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Unformatted text preview: 1 Beaches and Coastal processes I- Introduction: A beach is a gently sloping shore covered by silt, sand or gravel that is washed by waves and tides. A shoreline is a line made by the sea water's edge on the land. Beaches and shorelines are dynamic environments with numerous erosional and depositional features. Because oceans and seas generally resist changes in temperatures, beaches and coasts are cooler in the summer and warmer in the winter compared to continental interiors. Beaches and coasts are therefore very popular places for living and for visiting. However, because the erosional and depositional processes on beaches and shorelines are among the fastest known geological processes, they have a large impact on mankind. II- Agents of weathering, erosion and deposition on beaches: 1- Waves : Waves are caused by wind blowing across the water. It should be noted that the water in waves does not move very far, but that waves are a means of transporting energy from one place to another. The motion of water in a wave follows a circular orbit which becomes larger closer to the surface exposed to the blowing winds. However, at shallow depths, the water motion follows progressively more elliptical paths, and the wave develops into a breaker (Fig. 1a & b). Waves are also refracted as they approach coasts that are not straight (or when they approach these coasts at an angle). This refraction results in the lines connecting the wave crests to bend; becoming convex towards the shore (Fig. 2). Factors controlling the size of waves: 1- wind speed 2- length of time the wind blows across seawater 3- distance over which the wind has traveled without interruption....
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- Fall '08