Wave-formed oscillation ripple marks are described in textbooks as symmetrical in cross-section while asymmetrical ripple marks are described as always formed by current action. Observation shows that asymmetrical ripple marks having their steep sides toward the shore are very common in the shallow water along the shores of lakes having a sandy bottom. A study of the method of formation of these asymmetrical ripples shows that they are not usually produced by currents but are formed by the oscillatory movements set up on the bottom by the passing breakers. These movements are unequal in time and intensity in opposite directions. The result is asymmetrical ripple marks which usually migrate in the direction of wave travel. Therefore wave-formed ripple marks should be divided into two classes: Symmetrical oscillation ripples and asymmetrical oscillation ripples.

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