Small-Scale Sand Forms. Transverse Ripples and Ridges

Abstract

THOUGH the cross-section of a rippled sand surface often assumes an outline which closely resembles both the actual cross-section of a disturbed water-air surface, and also the graph on a time basis of any kind of simple vibration, the resemblance is in appearance only. For the essence of a true wave is in the propagation of energy, either through the body of a material as in the case of sound, or along its surface as with a surface water wave. In a sand ripple or wave there is no such propagation of energy. A sand ripple is merely a crumpling or heaping up of the surface, brought about by wind action, and cannot be regarded as a true wave in a strict dynamical sense. The similarity lies only in the regular repetition of surface form.