The Bird in the Waterfall by Jerry Dennis and Glenn Wolff

A Breeze
Jerry Dennis & Glenn Wolff

As a breeze touches a calm lake, areas of ripples appear, often in uneven, roundish shapes mariners have for centuries called "cat's- paws." If the breeze continues, capillary waves offer upright surfaces that catch additional wind, like tiny sails, allowing a more efficient transfer of energy to the water. Ripples spread across the surface, forming distinct streams of disturbance or blossoming suddenly into flower shapes. Farther from shore, away from the protection of hills and trees, the wind picks up momentum and gains strength, building ripples into wavelets, then larger waves, then, if the wind is strong enough, into whitecaps. By the time the waves reach the far shore and enter shallow water they are large enough to become breakers. From the lee shore of a lake on a windy day you can watch the whole process: calm water before you, ripples a short distance out, larger waves rushing away across the open lake.

Once acted upon by a generating force such as wind or a passing boat, large waves drive forward and gravity tries to fill every trough with a crest. This chasing of crest after trough is an effort to achieve the equilibrium of a flat surface. Gravity wants to create calm seas, which is why most waves larger than ripples are known as gravity waves.

Most gravity waves are produced by wind, and their size is determined by the wind's speed, duration, and "fetch," Wave Chart--Click for a Full Viewor the distance it blows unhindered. An increase in any of those factors results in increased wave height, which is the distance from the bottom of a trough to the top of a crest; greater wave length, which is the distance from one crest to the next; and longer period, which is the time it takes a wave to pass from crest to crest.

Wind can produce several distinctive kinds of waves. Ripples grow into wavelets, then into increasingly larger waves. In the open ocean, sea waves (also called chop) are always under the direct influence of the wind and are likely to have smooth, rounded troughs between sharply peaked crests. They often occur in complex patterns, with waves of many sizes coming from several directions, creating confused, choppy, unpredictable seas. The roughest seas are typically composed of short, steep, sea waves produced by storms.

Swell waves travel beyond the wind, either leaving the area where it is blowing or continuing on after the wind has ceased.

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