Observations of beach cusps at Mono Lake, California

Beach cusps, uniformly spaced mounds or ridges of sediments that trend at right angles to the shoreline, are observed at Mono Lake, California. The cusps have spacings ranging from 11 to 59 cm, making them some of the smallest examples of natural beach cusps that have been described in geologic literature. They possess all the features observed in the much larger cusps found on ocean beaches: the same basic morphology, similar sediment sorting, and the same water circulation about the cusps. They form best when the lake is essentially glassy smooth and only surging, nonbreaking waves arrive at the shoreline. It is concluded that edge waves, waves trapped by refraction to the nearshore, probably account for the cusp formation and rhythmic spacing. © 1973 Geological Society of America.