Lake Nyos

The CO2 gas cloud, which was released from Lake Nyos on August 21, 1986, covered a total surface area of 34.6 square kilometers. This value was obtained by detailed mapping of compounds (houses) within the Lake Nyos region from December 1986 to March 1987. Fatalities (pdf)

The gas cloud reached an elevation of 100 meters above the lake surface on the south side. This is the only area where humans and livestock were affected by carbon dioxide, which is at a higher elevation than the lake surface.

The gas flowed over the spillway into Nyos valley from the northwest and the northeast drainage and spread throughout Nyos valley. Of the total volume of the gas released from the lake, 90% passed though Nyos-Acha causing a 98% fatality rate.

The CO2 cloud passed through Nyos-Acha into the narrow valley to the east and west of the Nyos-Acha. Subum is to the east of Nyos-Acha in a flat wide area. There was a 50% fatality rate at Subum. The gas spread throughout the valley heading north following the Kimbi River drainage and south (upriver). To the south, the gas reached as far as Mbonge (Bwabwa). There were no deaths in Mbonge. However, people were affected by the gas on the northern edge of Mbonge.The gas traveled a total distance of 15 km to the east of Lake Nyos.

To the west of Nyos-Acha, the gas flowed into a small valley towards Cha village. Cha had a 45% fatality rate. From Cha the gas flowed north, following the Mbum River, a distance of 21 km from Lake Nyos. Four children died the night of August 21, 1986 at Fang Overside along the Mbum River.

Villagers reported smelling gunpowder (gas) the next day, all the way up to Mashi Overside. One child died the next morning (8/22/86), just before the junction of the Katsina and Mbum River. It is not certain if this fatality was due to the CO2 gas. However, it's conceivable that a pocket of gas flowed slowly downstream along the river.

The following villages were unaffected by the gas: Upper Nyos, Isu Sowe, Cha-mmem, Mbuh, Fang, Bu, Ahar, Koskin, Missong and Mashi.

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