Ocean Motions Chapter 13 How Waves Form wave

Ocean Motions Chapter 13

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.

• 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.

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.

• 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

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.

• 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.

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

• 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

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.