Ol Doinyo Lengai

Coordinates: 2°45′50″S 35°54′50″E / 2.764°S 35.914°E / -2.764; 35.914
Source: Wikipedia, the free encyclopedia.
Ol Doinyo Lengai (Oldoinyo Lengai)
Highest point
Elevation2,962 m (9,718 ft)[1]
Prominence1,360 m (4,460 ft) Edit this on Wikidata
Isolation16.68 km (10.36 mi) Edit this on Wikidata
Coordinates2°45′50″S 35°54′50″E / 2.764°S 35.914°E / -2.764; 35.914[1]
Geography
Ol Doinyo Lengai (Oldoinyo Lengai) is located in Tanzania
Ol Doinyo Lengai (Oldoinyo Lengai)
Ol Doinyo Lengai (Oldoinyo Lengai)
Parent rangeEast African Rift
Geology
Mountain typeStratovolcano
Last eruption2023 AD

Ol Doinyo Lengai is an active volcano in northern Tanzania. It consists of a volcanic cone with two craters, the northern of which has erupted during historical time. Uniquely for volcanoes on Earth, it has erupted natrocarbonatite,[2] an unusually low temperature and highly fluid type of magma. Eruptions in 2007–2008 affected the surrounding region.

Name

The

Engai, who withdrew there after being hit by a hunter with an arrow.[3] Other names are Basanjo, Donjo Ngai, Duenjo Ngai, Mongogogura, Mungogo wa Bogwe, and Oldonyo L'Engai.[4]

Geography and geomorphology

Ol Doinyo Lengai lies in the Arusha region of Tanzania,[5] 16 kilometres (9.9 mi) south of Lake Natron[6] and 120 kilometres (75 mi) northwest of the city of Arusha.[7] The summit was first explored between 1904 and 1915.[8] As of 2012, about 300,000 people live in the region, and livestock farming is the most important economic activity, although tourism is increasingly important.[9]

Ol Doinyo Lengai is a symmetric cone

parasitic vents on Ol Doinyo Lengai's flanks,[15] such as Kirurum Crater on the western, the Nasira cones on the northern, Dorobo crater on the northeastern, and Oltatwa Crater on the eastern flank.[16]

There are deposits of past

debris avalanches around the volcano, especially on its northern flank;[17] one such event has left a scar on the volcano's flanks.[18] Their occurrence may have been influenced by regional fault systems.[19]

Geology

Ol Doinyo Lengai is part of the

continental rift extending from eastern to southern Africa over a length of 4,000 kilometres (2,500 mi),[20] where there is high heat flow through a thinner crust.[21] In the Gregory Rift, spreading began about 1.2 million years ago[20] and is ongoing at a rate of about 3 millimetres per year (0.12 in/year).[22] The Natron Fault, the western boundary of the Gregory Rift in the area, passes just southwest of the volcano.[23]

The volcano is part of the

Kilimanjaro mountain east of the volcano.[10]

Composition

Most of the volcanic cone is formed by

carbonatitic lavas[d] during historical times,[1] although these rocks make up only a small fraction of the volcano[15] and only occur in the northern crater;[e][27] they only recently appeared on the volcano.[13] The properties of Ol Doinyo Lengai's magmas have been used as an analogue for the conditions on carbon planets; these are planets which are rich in carbon.[21]

Chemical composition:

The carbonatite lavas are rapidly

zeoliths.[34]

The chemical composition of the erupted rocks is not steady, with an increase of silicic magma emplacement noted after 2007-2008, after an episode of increased spreading in the Gregory Rift.[35] The carbonatitic magmas appear to form through the separation of carbon-rich phases; the original magma is variously interpreted to be either nephelinitic or silicic.[21] The phonolites appear to have a separate origin from the other volcanic rocks.[36] There appear to be two magma reservoirs under the volcano,[37] and its plumbing system is complex, involving regional tectonic structures.[38]

Volcanic gases

Volcanic gas sampled at Ol Doinyo Lengai consists mostly of water vapor and carbon dioxide and originates in the mantle.[39] The volcano is a major source of volcanic carbon dioxide, producing about 80 kilograms per second (11,000 lb/min) of CO
2.[26]

