Limnic eruption, also known as Lake Overturn, is a rare natural disaster that consists of carbon dioxide suddenly erupting from deep lakes which may cause suffocation of wildlife, livestock and humans. There is a possibility that a limnic eruption may also cause a small tsunami in the lake as the carbon dioxide rises to the surface, displacing water. There have been evidence that landslides, volcanic activity, or explosions may set off the lake eruption. The occurrence of this natural disaster is dependent on its proximity to volcanic activity. Carbon dioxide saturation usually happens due to volcanic activity or decomposition of organic matter.
Lake Nyos is a lake that was formed in a volcanic crater in the Northwest Region of Cameroon located in west Central Africa. It has a surface area of 1.58 kilometres squared; a maximum depth of 208 metres and its water volume is 0.15 kilometres cubed. The lake lies within the Oku Volcanic Field, positioned close to the northern boundary of the Cameroon Volcanic Line. Villages situated near the lake include Cha, Nyos, Munji, Djingbe and Subum. A volcanic eruption that took place about 400 years ago formed a volcanic crater which was filled with water and is known today as Lake Nyos. Even though the lake is located within an extinct volcano, magma still exists under it. It is estimated that a pool of magma dwells 80 kilometres directly below the lake.
The disaster that took place on August 21, 1986 at Lake Nyos killed an estimate of 1,700 people and 3,500 livestock within 25 kilometres of the lake. The limnic eruption released about 1.6 million tonnes of carbon dioxide which ascended into the water’s surface at 100 kilometres per hour. It is not certain of what caused the eruption but geologist suspect a landslide; others believed that a miniscule volcanic eruption took place on the bed of the lake.
Approximately 4,000 inhabitants fled the area of the eruption, many of these people developed respiratory problems and paralysis as an after effect of the gases. On a regular basis, the lake’s water is blue but turned deep red as the carbon dioxide bursts through the water and rises to the surface. The water level of the lake dropped by about a metre and trees in the vicinity of the lake were all knocked down. Evidence gathered by scientist has shown that 91 metres of water and foam formed at the surface of the lake after the overturn. The massive amount of water rising so suddenly caused so much turbulence that a 24 metre wave formed which washed the entire shore of one side.
A solution has been developed by a team of French scientists to remove the carbon dioxide gas from limnically active lakes such as Lake Nyos in order to prevent another catastrophe like the 1986 disaster. By using siphons, the scientists were able to degas the waters of the lakes, which is a processing in which gas is removed using a pipe position vertically in the lake to the surface of the water. The carbon dioxide gas is then diverted out of the water through the pipeline to the surface in small amounts. As the water rises to the surface, carbon dioxide gas comes out of solution and forms bubbles.