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MOTION IN THE OCEAN

MOTION IN THE OCEAN. Waves and Tides. Waves. A disturbance which moves through or over the surface of a fluid Mostly caused by winds (Also earthquakes, volcanoes, grav. pull) Form of great energy. Wave Characteristics. Parts of a Wave Crest = high point Trough = low point

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MOTION IN THE OCEAN

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  1. MOTIONIN THE OCEAN Waves and Tides

  2. Waves • A disturbance which moves through or over the surface of a fluid • Mostly caused by winds (Also earthquakes, volcanoes, grav. pull) • Form of great energy

  3. Wave Characteristics • Parts of a Wave • Crest = high point • Trough = low point • Height = vertical distance from crest to trough • Wavelength = Horizontal distance between crest to crest or trough to trough

  4. Size of Wind Generated Waves • Depends on 3 things: • Wind Speed • Wind Duration (length of time wind blows) • “Fetch” Extent of open water across which the wind can blow

  5. Water Motion in Waves • Water travels in vertical circular orbits • Wave moves, particles don’t!

  6. Importance of Waves • Shaping Coastlines • Erode cliffs • Grind rock into sand • Ecology • Returns O2 to water • Stir up food for filter feeders

  7. Types of Waves CHOP – Short period (back bays) SWELL – Long period (boat rolls; seasickness) SWASH – water up beach BACKWASH – back down

  8. Links/Videos Wave activity • http://www.montereyinstitute.org/noaa/lesson09/l9la1.html

  9. TSUNAMI = “harbor wave” in Japanese Caused by undersea quake or volcano • Wavelength = ~150 mi. • Wave height = 6” – 1’ • Can NOT perceive in boat • Speed > 500 mph Slows down to ~25 mph at shore; water builds up to ~65+ ft

  10. Tsunami Waves

  11. Indian Ocean Tsunami 2004 • http://www.montereyinstitute.org/noaa/lesson09/l9ex1.htm Indian Ocean 2004 • http://www.montereyinstitute.org/noaa/lesson09.html Global Impact • December 26, 2004 • 9+ magnitude earthquake • Indian plate slid under Burma Plate, off coast of Sumatra • 250.000 dead • 15,000 missing • 2 million displaced

  12. Tsunamis

  13. Tides The rhythmic rise and fall of the ocean’s water • High tide = rising, incoming tide, flow • Low tide = receding, outgoing tide, ebb • Slack tide = vertical movement stops

  14. Tides are very long, slow waves • They have a wave period of 12 hours 25 min • Tidal day is 24 hours 50 min

  15. 1. Gravitational pull of sun & moon on Earth What Causes Tides? • Although Sun is HUGE, Moon closer, therefore > effect • Like magnet, pulls water away from surface = TIDAL BULGE

  16. 2. Centrifugal Forces • Bulge on opposite side because centr. force > pull of moon • Produced by motions of Earth, sun, & moon

  17. Types of Tides 2x’s/month • Spring Tide • Moon and sun are in direct line with one another • Results in unusually high tidal range • Tidal Range = vertical distance between high • & low tides

  18. Neap Tide sun and moon are at right angles Pulls cancel each other out – causes a weak pull unusually low tidal range 2 x’s / month

  19. Spring vs. Neap Tides

  20. Distance bet. Moon & Earth Perigee Tides Moon closest to earth, very high tides (causes flooding) Apogee Tides Moon farthest away from earth, very low tides

  21. Types of Tides Continued • Diurnal Tides • 1 high & 1 low / day • Parts of Gulf of Mexico and Asia • Semi-Diurnal Tides • 2 high & 2 low / day • Atlantic coasts of North America and Europe • Mixed • 2 high & 2 low / day (height varies) • Pacific coast Why different types of tides?

  22. Types of Tides

  23. Importance of Tides • Expose & submerge orgs • Circulate water in bays & estuaries • Circulates food, wastes, etc • Trigger spawning (grunion, horseshoe crab)

  24. Currents • What are currents? - “Rivers” of circulating water • Causes - Wind - Rotating Earth - Density Changes

  25. Surface Ocean Currents • Broad, slow drifts; never cross equator • Wind generated; circular gyres

  26. Coriolis Effect - N. Hemis – clockwise; Right - S. Hemis – counterclockwise; Left

  27. Gulf Stream - N. Atlantic - Brings warm water from equator north along east coast of N. A. • Sometimes form eddies – circulating water that pinches off from the current

  28. IMPORTANCE OF SURF. CURRENTS NAVIGATION MIGRATION WEATHER

  29. Localized Surface Currents Longshore Current. Flows parallel to shore; move sediment

  30. RIP CURRENT - Caused by converging longshore currents - Very dangerous ; Red Flag - DO NOT fight rip current; swim parallel to shore to get out of channel

  31. Deep Ocean Currents Separated from surface currents by boundary called a “Thermohaline” (diff in densities) • Flow beneath surface; cross equator • Move North to South

  32. Importance Of Deep Currents • Upwelling • Brings deep water to surf. • Circulates nutrients up • Moves plankton & larvae

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