Eruption history

before present produced a tephra fallout west of Ol Doinyo Lengai, that is presently being eroded by wind and forming dunes including the Shifting Sands of the Olduvai Gorge.[43] A large eruption deposited the Namorod Ash in the gorge, about 1,250 years ago,[34] and another about 600 years ago formed the so-called "Footprint Tuff".[34] Ol Doinyo Lengai is the only presently active volcano of the Gregory Rift.[10]

Records of eruptions go back to the 1880s.

gullies into volcanic deposits.[48] Steam jets have also been observed.[45]

There is evidence of underground magma intrusions.[22] Satellite observations have shown deformation of the volcano during eruptions,[49] and ground-based observations have identified movement in neighboring fault systems such as the Natron Fault caused by magma originating at Ol Doinyo Lengai.[50]

Recent eruptive period: 1983 and subsequent

Summit of Ol Doinyo Lengai in February, 2006

After a phase of quiescence,[26] renewed activity commenced in 1983 and continues[11] with several interruptions to this day.[51] During the 1983 eruption, ashfall occurred at tens of kilometers from the volcano.[26] The emission of a lava flow onto the western flank of Ol Doinyo Lengai in 2006 was accompanied by the formation of a pit crater on the summit.[52]

A large

seismic activity, which was frequently mistaken for renewed eruptions,[62] and the intrusion of a dyke less than 20 kilometres (12 mi) from Ol Doinyo Lengai.[38]

General appearance of lava flows

White surface of solidified lava flows at Ol Doinyo Lengai, August 2001

Lavas erupted by Ol Doinyo Lengai initially have brown or black colors, but within days[45] to hours become white like snow.[11] The lavas of Ol Doinyo Lengai have temperatures of 540–593 °C (1,004–1,099 °F);[5] they are so cold that during the day they look like mudflows[i] or oil and glow only during the night.[7] They are highly fluid (reaching flow speeds of 1–5 metres per second (3.3–16.4 ft/s),[5] making them the most liquid known lavas) and form short (few tens of meters) and thin (few centimeters thick) lava flows.[11] More viscous flows containing silicic rocks have also been observed, for example during the 1993 eruption.[64]

Hazards

Potential threats from Ol Doinyo Lengai eruptions are scarcely established.

GNSS stations.[66]

Climate and vegetation

Vegetation in the area consists mostly of grassland, which reaches an elevation of 1,750 metres (5,740 ft) above sea level.[9] Volcanic ash from Ol Doinyo Lengai influences the surrounding landscape, favoring the growth of nutrient-rich plants.[67] Precipitation falls during two wet seasons in March–May and October–December.[9]

Gallery

  • Ol Doinyo Lengai erupting in March 2008
    Ol Doinyo Lengai erupting in March 2008
  • Satellite image of Ol Doinyo Lengai after an explosive eruption
    Satellite image of Ol Doinyo Lengai after an explosive eruption
  • Ol Doinyo Lengai in February 2012
    Ol Doinyo Lengai in February 2012
  • Aerial photo of Oldoinyo Lengai in January 2011
    Aerial photo of Oldoinyo Lengai in January 2011
  • Image of 1966 eruption
    Image of 1966 eruption
  • Crater of Ol Doinyo Lengai in January 2011
    Crater of Ol Doinyo Lengai in January 2011

See also

Notes

  1. ^ Known as hornitos.[13]
  2. ^ The Naibor Soito monogenetic volcanic field lies between Gelai and Ol Doinyo Lengai.[25]
  3. ^ Together they make up more than 90% of the cone.[13]
  4. ^ Carbonatites are magmas that consist of carbonate compounds.[10] At Ol Doinyo Lengai, they are made up of nyererite (Na
    2    Ca(CO
    3    )
    2    ) and gregoryite ((Na
    ,    K
    ,    Ca)
    2    CO
    3    ).[5]
  5. ^ Silicic lavas mostly issued from the southern crater.[13]
  6. ^ The volcanic rocks contain up to several percent chlorine and fluorine by weight.[33]
  7. ^ Eruptions have been recorded in 1880, 1894 (?), 1904, 1913-15, 1917, 1921, 1926, 1940-41, 1954-55, 1958, and 1960.[45]
  8. ^ 1966 saw explosive eruptions in August and October, which formed a deep crater.[11]
  9. ^ And have been confused for mud by non-volcanologists.[63]

