Tides

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Section 13 - 2

• Tides
• EQ What causes tides?

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Tides

• What causes tides?
• How can tides be used to generate electricity?
• Describe the positions of the sun and the moon,
  in relation to Earth when spring tides occur.

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Tides

• A tide is the rise and fall of the oceans
  surface caused mostly by the gravitational pull
  of the moon.

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Tides

• At high tide, the ocean water has risen as high
  as it will go on a shore.

• At low tide, the ocean water has fallen as low as
  it can go on a shore.

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Tides

• A tide is the rise and fall of the oceans
  surface caused mostly by the gravitational pull
  of the moon.

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Tides
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Tides

• Earths rotation on its axis affects which tides
  will occur at a certain place on Earth.
• High tides occur about every 12 hrs.
• Low tides occur about every 12 hours.
• The time between low tide and high tide is about
  6 hrs.

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What causes tides?

• Tides are caused by the interaction of Earth, the
  moon, and the sun.
• The moon pulls on the water on the side closest
  to it more strongly than it pulls on the center
  of the Earth.

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What causes tides?

• The moons pull creates a bulge of water, called
  a tidal bulge, on the side of Earth facing the
  moon.
• The water opposite the moon is pulled toward the
  moon less strongly than the water facing the
  moon.
• This water is left behind, forming a second
  bulge.

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The Daily Tide Cycle

• As Earth turns completely around once each day,
  people on or near the shore observe the rise and
  fall of the tides as they reach the area of each
  tidal bulge.
• The high tides occur about 12 hrs. and 25 mins.
  Apart in each location.

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Tides occur at different locations on Earth
because the Earth rotates more quickly than the
moon revolves around the Earth.
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Effects of Daily Tides
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Photos Showing Progress of high tide coming in
http//www.watchknowlearn.org/Video.aspx?VideoID
23446CategoryID6422
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The Monthly Tide Cycle

• Changes in the positions of Earth, the moon, and
  the sun affect the height of the tides during a
  month.

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The Monthly Tide Cycle

• Twice a month, at the new moon and the full moon,
  the sun and moon are in a straight line.
• Their combined gravitational pull produces the
  greatest range between high and low tide, called
  a spring tide.

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The Monthly Tide Cycle

• In between spring tides, at the first and third
  quarters of the month, the sun and moon pull at
  right angles to each other, producing a neap
  tide.
• A neap tide is a tide with the least difference
  between low and high tide.

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The Monthly Tide Cycle
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The Monthly Tide Cycle
Spring Tide
Neap Tide
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The Monthly Tide Cycle

• The movement of large amounts of water between
  high and low tide are a source of potential
  energyenergy that is stored and waiting to be
  used.
• Spring tide
• Full moon-highest tide
• New moon
• Neap Tide- half moon

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Spring Tides and Neap Tides
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Spring Tides and Neap Tides
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Spring Tides and Neap Tides