Ol Doinyo Lengai

Ol Doinyo Lengai is an active volcano in Tanzania's Arusha Region, about 16 kilometers south of Lake Natron, rising to an elevation of 2,962 meters and standing more than 1,800 meters above the surrounding East African Rift floor. It is the only volcano on Earth known to have erupted natrocarbonatite lava in historical times, an unusually fluid, sodium-and-carbonate-rich magma that erupts at a comparatively low temperature of roughly 540 to 593 degrees Celsius and is the least viscous lava known, capable of flowing at 1 to 5 meters per second in thin, short-lived flows. Its cone is built largely from melilite, nephelinite and phonolite rock, with the carbonatite lavas themselves containing fluorite and sylvite alongside accessory minerals such as apatite, galena and magnetite. Radiometric dating shows volcanic activity beginning somewhere between 500,000 and 22,000 years ago, with the volcano reaching roughly its present shape about 15,000 years ago; recorded eruptions go back to the 1880s, with notable activity in 1983, 2007-2008 and into 2024. This entity documents Ol Doinyo Lengai specifically as a geological formation defined by its unique carbonatite volcanism.