geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

, a chott, shott, or shatt (; ) 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 liter). I ...

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

Maghreb The Maghreb (; ), also known as the Arab Maghreb () and Northwest Africa, is the western part of the Arab world. The region comprises western and central North Africa, including Algeria, Libya, Mauritania, Morocco, and Tunisia. The Maghreb al ...

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, along with occasional rainwater or

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

sources in the

Sahara The Sahara (, ) is a desert spanning across North Africa. With an area of , it is the largest hot desert in the world and the list of deserts by area, third-largest desert overall, smaller only than the deserts of Antarctica and the northern Ar ...

, such as the Bas Saharan Basin.

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 Albedo ( ; ) is the fraction of sunlight that is Diffuse reflection, diffusely reflected by a body. It is measured on a scale from 0 (corresponding to a black body that absorbs all incident radiation) to 1 (corresponding to a body that reflects ...

, albeit with comparable variability as well. While

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as oce ...

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 Aeolian commonly refers to things related to either of two Greek mythological figures: * Aeolus (son of Hippotes), ruler of the winds * Aeolus (son of Hellen), son of Hellen and eponym of the Aeolians * Aeolians, an ancient Greek tribe thought to ...

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 The Sahara Sea was the name of a hypothetical macro-engineering project which proposed flooding endorheic basins in the Sahara with waters from the Atlantic Ocean or Mediterranean Sea. The goal of this unrealised project was to create an inlan ...

") 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 Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

. Although there are considerable differences between terrestrial and

Martian Mars, the fourth planet from the Sun, has appeared as a setting in works of fiction since at least the mid-1600s. Trends in the planet's portrayal have largely been influenced by advances in planetary science. It became the most popular celes ...

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 el Djerid ( ') also spelled ''Sciott Gerid'' and ''Shott el Jerid'', is a chott, a large endorheic salt lake in southern Tunisia. The name can be translated from the Arabic into English as "Lagoon of the Land of Palms". Geography The bottom ...

Chott ech Chergui Chott Ech Chergui () is a large endorheic salt lake in Saïda Province, northwestern Algeria. It is located at in the level terrain of the ''Hautes Plaines'' region between the Tell Atlas and the Saharan Atlas and is one of the largest lakes in Al ...

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. It was for ...

Chott el Fejej In geology, a chott, shott, or shatt (; ) is a salt lake 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 cap ...

* Chott el Hodna *

Shatt al Gharsah Shatt al Gharsah, Chott el Gharsa () is a sedimentary basin and also intermittent salt lake (a chott) in Tunisia, near the border with Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb reg ...

References

{{reflist Lakes Salt flats

Water sources

Sahara Sea

Analogue to Martian landforms

List of major chotts

See also

References