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Waves

Waves. Marine Science. Introduction. Waves transmit energy Water molecules move in a circular pattern Ex: gull resting on the water, or the wave at a baseball game. Wave Terms. Crest & Trough High & low points Height Vertical distance between crest & trough Wavelength

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Waves

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  1. Waves Marine Science

  2. Introduction • Waves transmit energy • Water molecules move in a circular pattern • Ex: gull resting on the water, or the wave at a baseball game

  3. Wave Terms • Crest & Trough • High & low points • Height • Vertical distance between crest & trough • Wavelength • Horiz. distance between two crests • Period • Time for one full wavelength • Frequency • # of waves per second

  4. What Causes Waves? • Wind • The larger the area exposed to wind, the larger the wave • Landslides • Volcanic eruptions • Faulting / Eqs (Tsunamis) • The Moon/Sun (Tides)

  5. Interference & Rogue Waves • Interference: when two waves meet, they add to or subtract from one another • This explains wavesets • Interferences in the open ocean can result in abnormally large rogue waves

  6. Swells • Swell: formation of long wavelength surface waves • Formed by distant storms • Waves of same speed group together • Stable in their direction & frequency, free of chop

  7. Waves Approaching Shore • As waves approach shore… • Wave begins to “feel” the bottom • Circular motion of molecules becomes elliptical • Bottom of the wave slows through friction • Wave becomes too high for its length & breaks

  8. Refraction, Diffraction • Waves bend around barriers resulting in sand build-up or erosion

  9. Storm Surge • Abrupt bulge of water driven ashore by a large storm • Low atm pressure causes ocean surface to dome • Looks like a sudden, very high tide

  10. Tsunamis • Causes • EQs, landslides, volcanic eruptions • Gravity + H2O displacement make waves • Characteristics • Fast, not steep, long wavelength, approach like a wall of water

  11. Tides • Daily variations in the ocean’s level • Results of gravitational pull of the moon & sun • Create a bulge in the ocean (high tide)

  12. Tidal Patterns • Tidal patterns vary with location • Diurnal tide • Single high tide & single low tide daily • Semidiurnal tides • 2 ~ equal high & low tides daily • Mixed tides • 2 unequal high & low tides daily

  13. Tidal Patterns

  14. Spring and Neap Tides • Moon has more gravitational effect on earth than the sun • When Moon + Sun + earth are aligned, Spring tides are created • Higher than average tides • When moon is 90º to earth & sun, Neap tides are created • Lower than average tides

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