Chott

For the village, see Chott, Algeria. For the American actor and comedian, see Bill Chott. For the Filipino basketball head coach, see Chot Reyes.

In geology, a chott, shott, or shatt (/ˈʃɒt/; Arabic: شط, romanized: šaṭṭ, lit. 'bank, coast') 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 capillary fringe, with sediment deflation occurring when the water table falls and sediment accumulation occurring when the water table rises.^[1] They are formed—within variable shores—by the spring thaw from the Atlas mountain range, along with occasional rainwater or groundwater sources in the Sahara, such as the Bas Saharan Basin.^[2][3]

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.^[3] This salt accumulation can lead chotts to have particularly high albedo, albeit with comparable variability as well.^[3] 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.^[4]

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.^[5]

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.^[4]

List of major chotts

• Chott el Djerid
• Chott ech Chergui
• Chott Melrhir
• Chott el Fejej
• Chott el Hodna
• Shatt al Gharsah

See also

• Djerid
• Sabkha
• Shatt al-Arab
• Nouakchott

References

1. 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.
2. Ramdani, Mohammed; Elkhiat, Najat; Flower, Roger J (2010). "Africa: North of Sahara". In Likens, Gene E. (ed.). Encyclopedia of Inland Waters. Vol. Lake Ecosystem Ecology. San Diego, CA: Academic Press. ISBN 978-0123820020. Retrieved 16 December 2012.
3. Laity, Julie J. (2009). Deserts and Desert Environments. Environmental Systems and Global Change Series. Chichester, UK: John Wiley & Sons. ISBN 978-1444300741. Retrieved 16 December 2012.
4. Komatsu, Goro; Ori, Gian Gabriele; Marinangeli, Lucia; Moersch, Jeffrey E. (2007). "Playa environments on Earth: Possible analogs for Mars". In Chapman, Mary (ed.). The Geology of Mars: Evidence from Earth-Based Analogs (5th ed.). Chichester, UK: Cambridge University Press. ISBN 978-0521832922. Retrieved 16 December 2012.
5. Spinage, Clive Alfred (2012). African Ecology: Benchmarks and Historical Perspectives. Springer Geography (Illustrated ed.). New York: Springer. ISBN 978-3642228711. Retrieved 16 December 2012.