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USGS Geology in the Parks

Lagoons

Lagoons are relatively shallow bodies of water, mostly-enclosed, with an oceanic source, separated by a low-lying swatch of land, such as a spit or barrier island. This oceanic source may be continual or episodic, such as storm-induced overwash, and generally has a different salinity as a result of its restricted access. Lagoons hare protected from the waves and currents of the ocean by barrier islands, sand bars or reefs. The margins of lagoons are generally composed of marshy environments, overwash flats, and are salty, brackish, or hyper-saline depending upon the amount of runoff input into the lagoon versus oceanic input and evaporation.

Bays:

Larger than lagoons, Bays are irregularly shaped bodies of water between the mainland and strips of land such as a barrier island, or peninsula.

Sounds:

A sound is larger and deeper than a lagoon. It acts as a long, wide conduit between two bodies of water, such as the ocean and a river. There is more flow and mixing associated with a sound than a lagoon, and tides can be large, but the protection of the island or reef insulates the body of water from wind and waves, allowing for wetland production on the edges. Because of the sheltered nature of these bodies of water the sediments they collect provide a particularly interesting history of the coast and environmental change. Investigate current research is investigating these deposits.

Salt Flats:

Salt flats are areas of overwash by the ocean into a region that has more evaporation than oceanic or runoff input. Due to the high level of evaporation the salts within the ocean and run-off waters are present in the soils of the area is highly concentrated amounts. This high concentration of salts makes it difficult for plants to grow, leaving apparently barren areas of soil on the coast. When inundated with water, either by overwash, rainfall or from episodic runoff the water dissolves some of these salts. These flows of highly saline (high levels of salts) can flow and redistribute the salts, which are left behind as the new source of water dries up. The minerals and salts of these areas are of great interest, as are the few species of plants that can live within and on the perimeters of these areas.


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