Wind creates waves. As an air current (moving stream of air) moves over an undisturbed water surface, friction between air and water creates a series of waves that move across the surface. The size of the waves depends on the wind speed, the duration of the wind, and the distance over which the wind blows. (The distance of open water surface that the wind blows over is called the fetch.) A week-long tropical storm in the Pacific Ocean might produce waves as tall as three-story houses; a ten-minute gust blowing across a small lake might make waves that are only a few inches tall.

Waves move away from their point or area of origin in widening circles, like ripples moving away from a pebble dropped into a pool. In an ocean basin (the deep ocean floor), waves from many different wind events are moving across the sea surface...