Trou au Natron
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Trou au Natron (French: "hole of natron") or Script error: No such module "Lang". (Teda: "big hole")[1] is a volcanic caldera of the Tibesti Massif in the nation of Chad in Northern Africa.[2][3] The volcano is extinct. It is unknown when it last erupted.[4][5] Its volcano number is 0205–01.[6] Trou au Natron is located just south-east of Toussidé, the westernmost volcano of the Tibesti Mountains. Its edge cuts into the nearby Yirrigue caldera.
Geology
The caldera sits at an elevation of Template:Cvt.[7] It has an irregular diameter of approximately Template:Cvt and is up to Template:Cvt deep.[2] Four smaller volcanic cones, made of scoria or andesitic tuff sit on the floor of the caldera.[2][8] Numerous smaller vents and hot springs on the caldera's floor emit hot steam and mineral water.[2]
Because of its irregular shape, it has been theorized that the caldera was formed as a result of multiple massive explosions, each of which deepened the enormous pit.[2] During these explosions, chunks of debris up to Template:Cvt in size may have been hurled up to Template:Cvt from the crater.[2] Its exact period of formation is unconfirmed, although a Pleistocene formation has been suggested.[6] It is known to be one of the youngest formations on the Tibesti Massif.[4]
Much of the surface of the caldera is lined with a white crust of carbonate salts such as sodium carbonite and natrolite.[8] This substance is also known as natron, leading to the French name for the site. This crust is sometimes known as the Tibesti Soda Lake.[2][9] The crusts are formed when mineral-rich steam is emitted from small vents on the crater's floor. When this water evaporates in the desert heat, the minerals remain behind as part of the crust.[2]
Both the slopes and the floor of the caldera contain thick layers of fossilized aquatic gastropods and diatoms, indicating that the caldera was once home to a deep lake. During the Last Glacial Maximum, the lake may have been up to Template:Cvt deep. Radiocarbon dating on some of these samples indicates an age of approximately 14,500–15,000 years Before Present.[10]
Gallery
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Satellite image of Trou au Natron via Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER)
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Satellite image of the Tousside volcano (large dark area in centre). Trou au Natron is visible below and to the right (smaller white area).
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Satellite overview of the Tibesti Massif. Trou au Natron is located to the left; it is highlighted in the full-size view of the image.
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Overview of Trou au Natron's caldera from its summit
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References
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