Waves might look like chaos (top), but there is a pattern to them (bottom).
Click on image for full size
Top image courtesy of NASA; bottom image courtesy of NOAA
Ocean waves are usually formed by wind. Large waves will form if the wind is strong, if it blows over a large distance, and if it blows for a long time.
Waves may look chaotic when they approach a beach –crashing and full of sea foam. However, waves do have organization to them, especially in open water when they are not crashing.
A wave’s highest point is called its crest. The low point between two waves is called a trough. The vertical distance between crest and trough is called the wave height. The distance between two waves is called the wavelength and it is usually measured either from one crest to the next or from one trough to the next. The time it takes for waves to pass is called the wave period.
Why is it important to measure the waves? Sailors look at reports of the size of waves when planning where to travel in their ships. Surfers look at reports of the size of waves when searching for places to surf. Waves have an impact on currents at the coast too.
There are other types of large waves that are very rare such as rogue waves, which often travel alone and not in the direction of the other waves. A tsunami is also a powerful wave that is not caused by wind. Large waves that travel very long distances are called swells.
As waves move into shallow water, the energy in the wave runs into the shallow seafloor. This causes the wave to steepen and eventually to topple over or break.
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The Spring 2010 issue of The Earth Scientist
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