Figure 1.-- A, View looking along the trend (indicated by arrows) of a slide-bounding strike-slip fault on the Slumgullion landslide in Colorado. The ridges parallel and adjacent to the fault, often called levees, are composed of unconsolidated, highly dilated sandy soil. B, View along the trend of the strike-slip San Andreas fault in the Carizzo Plains of California. Note the similarity between the adjacent ridges, often attributed to differential erosion of fault and surrounding material, and the levees of the Slumgullion. We suggest that such structures are common to strike-slip faults of all scales, but, because of the slower slip rates along crustal faults, the levee formation is overtaken by more rapid erosion.