Waves, tides, and currents...

1. OCEAN
MOVEMENTS
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2. Waves
A wave is a rhythmic movement that
carries energy through space or
matter, such as ocean water.
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3. Waves
In deep water, a wave is a forward
motion of energy, not water. In fact,
the water does not move forward with
a wave. If we followed a single drop
of water during a passing wave, we
would see it move in a circular pattern
returning to a point near its original
position at the wave’s end.
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4. Wave Characteristics
• A crest is the highest point of a
wave.
• A trough is the lowest point of a
wave.
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5. •The vertical distance between crest
& trough is the wave height.
•The horizontal crest-to-crest
distance is the wavelength.
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Wave Characteristics

6. Wave Characteristics
• The wavelength determines the
wave base, which is the depth to
which the wave disturbs the
water.
• Wave speed increases with
wavelength.
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7. Wave Height
Wave height is determined by:
the strength of the wind, the expanse of water that the wind blows across (or the fetch), & the length of time of the dust (or duration.)
Large storm waves have higher than average heights.
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8. Breaking Waves
 Ocean waves begin to lose energy
& slow down near the shore
because of friction with the ocean
bottom.
 As the wave approaches more
shallow water, or water that is
half the wavelength or less deep,
the incoming wave crests gradually
catch up with the slower wave
crests ahead.
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9. collapse
forward when
the wave
becomes higher,
steeper, &
unstable as it
nears shore.
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Breakers occur
where the crests

10. Breaking Waves

11. Breaking Waves
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12. Tides
• Tides are the periodic rise &
fall of sea level.
• High tides are the highest
level to which water rises in
an area.
• Low tides are the lowest level
to which water recedes in an
area. 12

13. Tides
Generally, the daily cycle of tides is
determined by the Earth’s rotation &
the Moon’s orbit around Earth. As
the Earth rotates once on its axis (in
24 hours), the Moon is revolving
1/30th
of the way around in its orbit.
It takes a given location on Earth
about 50 minutes to “catch up with”
the orbiting Moon, so a particular
tide returns in approximately 24
hours & 50 minutes. 13

14. Differences in topography & latitude
cause three different daily tide
cycles.
The 3 tide cycles are:
1) Areas with semidiurnal cycles
experience two high tides per day.
2) Areas with mixed cycles have
one pronounced & one smaller high
tide each day.
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Different Daily Tide Cycles

15. 3) Areas with diurnal cycles have
one high tide per day.
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Different Daily Tide Cycles

16. 16
Different Daily Tide Cycles

17. Causes of Tides
• The basic causes of tides are the
gravitational attraction among the
Earth, Moon & Sun, as well as
the fact that gravitational
attraction decreases with
distance.
• The Moon has a greater affect
because it is closer to Earth. The
Sun, even though it is much larger
than the Moon, has a lesser affect
because it is farther from Earth. 17

18. 18
Monthly Tide Cycles: Spring & Neap Tides

19. 19
Monthly Tide Cycles: Spring & Neap Tides

20. Spring tides occur twice a month
during the full & new Moon. When
the Sun, Earth, & Moon are
aligned causing high tides to be
higher than normal & low tides to
be lower than normal.
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Monthly Tide Cycles: Spring Tides
Spring think “straight line.”

21. Neap tides occur when the Sun,
Earth, & Moon form a right angle, as
seen during 1st
& 3rd
quarter Moon
phases. The gravitational pull of the
Sun & Moon “fight” each other, & we
notice smaller difference between
high & low tides. High tides are lower
& low tides are higher than normal.
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Monthly Tide Cycles: Neap Tides
Neap think “ninety degrees.”

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Monthly Tide Cycles: Spring & Neap Tides

23. Ocean Currents
Currents are the movement of
water caused by differences in
temperature & salinity (density),
or caused by wind.
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24. What causes the currents to flow in
different directions?
The CORIOLIS EFFECT
• The CORIOLIS EFFECT occurs
because Earth rotates East to West,
water and particles are deflected.
• In Northern hemisphere currents flow
clockwise & in the Southern
hemisphere currents flow
counterclockwise.
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CORIOLIS EFFECT is responsible
for the patterns of currents &
WEATHER!

25. Surface Currents: Caused by the
movement of wind across the
oceans surface.
Deep or Denisty Currents: Caused
by the differences of temperature
or salinity of the water. 25

26. Surface Currents you need to know:
Gulf Stream, Canary, California,
North Equatorial, South Equatorial,
Kuroshio, East Australia, Peru,
Benguela, Antarctic Circumpolar,
Aguihas, North Atlantic, Greenland,
Labrador, & Brazil currents.
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27. Deep Ocean or Denisty Currents:
Currents caused by the differences
in temperature & salinity. Not
affected by wind because they are
too deep.
These
currents are
known as
the Global
Conveyor
Belt.
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28. Other Important Ocean Movements
Upwelling is where low-oxygen deep
water is moved up to the surface
due to differences in density. This
water is rich in nutrients which
supports marine life.
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