With the diffusion-equation representation of landform evolution providing reference calculations, quantitative comparisons between profiles of the high stand of Lake Lahontan presented here and profiles of the Lake Bonneville shoreline scarps analyzed elsewhere reveal that the two sets of scarps are nearly identical morphologically. When care is exercised in the selection of profiles, the Lahontan high-stand scarps are remarkably reproducible from one profile to the next, highly suggestive evidence that the processes that have shaped and changed the shape of these landforms are correspondingly regular. Slope-angle differences of only 2° are both discernible and interpretable features of these late Quaternary landforms cut in weakly consolidated alluvium. At a level of uncertainty of no more than 50 per cent, the mass diffusivity (κ) of the Lahontan high stand is the same as the Lake Bonneville shoreline κ, 1.1 GKG (1 GKG = 1 m2/ka). This result suggests that much can be learned about the ages of late Quaternary fault scarps cut in weakly consolidated alluvium throughout the Basin and Range Province from their morphology alone. The Beachfront fault scarps, themselves truncated by Lake Lahontan in our study area, are morphologically only slightly older (15 to 18 ka BP) than the Lahontan high stand (∼12 ka BP).