Wave Action

I. What is a Wave? 1.The movement of energy through a body of water. Begins with the WIND. Most waves form when wind blows across the surface of the water and transfers their energy to the water. Waves start in the open ocean.

A. Wave Size Depends on: the strength of the wind a. gentle breeze creates small waves b. stronger winds create larger waves. 2. the length of time it blows. 3. the distance over which the wind blows. a. ex: longer distance = bigger waves shorter distance = smaller waves

B. Wave Energy In deep water, the water does not move forward toward the shore. Instead, the ENERGY moves toward the shore, but the water remains in place. As the wave passes, water particles move in a circular path. C. Water Motion 1. The wind affects the water at the surface more than if affects the deep water. 2. Below a certain point, the water does not move at all.

D. Parts of Wave 1. Crest- top of wave 2. trough- bottom of wave 3. wavelength- distance between crests or troughs. 4. Wave height- vertical distance from crest to trough. Determines the energy and strength of the wave. 5. frequency- Number of waves that pass a given point in a certain amt. of time.

Oceans- wind

II. How Waves Change Near Shore Breakers- white-capped waves that crash near shore. 1. In deep water, waves travel as long, low waves called swells. 2. as water approaches shore, water becomes shallower. 3. bottoms of the wave touch the sloping ocean floor and causes water to slow down and get higher.

4. Near shore, wave height increases and wavelength decreases. When the wave reaches a certain height, the crest topples and the wave breaks onto the shore, forming surf. 6. The water that moves up the beach in a wave flows back out to sea. Why?

Tsunamis They are caused by earthquake beneath ocean. Earthquake sends pulses of energy through water above it. People on a ship may not realize they are going over a tsunami. Why? When the tsunami reaches shallow water near the coast, friction with the ocean floor causes the long wavelength to decrease suddenly. The wave height increases as the water piles up. Tsunamis are most common in the Pacific Ocean, often striking Alaska, Hawaii, and Japan.

Tsunami

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III. How Waves affect the Shore Waves roll toward shore at an angle b/c wave direction is determined by wind. Longshore Drift- As waves come into shore, water washes up the beach at an angle, carrying sand grains. The water and sand then run straight back down the beach. As the waves slow down, they deposit the sand on shallow, underwater slope in a long ridge called a sandbar. Rip Currents- a rush of water that flows rapidly back to sea through a narrow opening. These can carry a swimmer out into deep water. B/c rip currents are narrow, a strong swimmer can usually escape by swimming across the current, parallel to the beach.

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III. Wave and Beach Erosion Waves shape a beach by eroding the shore in some places and building it up in others. Barrier Beaches- protects shorelines from waves. a. Sand deposits these beaches parallel to the shore. They are separated from the mainland. b. Waves break against the barrier beach instead of the mainland.

3. Sand Dunes- deposits of windblown sand. 4 3. Sand Dunes- deposits of windblown sand. 4. Groin- wall of rocks or concrete outward from the beach.