Ocean WavesOcean Waveswave a periodic disturbance in a

solid, liquid, or gas as energy is transmitted through a medium

two basic parts—a crest and a trough

wave period the time required for two consecutive wave crests to pass a given point

wave height: vertical distance between crest and trough

Wavelength: distance between two crest or troughs

Wave EnergyWave EnergyLonger wind blows the more

energy is transferred into the water = larger waves.

Wave movement:◦Energy in waves move from water

molecule to water molecule in the direction of the wave

◦circular motion◦in a single wave period, each water

particle moves in one complete circle◦Only the energy not the water moves

across the surface of the ocean.

Wave SizeWave SizeThree factors determine the size of

a wave.◦Speed of the wind, the length of time

the wind blows, and fetch.◦fetch the distance that wind blows

across an area of the sea to generate waves

Whitecaps: ◦When winds blow the crest of a wave

off◦reflect solar radiation, they allow less

radiation to reach the ocean

Waves and the CoastlineWaves and the CoastlineBreakers

◦ Wave moves into shallow water.

◦ The bottom of the wave is slowed by friction

◦ The top of the wave continues to move at its original speed.

◦ the top of the wave topples over and forms a breaker, a foamy mass of water that washes onto the coastline.

Start of Wave SequenceStart of Wave Sequence

End of Wave SequenceEnd of Wave Sequence

Refraction:◦ The bending of

the wave crest in response to changes in wave speed

◦ Shallow ocean water = slower speeds

◦ Deeper ocean water = faster speeds

Undertows and Rip Undertows and Rip CurrentsCurrentsUndertow:

◦Water carried onto a beach by breaking waves is pulled back into deeper water gravity

Rip currents:◦ form when water from larger

breakers returns to the ocean through channels that cut through underwater sandbars that are parallel to the beach.

Rip CurrentRip Current

Longshore CurrentsLongshore Currentscurrents form when waves

approach the beach at an anglecurrents flow parallel to the

shore. Great quantities of sand are

carried by longshore currentsThese sand deposits form low

ridges of sand called sandbars.

Longshore CurrentsLongshore Currents

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Longshore CurrentsLongshore Currents

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TsunamisTsunamis giant seismic ocean waves Most are caused by earthquakes on the ocean

floor, but some can be caused by volcanic eruptions and underwater landslides

Nick name is tidal wave, but they are not caused by tides

has a tremendous amount of energy◦ In open ocean water they travel at a rate of around

760Km per hour or 483mph, that similar to the speed of a jet aircraft.

Not dangers in open water, but when they come into shallower the energy is transferred into height = destruction

The arrival of a tsunami may be signaled by the sudden pulling back of the water along the shore

TsunamiTsunami

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