The Tanzanian peak looks like a classic conical volcano from a distance. But instead of the red-hot lava we associate with volcanoes, what pours out of Ol Doinyo Lengai looks more like motor oil. It’s the only active volcano in the world that spews “carbonatite” lava, composed primarily of carbonate minerals rather than more common basalt lava.
Despite its dark hue, carbonatite lava has the lowest viscosity of any known lava, making it extremely runny.
Studies of Ol Doinyo Lengai and its unusual lava may help solve a puzzle related to Venus, which has more than 1,000 volcanoes and a surface riddled with about 200 lava channels. One of these channels is about 4,200 miles long — the longest in the solar system and longer than the Nile. To create such a feature, lava would have to remain fluid over great distances, prompting geologists to suggest that Venusian volcanoes discharge carbonatite lava, just like that one oddball volcano on Earth, Ol Doinyo Lengai.