Lake Magadi

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Lake Magadi
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Lake Magadi
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Lake Magadi
Location Kenyan Rift Valley
Coordinates 1°55′S36°16′E / 1.917°S 36.267°E / -1.917; 36.267 Coordinates: 1°55′S36°16′E / 1.917°S 36.267°E / -1.917; 36.267
Basin  countriesKenya
Surface area100 km2 (39 sq mi)

Lake Magadi is the southernmost lake in the Kenyan Rift Valley, lying in a catchment of faulted volcanic rocks, north of Tanzania's Lake Natron. During the dry season, it is 80% covered by soda and is well known for its wading birds, including flamingos.

Contents

Lake Magadi is a saline, alkaline lake, approximately 100 square kilometers in size, that lies in an endorheic basin formed by a graben. The lake is an example of a "saline pan". The lake water, which is a dense sodium carbonate brine, precipitates vast quantities of the mineral trona (sodium sesquicarbonate). In places, the salt is up to 40 m thick. The lake is recharged mainly by saline hot springs (temperatures up to 86 °C) that discharge into alkaline "lagoons" around the lake margins, there being little surface runoff in this arid region. Most hot springs lie along the northwestern and southern shorelines of the lake. During the rainy season, a thin (less than 1 m) layer of brine covers much of the saline pan, but this evaporates rapidly leaving a vast expanse of white salt that cracks to produce large polygons. A single species of fish, a cichlid Alcolapia grahami , inhabits the hot, highly alkaline waters of this lake basin and is commonly seen in some of the hot spring pools around the shoreline, where the water temperature is less than 45 °C.

Lake Magadi was not always so saline. Several thousand years ago (during the late Pleistocene to mid-Holocene in the African humid period), the Magadi basin held a freshwater lake with many fish, whose remains are preserved in the High Magadi Beds, a series of lacustrine and volcaniclastic sediments preserved in various locations around the present shoreline. Evidence also exists for several older Pleistocene precursor lakes that were much larger than present Lake Magadi. At times, Lake Magadi and Lake Natron were united as a single larger lake.

Lake Magadi is also well known for its extensive deposits of siliceous chert. There are many varieties including bedded cherts that formed in the lake and intrusive dike-like bodies that penetrated through overlying sediments while the silica was soft. Most famous is "Magadi-type chert", which formed from a sodium silicate mineral precursor magadiite that was discovered at Lake Magadi in 1967.

Magadiite, a rare hydrous sodium-silicate mineral [NaSi7O13(OH)3·4(H2O)], was discovered about 50 years ago in sediments around Lake Magadi, a hypersaline alkaline lake fed by hot springs in the semi-arid southern Kenya Rift Valley. Today this harsh lacustrine environment excludes most organisms except microbial extremophiles, a few invertebrates (mostly insects), highly adapted fish (Alcolapia sp.), and birds including flamingos. Burrows discovered in outcrops of the High Magadi Beds (~25–9 ka) that predate the modern saline (trona) pan show that beetles and other invertebrates inhabit this extreme environment when conditions become more favourable. Burrows (cm-scale) preserved in magadiite in the High Magadi Beds are filled with mud, silt and sand from overlying sediments. Their stratigraphic context reveals upward-shallowing cycles from mud to interlaminated mud-magadiite to magadiite in dm-scale units. The burrows were formed when the lake floor became fresher and oxygenated, after a period when magadiite precipitated in shallow saline waters. The burrows, probably produced by beetles, show that trace fossils can provide evidence for short-term (possibly years to decades) changes in the contemporary environment that might not otherwise be recognised or preserved physically or chemically in the sediment record. [1]

Magadi township lies on the lake's east shore, and is home to the Magadi Soda factory, owned by Tata India since December 2005. This factory produces soda ash, which has a range of industrial uses.

The lake is featured in Fernando Meirelles's film The Constant Gardener , which is based on the book of the same name by John le Carré, and is used as a stand-in for Lake Turkana in the north of Kenya, where the book and film are set.

A causeway that crosses the lake provides access to the area west of the lake (Nguruman Escarpment). Recently accommodation for tourists is provided in air conditioned canvas tents.

