The document summarizes key concepts about motion in the ocean including waves, tides, and currents. It describes how waves are caused by wind and other disturbances, and the characteristics of different types of waves like chop, swell, and tsunamis. It explains how tides are caused by the gravitational pull of the sun and moon, and details the differences between spring, neap, perigeal, and apogee tides. It also discusses the causes and effects of various surface and deep ocean currents like the Gulf Stream and how the Coriolis effect influences their direction of flow.

1. MOTION IN THE
OCEAN
Waves, Tides, and Currents
Chapter 16.2

2. Waves
 A disturbance which
moves through or
over the surface of a
fluid
 Mostly caused by
winds
(Also earthquakes,
volcanoes, grav.
pull)
 Form of great energy

3. Wave Characteristics
 Parts of a Wave
 Crest = high point
 Trough = low point
 Height = vertical
distance from crest to
trough

Wavelength =
Horizontal distance
between crest to crest
or trough to trough

4. Wave period : time for 2 crests to pass fixed point (T) sec
Wave speed (C) : C = wavelength / T (m/s)
Wave steepness : H / wavelength
When H / wavelength = 1/7 or angle at crest 120 or less =
Breaker

5. Size of Wind Generated
Waves
 Depends on 3 things:

Wind Speed

Wind Duration (length of
time wind blows)

“Fetch” Extent of open
water across which the
wind can blow

6. Water Motion in Waves
 Water travels in vertical
circular orbits
 Wave moves, particles don’t!

7. Importance of Waves
 Shaping
Coastlines
 Erode cliffs
 Grind rock into sand
 Ecology
 Returns O2 to water
 Stir up food for filter
feeders

8. Types of Waves
CHOP – Short period (back bays)
SWELL – Long period (boat rolls; seasickness)
SWASH – water up beach BACKWASH – back down

9. TSUNAMI “TIDAL WAVE”
Caused by undersea quake or volcano
• Wavelength = ~150 mi. Wave height = 6” – 1’
Can NOT perceive in boat Speed > 500 mph
Slows down to ~25 mph at shore; water builds up to ~65+ ft

10. Tsunami Waves

11. Creation of a Tsunami

12. Tides
 The rhythmic rise and
fall of the ocean’s water
High tide = rising, incoming
tide, flow
Low tide = receding, outgoing
tide, ebb
Slack tide = vertical movement
stops

13.  Tides are very long,
slow waves
 They have a wave
period of 12 hours 25
min
 Tidal day is 24 hours
50 min

NJ has 2 high and 2
low tides daily

14. What Causes Tides?
1. Gravitational pull of
sun & moon on Earth
• Moon closer, therefore
> effect
• Like magnet, pulls water
away from surface
= TIDAL BULGE

15. 2. Centrifugal Forces
• Bulge on opposite side
• Produced by motions of
because centr. force >
Earth, sun, & moon
pull of moon

16. Types of Tides
•Spring Tide
- Moon and sun are in direct
line with one another
- Results in unusually
high tidal range
-Tidal Range = vertical
distance between high &
low tides
 2x’s/month

17.  Neap Tide
 sun and moon are at
right angles

Pulls cancel each
other out – causes a
weak pull
 unusually low tidal
range
 2 x’s / month

18. Spring vs. Neap Tides

19. Distance bet. Moon & Earth
Perigee Tides
• Moon closest to earth, very high tides (causes
flooding)
Apogee Tides
• Moon farthest away from earth, very low tides

21. Types of Tides Continued
 Diurnal Tides

1 high & 1 low / day

Parts of Gulf of Mexico and Asia
 Semi-Diurnal Tides

2 high & 2 low / day

Atlantic coasts of North America and Europe
 Mixed
 2 high & 2 low / day (height varies)
 Pacific coast

22. Importance of Tides
• Expose & submerge orgs
• Circulate water in bays &
estuaries
• Circulates food, wastes, etc
• Trigger spawning (grunion,
horseshoe crab)

23. Currents
• What are currents?
- “Rivers” of circulating water
• Causes
- Wind
- Rotating Earth
- Density Changes

25. Surface Ocean Currents
• Broad, slow drifts; never
cross equator
• Wind generated; circular
gyres

26. • Coriolis Effect
- N. Hemis – clockwise; Right
- S. Hemis – counterclockwise; Left

27. • Gulf Stream
- N. Atlantic
- Brings warm water
from equator north along
east coast of N. A.
-Sometimes form eddies –
circulating water that pinches
off from the current

28. MIGRATION NAVIGATION
WEATHER

29. Localized Surface Currents
Longshore Current.

Flows parallel to shore; move sediment

30. RIP CURRENT
- Caused by converging longshore currents
- Very dangerous ; Red Flag
- DO NOT fight rip current; swim parallel to shore to
get out of channel

32. Deep Ocean Currents
Flow beneath surface; cross
equator
Move North to South
 Separated from surface
currents by boundary
called a “Thermohaline”
(diff in densities)

33. Importance Of Deep

Upwelling Currents
• Brings deep water to surf.
• Circulates nutrients up
• Moves plankton & larvae