1. Wave Action

2. Wave Action Wave: the movement of energy through a body of water
Waves are formed when the wind blows across the water’s surface and transfers its energy to the water.

3. Ocean Waves

4. Waves occur on the Lake Superior, too!

5. Wave Size Wave size depends on three things: * Strength of the wind
* Length of time that the wind blows
* Distance the wind travels

6. 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.

7. 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

8. Water motion

9. 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

10. How do Waves Change near the Shore?
Breakers – white capped waves that crash onto the shore
* In deep water -> waves travel as long,
low waves called swells.
* In shallow water near the shore -> wave
height increases, wavelength decreases
and breakers are created.

11. 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

12. Tsunami

13. tsunami demo

14. 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.

15. 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.

16. Escape a Rip Current

17. 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?

18. Examples of Beach Erosion

19. Erosion after Hurricanes

20. Questions – Section 13-1 How do waves form?
Why does an ocean buoy bob up and down in the ocean?
How do wavelength and wave height change as a wave enters shallow water?
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.