Wave Action

1
Wave Action

• Chapter 13
• Section 1

2
Key Terms

• Wave
• Wavelength
• Frequency
• Wave Height
• Tsunami
• Longshore Drift
• Rip Current
• Groin

3
Things to Ponder.

• What are the main parts of a wave?
• How do waves form?
• How do waves change near the shore?

4
What Is a Wave?

• Wave movement of energy through a body of water
• Wave development USUALLY begins with wind.
  Otherwise, the ocean would be smooth.
• What else could start a wave?
• Tsunamis
• Animals

5
Wave Size

• Depends on three factors
• Strength of the wind
• Length of time the wind blows
• Distance over which the wind blows
• What would produce the largest waves?
• Strong wind, blowing for a long time, over a long
  distance.

6
Wave Energy

• In the OPEN OCEAN, water does not move. Only the
  energy of the wave moves
• Floating objects will move in a circular motion
  and return to the starting point.
• The further down you go, the less the waves
  affect the water.
• Once a certain depth is achieved, waves no longer
  affect the water and its contents.

7
Parts of a Wave
Crest
Wavelength
Wave Height
Trough

• Crest top of wave Trough bottom of wave
• Wavelength Horizontal distance between crests
  or troughs
• Wave Height Vertical distance from crest to
  trough
• Frequency number of times a wave crest passes a
  point in a certain amount of time.

8
How Waves Change Near Shore

• White-capped waves that crash onto shore are
  called breakers
• Open ocean waves are called swells.
• As they approach the shore, friction occurs
  between the water and the land, which causes the
  waves to slow down
• This causes wave height to increase and
  wavelength to decrease
• Creates a traffic jam of water and forces waves
  to break. (Diagram on board)

9
How Waves Change Near Shore
10
Tsunamis

• Caused by an earthquake beneath the ocean
• Sends a pulse of energy through the water
• Due to water depth, the wave is very small as a
  swell at sea. As it approaches the land, it
  rises to incredible heights due to shallow water.

11
How Waves Affect the Shore

• Longshore Drift as waves hit the shore at an
  angle, it carries the grains of sand down the
  beach.
• Rip Currents a rush of water that flows rapidly
  back to sea through a narrow opening, usually
  between sand bars.
• How do you escape a rip current if you are
  swimming and get trapped?

12
How Do We Prevent Beach Erosion?

• Nature protects by creating barrier beaches and
  sand dunes to slow down the erosion process
• Humans help by building groins or jetties, which
  are walls that prevent longshore drift from
  occurring.

13
Things to Ponder.

• What are the main parts of a wave?
• Crest, trough, wavelength, wave height
• How do waves form?
• Primarily wind, also tsunamis, animals, etc.
• How do waves change near the shore?
• Wavelength decreases and wave height increases