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Currents_ Waves_ and Tides

VIEWS: 8 PAGES: 14

  • pg 1
									Currents, Waves, and Tides
         Donnelly
         Science 6
              Surface Currents
• Surface currents are currents in the ocean (like a
    river) caused by Earth’s winds, continents, and
    the Coriolis Effect (rotation of Earth).
•   The currents do not affect the ocean floor, they
    stay on the surface.
•   Surface currents that begin in warm areas carry
    warm water, whereas those that begin near the
    North and South poles carry cold water.
     Surface Currents are caused by
                  Wind
• Prevailing winds on Earth create currents-winds
    are caused by the uneven heating of the Earth’s
    surface.
•   Trade winds: move from east to west toward
    the equator. As the trade winds move over the
    oceans, they push surface currents from east to
    west.
•   Westerlies: blow from west to east pushing
    surface currents along with them.
  Surface Currents are caused by
            Continents
• Land masses throughout the ocean cause
 currents to turn or deflect.
Surface Currents are caused by the
          Coriolis Effect
• The curving motion caused by Earth’s
  rotation is called the Coriolis Effect.
• The Coriolis Effect causes a clockwise
  turning of the Northern Hemisphere and it
  causes a counter clockwise turning in the
  Southern Hemisphere.
     Effect of Currents on Earth
               (Climate)
• Cold currents cool the air above them and
  bring cold air to nearby regions (Ex.
  California current, Canary current)
• Warm currents bring warm, moist air to a
  nearby region. For example, the Gulf
  Stream warms the East coast of the U.S.
  and also warms Great Britain.
     Effect of Currents on Earth
          Ocean Navigation
• Currents, like the Jet Stream, increase the
 speed a ship can go if traveling in the
 same direction as the current. Traveling
 against the current would slow a ship
 down.
    Effect of Currents on Earth
 Fish Movement and Pollution and
              Garbage
• Currents help fish move from place to
  place.
• Garbage and pollutants will be moved
  throughout the World Ocean.
How Surface Currents are Different
     from Density Currents
• For the most part, deep ocean currents are
    driven by differences in water density.
•   It is the sinking of dense water that starts deep
    water currents moving.
•   The density of ocean water depends on three
    things: salinity, temperature, and sediment
    content.
•   Cold water is more dense than warm water,
    therefore, the cold water would tend to sink
    below the warm water.
                     Waves
• The transfer of energy through matter and
    space (water)
•   The longer and harder the wind blows, the
    larger the wave will be.
•   Parts of a wave: crest, trough, wave height,
    wavelength, period
•   Fetch: the distance the wind blows over open
    water
•   Breaker: as a wave approaches shore, the wave
    falls over
               Parts of a Wave
• Crest: top of a wave
• Trough: Lowest part of a wave
• Wave height: the distance from the crest to the
    level ocean surface
•   Wavelength: the distance between two
    successive waves
•   Period: the time it takes for two successive wave
    crests to pass the same point.
                        Tides
• The alternating rise and fall of the ocean waters.
• Caused by the gravitational pull of the moon and
    sun on the Earth and the Earth’s waters.
•   Spring tide: (spring up!) Unusually high high tide
    or very low low tide. Sun and moon are lined up
    and pull together causing the tides to be
    extreme. (Occurs during a full and new moon)
•   Neap tides: less extreme tides because the sun
                               ̊̊̊̊̊̊̊̊
    and moon form a 90 ̊̊̊̊̊̊̊̊ angle with the Earth. The
    gravity of the sun and moon are lessened
    because they are going against each other.
    (Occurs during the Moon’s first and third quarter
    phases)
                  Tides

• The Moon’s gravity pulls most strongly on
  the water facing the Moon, since this
  water is closest to the Moon. As a result,
  a bulge in the ocean called high tide
  occurs.
• Because Earth rotates on its axis every 24
  hours, most shores have two high tides a
  day and two low tides a day.
             Ocean Terms

• Upwelling: the rising of deep water to the
  surface
• Turbidity current: when sediment mixes
  with ocean water and sinks

								
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