The Arusha region of Tanzania, in the north of the country and bordering Kenya, is home to many outstanding natural features. Not only is there the second highest mountain in Tanzania after Kilimanjaro, Mount Meru, or the famous Olduvai Gorge whose archaeological and paleontological sites give it the nickname of cradle of humanity.
In addition, Arusha has numerous craters and extinct volcanoes, and one in particular that is still active but is unlike any other volcano in the world.
The Maasai, who have been the people with the majority presence in the area for centuries, call it Ol Doinyo Lengai What does it mean god’s mountain. It has an altitude of 2,960 meters and the age of its volcanic cone is estimated to be around 370,000 years old.
Volcanic lava is normally rich in silicates and rises to the surface at temperatures between 700 and 1,200 degrees Celsius, with the incandescent red glow that is the most common iconography of volcanic eruptions.
but the volcano Ol Doinyo Lengai is different. Here the lava is of a different type (in fact it is the only active volcano with this characteristic). Its unusual composition causes it to erupt at relatively much lower temperatures, between 500 and 600 degrees Celsius, losing its incandescence and appearing dark, black in sunlight, turning gray and even white over time in contact with water. That is why in the past it was often confused with marble.
This type of lava, which is also less viscous than water, produces a strange and deceptive effect when flowing outside.
It is called natrocarbonatite lava and is formed from carbonatite rocks, which have more than 50 percent of their mass composed of minerals derived from carbonic acid.
Precisely the rapid color change from black to greyish, which turns white in a few hours, of this lava is due to the fact that the carbonates it contains (nyerereite and gregorite) are unstable in contact with the atmosphere, and susceptible to rapid weathering or decomposition.
Thus, to the unusual spectacle of the quasi-liquid eruption is added the amazing resulting volcanic landscape, unparalleled in any other part of the world.
The last eruption of Ol Doinyo Lengai it occurred in 2013, during which the crater resulting from previous explosive eruptions in 2007 and 2008 began to fill with natrocarbonatite lava, changing the appearance of the caldera, at least temporarily.
St Lawrence University / Ol Doinyo Lengai, The Mountain of God / Stromboli Online / Wikipedia.