarps produced by normal faulting of cohesionless materials indicate that older scarps are steeper than younger ones, and that slope angles are less for lower scarps of the same age. These observations may be explained by a simple quantitative model of slope degradation in which the rate of change of elevation at a point on a slope profile is proportional to the curvature of the profile at that point. The convex-upward (negative curvature) slope crest will be lowered and the concave-upward (positive curvature) slope base will be raised. The model assumes that the slope remains covered with loose debris and that the local rate of downslope movement of the debris is proportional to the local hillslope gradient. The model provides a simple morphologic dating technique for fault scarps in cohesionless material. It predicts that the rate at which the maximum slope angle of a scarp decreases is related to the initial height of the scarp. It may also be possible to apply the morphologic dating technique to hillslopes formed in other ways.