![]() ![]() 5 Department of Thematic Studies – Environmental Change, Linköping University, 581 83, Linköping, Sweden.Milton Tavares de Souza, s/no., Niterói, RJ, 24210-346, Brazil 4 Physical Geography Laboratory (LAGEF-UFF), Department of Geography, Graduate Program in Geography, Universidade Federal Fluminense, Av.3 Graduate Program in Geosciences (Environmental Geochemistry), Department of Geochemistry, Universidade Federal Fluminense, Niterói, RJ, 24020-141, Brazil.Edmundo March, s/n extdegree, Niterói, RJ, 24210-310, Brazil 2 Ecosystems and Global Change Laboratory (LEMG-UFF), International Laboratory of Global Change (LINCGlobal), Biomass and Water Management Research Center (NAB), Universidade Federal Fluminense, Av.1 National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, P.O. Box 4321, Coffs Harbour, NSW, 2450, Australia.Many people are fascinated when they walk across the muddy sea floor at low tide for the first time. 1.25 > The Wadden Sea on the margin of the North Sea is very popular with tourists. These, however, are not “open” tidal flats, but covered by salt-resistant mangrove trees.įig. ![]() Island tidal flats are also found on the Pacific coast of Colombia, for example. ![]() As a rule, the tidal range here is between 3 and 3.5 metres. A prerequisite for the formation of these island or backshore tidal flats is a significantly large tidal range, the difference in the water level between low and high tide, so that the area is regularly flooded and exposed as in the western European Wadden Sea. Because of the low-energy currents here, fine particles can be deposited on the sea floor. Tidal flats often form between the mainland and offshore islands. These salt marshes are important stopover and breeding sites for birds and thus represent a crucial habitat within the tidal flat environment. Specialized salt-resistant plants can then colonize here. The tidal flats grow upward on the order of decimetres through time, and thus become less frequently inundated by water. These form along low-energy segments of the coastline where rivers import large volumes of material that are primarily deposited in shallow areas near the shore. Salt marshes have formed at many locations between Florida and the peninsula of Cape Cod in Massachusetts, which defines them as “closed” tidal flats. On the east coast of the USA, however, the situation is quite different. The bulk of these are transported over a distance of around 600 kilometres from the mouth of the Orinoco in Venezuela, through the Atlantic and into the calm waters off Suriname. Here, even the finest clay and silt particles can be deposited to form thick muddy sediment packages. Thus, in the strict sense, this tidal flat is considered to be a sandy coast.Ī true “open” muddy coast, on the other hand, is found in the South American country of Suriname, where the coastal Atlantic currents are very weak. But technically this area cannot be referred to as a muddy coast because of the relatively high sand content in most areas. The intertidal area here contains the typical mud consisting of 30 per cent clay, 30 per cent fine silt and more than 30 per cent sand as well as dead biomass. It has been listed as a World Natural Heritage Site by UNESCO (United Nations Educational, Scientific and Cultural Organization) since 2009. The largest tidal flat area in the world extends across broad stretches of the Dutch, German and Danish coasts of the North Sea and is an “open” tidal flat. A distinction can be made between “closed” tidal flats, characterized by plant growth, and “open” tidal flat areas where the sediments are exposed. These tidal flat areas, however, do not look the same everywhere. On many low-energy coasts around the world tidal flats are formed when large amounts of clay, silt and fine sand particles are imported by rivers. ![]()
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