In deep waters, only wavelength and wave period affect a waves speed. As the wave approaches shallow water, or water that is half the wavelength or less deep, the ocean floor begins to affect the wave's shape and speed. Wave height increases, and the crests become more peaked. As the steepness increases, the wave becomes unstable. The forward speed of the crest becomes faster than the speed of the wave, and the wave breaks.
We can describe breaking waves in three different ways: Surging Breakers, Plunging Breakers and Spilling Breakers. You see examples of these at the beach.
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Plunging Breakers happen on beaches where the slope is moderately steep. This kind of wave normally curls over forming a tunnel until the wave breaks. Expert surfers love this type of wave! |
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Spilling Breakers occur on beaches with gentle slopes. These waves break far from the shore, and the surf gently rolls over the front of the wave. |
Information provided by: http://www.onr.navy.mil