Most beach-goers have probably wondered just what makes the waves coming in to shore rear up and break. The secret lies in the depths–or rather the lack thereof–beneath the waves. Far from shore, the wave’s length scale is small compared to the ocean depth, and the ocean’s bottom is effectively infinitely far away to all parts of the wave. But, as the wave rolls toward shore, the depth decreases and the ocean bottom begins to influence the wave. In the trough, the ocean bottom slows the wave. Meanwhile, the crest of the wave carries forward, rising until its height reaches 80% of the water depth, at which point it will tip over and break.(Video credit: BBC)
Breaking Waves
