Report on Ol Doinyo Lengai (Tanzania) — 6 February-12 February 2008
Smithsonian / US Geological Survey Weekly Volcanic Activity Report,
6 February-12 February 2008
Managing Editor: Sally Kuhn Sennert
Please cite this report as:
Global Volcanism Program, 2008. Report on Ol Doinyo Lengai (Tanzania). In: Sennert, S K (ed.), Weekly Volcanic Activity Report, 6 February-12 February 2008. 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 Frederick Belton's Ol Doinyo Lengai website, a local camp manager reported to a visitor, that several large explosive eruptions accompanied by "bangs" on 1 February. The manager noted that ash plumes were originating from a location in the crater that was further N than previous locations. The visitor saw ash plumes on 3 February that rose to altitudes of 3.2-3.3 km (10,500-10,800 ft) a.s.l. The next day, an ash plume rose to an altitude of 4.3 km (14,100 ft) a.s.l. Eruptions also occurred on 6 February.
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.
Source: Ol Doinyo Lengai (Fred Belton)