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

2. Tide-producing forces
 Gravity and
motions among
Earth, Moon,
and Sun
Fig. 10-2

3.  Centripetal force
“tethers” Moon
to Earth
 Directed away
from barycenter
 Click for ‘Kiddie’
version of tidesFig. 10-4 a,b

4. Resultant tidal forces
 Gravitational
force, Earth and
Moon
 Centripetal force,
Earth and Moon
 Resultant force
moves ocean
water horizontallyFig. 10-7
Fig. 10-6

5. Tidal bulges
 Two equal and
opposite tidal
bulges
 Earth rotates
beneath tidal
bulges
 Two high tides
 Two low tides
 Per day
 Click on picture Fig. 10-8

6. Complications to simplest
equilibrium theory
 Oceans do not cover entire Earth
 Oceans do not have uniform depth
 Friction between ocean and seafloor
 Continents
 Moon not always in same place with
respect to Earth
 Lunar day longer than solar day

7. Lunar day
 Moon revolves around Earth
 Earth has to “catch up” with Moon to
reach same position
Fig. 10-9

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

9. Solar tidal bulges
 Tide-producing force of Sun
less than half of Moon’s
 Sun much farther away

10. Month tidal cycle
 Spring tides
 New Moon, Full
Moon
 Earth, Moon,
Sun syzygy
 Higher than
usual high tides
Fig. 10-12

11.  Neap tide
 First Quarter,
Last Quarter
 Earth, Moon, Sun
quadrature
 Lower than usual
high tide
Fig. 10-12

12. Declination of Sun and Moon
 Orientation of Sun, Moon to Earth’s
equator
 Sun 23.5o
N and S, yearly cycle
 Moon 28.5o
N and S, monthly cycle
 Unequal tides
 Successive tides different tidal range

13. Unequal tidal range
Fig. 10-15

14. Elliptical orbits
 Click picture for
Moon phases
 Perigee
 Lunar tidal force
greater
 Higher high tides
 Apogee
 Lunar tidal force
lesser
 Lower high tides
Fig. 10-16

15. Dynamic theory of tides
 Tide shallow-water wave
 Speed varies with depth
 Lags behind Earth’s rotation
 Rotary flow in open ocean basins
 Amphidromic point
 Cotidal lines

16. Rotary flow
 Crest (high tide) rotates
 Counterclockwise in Northern
Hemisphere
 Clockwise in Southern
Hemisphere

17. Tidal patterns
 Diurnal
 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

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

19. Standing waves
 Forced standing
wave caused by
tides
 Free-standing
waves caused by
strong winds or
seismic
disturbances
Fig. 10-22

20.  Node maximum
horizontal flow
 Antinode
maximum
vertical flow
Fig. 10-23

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)
 Click picture to see
Fig. 10-24

22. Tidal bores
 Wave created by
tide rushes
upstream
 Large tidal range
 Low-lying coastal
river
 Max 8 m high
 Click picture to see
a tidal bore.
Fig. 10A

23. End of Chapter 10: Tides
Fig. 10-7
Fig. 10-6