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Published byCandace Parrish Modified over 8 years ago
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Ocean Waves Nov. 22, 2013 CGF3M
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Along the shores of oceans and lakes, waves break against the land, tearing it down in some places and building it up in others Surface waves are movement at the water’s surface, due to wind Wave height and length can be much greater in areas where the wind is able to blow for long distances
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As the wind moves along the surface of the water, it transfers some of the energy to the water itself This causes the water molecules to move in a circular motion In shallower water, the circular wave motion is squeezed into an elliptical orbit
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Breaking Waves When a wave approaches shore, the water becomes shallower and begins to influence wave behaviour At a depth of ½ its wave length, the wave is said to “feel bottom” and the water movement at the wave’s base slows As the wave continues towards shore, the water at the top moves forward at a faster rate The wave height builds until the wave collapses (breaks) and moves up the shore VIDEO: How does a wave break? VIDEO FLASH DIAGRAM Flash Diagram 2 FLASH DIAGRAMFlash Diagram 2 There are 3 types of breaking waves:
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1. Spilling Breakers Found on gradually sloping coasts Break slowly over a long distance Carry deposits such as sand and build up beaches Safest for swimming
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2. Plunging Breakers Found on steeper coasts Create a hollow tube when they break Plunge toward the base- can pick swimmers up and dump them onto shallow sandbanks or reefs with force Can loosen and transport rocks and sediments, causing erosion Preferred by more experienced surfers
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3. Surging Breakers Appear on steep coastlines or on rock platforms Waves break right on the beach Can knock swimmers out and pull them into deeper water
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Wave Refraction Rarely do waves approach shore straight on As the water breaks and washes up on the beach, it does so on a diagonal The backwash returns to the ocean in a straight line This pattern, called beach drift, affects sediment transport, moving the particles in a zigzag pattern along the beach Beach drift FLASH animationFLASH
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Rip Current If backwash becomes concentrated in a particular area at a particular time, the result is a rip current this is a narrow but powerful current running perpendicular to the shore out to the ocean Happens when the water finds an opening in a sandbar Can be dangerous for swimmers Experienced surfers use rip currents as a shortcut to get quickly back out to sea Can also cause shoreline erosionVIDEOVIDEO
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Surf’s Up? Where is the closest place to Sioux Lookout to catch a wave? Along the North Shore of Lake Superior- VIDEOVIDEO
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