The only volcano on Earth that erupts black lava.

In Africa, the Ol Doinyo Lengai volcano erupts an unusual type of lava that is rich in carbonates, not red-hot but black and viscous like engine oil.

Ol Doinyo Lengai is one of the strangest volcanoes on Earth, and perhaps even in the Solar System. From a distance, the mountain looks unremarkable, but when looking at its northern vent, observers will see it erupting a unique form of black lava that is relatively cool and flows like machine oil.

Located in the East African Rift, north of Tanzania, Ol Doinyo Lengai is the only known active volcano capable of erupting carbon-based lava, or natrocarbonatite. There is some evidence that volcanoes on Venus may have also erupted natrocarbonatite, but on Earth, Ol Doinyo Lengai is the only active volcano of this type.

Most volcanoes erupt lava rich in silicate minerals, causing melting points to reach over 900 degrees Celsius. Ol Doinyo Lengai's lava is relatively low in silicate but contains a high concentration of carbonate minerals, allowing it to remain 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 erupting black motor oil.

Given the viscosity of the lava, scientists were surprised that Ol Doinyo Lengai could erupt so violently. This type of explosive eruption usually occurs in other volcanoes because gas bubbles can get trapped in the thick, viscous lava. Ol Doinyo Lengai was still able to erupt violently with a stream of liquid lava, possibly due to its high content of dissolved CO2 and other gases, causing it to bubble like carbonated water.

With a height of 2,962 meters, this volcano has two vents, but only the northern vent is erupting. The most recent eruption began in April 2017 and is still ongoing, according to the latest report in March 2024.

In 2009, a group of volcanologists collected gas samples from Ol Doinyo Lengai to study its unique carbon-based lava flow. They discovered that its composition was very similar to that of gases erupting from mid-ocean ridges, even though Ol Doinyo Lengai is located quite far inland.

This led the research team to conclude that the carbon-rich lava originated from melted minerals in the upper mantle—the thick layer of rock just below the Earth's crust. "The chemical properties and isotopic composition of the gases suggest that the CO2 originated directly from the upper mantle, beneath the East African Rift Zone," said David Hilton, professor of geochemistry at the Scripps Institution of Oceanography at the University of California San Diego, and co-author of the 2009 study.

The East African Rift has been tectonically active for approximately 25 million years and remains one of the world's most fascinating geological hotspots. It's a massive fissure in the African plate that's pulling apart at a rate of a few millimeters per year. Over time, it could eventually tear Africa in two, creating a new ocean between East Africa and the rest of the African plate. Besides Ol Doinyo Lengai, the East African Rift has also contributed to the formation of many of the region's towering mountains, such as Mount Kilimanjaro and Mount Kenya.

Thu Thao (According to IFL Science )

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