Oldoinyo Lengai, Tanzania (2.76° S, 35.91° E) is the only active volcano in the world that produces natrocarbonatite lava. These carbonate-rich lavas are unique in that they have relatively low temperatures (500-600 C) compared with typical lavas (600-1100 C). They have low silica content (<1%) and low viscosity, behaving more like a mud flow than a lava flow; in fact they can flow faster than a person can run!

Oldoinyo Lengai (OL) has been erupting on and off since 1983 with effusive carbonatite flows mostly constrained to the summit crater; the last eruption period was in March 2006. Satellite thermal monitoring since June 2007 indicates that another active eruption phase has been ramping up and in early September OL erupted again - this time more explosively than usual, sending ash high into the atmosphere. Explosive ash-producing eruptions at OL are rare (the last one was in the 1960s) and indicate a mixture of natrocarbonatite and more silica-rich volcanic products.

In this ASTER image acquired September 4, 2007 OL can be seen erupting with an ash plume emanating from the summit. Thermal infrared data also confirm a temperature anomaly at the summit. Comparison to a visible image acquired the previous month (August 3, 2007) indicates that the dark areas along the west, northwest, and also east side of the volcano are recent burn scars, likely caused by lava spatter or narrow lava flows down the flanks. ASTER channels 2, 3, and 1 are displayed as R, G, and B, generating this false color image with 15-m pixels (the image covers ~15 km by 14 km, and north is approximately at the top).

ASTER is one of five Earth-observing instruments launched in December 1999 on NASA's Terra spacecraft. The instrument was built by Japan's Ministry of Economy, Trade and Industry and a joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. For more information about ASTER see http://asterweb.jpl.nasa.gov.

OL is one of many volcanoes in the world, and especially Africa that are not regularly monitored. It is only through sporadic reports from tourists in the area and satellite data, like ASTER, that we know anything at all about this volcanic activity.

PSI Associate Research Scientist Dr. R. Greg Vaughan is collaborating with scientists in Africa, Europe and the US to continue monitoring this eruption with high resolution satellite data.

Image credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team.