1. Waves Chapter 14 Section 3 By Caroline Hollar, Hannah Greenwald, Annie Klopp, and Shannon Consolo

2. What is a Wave?  A wave is a traveling disturbance that carries energy.  It is the energy that moves, not the medium (stuff or material) the wave is passing through.

3. Medium  Medium the material of which a wave moves, (for an ocean wave it is the ocean)  In a rope wave it is the rope.  In sound waves it is the air.

4. Types of Waves  Compressional (longitudinal): the energy travels parallel to the direction of travel. Example: Sound waves, P waves. (Slinky wave)  Transverse: the energy is at right angles to the direction of travel. Example: rope, water, and S waves.

5. Parts of Waves  There are several main parts of a wave…  There is the crest, the point at the top  The trough, the point at the bottom, (opposite of crest)  Wavelength, the space between two crests measured in meters  Amplitude: the distance from the 0 line to the crest or trough (energy)  Wave height: distance from trough to crest ---wavelength---- medium trough crest Wave direction

6. Parts of a wave

7. How Waves Form  The wind blows across the water in open ocean, giving the water the winds energy.  The size of the wave depends on the speed of the wind, its duration and the fetch (distance the wind acts on the wave) that hits it and how.  Without the wind, the ocean would be completely flat

8. Forming Waves  These are the steps in forming a wave…  1) wind speed  2) wind duration (time)  3) the area over which the wind blows (fetch)  The more of each, the bigger the wave, as more and more energy gets added to the wave

9. Section 3 Waves Formation and Movement of Ocean Waves Chapter 14 Click below to watch the Visual Concept. Visual Concept

10. Wave Formation and Movement   Most waves form as wind blows across the water’s surface and transfers energy to the water.   As the energy moves through the water, so do the waves. But the water itself stays behind, rising and falling in circular movements.

11. Why Waves Break As waves move closer to land the medium changes because shallow water is different than deep water. In the shallow water the sand at the bottom catches the wave and eventually slows the bottom part of the wave down. The top part of the wave is still moving faster, so it rides up on top of the slower moving water. Eventually it gets too tall and falls over, breaking on the beach. So wave height increases while the wavelength decreases

12. As deep-water waves become shallow-water waves, the water particles slow down and build up. This change forces more water between wave crests and increases wave height. Gravity eventually pulls the high wave crests down, which causes them to crash into the ocean floor as breakers. The area where waves first begin to tumble downward, or break, is called the breaker zone. Waves continue to break as they move from the breaker zone to the shore. The area between the breaker zone and the shore is called the surf.

13. How waves Change near shore

14. Types of Waves, continued Shore Currents When waves crash on the beach head-on, the water they moved through flows back to the ocean underneath new incoming waves. This movement of water forms a subsurface current that pulls objects out to sea and is called an undertow.

15. Types of Waves, continued   Storm Surges are local rises in sea level near the shore that are caused by strong winds from a storm.   Winds form a storm surge by blowing water into a big pile under the storm. As the storm moves onto shore, so does the giant mass of water beneath it.

16. Longshore Drifts  When waves come to shore, sometimes the waves water comes to the beach at an angle and carries sand shore, sometimes the waves water comes to the beach at an angle and carries sand with it with it  A longshore drift occurs when this happens  This pushes sand further down the beach  So the beach gets eroded in the direction of the current, and built up further down the beach  When the waves move slower they put the sand on the underwater slope, making a sandbar Longshore Drift

17. Rip Currents  Rip Current- a rush of water that flows rapidly back to the sea through one narrow opening.  When a sandbar gets larger, it traps the water flowing on the shore.  Water sometimes breaks through the sand bar and flows back down which forms a rip current.  Rip currents are very dangerous.  When you get caught in a rip current you should swim parallel to the shore until you get out of the current.  Like we said before, it carries water out to sea, and can take you with it.

18. Tsunami  Large waves caused when a large body of water is moved up and down.  Caused by underwater earthquakes, volcanic eruptions, landslides or meteorite/comet impacts.