Ripple Mark

Ripple-Mark, an undulation of the surface of sand or other fine-grained rock produced either directly by the action of the wind upon the surface when wet, or indirectly by its action on shallow water. In either case the rippling consists of alternating long slopes to windward and short steep slopes to leeward. If slightly sun-baked between tides, a fresh layer of sediment may preserve a ripple-mark, and we find hundreds of feet of sandstones thus rippled throughout and evidencing steady subsidence keeping pace with deposition. When in situ ripple-marked beds tell us the direction of the wind when they were laid down. The under-surface of the next layer will present a cast which has been termed a negative ripple-mark. Ripple-marks are often associated with sun-cracks, rain-prints, and foot-prints, all signs of shore conditions.