Lagoon
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This mid bay barrier in Narrabeen, a suburb of Sydney (Australia), has blocked what used to be a bay to form a lagoon. |
This article is about natural lagoons. For artificial "lagoons" used to treat waste water, please see anaerobic lagoon and aerated lagoon. For the Super NES game, see
Lagoon (video game).
A lagoon is a body of comparatively shallow salt water separated from the deeper sea by a shallow or exposed sandbank, coral reef, or similar feature. Thus, the enclosed body of water behind a barrier reef or barrier islands or enclosed by an atoll reef is called a lagoon
. This application of lagoon
in English dates from 1769. It adapted and extended the sense of the Venetian laguna
(cf
Latin lacuna, 'empty space'), which specifically referred to Venice's shallow, island-studded stretch of saltwater, protected from the Adriatic by the barrier beaches of the Lido (see
Venetian Lagoon). Lagoon'' refers to both coastal lagoons formed by the build-up of sandbanks or reefs along shallow coastal waters, and the lagoons in atolls, formed by the growth of coral reefs on slowly sinking central islands.
Coastal lagoons are usually found on
coasts with relatively small tidal ranges. They constitute approximately 13 percent of all coastlines. They generally extend parallel to the coastland, separated from the sea by barrier islands, sand and shingle bars or coral reefs. Non-reef lagoon barriers are formed by wave-action or
longshore currents piling up coarser
sediments off shore of the beach. Once a lagoon barrier has formed, finer sediments can settle out in the relatively quiet water behind the barrier, including sediments brought into the lagoon by rivers. Coastal lagoons typically have only constricted openings to the sea. As a result, water conditions in the lagoon can differ significantly from the open water of the sea in
temperature,
salinity,
dissolved oxygen and sediment load.
In many English-speaking countries, coastal lagoons are sometimes called
sounds,
bays,
rivers, or
lakes.
Albemarle Sound in
North Carolina,
Great South Bay, between Long Island and the barrier beaches of
Fire Island in
New York,
Banana River in
Florida and
Lake Illawarra in
New South Wales are all lagoons. In the UK there are lagoons at
Montrose, (Scotland) and
Tywyn, (Wales), whilst the expanse of water inside
Chesil Beach, England, known as the fleet, could also be described as a lagoon. There is also one near the small town of
Dingle in western Ireland.
In Mexico often the use of "laguna", which
lagoon translates to, is used to describe a lake, such as
Laguna Catemaco.
*
Atoll*
:Category:Atolls*
:Category:Lagoons*Encyclopedia Britannica. 2005. Lagoon.
Encyclopedia Britannica Premium Service. [
1] - accessed
December 7, 2005.
*
What is a lagoon? - accessed
December 7, 2005.
