1. Ocean Motions
Chapter 13

2. How Waves Form wave is the movement of energy through a body of water.
process begins with wind
winds blowing across the water's surface transmit their energy to the water.
Stronger winds create larger waves.
Winds blowing across longer distances build up bigger waves.

3. Although waves may appear to carry water toward shore, the water does not actually move forward in deep water.
As the wave passes, the object lurches forward a little, then bobs backward.
The wind affects the water at the surface more than the deep water.

5. Describing Waves the highest part of a wave is the crest.
horizontal distance between crests is the wavelength.
Long, rolling waves with lots of space between crests have long wavelengths. Short, choppy waves have shorter wavelengths.
frequency, the number of waves that pass a point in a certain amount of time.

6. the lowest part of a wave is the trough
vertical distance from the crest to the trough is the wave height
The energy and strength of a wave depend mainly on its wave height

7. How Waves Change Near Shore
In deep water, waves usually travel as long, low waves called swells.
The wave breaks onto the shore, forming surf.
Near shore, the wave height increases and the wavelength decreases.

8. The water that moves up the beach flows back into the sea.
This pull, often called an undertow, carries shells, seaweed, and sand away from the beach.

9. How Waves Affect the Shore
Since wave direction at sea is determined by the wind, waves usually roll toward shore at an angle.

10. longshore drift, The movement of water and sediment along a beach caused by waves coming into shore at an angle.
Sandbar, A ridge of sand deposited by waves as they slow down near shore.
rip current, a rush of water that flows rapidly back to sea through a narrow opening

11. Reducing Beach Erosion
erosion can wear away the beach
One method of reducing erosion along a stretch of beach is to build a wall of rocks or concrete, called a groin, outward from the beach.