# Waves. © 2006 Brooks/Cole, a division of Thomson Learning, Inc. Ocean Waves Move Energy across the Sea Surface  Ocean waves are visual proof of the transmission.

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Waves

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Ocean Waves Move Energy across the Sea Surface  Ocean waves are visual proof of the transmission of energy across the surface of the ocean.  A floating sea gull demonstrates that wave forms travel but the water itself does not.

Fig. 10-1, p. 266 Wave direction Wave Stepped Art

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© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Wavelength Is the Most Useful Measure of Wave Size  Waves transmit energy across the ocean’s surface.  Wave energy in the ocean is a function of the wave period.  Most wave energy is typically concentrated in wind waves.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Progressive waves.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Wave Speed (m/sec)  equal to wavelength divided by period.  Example: What is the speed of a wave whose wavelength is 40 m and the period is 20 sec? speed = 40 m/20 sec = 2 m/sec

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Wind Blowing over the Ocean Generates Waves  Wind waves are gravity waves formed by the transfer of wind energy into water waves.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Larger Swells Move Faster  Swell: The smooth curve of water caused by a wave

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Wave Development Wind strength – Faster wind= stronger waves Wind duration – Winds blowing longer=bigger waves Fetch - the uninterrupted distance over which the wind blows without changing direction. More fetch= stronger waves

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. When does a wave break? (1) The swell “feels” bottom when the water is shallower than half the wavelength. (2) The wave crests become peaked because the wave’s energy is packed into less water depth. (3) Circular wave motion is halted by hitting the ocean floor and slows the wave, while waves behind it maintain their original rate.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. (4) The wave approaches the critical 1:7 ratio of a wave height to wavelength. (5) The wave breaks when the ratio of wave height to water depth is about 3:4.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.  http://ca.pbslearningmedia.org/content/kqe d07.sci.ess.bigwave/

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

Tsunami  Tsunami are long-wavelength, shallow-water, progressive waves caused by the rapid displacement of ocean water.  Tsunami generated by the vertical movement of earth along faults are seismic waves.

© 2006 Brooks/Cole, a division of Thomson Learning, Inc.

What else can generate tsunami? Landslides Icebergs falling from glaciers Volcanic eruptions Asteroid impacts Other direct displacements of the water surface

© 2006 Brooks/Cole, a division of Thomson Learning, Inc. Tsunami Have a Long and Destructive History Eleven destructive tsunami have claimed more than 180,000 lives since 1990.

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