1. Tides
Fig. 10-6
Fig. 10-7

2. What are tides????
Tide- the periodic, rhythmic rise and fall of the sea surface
- they are essentially huge standing waves (two waves moving in opposite directions)

3. Example: Poughkeepsie, New York

4. Tide-producing forces
1. Gravity and
motions among
Earth, Moon,
and Sun (causes the bulge toward the moon)

5. 2. Centripetal force “tethers” Moon to Earth
- Inertia- objects at rest will stay at rest or object in motion will say in motion unless acted upon by an external force
- (causes the bulge away from the moon)

6. Resultant tidal forces
Gravitational force and centripetal force
Resultant force moves ocean water horizontally
Fig. 10-6
Fig. 10-7

7. Tidal bulges Two equal and opposite tidal bulges
Earth rotates beneath tidal bulges
Two high tides and two low tides per day
Fig. 10-8

8. In the video clip ; Dr. Hoffman, from Old Dominion University, explains the tides.

9. Lunar day-24 hours and 50 minutes
Earth has to “catch up” with Moon to reach same position
Moon revolves around Earth every days ( days between full moons)
Fig. 10-9

10. Time between successive high tides shifts day after day
Moon rises later each successive night

11. Solar tidal bulges Tide-producing force of Sun is smaller
Sun much farther away

12. Month tidal cycle Spring tides New Moon, Full Moon
Higher than usual high tides
Fig

14. Neap tide First Quarter, Last Quarter Lower than usual high tide
Fig

15. Declination of Sun and Moon
Orientation of Sun and Moon is never directly over the equator
Sun 23.5o N and S, yearly cycle
Moon 28.5o N and S, monthly cycle
Unequal tides
Successive tides different tidal range

16. Unequal tidal range
Fig

17. Elliptical orbits Perigee Earth and Moon are closer
Lunar tidal force greater= Higher high tides
Apogee
Earth and Moon are futher away
Lunar tidal force lesser= Lower high tides
Fig

18. Tidal patterns Diurnal Semidiurnal
One high, one low tide per lunar day
Period of tidal cycle 24 hours 50 minutes
Semidiurnal
Two high, two low tides per lunar day
Period 12 hours 25 minutes
Equal range

19. Mixed Most tides are mixed Two high, two low tides per lunar day
Unequal range
Most tides are mixed

20. Standing waves Forced standing wave caused by tides
Free-standing waves caused by strong winds or seismic disturbances
Fig

21. Bay of Fundy Largest tidal range (spring tide max 17 m) Shape of basin
Oscillation period close to tidal period
Shoals and narrows to north
Basin oriented toward right (Coriolis moves water toward right)
Fig

22. The video clip shows tides in the Cape Cod Estuary, Massachusetts

23. The video clip shows tides on Cape Cod Beach, Massachusetts.

24. Tidal Calendars