A Volcanic Geyser of Motor Oil: The Unusual Lava Flows of Ol Doinyo Lengai in Tanzania

Ol Doinyo Lengai, a unique volcano in Africa, is known for its unusual black lava that flows like motor oil during eruptions. This volcano is located in northern Tanzania on the East African Rift and is the only known volcano to erupt carbon-based lava known as natrocarbonatite lava.

Unlike most volcanoes that spew red-hot silicate lava, Ol Doinyo Lengai’s black lava is viscous and can remain liquid at temperatures as low as 540 degrees Celsius due to its high carbonate mineral content. The resulting streams of liquid lava are filled with dissolved CO2 and other gases that bubble like carbonated water during eruptions. Despite its relatively low silicate content, Ol Doinyo Lengai’s lava remains extremely viscous and gives it the appearance of spewing black motor oil.

This tectonically active volcano has two vents, but only the northern vent erupts. The most recent eruption began in April 2017 and was ongoing as of March 2024. A team of volcanologists studying gas samples from the volcano in 2009 found that the composition of the gases was similar to those spewed from mid-ocean ridges, suggesting that the carbon-based lava is produced by minerals melting in the upper mantle.

Ol Doinyo Lengai is just one of many geological wonders in the East African Rift, a giant crack in the African plate that is slowly moving apart and could eventually tear Africa in half, creating a new ocean. In addition to Ol Doinyo Lengai, this tectonic activity has also created other towering mountains in the region such as Mount Kilimanjaro and Mount Kenya.