In
geology, a chott, shott, or shatt (; ar, شط, šaṭṭ, lit=bank, coast) is a
salt lake
A salt lake or saline lake is a landlocked body of water that has a concentration of salts (typically sodium chloride) and other dissolved minerals significantly higher than most lakes (often defined as at least three grams of salt per litre). ...
in
Africa's
Maghreb that stays dry for much of the year but receives some water in the winter. The elevation of a chott surface is controlled by the position of the water table and
capillary fringe
The capillary fringe is the subsurface layer in which groundwater seeps up from a water table by capillary action to fill pores. Pores at the base of the capillary fringe are filled with water due to tension saturation. This saturated portion of t ...
, with sediment deflation occurring when the water table falls and sediment accumulation occurring when the water table rises.
[Swezey, C.S., 2003, The role of climate in the creation and destruction of continental
stratigraphic records: An example from the northern margin of the Sahara Desert, in Cecil, C.B., and Edgar, N.T., eds., Climate Controls on Stratigraphy: SEPM (Society for Sedimentary Geology) Special Publication 77, p. 207-225.
] They are formed—within variable shores—by the spring thaw from the
Atlas mountain range
An atlas is a collection of maps; it is typically a bundle of maps of Earth or of a region of Earth.
Atlases have traditionally been bound into book form, but today many atlases are in multimedia formats. In addition to presenting geographic ...
, along with occasional rainwater or
groundwater sources in the
Sahara
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, such as the
Bas Saharan Basin
The Bas Saharan Basin () is an artesian aquifer system which covers most of the Algerian and Tunisian Sahara and extends to Libya, enclosing the whole of the Grand Erg Oriental
The Grand Erg Oriental (English: 'Great Eastern Sand Sea') is a large ...
.
Water sources
The chotts of the Sahara are fed intermittently during periods of infrequent rainfall. They are subject to a high evaporation rate, hence salts eventually accumulate in the surface of the sediment. In fact, annual evaporation rates per year in chotts often exceed 20 times the annual precipitation rate.
This salt accumulation can lead chotts to have particularly high
albedo, albeit with comparable variability as well.
While
evaporite deposition predominates on chotts, in more humid climatic periods, layers of mud can be deposited on the chott surface. When near a source of loose sand,
aeolian deposition can also play a role in the sedimentary deposition on the chott surface.
Sahara Sea
As many lie below sea level, the chotts of the Sahara were viewed by some European colonialists and engineers as an opportunity to create an inland sea in the Sahara Desert (known by many as the "
Sahara Sea") by cutting a canal to the Mediterranean Sea (or in some cases, the Atlantic Ocean). Such a channel would allow water from the sea to flow inland. The hope was that this would facilitate trade and naval warfare, as well as change the climatic conditions of the Sahara.
Analogue to Martian landforms
Chotts have also been studied because they are believed to be an Earth analogue to similar features on the planet
Mars. Although there are considerable differences between terrestrial and
Martian geology, some features on Mars are also believed to be evaporite basins, and consequently share at least some features of chotts. One example of a suspected Martian evaporite basin is
Holden Crater.
List of major chotts
*
Chott el Djerid
*
Chott ech Chergui
*
Chott Melrhir
Chott Melrhir () also known as Chott Melghir or Chott Melhir is an endorheic chott-kind of salt lake in northeastern Algeria. It is the westernmost part of a series of depressions, which extend from the Gulf of Gabès into the Sahara. They were ...
*
Chott el Fejej
Chott el Fejej, also known as Chott el Fedjedj and Chott el Fejaj, is a long, narrow inlet of the endorheic salt lake Chott el Djerid in southern Tunisia.
History and geography
The bottom of Chott el Fejej lies below sea level and runs in a narro ...
*
Chott el Hodna
*
Shatt al Gharsah
See also
*
Djerid
el-Djerid, also al-Jarīd, ( ar, الجريد; Derja: ''Jerīd''; ) or more precisely the South Western Tunisia Region is a semi-desert natural region comprising three southern Tunisian Governorates, Gafsa, Kebili and Tozeur with adjacent parts o ...
*
Sabkha
*
Shatt al-Arab
The Shatt al-Arab ( ar, شط العرب, lit=River of the Arabs; fa, اروندرود, Arvand Rud, lit=Swift River) is a river of some in length that is formed at the confluence of the Euphrates and Tigris rivers in the town of al-Qurnah in ...
*
Nouakchott
References
{{reflist
Lakes
Salt flats