ABSTRACT

The two processes by which the composition of debris becomes stabilized after traveling 10 to 12 miles by eolian saltation and creep are called rectification, in analogy with the process that takes place in the rectifying section of a distillation column, and selective horizontal dispersion. The two processes interact. The process of rectification is described in this paper.

Rectification of wind-blown sand occurs by repeated interaction of a saltation and a creep fraction that are almost in equilibrium. Mathematical models are developed to analyze the process. Sands may be classified as unimodal, bimodal, or polymodal by their saltability-frequency curves. The models predict that in some cases an initially unimodal sand may become bimodal, and later unimodal again as rectification becomes more nearly complete and distance from the source of sand supply increases. In some cases in a sand mixture the per cent of grains of a given saltability class may reach a maximum and then decrease as rectification proceeds.