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Lake Natron is a salt and soda lake in the Arusha Region of northern Tanzania. The lake is close to the Kenyan border and is in the Gregory Rift, which is the eastern branch of the East African Rift.〔("Eastern Africa: Northern Tanzania, on the border with Kenya", World Wildlife Fund, accessed 24 November 2014 )〕 The lake is within the Lake Natron Basin, a Ramsar Site wetland of international significance.〔(Lake Natron Basin, Ramsar Sites Information Service, accessed 25 November 2014 )〕 The lake is fed principally by the Southern Ewaso Ng'iro River, which rises in central Kenya, and by mineral-rich hot springs.〔 It is quite shallow, less than deep, and varies in width depending on its water level. The lake is a maximum of long and wide.〔 The surrounding area receives irregular seasonal rainfall, mainly between December and May totalling per year.〔 Temperatures at the lake are frequently above .〔 High levels of evaporation have left behind natron (sodium carbonate decahydrate) and trona (sodium sesquicarbonate dihydrate). The alkalinity of the lake can reach a pH of greater than 12. The surrounding bedrock is composed of alkaline, sodium-dominated trachyte lavas that were laid down during the Pleistocene period. The lavas have significant amounts of carbonate but very low calcium and magnesium levels. This has allowed the lake to concentrate into a caustic alkaline brine.〔("Alkaline Environments", authored by W. D. Grant and B. E. Jones, in ''Encyclopedia of Microbiology'', editor-in-chief Joshua S. Lederberg, Academic Press, 2010, page 129, accessed 24 November 2014 )〕 The alkaline water in Lake Natron has a pH as high as 10.5 and is so caustic it can burn the skin and eyes of animals that aren't adapted to it. The water's alkalinity comes from the sodium carbonate and other minerals that flow into the lake from the surrounding hills. And deposits of sodium carbonate — which was once used in Egyptian mummification — also acts as a type of preservative for those animals unlucky enough to die in the waters of Lake Natron. Despite media reports, the animals do not simply turn to stone and die after coming into contact with the lake's water. Lake Natron's alkaline waters support a thriving ecosystem of salt marshes, freshwater wetlands, flamingos and other wetland birds, tilapia and the algae on which large flocks of flamingos feed. Photographer Nick Brandt did, however, captured haunting images of the lake and its dead in a book titled "Across the Ravaged Land" (Abrams Books, 2013). (Lake Natron Gives Up Its Dead ) Brandt discovered the remains of flamingos and other animals with chalky sodium carbonate deposits outlining their bodies in sharp relief. "I unexpectedly found the creatures — all manner of birds and bats — washed up along the shoreline of Lake Natron," Brandt wrote in his book. "No one knows for certain exactly how they die, but … the water has an extremely high soda and salt content, so high that it would strip the ink off my Kodak film boxes within a few seconds." "I took these creatures as I found them on the shoreline, and then placed them in 'living' positions, bringing them back to 'life,' as it were," Brandt wrote, referring to the way he repositioned the animals. "Reanimated, alive again in death." ==Flora== The color of the lake is characteristic of those where very high evaporation rates occur. As water evaporates during the dry season, salinity levels increase to the point that salt-loving microorganisms begin to thrive. Such halophile organisms include some cyanobacteria that make their own food with photosynthesis as plants do. The red accessory photosynthesizing pigment in the cyanobacteria produces the deep reds of the open water of the lake and the orange colors of the shallow parts of the lake. The alkali salt crust on the surface of the lake is also often colored red or pink by the salt-loving microorganisms that live there. Salt marshes and freshwater wetlands around the edges of the lake do support a variety of plants. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lake Natron」の詳細全文を読む スポンサード リンク
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