Lake Nyos was the site of the deadly 1986 limnic eruption in Cameroon.
On August 21, 1986, Lake Nyos suddenly released a huge cloud of carbon dioxide that had accumulated in deep water. The gas flowed into nearby valleys and suffocated about 1,700 people, along with thousands of livestock. The event is known as a limnic eruption, or lake overturn.
Lake Nyos sits in a volcanic region where carbon dioxide from underground magma can dissolve into deep lake water. Because the deep water was not regularly mixed, the gas remained trapped under pressure until the lake was disturbed and rapidly overturned.
A related disaster occurred at Cameroon’s Lake Monoun in 1984, where a similar gas release killed dozens of people. Degassing pipes were later installed at Lake Nyos to remove carbon dioxide gradually and reduce the risk of another catastrophic buildup.