[WORLDKINGS] The Constant World Records Seeking Journey (P.88) Oldoinyo Lengai Volcano : The only volcano to erupt sodium carbonatite lavas in the world

14-01-2021

(WorldKings.org) Oldoinyo Lengai is the only active carbonatite volcano in the world and is known for the unusually alkali-rich composition of its carbonatite lavas. Natrocarbonatite characterises the recent activity which is expressed by the current quiet effusions in the northern summit crater. It is inferred from historical reports that this type of activity goes back more than 100 years (Dawson et al., 1995a).

Based on the world record nomination from Africa Records Institute (AFRI)  and Decision WK/USA.INDIA/642/2021/No.98, World Records Union (WorldKings) officially declared  Oldoinyo Lengai is the only active carbonatite volcano in the world.

Oldoinyo Lengai is located in the eastern branch of the East African Rift System, south of Lake Natron (Fig. 1) and close to the ca. 400 m high Natron Escarpment of the Gregory Rift, which formed 1.2 Ma ago. Volcanic activity in the Gregory Rift started about 10 Ma ago in its northern part and propagated to the SW to the site of recent volcanic activity of Oldoinyo Lengai on the southern edge of the Lake Natron basin.

The summit of the volcano contains two craters, north and south, separated by an east-west aligned ridge. Volcanic activity forming the Younger Extrusives of the Gregory Rift, is thought to have started after the generation of the major North-South fault approximately 1.2 Myrs ago, which now marks the western boundary of the rift valley (Dawson, 2010). The onset of activity has been poorly constrained with age measurements of the oldest pyroclastics (as determined by stratigraphic positioning) at 0.37-0.22 Ma (Bagdasaryan et al., 1973).

The eruptive style of Oldoinyo Lengai is characterized by alternating periods (often months to years) of effusive activity, primarily contained within the northern crater and upper flanks, and explosive phases of Vulcanian / Plinian type volcanism lasting for shorter time periods of weeks to months. The effusive activity is predominantly carbonatitic material whilst explosive episodes can see the release of both alkaline silicate material and soda ash (Keller and Krafft, 1990). During its effusive phases Oldoinyo Lengai generates natrocarbonatite via lava fountains up to a few metres in height (Norton and Pinkerton, 1997, Keller and Krafft, 1990) from active spatter cones generating droplet lapilli. Lava flows from active vents are generally small (<100 m3) with low effusion rates (0.3 m3s-1) (Keller and Krafft, 1990). Interconnected lava lakes within the crater regularly overflow generating further lava flows which can top the crater rim and extend a few hundred metres down the upper flanks.

According to alexstrekeisen


Xiang Yun (Editor) - World Records Union (WorldKings)

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