- Location
- Northwest Cameroon
- Water
- Lake Nyos
- Period
- 21 August 1986
- Case status
- Explained
- Last reviewed
- November 5, 2026
Mass loss of life; no graphic descriptions. The gas-release mechanism is supported by research, while the initiating trigger requires separate treatment.
The event
On 21 August 1986, a catastrophic gas release from Lake Nyos caused at least 1,700 deaths. Kling and colleagues’ 1987 investigation identified carbon dioxide accumulated in the lake’s deep water and reported evidence consistent with carbon-dioxide asphyxiation. Their findings did not require a direct volcanic eruption at the time of the disaster.
The distinction is essential. A volcanic setting can supply gas to a lake without an eruption being the immediate cause of a fatal release.
What the water retained
A separate 1987 geochemical study by Kusakabe and Ohsumi reported that the lake remained stratified around fifty days after the disaster. Its authors described carbon-dioxide-rich deep water rising and releasing gas near the surface. They proposed an increase in warm, gas-bearing groundwater as a possible trigger; the proposal should not be treated as a witnessed event.
Where explanation stops
Identifying the gas and its storage is different from reconstructing the first disturbance. This entry treats the physical mechanism as explained and preserves uncertainty about the initiating sequence. The source abstracts were checked; the full papers have not been reviewed here.
Documented timeline
Open an event to read its account and supporting source. Dates may be approximate.
21 August 1986 A catastrophic gas release Documented
The event caused at least 1,700 deaths around Lake Nyos.
Source: The 1986 Lake Nyos gas disaster in Cameroon, West Africa
About fifty days later Water chemistry surveyed Documented
Sampling found that most of the lake remained layered by temperature and chemistry.
1987 Research findings published Documented
Investigators linked the disaster to stored carbon dioxide and examined possible triggers.
Source: The 1986 Lake Nyos gas disaster in Cameroon, West Africa
Sources & records
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The 1986 Lake Nyos gas disaster in Cameroon, West Africa
Original research, DOI 10.1126/science.236.4798.169. Abstract checked; full paper not examined. Fatality figure follows this paper’s stated lower bound.
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Outburst of carbon dioxide from Lake Nyos, Cameroon
Original research, DOI 10.14934/chikyukagaku.21.39. Abstract checked; full paper not examined. The suggested groundwater trigger is a hypothesis.