1986 Limnic Eruption of Lake Nyos, Cameroon
Poisonous Gas Cloud Killed Animals, Vegetation and People
Apr 22, 2009
A limnic eruption is also known as a lake overturn. It occurs when carbon dioxide (CO2) from the bottom of a deep lake is suddenly released. In addition to possibly causing tsunamis due to water displacement, this eruption also emits toxic gasses that cause instant death.
Lake Nyos, which is located in Cameroon, Africa was formed inside a deep crater of an inactive volcano. The lake lies within the Oku Volcanic Field, which is part of the Cameroon Volcanic Line.
Lake Nyos has all the characteristics that can cause a limnic eruption, such as:
- a cold lake bottom
- incoming water containing high levels of carbon dioxide
- different levels of carbon dioxide saturation
- close proximity to volcanic activity
Cause of the Lake Nyos Eruption
Although the last volcanic eruption around about 400 years ago, there is still magma sitting 50 miles below Lake Nyos. This pool of magma releases carbon dioxide and other gasses which travel through the earth.
The gasses reach the earth’s surface by leaking through the natural springs. In turn, the gasses flow into the lake. Scientific tests have proven that there is a high level of carbon dioxide and other gasses in Lake Nyos.
With most lakes, the carbon dioxide is slowly released into the atmosphere because the water temperature and the water pressure allow this to happen. Warm water at the bottom of a lake rises to the top and this is what is known as lake turnover. The rising of the bottom water causes a safe release of carbon dioxide.
The release of gas in Lake Nyos does not happen in the normal manner. The lake has a very deep bottom and it stays cold. With the absence of warm water, the water at the bottom of the lake does not rise. It becomes heavily saturated with gas.
Without turnover in Lake Nyos, the gasses stay trapped at the bottom and are released when there is a large buildup of pressure. An explosion can also occur when the lake is triggered by events such as earthquakes, heavy storms, or landslides.
On August 21st, 1986, between 9 and 10 pm, Lake Nyos suddenly released large quantities of carbon dioxide that proved to be fatal. Carbon dioxide is heavier than air and can’t rise easily so this cloud of poisonous gas slid down the slopes of the crater and overtook the valley below. As a result, all living organisms within 15 miles of Lake Nyos died of suffocation.
Aftermath of the Lake Nyos Eruption
According to John Seach, of Volcano Live, “In 1986 a gas cloud released from Lake Nyos killed 1746 people from Kam-Nyos, Subum, Cha, and other villages. The main eruption of gas was accompanied by a tsunami with a wave height of about 20m.” (Twenty meters is approximately 60 feet).
Over 3,000 livestock were killed and people who lived outside of the 15-mile radius of Lake Nyos were affected by respiratory problems, lesions and paralysis.
The lake, which was once clear blue in color became brown and full of silt after the explosion.
Degassing Lake Nyos
After extensive research, it was proposed that the placement of degassing columns in Lake Nyos would force the release of gas from the bottom of the lake. In 1995, a French team of scientists and engineers demonstrated the feasibility of this process by placing a large plastic stack in Lake Nyos.
The experiment was successful because gas and water spewed out of the pipe. In 2001, permanent columns were placed in Lake Nyos and it continues to help reduce the amount of carbon dioxide in the water.
In 2008, Lake Nyos was named the deadliest lake by the Guinness World Records.
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