Aeolian Bedforms—their Development and Origins

Bedforms are defined and their variety outlined. Aeolian bedforms are shown to arise spontaneously by a two‐way interaction between surface form and airflow involving piecemeal material transfer between them. They eventually reach a dynamic equilibrium and transverse elements migrate downwind. Aeolian bedforms may be compounded of elements from four groups i.e., draas, dunes, aerodynamic ripples and impact ripples, each subdivided into transverse and longitudinal elements. There are no transitional forms between the elements of one of these eight subgroups and those of another and they are interpreted as being formed by different mechanisms. The possible nature of these mechanisms is considered and qualitative models for the development of generalised transverse and longitudinal elements given. Transverse and longitudinal elements may be combined in three different ways according to whether or not one element is displaced half a wavelength on crossing the other.