Report on Ol Doinyo Lengai (Tanzania) — 29 March-4 April 2006
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
29 March-4 April 2006
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2006. Report on Ol Doinyo Lengai (Tanzania). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 29 March-4 April 2006. 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 30 March, forcing villagers living near the volcano to evacuate. An article stated that, "Eyewitnesses said they heard a rumbling noise before the volcano began discharging ash and lava, prompting local residents to flee the area in their hundreds. District officials estimated that about 3,000 people from Nayobi, Magadini, Engaruka, Malambo, Ngaresero, Gelai Bomba, and Kitumbeine villages left their homes within a few hours of the eruption..." There were reports of polluted water sources and destroyed vegetation, but no reports of deaths or injuries.
Geological Summary. 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.