The mysterious cloud that killed more than 1,700 people and 3,500 heads of cattle

The mysterious cloud that killed more than 1,700 people and 3,500 heads of cattle


El Nyos is a volcanic lake in a remote area of ​​Cameroon in western Africa.

“Around 11 o’clock at night I woke up and could not get up, I was confused, I did not know what was happening,” one of the survivors later said.

It was August 21, 1986. As it was dawning, villagers in several villages in northwest Cameroon discovered upon awakening that many of their friends and neighbors had died during the night.

“The next morning I saw that there were people lying in the streets, some were dead,” said the witness. “In our town we lost a lot of people, about 75 people died.”

The total figure, however, was many times higher: that day some 1,700 people died in Cameroon.

The reason: the inhalation of toxic gases emanating from a volcanic lake.

Reports indicated that all victims lived in villages near Lake Nyos , near Cameroon’s border with Nigeria.

The disaster was so serious that the president of the country appealed for international aid.

The investigation

They spent several weeks of scientific research to find out what had happened in the area.

Experts from all over the world were called to help unravel the mystery. One of them was the British doctor Peter Baxter, who arrived in the area about two weeks after the disaster.

Survivors of Nyos
Copyright of the GETTY IMAGES image
Image caption All the victims lived in villages near Lake Nyos, near the Cameroon border with Nigeria.

“There were still bodies of dead people and animals scattered in the hills of the area.When we arrived at the town of Nyos, which was a group of small mud huts, everything was silent and there were no signs of life,” the doctor tells him. Baxter to the “Witness” program of the BBC.

“And when we approached the lake, Lake Nyos, which was reached by climbing a small hill, we saw that its waters were very calm, unaltered, but there were fish and vegetation dead on the surface on the banks of the lake.”

“The only life we ​​could see in the water were frogs, which are very resistant to alterations and seemed to be thriving in these waters,” adds Peter Baxter.

George Kling, a professor at the University of Michigan, was also invited to help with the investigation.

“When we arrived at Lake Nyos there was a chilling atmosphere , all the people and all the animals in the area were dead,” he says.

“There was silence, but all the buildings were standing and it did not look like there had been a hurricane or a flood or something like that.”

Dead cattle
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Image caption The toxic gas cloud killed 1,746 people and 3,500 head of cattle.

“When we went up to the lake we saw a zone of destruction, before the disaster the lake was a very beautiful place, with its blue crystalline waters, only a year before we had been swimming in the lake, but now everything was completely transformed”, continues Kling .

“The water on the surface was reddish brown, there were huge vegetation clusters floating along the length of the lake, that vegetation came from the banks where huge waves of the lake had destroyed and destroyed all the vegetation that was close to the place”, recalls the professor.


Physical evidence suggested that a wave about 40 meters high had been created as a result of an alteration in the depth of the lake.

But it was a mystery what had caused this alteration and what had caused the death of several hundred people.

Lake Nyos
Copyright of the GETTY IMAGES image
Image caption After the release of gas the surface water was a reddish brown color, and there were huge vegetation clumps floating along the length and breadth of the lake.

There was, however, a main suspect.

“Initial reports that emerged from the area suggested that a volcanic eruption had occurred and that volcanic gases had been released, but this was an extremely unusual event,” says Dr. Baxter.

“Because there was not a big explosion caused by an eruption nor the devastation that that explosion would have caused,” he explains.

“What we were facing was a situation in which a large number of people had died but in which there was very little damage to the land and buildings where people lived and where they had died,” he adds.

“Smell of rotten egg”

One of the witnesses in the area remembers: “I almost died, but when I stopped I started taking oil, and soon after I vomited something black that smelled like egg or gunpowder”.

It was those smells that gave the scientists a hint of what they were looking for and what led them to believe that the culprit – and responsible for several hundred deaths – was carbon dioxide : thousands of tons of this gas, which had been released from the depth of the lake and spilled on the top of the volcano and into the valley below it.

Lake Nyos
Copyright of the GETTY IMAGES image
Image caption The scientists found themselves in an extremely unusual situation because there was not a large volcanic explosion or other natural event.

“Many of the survivors reported that there was a smell of rotten eggs and gunpowder that is the unmistakable smell of sulfur gas, and we know that volcanoes produce a lot of sulfur,” Professor Kling explains.

“But when we went to the lake and began to analyze the samples, we found that there was no sulfur in the water , nor was there sulfur in the gas dissolved in the lake, nor in the plants that surrounded the site and that had been exposed to the gas cloud “.

“It was very difficult to reason out these findings until we found, in ancient medical documents, that a large concentration of CO2 had been used to produce evidence of oxidative stress in combat pilots,” says Kling.

“And it turns out that CO2 concentrations above 5% or 10% act as a sensory hallucinogen, that is, you see things and feel things that do not really exist, and one of the most common reports of combat pilots subjected to these tests is They smelled rotten eggs or gunpowder and they felt very hot, “says the professor at the University of Michigan.

Survivors of Nyos
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Image caption It is not known why hundreds of people died with the toxic gas but other hundreds who were also exposed managed to survive.

Apparently carbon dioxide had been forming in the depth of the lake for several years .

Scientists say it is the same effect that occurs when you shake a bottle of champagne and then remove the cork.

As George Kling explains: “Because the lake was stratified, that is, it is very deep and the upper layers do not mix with the lower layers, the gas that formed in the lower layers was essentially trapped . it will accumulate over time in a huge amount and with tremendous pressure. “

Scientists say it is the same effect that occurs when you shake a bottle of champagne and then remove the cork.

The survivors

But there was also another mystery: hundreds of people had died but hundreds had managed to survive in some way despite having been exposed to CO2 in the same way as those who died.

Many of the survivors were children. So one theory was that poisonous gas engulfed their homes during the night when the little ones were asleep inside and many of their parents were still outside.

It was also suggested that because the children fell into unconsciousness faster, they sucked the gas in a less deep way.

Copyright of the GETTY IMAGES image
Image caption “Surviving or dying due to the exposure of the gas really was a random event”.

“Some of the survivors woke up with dead people around them,” says Peter Baxter. “Surviving or dying due to the exposure of the gas really was a random event.”

“The gas causes unconsciousness quickly and those who survived felt that they were unconscious for a long time, 10 hours or more, before being conscious again, literally until the gas – which was suspended in the air – rose when the day began and the sun warmed the earth. “

“But it’s an extremely unusual situation, a very extraordinary story,” says Baxter.

There were also extravagant theories about what might have happened.

“Yes, locals began to say that foreign countries had used the area to test a secret bomb , for example, that they were somehow part of a conspiracy of international scientists, in fact they are quite fantastic ideas and have no credibility. “says Peter Baxter.

Still, however, there are many theories about what really caused the release of carbon dioxide from the lake in the first place. One is that the release was triggered by a loosening in the lake.

Lake Nyos remains a potential threat to the people living in the area, but a pipe system has been installed to allow CO2 to be safely diverted from the bottom and avoid a repeat of the disaster that occurred in 1986.

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