Article #12: Volcanic Fish Out of Water

Ol Doinyo Lengai is an unusual volcano that sits in the middle of the sinking Great Rift Valley located on the eastern part of Africa. It is the only volcano, out of the hundreds of active volcanoes in the world that is producing black, runny lava instead of the red, glowing thick lava that we are used to seeing. A team of international researchers think they know what is causing this black lava to form, which has to do with the location of the volcano and the future of the African continent.

The western part of Africa where the Great Rift Valley is located is sinking into the Indian Ocean, as the Ol Doinyo Lengai is raising 3000 meters. Its lava is made of carbonatite, which is free of silicon oxide, which in large amounts produces the blazing hot flaming red flow that is often associated to volcanoes. The carbonatite lava is much cooler and flows easily and rapidly like water. Once the black lava hits the air or water, it turns white. This volcano contains several small fissues inside its cone that vent gas that comes from the mantle deep below the surface, normal volcano vents are larger. The gas collected from these fissures contains carbon dioxide, helium, nitrogen, and argon--indistinguishable from volcanic gas released from vents in the sea floor (Berardelli 2009). Basically, the reason why the lava is dark is because it has characteristics of volcanic activities near the ocean, where the Great Rift Valley is headed.

The reason why the volcano is spilling out thin, runny carbonatite is because of the thin layer of the Earth’s crust beneath the volcano. Carbonatite is a component separated from nephelinite that is able to push through to the surface more easily when the crust is thin. However, the eruption of carbonatite is ending so normal eruptions that contain nephelinite will be switched back.

Citation Information
Berardelli, Phil. 2009 “Volcanic Fish Out of Water” ScienceNOW Daily News[Internet] Washington DC and Cambridge, UK: High Wire Press; 2009 [cited 2009 May 25]. Available from http://sciencenow.sciencemag.org/cgi/content/full/2009/506/1