J.B. Dawson

J.B. Dawson mapped the volcano in 1960 (Dawson 1962) and established the following sequence, from oldest to youngest:

Yellow tuffs and agglomerates with interbedded lavas. These make up the main bulk of the volcano, the result of many episodes of explosive activity. The tuffs are made of crystals of nepheline and pyroxene, set in a fine-grained yellow matrix of zeolite, limonite and carbonate. The lava flows within the pyroclasts are composed of nephelinite and phonolite. These rocks have been correlated with rocks exposed in the Olduvai Gorge succession which range in age from about 0.15 to 0.4 Ma (Dawson et. al 1995).

This eruption was first observed by airline pilots on 14th August 1966, and two geologists, J.B. Dawson and G.C. Clark, visited the volcano six days later and climbed to the active crater rim on 21st August.

The following description of the eruption is drawn from the account by Dawson, Bowden and Clark published in 1968. They first sighted the volcano at 2.30 p.m. on 20th August 1966, when "a Vulcanian-type eruption was in progress. A thick column of black ash was rising for approximately three thousand feet above the volcano and, due to the dominantly southerly wind, was drifting away northwards towards lake Natron; the ash fall was very heavy on the upper northern slopes of the volcano" (page 868).