Wind creates most familiar ocean waves. Their size depends on wind speed, how long it blows and the fetch—the distance over which it acts. The energy travels forward while individual water particles mostly move in orbital paths.
Three things to know
- Energy source
- Mostly wind
- Earthquakes, landslides and gravity generate other wave types.
- Growth controls
- Speed · time · fetch
- Stronger, longer winds across more water can build larger seas.
- At the coast
- Shoaling
- Shallow water slows the wave base, shortens wavelength and can force breaking.
Energy crosses the surface
A breeze first roughens the water with capillary waves. Continued wind transfers more energy, building gravity waves. Water parcels generally trace circles or ellipses rather than riding from the storm all the way to shore, which is why floating objects can bob while the wave pattern moves onward.
Sea becomes swell
Close to a storm, waves of many periods and directions produce a confused sea. As the field travels, longer-period waves move faster and organize into smoother swell. A beach can therefore receive large, regular waves from weather far beyond the horizon.
Why waves break
As a wave enters water shallower than about half its wavelength, it interacts with the bottom. The wave slows and steepens while its energy is compressed into less depth. When the crest outruns the support beneath it, the wave breaks, transferring energy into turbulence, currents and sediment movement.
What people usually ask
Do waves carry water across the whole ocean?
They mainly transmit energy. There can be some net transport, but water particles usually follow small orbital paths.
Is a tsunami a giant wind wave?
No. A tsunami usually begins with sudden displacement of a large water volume by an earthquake, landslide or volcanic event.
Here’s where the answer came from
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