- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States
The oscillatory motion of swash and backwash produces high-index ripple marks which are essentially symmetrical. They differ from water-current and water-wave ripple marks in that they have high indices (30 to 100). They differ from eolian ripple marks in that they have relatively high symmetry. The swash zone features appear to be the product of bed shear, without eddy-type augmentation.