In 1986, A Lake Suffocated Over 1,746 People in a Single Night

"I could not speak. I became unconscious. I could not open my mouth because then I smelled something terrible ... I heard my daughter snoring in a terrible way, very abnormal.... When crossing to my daughter's bed ... I collapsed and fell ... I wanted to speak, my breath would not come out.... My daughter was already dead."

These are the words of Joseph Nkwain, who on Aug. 21, 1986, survived one of the strangest natural disasters in history.

Lake Nyos is a crater lake in northwest Cameroon created as recently as 400 years ago. Formed by subterranean volcanic activity, crater lakes commonly have high levels of carbon dioxide. Under normal circumstances, these gases dissipate over time as the lake water turns over.

But Lake Nyos is different as it was unusually still. Over hundreds of years, its deep waters became a high-pressure storage unit, loaded with more gases. More than five gallons of carbon dioxide were dissolved in every one gallon of water. Pressurized to the physical limit, Lake Nyos was a ticking time bomb.

On Aug. 21, 1986, something in the lake went off. No one knows what the trigger was — it may have been a small volcanic eruption, a landslide, or even something as small as cold rain falling on the edge of the lake. Whatever it was, the result was catastrophic. The lake literally exploded in what's known as a limnic eruption; a fountain of water was sent 300 feet into the air, creating a small tsunami.

But far more deadly than the water was the gas. Hundreds of thousands of tons of CO2 was released in just about 20 seconds and burst forth at 60 miles an hour, suffocating people up to 15 miles away. Villages near the lake had almost no chance of survival. Of the 800 residents of nearby Nyos, only six survived. (Those who did survive mostly did so by quickly escaping to higher ground on motorcycles.)

The cloud swept through the countryside. Nearby villagers who came out of their houses to find out what the sound they had heard was about were overtaken by clouds of gas and fell dead at their doorsteps.

In all, 1,746 people perished and more than 3,500 livestock were lost in a matter of minutes.

Since this tragic event, a degassing program was put in place by French scientists. In 2001 they installed a pipe that runs to the bottom of the lake and allows the gas to escape regularly at a controlled rate. Two more pipes were added in 2011. A solar-powered alarm system was also installed to monitor carbon dioxide levels, ensuring that should the lake explode again, there will at least be a warning.

Also worrisome is Lake Kivu, a lake over 1,000 times larger than Nyos and in a much more populous area. There's a historical record that it had been causing creatures in the lake to go extinct approximately every thousand years. Scientists believe that a volcanic disturbance could cause the same kind of event seen at Nyos but on a much, much larger scale. The question is when.

H/T Atlas Obscura

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