Know Your Waves

Waves traveling in water deeper than one-half their wavelength are called deep water waves. Waves traveling in water shallower than one-twentieth of their wavelength are called shallow-water waves. Shallow-water waves interact with the ocean floor. As waves enter shallow water their speed and and wavelength decrease, but their height increases.

Artist's rendering of the Jason-1 satellite and a wave

How large can waves grow? Waves will continue to grow in size until they reach a maximum size that is determined by the wind speed and fetch. When the waves can no longer grow in size because the energy supplied by the existing winds equals the energy lost by waves breaking and leaving the fetch area, we refer to it as a fully developed sea.

Giant waves can be caused by storm surges. One type of giant wave mistakenly referred to as a tidal wave is created by seismic activity under or near the ocean. These waves actually have nothing to do with tides. Scientist use the Japanese word, tsunami (the "t" is pronounced the same as the "ts" in "lets"), for these large waves caused by underwater earthquakes and volcanoes. Tsunamis contain a tremendous amount of energy. As they approach the shore (shallow water), they grow in height (sometimes 30m) causing great destruction and loss of life.