2. Waves Transmit energy (not mass) across the ocean’s surface
Wave – disturbances caused by the movement of energy through some medium (solid, liquid, gas)

3. Waves Most generated in the open ocean Wave height depends on
Wind velocity
Wind duration
FETCH – distance over which the wind blows – usually generated by a big storm

5. Waves Described by Crest – highest part Trough – lowest part
Wavelength (L) – distance between crests/troughs
Wave Height (H) – vertical distance between crest and trough

6. Waves
Wave Period (T) – time for successive waves to pass a fixed point
Frequency – number of wave crests/troughs passing a fixed point every second

7. Types of Waves Deep Water Waves
Move through water > ½ wavelength of the wave
Do not feel the bottom
Wave motion is circular

8. Types of Waves Shallow Water Waves
Move through water < ½ wavelength of the wave
Feel the bottom
Cannot move in a circular path, only back and forth
Most waves are shallow water waves

9. Deep Water Waves Move in an orbital / circular motion
Waves do not carry water very far, but transfer energy
Diameter of circle decreases with depth
Wave motion non-existent below ½ wavelength

12. Deep Water Waves When waves approach shore
Interact with seabed when depth equals ½ the distance between wave crests
Orbits become restricted and elliptical
Waves slow down and bunch up
Waves become shallow water waves
Eventually they form breakers

13. Breakers At water depths < ½ wavelength, waves feel the bottom
Wave height increases
Wave length decreases
Velocity decreases because waves are dragging on the bottom
Wave period stays the same
When wave reaches 1.3 H => Breakers

15. Wave Refraction
Wave crests can refract, or bend, if they approach the shore at an angle
Caused by the change in velocity of waves as a function of water depth
Only a small part of each wave feels bottom at a time so only a small part of wave slows

18. Waves Classified By-
Disturbing force – energy that causes the wave to form
Restoring force – force that returns the water surface to flatness after the wave formed
Wavelength – longest waves move the fastest

21. Types of Waves Capillary waves – first to form when wind blows
Important in transferring energy from air to water to drive ocean currents
Wind waves – form when wind blows over ocean surface
Both are deep water waves

22. Types of Waves Seiche – pendulum-like rocking of water in a basin
No crest or trough

24. Types of Waves
Tsunami – caused by the rapid displacement of ocean water
When caused by the sudden vertical movement of Earth along faults called seismic sea wave
Also caused by landslides, icebergs calving, volcanic eruptions, asteroid impacts

25. Types of Waves Tsunami Resemble fast, onrushing tide
Not dangerous in open water
Can travel at 212 meters per second (470 mph)

26. Although rare, there have been six major tsunamis since the U. S
Although rare, there have been six major tsunamis since the U.S. set up an early warning system in the Pacific after the 1946 tsunami in the Aleutian Islands.
USGS
The most devastating one in history occurred on the same subduction zone as Krakatua on Dec. 26, It was caused by the fourth largest earthquake of the last century. Nearly 300,000 people were killed and more than 1 million were displaced by the tsunami that devastated 10 countries around the Indian Ocean.

35. Types of Waves
Tides
Caused by the gravitational attraction of Earth, moon and sun
Tides move at a rate of 1600 km (1000 mi) per hour

36. Shallow Water Waves
Seiches, tsunami and tides are all shallow water waves
They have extremely long wavelengths
They are always in water less than ½ their wavelength
These waves move extremely fast

37. Rogue Waves
Rogue waves are caused when wave trains traveling at different speeds and directions meet.
They appear suddenly and may capsize boats.