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Report on Ol Doinyo Lengai (Tanzania) — 5 September-11 September 2007

Ol Doinyo Lengai

Smithsonian Institution / US Geological Survey
Weekly Volcanic Activity Report, 5 September-11 September 2007
Managing Editor: Sally Sennert.

Please cite this report as:

Global Volcanism Program, 2007. Report on Ol Doinyo Lengai (Tanzania) (Sennert, S, ed.). Weekly Volcanic Activity Report, 5 September-11 September 2007. Smithsonian Institution and US Geological Survey.

Weekly Report (5 September-11 September 2007)

Ol Doinyo Lengai


2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)

An eruption of Ol Doinyo Lengai on 4 September produced an ash plume that was reported by a pilot and visible on satellite imagery. Ashfall lasted about 12 hours in the village of Engare Sero, about 18 km N. Dark areas on the NW, W, and E flanks that were noticeable on satellite imagery from 4 September were possibly due to recent lava flows and burned vegetation or both. An ash plume was also visible, drifting SSW.

Multiple thermal anomalies at and around the summit were present on satellite imagery since 21 August 2007, and on the flanks on 31 August and 1 September.

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.

Sources: Greg Vaughan, Jet Propulsion Laboratory, Thomas M. Holden, Nature Discovery, The Guardian News, Ol Doinyo Lengai (Fred Belton), Frank Moeckel, Matthieu Kervyn, Mercator and Ortelius Research Center for Eruption Dynamics, Ghent University