Characteristic features of fault-generated range fronts, such as those on the Humboldt and Tobin Ranges, include sets of elongate basins extending normal to the range crest, interbasin spurs having crests sloping 10° to 20° toward the range front, spur facets having slopes of 25° to 35°, basin headwalls having slopes of 20° to 30°, and a basal fault scarp. The basal fault scarp is rejuvenated by vertical movements recurring at intervals on the order of 10 000 years. Fault scarps in colluvium that lie within a few tens of meters of the base of faceted spurs remain clearly recognizable for only a few tens of thousand years. Initial fault-scarp slopes of 50° to 90° are replaced by debris-controlled slopes of 30° to 37° within a few thousand years. In fractured bedrock, slope angles in the range of 25° to 35° remain relatively stable for hundreds of thousands of years and account for the relative stability of facets on spurs. Piedmont slopes are greatly affected by tectonic tilting or warping toward or away from the range front. The formation of pediments is believed to result from a low ratio of uplift relative to downcutting. A few million years is required for the development of a pediment a few kilometers wide.
