Part one of the Tides notes

1. Tides

2. Description of tides
tides - periodic rise and fall of ocean waters

3. Tides are caused by:
Main Factor #1: Gravitational pull of the moon and sun
Main Factor #2: Centripetal force of the rotating Earth

4. Main Factor #1: Gravitational Pull
the gravitational pull of the moon and sun
The force of gravity depends on...
earth
moon
sun

5. Main Factor #1: Gravitational Pull
Gravitational Force

6. Main Factor #2: Centripetal and Centrifugal Forces

7. Main Factor #2: Centripetal and Centrifugal Forces
The earth-moon system revolves around the
barycenter.
earth
moon

8. Main Factor #2: Centripetal and Centrifugal Forces
GRAVITATIONAL FORCE
CENTRIPET
AL
GRAVITATIONAL &
CENTRIPETAL

9. GRAVITATIONAL &
CENTRIPETAL

10. Tidal Patterns
Semidiurnal tides- two high and two low per day; Cape Cod, MA
(high latitudes)
Diurnal tides- one high and one low per day; Mobile, AL (low
latitudes)
Mixed pattern tides- Two high and two low tides per day BUT with
successive high tide levels that are VERY DIFFERENT from each
other; Hawaii (mid latitudes)

12. Tidal Patterns
Type of tide depends on:
Position on the globe
Water depth
Contour- shape of ocean basins
geography of coastlines

14. How do Tides Vary?
A tidal range is the difference between levels of ocean water at high tide and
low tide.
The combined forces of the sun and the moon on Earth produce different
tidal ranges.

15. The Bay of Fundy: Site of the world’s largest tidal range
Tidal energy is focused by shape and shallowness of bay
Maximum spring tidal range in Minas Basin = 17 meters (56 feet)

16. Bay of Fundy
High tide
Low tide
( hours later)
6

17. Nova Scotia Tides
Wolfville, NS (16 m tidal range)
Diurnal Tides (one high and one low every 12 hours and 25 minutes

18. Timing the Tides
The moon revolves around Earth much more slowly than Earth rotates.
High and low tides at that place happen 50 min. later each day.

19. By the time the Earth has completed one revolution (one day), the moon has moved slightly, so the Earth needs
to rotate a bit more to catch up with the moon…

20. Tidal Cycles
Diurnal Tide:
Semi Diurnal Tide:
Mixed Tide:
24 hr 50 min cycle
12 hr 25 min cycle
12 hr 25 min cycle

21. Explain to your neighbor
A: Why are there two tides on both sides of the Earth?
B: Explain why tides do not occur at the same time each
day.