tends to pile up against the land. Strong winds create wind setup or stovm 

 suvges in this way. The height of storm surge depends on wind speed and 

 direction, fetch, atmospheric pressure, offshore bathymetry, and nearshore 

 slope. In violent storms, storm surge may raise the water level at the shore 

 as much as 6 meters (20 feet). In the United States, larger surges occur on 

 the gulf coast because of the shallower and broader shelf off that coast com- 

 pared to the shelf off both the Atlantic and Pacific coasts. Storm surges 

 may also be increased by a funneling effect in converging shorelines within 

 estuaries. 



When waves approach the beach at an angle, they create a current in shallow 

 water parallel to the shore, known as the longshore aurrent. This current, 

 under certain conditions, may turn and flow seaward in what is known as a vip 

 current . 



Tsunamis are waves created by earthquakes or other tectonic disturbances on 

 the ocean bottom. These long-period waves can travel across entire oceans at 

 speeds exceeding 800 kilometers (500 miles) per hour. Tsunamis can cause 

 extensive damage at times, but fortunately major tsunamis do not occur 

 frequently. 



2. The Beach and Nearshore Zone . 



The shoreline, the intersection of the land and the sea, is where tides, 

 winds, and waves attack the land; and it is where the land responds to this 

 attack by a variety of "give and take" measures which effectively dissipate 

 the sea's energy. The shores of the United States include practically all 

 known landforms of many clastic materials from various stages of geologic 

 evolution. The areas most directly affected by the forces of the sea are the 

 heaeh and the nearshore zone regions that experience the full impact of the 

 sea's energy. Hence, they are the most dynamic areas in the coastal zone. 



Beach sediments on most beaches range from fine sands to cobbles. The size 

 and character of sediments and the slope of the beach are related to the 

 forces to which the beach is exposed and the type of material available on the 

 coast. Much of the beach material originates many miles inland where weather- 

 ing of the mountains produces small rock fragments that are supplied to the 

 beach by streams and rivers. When these fragments reach the shore as sand, 

 they are moved alongshore by waves and currents. This longshore transport is 

 a constant process, and great volumes may be transported. Beach material is 

 also derived from erosion of the coastal formations caused by waves and cur- 

 rents and, in some cases, by onshore movement of sediment from deeper water. 

 In some regions, a sizable fraction of the beach material is composed of 

 marine shell fragments, coral reef fragments, or volcanic materials. Clay 

 and silt do not usually exist on ocean beaches because the waves create such 

 turbulence in the water along the shore that these fine particles are kept in 

 suspension. The particles settle and deposit on the bottom only after moving 

 away from the beaches into the quieter water of lagoons and estuaries or the 

 deeper water offshore. 



Beach characteristics are usually described in terms of average size of the 

 sand particles that make up the beach, range and distribution of sizes of the 

 sand particles, sand composition, elevation and width of berm, slope or 



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