AfricaOl Doinyo Lengai volcano spews unusual lava rich in carbonate, not red hot but black and viscous like motor oil.
Ol Doinyo Lengai is one of the strangest volcanoes on Earth, even in the solar system. From a distance, this mountain is nothing special, but when looking at the northern vent, observers will see it spewing a unique form of black lava, relatively cool and flowing like motor oil.
Located on the East African Rift in northern Tanzania, Ol Doinyo Lengai is the only active volcano known to erupt carbon-based lava, or natrocarbonatite lava. There is some evidence that volcanoes on Venus may also have spewed natrocarbonatite lava, but on Earth, Ol Doinyo Lengai is the only volcano to do so.
Most volcanoes erupt lava rich in silicate minerals, causing melting temperatures to reach more than 900 degrees Celsius. Ol Doinyo Lengai’s lava is relatively low in silicate but contains a lot of carbonate minerals, allowing the lava to maintain its state. liquid at a temperature of only 540 degrees Celsius. The lack of silicate makes the lava extremely viscous. When an eruption occurs, instead of spewing red-hot lava, the mountain looks like it’s spewing black motor oil.
Given the lava’s viscosity, scientists were surprised that Ol Doinyo Lengai could erupt so violently. This type of explosive eruption is common in other volcanoes because air bubbles can become trapped in thick, viscous lava. Ol Doinyo Lengai can still erupt violently with streams of liquid lava that may be filled with dissolved CO2 and other gases, causing it to bubble like carbonated water.
With a height of 2,962 m, this volcano has two vents, but only the northern vent erupts. The most recent period of eruption began in April 2017 and was still ongoing according to the latest report in March 2024.
In 2009, a team of volcanologists collected gas samples from Ol Doinyo Lengai to study the unique carbon-based lava flow. They discovered that their composition is very similar to gases spewed from mid-ocean ridges, even though Ol Doinyo Lengai is located quite deep inland.
This led the team to conclude that carbon-rich lava is produced by minerals melting in the upper mantle – the thick layer of rock just below the Earth’s crust. “The chemical properties and isotopic composition of the gases show that CO2 originates directly from the upper mantle, below the East African Rift,” said David Hilton, professor of geochemistry at the Scripps Institution of Oceanography. University of California San Diego, co-author of the 2009 study, said.
The East African Rift has been tectonically active for about 25 million years and remains one of the world’s most interesting geological hotspots. This is a giant crack in the African plate that is moving apart at a rate of a few millimeters per year. Over long periods of time, it could eventually tear Africa in half, creating a new ocean between East Africa and the rest of the African plate. In addition to Ol Doinyo Lengai, the East African Rift also contributes to creating many towering mountains in the region such as Mount Kilimanjaro and Mount Kenya.