On 21 August 1986, at Lake Nyos, one of the strangest and most mysterious natural disasters in history happened. The lake Nyos is a lake formed atop a volcanic crater in northwest Cameroon.
That day, without warning, the lake released hundreds of thousands of tones toxic carbon dioxide which estimates range from 300,000 to up to 1.6 million – and this silent death cloud spread out over the countryside at nearly 100 km/h (62 mph), suppressing an estimated 1,746 and more than 3,500 livestock within minutes.
The effect was as devastating as it was fast, and it felled locals and wildlife alike by starving the air of oxygen within a 25-km (16-mile) radius of the lake.
Lots of people from the villages of Nyos, Cha and Subum were silently asphyxiated in their sleep. Some of them had blood around their noses and mouths when they were found.
When the few remaining survivors woke up, they found no disturbances, no violence – just corpses. Even the flies were dead.
Reporters who were witnesses of the disaster the day after, described it as like looking at the aftermath of a neutron bomb.
Joseph Nkwain, the survivor who woke up 3 hours after the cloud hit, recounted the experience to Plymouth University researcher, Arnold H. Taylor:
“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. … My arms had some wounds, I didn’t really know how I got those wounds. I wanted to speak, my breath would not come out… My daughter was already dead.”
It’s one of the most gut-wrenching natural events in recorded history, and scientists still have no idea what triggered it.
George Kling, an ecologist at the University of Michigan, told The Guardian back in 2005:“It was one of the most baffling disasters scientists have ever investigated. Lakes just don’t rise up and wipe out thousands of people.”
So what do we know?
Researchers determined that Lake Nyos had released a massive amount of CO2 at around 9pm. Because CO2 is heavier than the surrounding air, it quickly sunk into the valleys below, blanketing everything in a sheet of toxic gas 50 meters thick.
Usually, those hundreds of thousands tones of CO2 are kept contained in the lake, but this time, something blew the lid off.
As David Bressan explains, volcanic gases emanating from the ground below the lake dissolve and become concentrated in its deepest waters, and the tropical temperatures form a sort of ‘cap’ of warm water above this cooler water.
It’s still not clear what ‘broke the seal’ and allowed the deep, contaminated water to rise, but it could be an earthquake, a landslide, maybe a volcanic eruption, or even something as simple as heavy runs muddling the water levels.
Although the trigger was silent, the effects were catastrophic.
Atlas Obscura reports: “The lake literally exploded in what’s known as a limnic eruption, sending a fountain of water over 300 feet (91 metres) into the air and creating a small tsunami.”
In the absence of a scientific explanation, there are many conspiracy theories reared their inevitable heads, where some locals convincing themselves that the eruption had been triggered by an undisclosed bomb test, carried out by the Israeli and Cameroon governments.
Still, the timeline just doesn’t fit.
A similar event happened nearby two years earlier at Lake Monoun, where a CO2 eruption took 37 people’s lifes. What triggered that eruption is unknown either.
In 2001, in order to prevent these lakes from exploding once more, engineers installed pipes in both to suck CO2 from the lake bed, and release it very gradually into the air.