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). See the photograph to the right, taken by Gordon Davies in August 1966.

During the climb on 21st August, the lower slopes were covered with about half an inch of new, snow white ash which reached a thickness of about 2 inches closer to the summit. The active crater was full of swirling ash and dust. In it was a new ash cone in whose summit was a shallow bowl-shaped pit about 100 yards in diameter. In the centre of this pit was a small double vent from which there was a continuous discharge of gas and whitish-grey ash and dust. There was a continuous roaring noise and a strong smell of sulphur. Ash was scattered all over most of the inside of the crater and there was about 6 inches of new black ash on the outer slopes of the east rim. The crater was observed from 10.30 a.m. to 1.50 p.m., during which period no lava extrusion was seen, and the ejected material was not larger than ash size.The photograph below (taken by Gordon Davies) shows the active crater in August 1966.

At 2.45 p.m. on 21st August there was a violent harsh explosion and a dense column of black ash rose vertically above the crater. A series of loud explosions occurred at intervals of less than 15 seconds, each one accompanied by the expulsion of more ash. This continued until about 4.0 p.m., when the explosions ceased, though the ejection of ash continued all that day and throughout the night.

At 11.30 a.m. on 22nd August, when these observations ended, the pine-tree shaped cloud of a Plinian-type eruption was towering above the volcano.

On the morning of 23rd August activity had almost ceased; only a small amount of ash was rising to a few hundred feet above the volcano. The ash cone within the northern crater had grown higher.

On 1st September another violent ash eruption was reported.

On 3rd and 4th September activity continued; a column of ash rose above the volcano and drifted away to the north. The summit crater was almost infilled with ash, though there was still a deep pit in its centre.

On 11th October the volcano was still active; the local Maasai pastoralists and the wild game animals had moved out of the area, probably because the water and grazing supplies were contaminated by the ash. The photograph to the right, taken by Joan Westenberg in August 1966, shows the thickness of ash on the lower slopes of the volcano. Ash fall was reported as far as Seronera (130 km west), Loliondo (70 km north-west) and Shombole (70 km north).

On 28th October the volcano was seen to be covered with white ash, and was still active, with a light plume of ash blowing away to the north-west.

Observations in late December 1966 and on 1st January 1967 established that there was no activity.

A major explosive eruption was reported on 8 - 9th July 1967. Ash fell at Arusha (110 km southeast) and at Wilson Aerodrome in Nairobi, 190 km to the northeast. After this the volcano seems to have remained dormant for several years. Click here to see what happened in 1983.