1. Tides

5. What causes tides? Tides are created by the imbalance between two forces: 1. Gravitational force of the Moon and Sun on Earth If mass increases (  ), then gravitational force increases (  ) If distance increases (  ), then gravitational force greatly decreases (  ) 2. Centripetal (center-seeking) force required to keep bodies in nearly circular orbits

6. Gravitational forces on Earth due to the Moon Force decreases with increasing distance.

7. Centripetal forces on Earth due to the Moon

8. Resultant forces Resultant forces are: The difference between gravitational (G) and centripetal (C) forces

9. Tide-generating forces Tide-generating forces are the horizontal component of the resultant force. Maximized along a “latitude” of 45º relative to the “equator”.

10. Tidal bulges Tide-generating forces produce 2 bulges: 1. Away from Moon on side of Earth opposite Moon 2. Toward Moon on side of Earth facing Moon Earth rotates in and out of tidal bulges, creating high and low tides

12. Relative sizes and distances on Earth, Moon, and Sun The Sun is much more massive than the Moon but much further away. Solar bulges are 46% the size of lunar bulges

14. The Monthly Tidal Cycle About every 7 days, Earth alternates between: Spring tides (2)[Super Tides] Lunar and solar bulges add together Large tidal range Earth-Moon-Sun system at 180 0

15. Neap tides (2)[No Tides ?] Earth-Moon-Sun system at right angles Lunar and solar bulges destructively interfere

16. Sun and Moon Influence Tides Together

17. Earth-Moon-Sun positions and the monthly tidal cycle

18. Tidal Patterns Diurnal One high and one low tide each (lunar) day Semidiurnal Two high and two low tides of about the same height daily Mixed Characteristics of both diurnal and semidiurnal Not This!

20. Tidal patterns in the N.A

21. Tides in the ocean Shape and locations of coastlines creates irregular tides on our earth.

22. Tidal Patterns Vary with Ocean Basin Shape and Size The numbers indicate the hourly positions of tide crests as a cycle progresses. Dashed lines show the tide heights when the tide crest is passing.

23. Monthly tidal curves

24. The Bay of Fundy: Site of the world’s largest tidal range Super tides creates by shape and shallowness of Bay of Funday (17meters )

28. Tidal bore = a true tidal wave Wall of water that moves upriver Caused by an incoming high tide Occurs in some low-lying rivers

32. Grunion and the tides Spawning cycles are timed precisely with the tides

35. Hurricanes and Tides

36. Hurricanes produce extra high tides called storm surges

39. Tides have high potential for tidal power generation

40. Power Plant at La Rance, France