; Currents_ Waves_ and Tides
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Currents_ Waves_ and Tides


  • pg 1
									Currents, Waves, and Tides
         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
• Prevailing winds on Earth create currents-winds
    are caused by the uneven heating of the Earth’s
•   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
•   Westerlies: blow from west to east pushing
    surface currents along with them.
  Surface Currents are caused by
• 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
• 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
    Effect of Currents on Earth
 Fish Movement and Pollution and
• Currents help fish move from place to
• 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
•   Cold water is more dense than warm water,
    therefore, the cold water would tend to sink
    below the warm water.
• 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
•   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.
• 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

• 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
• 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
• Turbidity current: when sediment mixes
  with ocean water and sinks

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