1. Tides

2. The cause of tides
The gravitational tugs between the Earth, Sun, and Moon
What force is responsible?
Gravity!!!!

3. Lunar and Solar Tides
Since the Sun and Moon are responsible, we can divide the discussion into 2 tides
Lunar and Solar

4. Let’s start with Lunar Tides
There is a gravitational pull between the Earth and the Moon.
Which pulls more, the Earth on the Moon or the Moon on the Earth?
They pull equally.
Remember, Newton’s 3rd Law! Equal but opposite!

5. So to simplify the idea…
Let’s imagine Earth surrounded completely by an even layer of water all over.

6. Moon pulls water toward Earth

7. Lunar Tide

8. The “A” Bulge seems obvious

9. But why the bulge at “C”?

10. Differential Gravitational Pull

11. Why Differential Gravitational Pull?
Fg = Gm1m2/d2
Law of Universal Gravitation!
Bigger the bodies, more the Gravitation Force
The closer they are, more Gravitation Force

12. So A is pulled more than B, which is pulled more than C

13. Okay, now for Solar Tides
SUN

14. Solar Tides work very similarly to Lunar Tides, but to a lesser degree

15. But now when we put them both into the same diagram
NEW MOON

16. But now when we put them both into the same diagram
Full Moon
At New Moon and Full Moon the lunar and solar tides work together, producing really high, high tides, and really low, low tides.

17. These really high and really low tides are called SPRING Tides
Spring tides occur and New and Full Moons
Spring tides have nothing to do with the Seasons!
Spring Tides = GREAT TIDAL RANGE!!!

18. But now at right angles to each other (Quarter Phases)

19. At Quarter Phases, Lunar and solar tides work against each other producing low high tides, and high low tides.

20. These tides of “low tidal range” are called NEAP tides and occur at the Quarter Phases
Neap tides = low tidal range

21. So how often do you high tides occur for a given area?
A tidal day is NOT 24 hours
Remember the moon is orbiting and therefore rises about every 50 min later each day.
Tidal Day
~ 24 hrs 50 min
high to high tide
~ 12 hrs 25 min
high tide to low tide
~ 6 h 12.5 min
low to low
low to high tide

22. Most dramatic Tide Example
Most dramatic Tide Example is at the Bay of Fundy, in Canada

26. Example of Great Tidal range