Beach cusps

Beach cusps are shoreline formations in which sediment of different grades is arranged in a series of arcs. The pointed horns are built of coarser material, while the curved embayments between them hold finer sediment. They occur all over the world and are most noticeable on coarse shores such as pebble beaches, although they can form in sediment of any size. They nearly always appear in a regular pattern, with cusps of equal size and spacing along a stretch of shoreline, and each one is usually a few metres long, though some reach about 60 metres across. How they first form has not yet been proven, but once established they sustain themselves. An incoming wave striking a horn is split in two and slowed, so it drops coarser sediment on the horn, while the water running along the embayments picks up finer sediment and carries it away, which keeps the horns and embayments at least at their size and sometimes enlarges them.