- GeoRef, Copyright 2008, American Geological Institute. Reference includes data from Bibliography and Index of Geology Exclusive of North America, Geological Society of America, Boulder, CO, United States
"When other controlling conditions are constant, the wave length of ripple marks is directly related to the size of the sand. A very slight tidal action can cause profound changes in the ripple mark form. In Giorgimpopoli, Libya, normal symmetrical oscillation ripple marks are first made asymmetric, then flat-topped, and finally buried as the tide moves out and then in."