The Lake Nyos disaster was a carbon dioxide eruption that killed over 1,700 people in Cameroon on Aug. 26, 1986. Carbon dioxide trapped near the bottom of Lake Nyos rose to the surface and escaped into the atmosphere, suffocating people who lived near the lake. The exact cause of the eruption was never determined, but a pump was installed in 2001 to degas the lake and help prevent future eruptions.
Only three lakes in the world have been determined to be capable of a carbon dioxide eruption. All three are in Africa and include Lake Nyos and Lake Monoun in Cameroon and Lake Kivu on the border between Rwanda and the Democratic Republic of the Congo. Lake Monoun suffered a similar eruption in 1984, in which 37 people died. Lake Kivu's last eruption was prior to the beginning of recorded history, but geological records indicate that it has erupted in the past.
A pump similar to the one in Lake Nyos was also placed in Lake Monoun, but no degassing system has been installed in Lake Kivu. Measurements of dissolved gases in both lakes indicated that, despite the pump systems, both lakes had the potential to erupt again. Funds have been allocated to improve eruption prevention in both lakes.