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Tides

Tides. Tide You Tube videos. http://www.youtube.com/watch?v=qvzc9yF3g6c http://www.youtube.com/watch?v=5W2sM1Ma7YA&feature=related http://www.youtube.com/watch?v=YiHP8EG_Wq4&feature=related http://www.youtube.com/watch?v=4DlqVuNMydk&feature=fvw. Tidal Waves.

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Tides

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  1. Tides

  2. Tide You Tube videos http://www.youtube.com/watch?v=qvzc9yF3g6c http://www.youtube.com/watch?v=5W2sM1Ma7YA&feature=related http://www.youtube.com/watch?v=YiHP8EG_Wq4&feature=related http://www.youtube.com/watch?v=4DlqVuNMydk&feature=fvw

  3. Tidal Waves Qiantang River,China, Peter Wang • Large waves (bores) occur in mouth of rivers—Amazon, Ganges, Seine • Most less than 1m • Max is 8 m-Qiantang River,China • Moves 40 km/hr

  4. Tides • Shallow water wave with longest wavelength • Tides defined: • Periodic, short-term changes in ocean water level due to combination of gravitational force of moon, sun, and motion of earth • Are forced waves • Pull of two bodies proportional to masses of bodies buy inversely proportional to square of distance • Tides caused by gravitational attraction between ocean, sun, moon, buy • Tidal generating force varies inversely with cube of distance, therefore distance more important than mass

  5. Earth-Moon System • Gravity pulls earth moon toward each other • But inertia (tendency for moving object to continue in a straight line) keeps them apart • Gravity attracts ocean surface toward moon • Earth motion around center of mass produces bulge on other side

  6. on the earth, there is an imbalance between the centripetal (inward) and centrifugal (outward) accelerations. The centrifugal acceleration is the same everywhere on the earth, but the gravitational force due to the moon varies over the surface of the earth.

  7. earth-moon system tidal bulges

  8. More realistic representation of tides and earth/moon orientation • Note the path that tides will take around the earth • Note the unequal high tides at the same latitude

  9. Why do Tides Rise and Fall • Earth rotates beneath the bulges • Bulges appear to move • Bulges want to stay under moon • Wavelength of tides up to 12,500 miles

  10. Tidal Day • Earth rotates in 24 hr • A tidal day is 24hr 50min • Earth is spinning but moon is also rotating around the earth • When earth makes one rotation, the moon has moved 12 degrees • Takes an extra 50 minutes for earth to get back to original position under moon. • Therefore high tide arrive 50 minutes later each day

  11. Changing Position of Moon • Moon not always over equator • Moves from 281/2 degree N&S • Will have higher high tide, lower high tide, low tide • More realistic representation of tides and earth/moon orientation • Note the path that tides will take around the earth • Note the unequal high tides at the same latitude

  12. Solar Tides • Sun also influences tides • 27 millions times as massive as moon • But 387 times further • Therefore sun’s influence on tides is 46% that of the moon • These are slower moving tides because takes earth 1 year to move around the sun

  13. Spring & Neap Tides • When earth, moon, sun aligned get higher high tides and lower low tides • Highest tides called spring tides • Lowest called neap tides • When earth, moon, sun at right angles get lowest high tides and highest low tides

  14. Spring Tides The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth. Moon Moon Moon Earth Phase of the moon? Phase of the moon? Phase of the moon? New Moon Full Moon New Moon Higher high tides and lower low tides

  15. Neap Tides The gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth. Third Quarter Moon Phase of the moon? Earth Phase of the moon? Moon First Quarter Lowest high ties and highest low tides

  16. Combined lunar and solar tide

  17. Tidal Patterns • Vary with position of continents, shape of the basins • Continent beneath moon interferes with tides • These influence cause • Semidiurnal tides (2high & 2 low) • Diurnal (1high, 1 low) • Semidiurnal mixed (2 unequal high & low)

  18. 09_15tr P

  19. 09_15cr P

  20. 09_15br P

  21. 09_16 Min. Max. Min. Max. P

  22. Los Angeles Tides

  23. Ampidromic point is where don’t have a tide • Wave rotates around the node or ampidromic point

  24. Tide in ocean stays to right • Rotates counterclockwise around ampidromic point • Height of tide increase with distance from AP point.

  25. S Amphidromic Points

  26. The Tides of the Bay of Fundy S • Size of the Tides • Origin of the Tides

  27. 09_17 S

  28. Resources The following web site is a good resource to look for definitions of tidal terms you are unfamiliar with: http://co-ops.nos.noaa.gov/publications/glossary2.pdf (pdf) The following web site will let you review and test your knowledge of tides, as well as introduce some material about tides which we didn't cover here.http://www.es.flinders.edu.au/~mattom/IntExerc/basic5/index.html

  29. 09_17 S

  30. The point “Z” stays fixed, and the earth-moon system rotates about it

  31. STOP HERE

  32. The Tidal Day is 24 hrs 50 min

  33. At 1&2 gravitational attraction greater than outward movement of inertia • Water moves to point twoard moon • AT 3 & 4 inertia greater than gravitational attraction • Water moves to point opposite moon

  34. P

  35. S

  36. S Amphidromic Points

  37. S

  38. The Tides of the Bay of Fundy S • Size of the Tides • Origin of the Tides

  39. 09_17 S

  40. 09_17 S

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