1. Tides

2. Tidal Wave Form
Differ from other waves because caused by the interactions between the ocean, Sun and Moon
Crest of the wave form is high tide and trough is low tide

3. Tidal Wave Form Tidal Range = Vertical difference
Tidal period = time between consecutive high or low tides

4. Tidal Range
Over a month the daily tidal ranges vary systematically with the cycle of the Moon.
Also altered by shape of basin & sea floor

5. Measuring Tidal Range
Tide gauges automatically record tidal fluctuations
Satellites pick up data, post on internet

6. Gravitational Force
Gravity varies directly with mass, but inversely with distance

7. Gravitational Force
Moon exerts twice the gravitational attraction and tide-generating force as the Sun - WHY???

8. Centrifugal Force
The push outward from the center of rotation

9. Gravitational Attraction
Pulls ocean towards Moon & Sun, creating two gravitational tidal bulges

10. Centrifugal Force
Centrifugal force makes water slosh away from the Earth on the exact opposite side that the moon's gravity is pulling on

11. Spring Tides
Earth, Moon & Sun aligned in a straight line (New moon & full moon)
Tidal bulges display constructive interference, producing very high, high tides and very low, low tides.

12. Neap Tides
Earth, Moon and Sun aligned at right angles (1st & 3rd quarter moon)
Display destructive interference, producing low high tides and high low tides.

13. Tide Cycles

14. Seasonal Tides
Latitude of the tidal bulges is determined by tilt in Earth’s axis

15. Seasonal Tides
Moon cycle does not exactly match Earth’s rotational cycle
Causes tides to occur 50 min later each day

16. Monthly Tide Patterns

17. Movement of tides Deflected by Coriolis
Blocked by continental landmasses
Forms a rotary wave

18. Movement of tides Semidiurnal - 2 cycles of even heights
Mixed - 2 cycles of uneven heights

19. Movement of tides
Diurnal - one cycle per day

20. Basins
Tidal ranges increase if a bay tapers landward because water is funneled towards the basin’s narrow end

21. Tidal Bore
A wall of water that surges upriver with the advancing high tide

22. Bay of Fundy
World’s largest tidal range
Up to 10m per day

23. Tidal Currents
Movement of water high and low tides towards and away from land, generates tidal currents
Flow Tide = flow of water towards the land
Ebb Tide = flow of water away from the land
Slack Tide - Interval between tides

25. Tide-Dependent Animals

26. Grunion
Dependent on tides
Spawn 2-3 days after highest tide

27. Grunion Up to 12 inches: bait fish but tasty
Must be caught BY HAND (slippery)
Needs fishing license 16yrs or older
Courtesy of Chris Oakamoto

28. Daytime Spawn in Mexico
Courtesy of Chris Oakamoto

29. Grunion Males surround females as they lay eggs 8-10” deep
Courtesy of Chris Oakamoto

30. Grunion “Milt” (sperm) seeps down to fertilize eggs.
Hatch in days, at next high tide
Courtesy of Chris Oakamoto

31. Sea Turtles
Dependent on tides
Females come ashore, dig nests

32. Sea Turtles Young hatch at night in warm sand
Follow moonlight to water

33. Harnessing Tides Electricity generated from tidal currents
Only when tidal range is >5 m in a large bay connected to the ocean by a narrow opening.

34. Harnessing Tides Dam constructed across opening
Tide is allowed to flow into and out of bay when sufficient hydraulic head exist to drive turbines and generate power

35. Pro’s
If turbines work in both directions, energy generated 4 times a day
All advantages of normal hydroelectric power

36. Con’s Few suitable locations
Needs shallow, narrow inlet to form a tidal bore: Bay of Fundy
High cost of construction
Environmental impacts
Estuary degradation
Fish chewed up in turbines

37. Designed by Anne F. Maben These images are for viewing only and may not be published in any form