"Nature Guide Journal"

12 July 2001

It's summertime, and people are flocking to the beach. While beach-combing, bird-watching, or sand-castle-building; most of us find ourselves watching the ocean, mesmerized by it's action.

The sea is constantly in motion. That motion is caused by several different physical events: tides, currents, and, most noticeably, waves.

Most waves at the beach are generated by wind blowing over the water. Winds in the immediate area create whitecaps and "chop" on the ocean surface, called a "sea." As the irregular pattern of a sea travels over the ocean, the pattern becomes the more orderly ocean swells. Swells–and the beach lapping waves they become–are generated by winds perhaps several hundreds of miles away.

Swells reaching our beach at any given time are often generated by more than one wind or storm, in different parts of the Pacific. Each storm generates a unique wave pattern, since the speed, duration, and fetch (area blown) of the winds are unique to each. Speed, duration, and fetch together determine the height, length, and period (time between crests) of the waves.

Further, the swells from a given storm change as the storm evolves and ages, changing the height, length, and period of the waves. How the wave approaches the beach also depends on the shape of the shoreline and the contour of the bottom, which vary a little as the tide changes the depth of the water.

Shallow water slows waves down. As waves approach a headland, for example, the shallows slow the waves at that point, curving them and causing the waves to wrap around the headland.

Watching a bird resting on the surface riding the ocean swells outside the surf zone, you'll notice that the bird for the most part rises up and down with each passing wave, with very little forward movement. Seen from a stable vantage point, the water–and particles in the water–actually trace a circle as the wave rises and falls.

While the transfer of the wind's energy travels though the water, the water itself doesn't travel far until the wave reaches shore. As the water becomes shallow, the circular transfer is crowded and the wave length is shortened, eventually "breaking" the wave and creating a breaker. It's the breaker that significantly moves water, sand, and surfers.

As a pattern of waves approach the beach from one direction, they may interact at some level with waves originating from other directions. A trough of a wave from one pattern may match up with a crest of a wave from another, tending to cancel each other. Troughs of waves from different patterns may coincide, giving an apparent lull in the waves.

More importantly to people walking on the beach, crests of waves from different patterns may overlap, combining to make a very large wave that runs high up the beach. This unpredictable overlap is a major contributor to the "sneaker waves" that soak beachcombers' shoes or knock the unwary into the water.

Choppy seas, rhythmic swells, and breaking waves work together to produce the dynamic and hypnotic sea pageant we find so alluring.

Wavecrest Discoveries can craft your personal discovery of this delightful part of our world by customizing one of our distinctive guided excursions.   Our walks, tours, and special activities are wonderful ways to explore this fascinating region—and are the perfect entertainment for guests.