References

  1. ^ a b c d e f g GVP 2023, General Information.
  2. ^ Keller & Kraft 1990, p. 629.
  3. ^ Bernbaum 2022, p. 183.
  4. ^ GVP 2023, Synonyms & Subfeatures.
  5. ^ a b c d e f McFarlane, Lundberg & Belton 2004, p. 98.
  6. ^ Mangler et al. 2014, p. 43.
  7. ^ a b c Muthama, Mathu & Kamau 2012, p. 8.
  8. ^ Zaitsev, Keller & Billström 2009, p. 303.
  9. ^ a b c d e Rey et al. 2021, p. 72.
  10. ^ a b c d e Nyamweru 1988, p. 603.
  11. ^ a b c Sekisova et al. 2015, p. 1719.
  12. ^ a b c d e Gilbert & Williams-Jones 2008, p. 520.
  13. ^ Kervyn et al. 2010, p. 921.
  14. ^ a b c d e Mangler et al. 2014, p. 44.
  15. ^ Klaudius & Keller 2006, p. 174.
  16. ^ a b Delcamp et al. 2015, p. 7.
  17. ^ Delcamp et al. 2015, p. 8.
  18. ^ Delcamp et al. 2015, p. 17.
  19. ^ a b c Mollel & Swisher 2012, p. 274.
  20. ^ a b c Radebaugh, Barnes & Keith 2020, p. 1.
  21. ^ a b Jones et al. 2019, p. 2517.
  22. ^ Jones et al. 2019, p. 2522.
  23. ^ Mollel & Swisher 2012, p. 276.
  24. ^ Ho & Wauthier 2022.
  25. ^ a b c d Oppenheimer 1998, p. 55.
  26. ^ Klaudius & Keller 2006, p. 173.
  27. ^ Oppenheimer 1998, p. 60.
  28. ^ Morogan & Martin 1985, p. 1114.
  29. ^ Robertson et al. 2014.
  30. ^ Gilbert & Williams-Jones 2008, p. 524.
  31. ^ Zaitsev, Keller & Billström 2009, p. 302.
  32. ^ Mangler et al. 2014, p. 51.
  33. ^ a b c Hay 1989, p. 80.
  34. ^ Jones et al. 2019, p. 2518.
  35. ^ Mangler et al. 2014, p. 48.
  36. ^ Daud Masungulwa et al. 2021.
  37. ^ a b Biggs et al. 2021, p. 3.
  38. ^ a b c Fischer et al. 2006.
  39. ^ Mollel & Swisher 2012, p. 278.
  40. ^ Klaudius & Keller 2006, p. 176.
  41. ^ Hay 1989, p. 78.
  42. ^ Makongoro et al. 2022, p. 209.
  43. ^ Meshili & Kwon 2020, p. 401.
  44. ^ a b c Nyamweru 1988, p. 604.
  45. ^ Nyamweru 1990, p. 389.
  46. ^ Kervyn et al. 2010, p. 926.
  47. ^ Nyamweru 1990, p. 387.
  48. ^ GVP 2023, Deformation history.
  49. ^ Jones et al. 2019, p. 2525.
  50. ^ GVP 2023, Eruption history.
  51. ^ Kervyn et al. 2010, p. 915.
  52. ^ a b Kervyn et al. 2010, p. 914.
  53. ^ Laxton 2020, p. 438.
  54. ^ Kervyn et al. 2010, p. 924.
  55. ^ Muthama, Mathu & Kamau 2012, p. 9.
  56. ^ Muthama, Mathu & Kamau 2012, p. 15.
  57. ^ Vye-Brown et al. 2014, p. 4.
  58. ^ a b Vye-Brown et al. 2014, p. 25.
  59. ^ Vye-Brown et al. 2014, p. 2.
  60. ^ Biggs et al. 2021, p. 9.
  61. ^ Kervyn et al. 2010, p. 916.
  62. ^ Nyamweru 1988, p. 610.
  63. ^ Dawson et al. 1994, p. 799.
  64. ^ Rey et al. 2021, p. 79.
  65. ^ a b Dye et al. 2022, p. 30.
  66. ^ Morrison & Bolger 2014, p. 619.

Sources

External links
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