Ocean Waves Text Book Page 358 365 Waves

Ocean Waves Text Book Page # 358 - 365

Waves • A Wave is a rhythmic movement that carries energy through matter or space. • In oceans, waves move through seawater. • A water wave is the movement of energy through a body of water.

Ocean Waves Caused by: • Wind • Earthquakes http: //david. li/waves/

Most waves form when winds blowing across the water’s surface transmit (transfer) their energy to the water.

Wave size depends on the v strength of the wind, and duration (length of the time) it blows for. (A gentle breeze creates small ripples on the surface of the water and a stronger wind creates larger waves. ) v Distance over which the wind blows. (Winds blowing across longer distances build up bigger waves. )

Wave Energy The wave’s energy moves, but the water mostly stays at one place. Individual water molecules move up and down but they do not move forward or backward.

Water Motion • As a wave passes, water particles moves in circular motion. • Deeper water particles moves in a smaller circles than those near the surface. • The wind affects the water at the surface than it affects the deep water. • Below a certain depth, the water does not move at all as the wave passes.

Wave Parts Wavelength Wave Height Crest Still Water Trough

Parts of a Wave • Crest – The highest point on a wave. • Trough – The lowest point on a wave. • Wave Height – The vertical distance from the crest of a wave to the trough. • Wavelength – The horizontal distance between two neighboring crests. • Frequency – The number of waves that pass a point in a certain amount of time.

Breakers & Swells The white-capped waves that crash onto shore are called breakers. In deep water, these waves usually travel as long, low waves called swells.

How breakers changes near shore 1. As the waves approach the shore, the water becomes shallower. 2. The bottoms of the waves begin to touch the sloping ocean floor. 3. Friction with the ocean floor causes waves to slow down in the shallow water near the shore. Wavelength decreases

How breakers change near shore 4. Near the shore , wave height increases and wavelength decreases. 5. When the water reaches certain height, the crest outruns the trough and the crest collapses. 6. The waves breaks onto the shore, forming surf.

Feeling Undertow The water that had rushed up the beach flows back out to sea. This pull is called an undertow carries shells, seaweeds, and sand away from the beach.

Tsunami A giant wave usually caused by an earthquake beneath the ocean floor.

The abrupt movement of ocean floor sends pulses of energy through water above it. 20 m

1. At sea, a tsunami travels as a long, low wave. 2. Near shore, the wave height increases suddenly. 3. When tsunami reach the coast, they can be as devastating as an earthquake on land, smashing buildings and bridges.

Beach Erosion Sand Dunes – • Natural landform • Reduces beach erosion • Strong roots of dune plants, such as beach grass and sea oats, hold the sand in its place. Groins – • A wall made of rocks and concrete that is built outward (perpendicular) from a beach. • Reduces beach erosion