See also

Related Research Articles

Natron Carbonate mineral

Natron is a naturally occurring mixture of sodium carbonate decahydrate (Na2CO3·10H2O, a kind of soda ash) and around 17% sodium bicarbonate (also called baking soda, NaHCO3) along with small quantities of sodium chloride and sodium sulfate. Natron is white to colourless when pure, varying to gray or yellow with impurities. Natron deposits are sometimes found in saline lake beds which arose in arid environments. Throughout history natron has had many practical applications that continue today in the wide range of modern uses of its constituent mineral components.

Chert Hard, fine-grained sedimentary rock composed of cryptocrystalline silica

Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.

Sodium carbonate Chemical compound

Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals) is the inorganic compound with the formula Na2CO3 and its various hydrates. All forms are white, odourless, water-soluble salts that yield moderately alkaline solutions in water. Historically, it was extracted from the ashes of plants growing in sodium-rich soils. Because the ashes of these sodium-rich plants were noticeably different from ashes of wood (once used to produce potash), sodium carbonate became known as "soda ash". It is produced in large quantities from sodium chloride and limestone by the Solvay process.

Lake Natron Alkaline lake in Arusha Region, Tanzania

Lake Natron is a salt or alkaline lake located in north Ngorongoro District of Arusha Region in Tanzania. It is in the Gregory Rift, which is the eastern branch of the East African Rift. The lake is within the Lake Natron Basin, a Ramsar Site wetland of international significance.

Rift Valley lakes Group of lakes in the East African Rift

The Rift Valley lakes are a series of lakes in the East African Rift valley that runs through eastern Africa from Ethiopia in the north to Malawi in the south, and includes the African Great Lakes in the south. These include some of the world's oldest lakes, deepest lakes, largest lakes by area, and largest lakes by volume. Many are freshwater ecoregions of great biodiversity, while others are alkaline "soda lakes" supporting highly specialised organisms.

Salt lake Landlocked body of water which has a high concentration of salts

A salt lake or saline lake is a landlocked body of water that has a concentration of salts and other dissolved minerals significantly higher than most lakes. In some cases, salt lakes have a higher concentration of salt than sea water; such lakes can also be termed hypersaline lakes, and may also be pink lakes on account of their colour. An alkalic salt lake that has a high content of carbonate is sometimes termed a soda lake.

Trona Hydrated sodium carbonate mineral

Trona (trisodium hydrogendicarbonate dihydrate, also sodium sesquicarbonate dihydrate, Na2CO3•NaHCO3•2H2O) is a non-marine evaporite mineral. It is mined as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production.

Lake Bogoria Body of water

Lake Bogoria is a saline, alkaline lake that lies in a volcanic region in a half-graben basin south of Lake Baringo, Kenya, a little north of the equator. Lake Bogoria, like Lake Nakuru, Lake Elementeita, and Lake Magadi further south in the Rift Valley, and Lake Logipi to the north, is home at times to one of the world's largest populations of lesser flamingos. The lake is a Ramsar site and Lake Bogoria National Reserve has been a protected National Reserve since November 29, 1973. Lake Bogoria is shallow, and is about 34 km long by 3.5 km wide, with a drainage basin of 700 km2. It is Located in Baringo County.

Thermonatrite

Thermonatrite is a naturally occurring evaporite mineral form of sodium carbonate, Na2CO3·H2O.

Lake Abert A highly-saline lake in Oregon, United States

Lake Abert is a large, shallow, alkali lake in Lake County, Oregon, United States. It is approximately 15 mi (24 km) long and 7 mi (11 km) wide at its widest point. It is located 3 mi (4.8 km) northeast of the small, unincorporated community of Valley Falls, Oregon. The lake was named in honor of Colonel John James Abert by explorer John C. Fremont during his 1843 expedition into Central Oregon. No fish live in the alkaline waters of the lake; however, its dense population of brine shrimp supports a variety of shorebirds. The lake is also an important stop on the bird migration route known as the Pacific flyway.

Lake Logipi is a saline, alkaline lake that lies at the northern end of the arid Suguta Valley in the northern Kenya Rift. It is separated from Lake Turkana by the Barrier volcanic complex, a group of young volcanoes that last erupted during the late 19th century or early 20th century. Saline hot springs discharge on the northern shoreline of Lake Logipi and at Cathedral Rocks near its southern limit, and help to maintain water at times of extreme aridity. During the rainy season, the lake is also recharged from the Suguta River which flows northward along the Suguta Valley, periodically forming a temporary lake that unites with Logipi.

