1. Ocean Waves
Chapter 10
Oceanography

2. Definition of a Wave
A wave is a disturbance caused by movement of energy from a source through some medium, either solid, liquid or gas.

3. Disturbing Force
Energy that causes waves to form is a disturbing force.
Examples:
Wind, landslides, earthquakes, & gravity are examples of disturbing forces.

4. Types of Waves & Disturbing Force
Restoring Force
Capillary Wave
Usually wind
Cohesion of water molecule
Ocean Waves
Wind
Gravity
Tsunami
Earthquake/Landslides/Volcano
Tides
Gravity & rotation of the Earth
Seiche (say-sh)
Storm surge

5. Anatomy of a Wave Wave Crest is the highest part of the wave.
Wave Trough is the valley between wave crests.
Wave Period is the time between two consecutive wave crests or troughs.
Wavelength is the distance between two consecutive crests or troughs.

7. Progressive Waves
In an ocean wave, ENERGY is moving at the speed of the wave, the water is NOT.
All waves except tides are progressive waves
A progressive wave continues after the disturbing force is gone.

8. Orbital Waves
Orbital waves transfer energy from water particle to water particle in circular paths, or ORBITS.
Orbits transmit energy across the ocean surface & cause the wave-form to move.
Orbital waves are a progressive wave.
There are two types of orbital waves:
Deep water waves
Shallow water waves

9. Orbital Waves below the Surface
The size of the orbital is equal to the height of the wave.

10. Visual of an Orbital Wave

11. Types of Orbital Waves

12. Deep-Water Waves: All wind waves are deep water waves.
Deep water waves form in water deeper than 1/2 its wavelength.

14. Characteristics of Deep-water Waves
Typical Wavelengths meters ( feet).
Wave speeds up to 70 mph (max).
Wave periods between 1 & 20 seconds.
Restoring Force for deep-water waves is gravity & surface tension.

15. Shallow-Water Waves
Waves form in water shallower than 1/20 of original wavelength are shallow-water waves.
Waves “feel bottom” as they move.
Examples of shallow-water waves:
Breaking waves
Tides
Tsunamis

16. Characteristics of Shallow-water Waves
Typical wave-length of shallow-water waves are:
200km (125 mi) for tsunamis
1/2 the earth’s circumference for tides.
Since most of the ocean is shallower than 6.2 miles deep (1/20th of 125 mi), all tsunamis & tides form in water shallower than 1/20th wavelength.
Therefore, they are SHALLOW WATER waves.

17. Shallow-Water Waves
Typical period of a shallow-water wave is about 20 minutes.
Larger the wave the faster it’s speed: tsunamis can travel typically 470 miles per hour!

18. Tsunami

20. Tides
Periodic short term changes in the height of the ocean surface caused by gravitational effects and the rotation of the Earth.
Tides are NOT progressive waves but are called forced waves.
Tides will disappear if disturbing force stops.

21. Characteristics of Tides
Wavelength: ½ circumference of Earth (20,000 KM or 12,500 miles)
Wave period is 12 hours.
Speed is 20,000 km divided by 12. (Do the math!!).
That is the world’s largest & fastest wave
1,666.7 km/hr