Nyos

Nyos is a small town in Cameroon, located on the shores of Lake Nyos, a crater lake formed in a volcanic region in the western highlands of the country. The lake and the town share the name Nyos, and the area is part of a geologically active zone known for its volcanic activity within the Cameroon Volcanic Line. The lake is deep and stratified, with chemistry that has attracted scientific study since the late 20th century.

In August 1986, Lake Nyos released a large cloud of carbon dioxide in a limnic eruption, a rare natural hazard where dissolved gases in a lake erupt suddenly. The dense CO2 gas flowed down the surrounding valleys, asphyxiating people and animals in nearby villages during the night. Estimates place the death toll at about 1,700 to 1,800 people and thousands of cattle, with fatalities occurring across several communities downwind of the lake. The disaster highlighted the risks posed by strange, invisible hazards in volcanic lakes.

In the years since the Nyos incident, mitigation efforts were undertaken to reduce the risk of a recurrence. A CO2 degassing system was installed on Lake Nyos to vent dissolved gas from the water and prevent accumulation. Ongoing monitoring and research have continued to study the lake’s behavior and the broader phenomenon of limnic eruptions. Nyos remains a site of scientific interest for volcanology and disaster risk reduction, as well as a reminder of the natural hazards associated with crater lakes in the region.