Ch 20 Beaches Mod 3-13-03

Ch 20 Beaches Mod 3-13-03 - The shoreline a dynamic...

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Unformatted text preview: The shoreline - a dynamic interface The shoreline is a dynamic interface (common boundary) between air, land, and the ocean The shoreline is constantly being modified by waves Today the coastal zone is experiencing intense human activity Waves Wind-generated waves provide most of the energy that shapes and modifies shorelines Characteristics of Waves Waves derive their energy and motion from the wind Wave parts and the movement of water particles Waves Characteristics of Waves Measurements of a wave – Wave period – the time interval between the passage of two successive crests Height, length, and period of a wave depend on – Wind speed – Length of time wind has blown – Fetch – the distance that the wind has traveled across open water Waves Types of waves Wave of oscillation – Wave energy moves forward, not the water itself – Occur in the open sea in deep water Wave of translation – Begins to form in shallower water when the water-depth is about one-half the wavelength and the wave begins to “feel bottom” Waves Types of waves Wave of translation – As the speed and length of the wave diminish, the wave grows higher – The steep wave front collapses and the wave breaks along the shore – Turbulent water advances up the shore and forms surf Changes that occur when a wave moves onto shore Wave erosion Breaking waves exert a great force Wave erosion is caused by Wave impact and pressure Abrasion by rock fragments Wave refraction and longshore transport Wave refraction Bending of a wave Causes waves to arrive nearly parallel to the shore Consequences of wave refraction – Wave energy is concentrated against the sides and ends of headlands Refraction of waves Wave refraction and longshore transport Wave refraction Consequences of wave refraction – Wave energy is spread out in bays and wave attack is weakened – Over time, eave erosion straightens an irregular shoreline Moving sand along the beach – Waves that each the shoreline at an angle cause the sediment to move along a beach in a zigzag pattern called beach drift Movement of sand by longshore current Wave refraction and...
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Ch 20 Beaches Mod 3-13-03 - The shoreline a dynamic...

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