Wind creates ocean's white caps

Melissa Hauptman, 7, a second-grader at Diamond Lake School in Mundelein, asked, "What makes the top of a wave white on a whitecap?"

Waves make the ocean wild and exciting. Wind currents create movement across the ocean surface creating ripples, waves or swells, depending on how hard the wind is blowing.

Dr. Stephen C. Riser, professor at Washington University's School of Oceanography in Seattle, said, "When there is little or no wind over the ocean, the sea surface can be very calm, almost glassy, or perhaps have some gentle waves.

"When the wind gets stronger, there is a tendency for the wind to blow the tops off of these waves, much as you could make a mess by blowing hard enough on the top of a glass or pan of water. This process of blowing the tops off the waves yields the whitecaps."

Those larger waves with bigger white caps lure surfers into the water. Reefs and other rock formations on the sea floor, as well as the coastline geography where the waves break, contribute to the types of waves that crest on beaches.

Certain places are favorite locations for surfers because the waves are huge. Bonzai Beach on the northern coast of the Hawaiian island of Oahu attracts surfers who shimmy along 12-foot barrel-shaped waves called pipelines.

Why is the crest of the wave called a whitecap?

Professor Riser said, "When the wind blows the tops off the waves, some of the moving air in the wind enters the water and we see bubbles form. The bubbles appear white, and that is what makes the top of the waves white on a sufficiently windy day."

For more information

The Vernon Area Library in Lincolnshire suggests these titles on oceans:

• "I Wonder Why the Sea is Salty," by Anita Ganeri

• "Our Amazing Ocean," by David Adler

• "Science Files: Oceans," by Anita Ganeri

• "How Big is the Ocean?," Time Life for Children

• "Seas and Oceans," by David Lambert

• "Caring for the Planet: Seas and Oceans," by Neil Champion