Schematic of procedure for assigning morphologic ages to fan surfaces

Images of shaded digital elevation models of alluvial fan surfaces. The images across the top row shows an active and progressively older alluvial fans. Older fan surfaces appear smoother than active surface, due to the modification of the topography by surface processes. Bottom row shows two images of models of the active fan surface after a perscribed amount of modification by surface processes. Arrows highlight how comparison between observed and modelled surfaces can be used to assign a 'morphologic' age to these surfaces.