- Lake Nyos
- 1600–1800 people
- Cameroon ()
The lake responsible for the most deaths without drowning is Lake Nyos in Cameroon, Central Africa. On the night of 21 August 1986, between 1,600 and 1,800 people and countless animals were killed by a large natural release of carbon dioxide gas.
Scientists disagree on the source of the deadly gas within Lake Nyos. Some believe that the decomposition of organic material near the bottom of the lake causes the gas to build up, and seasonal changes in surface temperature triggers mixing of deep and shallow water, allowing the gas to be released. Because Nyos lies in the crater of an old volcano, others believe that the gas is volcanic in origin. Somehow, the pressure of the submerged gas reached a tipping point. It shot to the surface and up to a height of around 300 feet (91.4 metres), then passed down into the surrounding valleys, suffocating those living in villages nearby, along with livestock.