Written by: Ethan Kinsey
Just the fact that they are active makes Nyiragongo at 3,740m and Oldonyo Lengai at 2,980m incredibly fascinating volcanoes. But Matembezi Safaris explains why there’s a lot more that makes these volcanoes unique.
Nyiragongo is found in the eastern Democratic Republic of Congo and Oldonyo Lengai is found in northern Tanzania – although they both make up part of the Great Rift Valley, each of them is found in a different arm of the valley.
Oldonyo Lengai is found in the Gregory rift, which was named after J.W. Gregory, a geologist who first coined the word “Rift Valley” back in 1896, while Nyiragongo is found in the Albertine rift, which is named after the Belgian King Albert I who ruled Belgium and Congo after King Leopold II. King Albert created the first national park in Africa, which is now called Virunga National Park.
Neither volcano stands alone
Oldonyo Lengai is part of a series of volcanoes found in a section of the rift called the Northern Tanzania Divergence and is one of more than 28 volcanoes including Kibo, the highest peak in Africa, and Ngorongoro, the world’s largest unbroken caldera. Nyiragongo, on the other hand, is part of a chain of 10 volcanoes in the Virunga field that actually includes another active volcano called Nyamulagira which last erupted in 2012. The extinct volcanoes in this chain are home to the last mountain gorillas.
Both volcanoes boast unique lava
Oldonyo Lengai’s lava is unique as it is the only volcano in the world that has erupted carbonatite lava in recorded history. In addition to this, it is also the coolest lava in the world as it erupts at a temperature of only about 500-600ºC, whereas most lavas are over 1000ºC. The carbonatite lava is also natrocarbonatite, which means that it is high in sodium and very low in silica – only 3% compared to 36-40% in Nyiragongo. Normally lavas that are low in silica are very liquid and not very explosive, like the lava in Nyiragongo, as the gases can escape easily. However, the unique composition of Oldonyo Lengai’s lava actually makes it absorb a lot of carbon dioxide, which then makes it highly explosive. Scientists are still trying to figure out where it comes from and why it is so unique, but it resembles something very similar to what’s happening on the surface of Venus.
Nyiragongo boasts the most liquid lava in the world that bubbles like a kaleidoscope in the world’s largest permanent lava lake at 200m in diameter. The lava, although much higher in silica than at Oldonyo Lengai, is actually relatively low in silica compared with other basalt lavas. It is also quite alkaline and volcanologists studying the lava think it’s actually a direct link to a plume in the earth’s mantle, as Nyamulagira, which is only a few kilometres away, has totally different lava.
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