Lake Nyos disaster | Description & Facts (2024)

Lake Nyos disaster, massive release of carbon dioxide from Lake Nyos in Cameroon on August 21, 1986. The disaster killed between 1,700 and 1,800 people.

On August 21, 1986, a cloud of magmatic carbon dioxide gas arose from the bed of Lake Nyos, a freshwater lake located in a volcanic caldera in the populous Northwest Region of the East African nation of Cameroon. The rare event, called a limnic eruption, was announced by a small explosion that residents of a market town near the lake described as being like distant thunder, but it was otherwise unannounced by anything else apart from a foul odour.

The 1.6 million ton cloud of magmatic gas was deadly, and a count of the fatalities indicated that 1,746 people, most from villages by the lake, had been asphyxiated by it, along with some 3,000 cattle and innumerable birds, insects, and other animals. The bodies of the dead showed no signs of trauma or struggle; these people had simply died where they were. A research team from France and the United States arrived at the sceneand noted that the lake was an unusual dark-brown colour, and that a surrounding raffia forest and several other expanses of vegetation had been flattened by both the explosion and the tsunami-like water wave that ensued. That the lake was responsible for the deaths was immediately clear to the scientists, but the mechanism involved was not.

Further research found that carbon dioxide had built up under high pressure in Lake Nyos, as it had two years earlier at another Cameroonian volcanic lake about 60 miles to the southeast, Lake Monoun, killing 37 people. A landslide into the lake may have caused the gas to be released from the cooler depths of the lake; a volcanic eruption under the lake or even a minor earthquake might also have been the cause. The result was that the carbon dioxide burst out of the lake and into the air, poisoning those in its path and then dispersing. The usual level of carbon dioxide in the air is much less than a tenth of 1 percent, but near Lake Nyos levels may have reached 10 percent.

The incidents at both Lake Monoun and Lake Nyos prompted international scientific research to arrive at ways to guard against limnic explosions by, for instance, controlled degassing, and how to develop effective warning systems so that people might evacuate an affected area before an explosion occurs.

Some scientists view Lake Nyos as a modern exemplar of an ancient process, positing that massive eruptions of gases such as carbon dioxide and methane and the resultant lowering of oxygen levels triggered the mass extinction of animals such as the trilobites and terrestrial plants during the late Permian period, about 250 million years ago.

Following initial degassing, fish were reintroduced to Lake Nyos in 1996, Further degassing has taken place at Lake Monoun and Lake Nyos, and no significant events have occurred at either since the explosions of the 1980s.