Wave Action

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Wave Action
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Wave Action

• Wave the movement of energy through a body of
  water
• Waves are formed when the wind blows across the
  waters surface and transfers its energy to the
  water.

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Ocean Waves
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Waves occur on the Lake Superior, too!
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Wave Size

• Wave size depends on three things
• Strength of the wind
• Length of time that the wind blows
• Distance the wind travels

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Wave Energy

• The energy of the wave can be moved from the
  middle of the ocean to the shore, but the water
  molecules will not end up at the shore.
• The energy transfers, the water molecules remain
  the same.

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Water Molecule motion during a wave

• Water particles move in a circular pattern in the
  upper portions of the water.
• The deeper you get, the less the circular motion.
• Eventually you get deep enough that the circular
  motion stops.
• This is why sunken treasure never moves

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Water motion
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Wave Characteristics

• Crest top of the wave
• Trough bottom of the wave
• Wave Height from the bottom of the trough to
  the top of the crest (just like your height)
• Wave Length horizontal distance between crests

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How do Waves Change near the Shore?

• Breakers white capped waves that crash onto the
  shore
• In deep water -gt waves travel as long,
• low waves called swells.
• In shallow water near the shore -gt wave
• height increases, wavelength decreases
• and breakers are created.

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Tsunamis

• Tsunamis are waves caused by an earthquake
  beneath the ocean floor
• Most common in the Pacific Ocean.
• Alaska, Hawaii and the Pacific
• Northwest (Oregon and Washington)
• are the United States main concerns
• December 26, 2004 Indian Ocean
• tsunami that killed over 200,000 people

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Tsunami
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tsunami demo
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How do waves affect the shore?

• Longshore Drift (Longshore current)
• Waves come into the shore at an angle, not
  straight into the shore
• When the wave goes back out, it pulls sediments
  with it.
• Waves go back in again, but the sediments are
  moved slightly down the beach
• Moves sediment slowly but constantly down the
  beach.

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Rip Currents

• Rip Currents are a rush of water that flows
  rapidly back to sea through a narrow opening
• They can be very dangerous, but narrow
• If you find yourself caught in one, you should
  swim parallel to the shore to avoid the current,
  then swim inland.

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Escape a Rip Current
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Waves Causing Beach Erosion

• Every minute of every day, the waves are
  constantly eroding the beaches. They move
  sediments from one place to the other. It becomes
  even worse when a storm is present.
• Local beaches have to compensate for the removal
  of sand by off shore dredging.
• How do the beach communities pay for this
  replacement process?

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Examples of Beach Erosion
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Erosion after Hurricanes
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Questions Section 13-1

1. How do waves form?
2. Why does an ocean buoy bob up and down in the
   ocean?
3. How do wavelength and wave height change as a
   wave enters shallow water?
4. Using what you know about wave height and wave
   length of tsunamis, propose and explanation of
   why tsunamis can cause so much damage when they
   reach the shore.