The gentle wave that laps at your feet when you walk on an ocean beach may have formed far away-and under not-so-gentle conditions. Waves are created by winds blowing over the water. Here, a fan creates a windy environment inside a water-filled bowl. Turn the knob to change the windspeed and watch how the waves change. You may even be able to create a small waterspout. As air moves over the water, small ripples form, then merge to make larger waves.
Out at sea, storm winds can generate waves that act like watery sails. As they gain energy from the wind, they can grow to enormous size and travel for thousands of miles. By the time one of these waves washes up on shore, its energy may be depleted, leaving no trace of its violent birth.
(c) The Exploratorium, 1996