Long, wide, but extremely low, parallel ridges of sand are believed to represent the eroded stumps of former longitudinal dunes. Lacking erosion channels of any kind, they are probably unique features. The former dunes are thought to have been degraded mainly by sheet erosion, which was effected by (1) a high-intensity rainfall, (2) a partial vegetation cover, and (3) an unconsolidated, permeable sandy terrain. Probably this combination of factors is rare.
Small basins in the troughs between the sand ridges are underlain by a mixture of sand and clay that came from the ridges. These basins are maintained by deflation, together with excavation by buffalo, elephant, and other large animals.
The history of the ridges implies Pleistocene climatic change. A very wet period succeeded a very dry period. Also a short, recent dry period is suggested.