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http://www.youtube.com/watch?v=rDYxRpucOQ4

http://www.youtube.com/watch?v=rDYxRpucOQ4. Waves. Transmit energy (not mass) across the ocean’s surface Wave – disturbances caused by the movement of energy through some medium (solid, liquid, gas). Waves. Most generated in the open ocean Wave height depends on Wind velocity Wind duration

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http://www.youtube.com/watch?v=rDYxRpucOQ4

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  1. http://www.youtube.com/watch?v=rDYxRpucOQ4

  2. Waves • Transmit energy (not mass) across the ocean’s surface • Wave – disturbances caused by the movement of energy through some medium (solid, liquid, gas)

  3. Waves • Most generated in the open ocean • Wave height depends on • Wind velocity • Wind duration • FETCH – distance over which the wind blows – usually generated by a big storm

  4. Waves • Described by • Crest – highest part • Trough – lowest part • Wavelength (L) – distance between crests/troughs • Wave Height (H) – vertical distance between crest and trough

  5. Waves • Wave Period (T) – time for successive waves to pass a fixed point • Frequency – number of wave crests/troughs passing a fixed point every second

  6. Types of Waves • Deep Water Waves • Move through water > ½ wavelength of the wave • Do not feel the bottom • Wave motion is circular

  7. Types of Waves • Shallow Water Waves • Move through water < ½ wavelength of the wave • Feel the bottom • Cannot move in a circular path, only back and forth • Most waves are shallow water waves

  8. Deep Water Waves • Move in an orbital / circular motion • Waves do not carry water very far, but transfer energy • Diameter of circle decreases with depth • Wave motion non-existent below ½ wavelength

  9. Deep Water Waves • When waves approach shore • Interact with seabed when depth equals ½ the distance between wave crests • Orbits become restricted and elliptical • Waves slow down and bunch up • Waves become shallow water waves • Eventually they form breakers

  10. Breakers • At water depths < ½ wavelength, waves feel the bottom • Wave height increases • Wave length decreases • Velocity decreases because waves are dragging on the bottom • Wave period stays the same • When wave reaches 1.3 H => Breakers

  11. Wave Refraction • Wave crests can refract, or bend, if they approach the shore at an angle • Caused by the change in velocity of waves as a function of water depth • Only a small part of each wave feels bottom at a time so only a small part of wave slows

  12. Waves Classified By- • Disturbing force – energy that causes the wave to form • Restoring force – force that returns the water surface to flatness after the wave formed • Wavelength – longest waves move the fastest

  13. Types of Waves • Capillary waves – first to form when wind blows • Important in transferring energy from air to water to drive ocean currents • Wind waves – form when wind blows over ocean surface • Both are deep water waves

  14. Types of Waves • Seiche – pendulum-like rocking of water in a basin • No crest or trough

  15. Types of Waves • Tsunami – caused by the rapid displacement of ocean water • When caused by the sudden vertical movement of Earth along faults called seismic sea wave • Also caused by landslides, icebergs calving, volcanic eruptions, asteroid impacts

  16. Types of Waves • Tsunami • Resemble fast, onrushing tide • Not dangerous in open water • Can travel at 212 meters per second (470 mph) • http://www.youtube.com/watch?v=5-zfCBCq-8I • http://www.youtube.com/watch?v=M2NvNoqal6I

  17. Although rare, there have been six major tsunamis since the U.S. set up an early warning system in the Pacific after the 1946 tsunami in the Aleutian Islands. USGS The most devastating one in history occurred on the same subduction zone as Krakatua on Dec. 26, 2004. It was caused by the fourth largest earthquake of the last century. Nearly 300,000 people were killed and more than 1 million were displaced by the tsunami that devastated 10 countries around the Indian Ocean.

  18. Types of Waves • Tides • Caused by the gravitational attraction of Earth, moon and sun • Tides move at a rate of 1600 km (1000 mi) per hour • http://www.youtube.com/watch?v=DyXWWfPGjQg • http://www.youtube.com/watch?v=5W2sM1Ma7YA&NR=1

  19. Shallow Water Waves • Seiches, tsunami and tides are all shallow water waves • They have extremely long wavelengths • They are always in water less than ½ their wavelength • These waves move extremely fast

  20. Rogue Waves • Rogue waves are caused when wave trains traveling at different speeds and directions meet. • They appear suddenly and may capsize boats. • http://www.youtube.com/watch?v=axW2XUhrjbo&feature=related • http://www.youtube.com/watch?v=B8P-sbOMkI0

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