Report on Ol Doinyo Lengai (Tanzania) — 18 July-24 July 2007
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 18 July-24 July 2007
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2007. Report on Ol Doinyo Lengai (Tanzania). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 18 July-24 July 2007. Smithsonian Institution and US Geological Survey.
Ol Doinyo Lengai
2.764°S, 35.914°E; summit elev. 2962 m
All times are local (unless otherwise noted)
According to news reports, an eruption began at Ol Doinyo Lengai around 19 July, forcing villagers living near the volcano to evacuate. An article stated that, "...more than 1,500 people, most of them Maasai families, vacated their homes in Ngaresero, Orbalal and Nayobi villages following the tremors that triggered the volcanic eruption." "Villagers are reported to have heard roaring...before the volcano started discharging ash and lava." There were reports of a damaged school and two injuries, but no reports of deaths.
Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.