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Ol Doinyo Lengai 27 October 2008

Posted by admin in Africa, eruptions, Ol Doinyo Lengai, Tanzania.
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The news that the Evangelical Lutheran Church of Tanzania is to offer 250 tonnes of food aid to people suffering the effects of eruptive activity at Ol Doinyo Lengai volcano in northern Tanzania has drawn my attention to the fact that The Volcanism Blog has so far run no coverage whatsoever of this remarkable and currently active and disruptive African volcano. This report is intended to make some kind of amends for this omission.

Rising 2886m above the Rift Valley, Ol Doinyo Lengai is one of the most fascinating volcanoes in the world. It is unique for erupting not silicate but natrocarbonatite lavas: cool (at ~510°C, about half the temperature of basaltic lavas), very fluid (a viscosity near that of water), and with low incandescence (at night flowing lava looks orange, by day black or brown). When natrocarbonatite lavas come into contact with moisture they turn white, becoming transformed into something akin to washing soda. This is all very unusual: as Andrew Alden remarks in his informative article about Ol Doinyo Lengai at About.com Geology, ‘The more you know about geology, the more mind-boggling Oldoinyo Lengai is’. All this carbonate weirdness produces a volcanic landscape like no other:

Ol Doinyo Lengai crater (Pedro Gonnet, 2007)
Image of Ol Doinyo Lengai crater from August 2007, taken from the south-west, showing recent lava flow. Credit: Pedro Gonnet. [Source and licensing information]

Eruptive activity at Ol Doinyo Lengai is usually effusive rather than explosive, but at times an increased proportion of silicate materials finds its way into the system and produces periods of explosive eruptions. Such a period of explosive activity has been under way since September 2007. Details of Ol Doinyo Lengai’s eruptive history can be found at the Global Volcanism Program and at the very detailed, informative and richly illustrated Ol Doinyo Lengai site run by Frederick A. Belton of Middle Tennessee State University.

The eruptive activity that began in 2007, and which is ongoing, has had a destructive impact on nearby communities. Ash columns have risen to between 3000 and 18300 metres altitude, and heavy ashfall has damaged crops and rendered farms and villages uninhabitable up to a radius of 50km from the volcano, with more than 10,000 people reportedly forced to flee their homes.

Tanzanians flee in volcano fear – BBC News, 19 July 2007
Panic as Oldonyo Lengai spits hot lava – IPP Media, 6 September 2007
Families flee as volcanic Mt Oldonyolengai erupts – IPP Media, 9 March 2008

Global Volcanism Program: Ol Doinyo Lengai – information about Ol Doinyo Lengai (0202-12=)
Ol Doinyo Lengai – latest news, detailed information and many images of Ol Doinyo Lengai at Frederick A. Belton’s site
The Oldoinyo Lengai web site – by Celia Nyamweru of St Lawrence University
Oldoinyo Lengai, world’s weirdest volcano – article at About.com Geology
Strangest volcano on Earth – a National Geographic feature on Ol Doinyo Lengai

The Volcanism Blog