Lake Elmenteita Lake in Kenya

Lake Elmenteita is a soda lake, in the Great Rift Valley, about 120 km northwest of Nairobi, Kenya.

<i>Alcolapia</i> Genus of fishes

Alcolapia is a genus of small fishes in the family Cichlidae. Their native range is restricted to margins of Lake Natron and Lake Magadi, as well as similar conditions in nearby hot springs, in Kenya and Tanzania. They live in waters that are warm, hypersaline and alkaline. Species from this genus have also been introduced to Lake Nakuru and Lake Elmenteita. They are the only fish in their range.

<i>Alcolapia grahami</i> Species of fish

Alcolapia grahami, the Lake Magadi tilapia or Graham's cichlid, is a vulnerable species of fish in the family Cichlidae. It is specialised to live in hot, alkaline waters in springs and lagoons around hypersaline lakes.

Magadiite

Magadiite is a hydrous sodium silicate mineral (NaSi7O13(OH)3·4(H2O)) which precipitates from alkali brines as an evaporite phase. It forms as soft (Mohs hardness of 2) white powdery monoclinic crystal masses. The mineral is unstable and decomposes during diagenesis leaving a distinctive variety of chert (Magadi-type chert).

Soda lake Lake that is strongly alkaline

A soda lake or alkaline lake is a lake on the strongly alkaline side of neutrality, typically with a pH value between 9 and 12. They are characterized by high concentrations of carbonate salts, typically sodium carbonate, giving rise to their alkalinity. In addition, many soda lakes also contain high concentrations of sodium chloride and other dissolved salts, making them saline or hypersaline lakes as well. High pH and salinity often coincide, because of how soda lakes develop. The resulting hypersaline and highly alkalic soda lakes are considered some of the most extreme aquatic environments on Earth.

Great Rift Valley, Kenya Part of an intra-continental ridge system that runs through Kenya

The Great Rift Valley is part of an intra-continental ridge system that runs through Kenya from north to south. It is part of the Gregory Rift, the eastern branch of the East African Rift, which starts in Tanzania to the south and continues northward into Ethiopia. It was formed on the "Kenyan Dome" a geographical upwelling created by the interactions of three major tectonics: the Arabian, Nubian, and Somalian plates. In the past, it was seen as part of a "Great Rift Valley" that ran from Madagascar to Syria. Most of the valley falls within the former Rift Valley Province.

Southern Ewaso Ngiro River in Kenya

The Southern Ewaso Ng'iro is a river in the Great Rift Valley in Kenya. It plays an important role in the ecology of Lake Natron, the main regular breeding site for near-threatened lesser flamingos. Changes to land use in the river's headwaters or in the marshes before the river enters the lake could have a serious impact on this species.

Pikrolimni (lake) Endorheic, alkaline salt lake in Kilkis prefecture, Greece

Lake Pikrolimni is an endorheic, alkaline salt lake in Kilkis prefecture, Greece. It is located on the border of the Kilkis and Thessaloniki regional units, about 40 km northwest of Thessaloniki. The lake is hypersaline, has rather shallow waters (0.5–0.7 m) and a shoreline of about 8.5 km. The water surface area shows significant seasonal variation (3.2–4.5 km2) due to evaporation in the summer months, with an average value of 3.7 km2.

Kenyaite is a mineral and is a peculiar sodium silicate having a layered structure. It has a chemical formula of Na2Si22O41(OH)8 • 6H2O, which means it is made up of variations of different materials including sodium, silicon, hydrogen, and oxygen. The chemical composition of kenyaite is subject to change: when the interlayer of water has different variations; it undergoes different physical conditions; by partial to full exchange of the sodium ions by protons when kenyaite comes into contact with water. This is typical for intracrystalline reactive materials.

References

  1. ↑ Buatois, Luis A.; Renaut, Robin W.; Owen, Richard Bernhart; Behrensmeyer, Anna K.; Scott, Jennifer J. (2020-04-22). "Animal bioturbation preserved in Pleistocene magadiite at Lake Magadi, Kenya Rift Valley, and its implications for the depositional environment of bedded magadiite". Scientific Reports. 10 (1): 6794. doi: 10.1038/s41598-020-63505-7 . ISSN   2045-2322. PMC   7176717 . PMID   32321943.
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