- Lake Nyos in Cameroon released a deadly carbon dioxide cloud on August 21, 1986
- Approximately 1,700 people died from suffocation
- The disaster was caused by a limnic eruption triggered by volcanic or seismic activity
A post widely shared on social media claimed that a lake in Africa "murdered" more than 1,700 people in a single night and that the world barely noticed. The post described villagers hearing a low rumble, seeing white mist rise from the water, and then collapsing silently in their homes. The lake was Nyos, located in north-western Cameroon.
What The Viral Post Claimed
The viral post said that on the night of August 21, 1986, villagers living near Lake Nyos heard rumbling noises, noticed a strange mist, and smelled something similar to rotten eggs. It claimed that within minutes, the lake released between 100,000 and 300,000 tonnes of carbon dioxide, which moved at high speed, sank into nearby valleys, and suffocated people in their sleep.
The post further stated that 1,746 people and thousands of livestock died without signs of struggle and that only those living at higher ground survived. It added that Lake Nyos remains dangerous today and warned that nearby Lake Kivu - far larger and filled with carbon dioxide and methane - could pose an even bigger threat.
Is The Incident True?
According to reporting documented by Encyclopaedia Britannica, Lake Nyos did indeed experience a rare and deadly natural event known as a limnic eruption.
On the night of August 21, 1986, Lake Nyos - a freshwater lake formed within an ancient volcanic crater - abruptly released a massive cloud of carbon dioxide gas that had been trapped deep beneath its surface. The release happened suddenly and without clear warning signs.
Residents in nearby areas reported hearing a sound similar to distant thunder. Shortly after, an invisible cloud of gas spread across surrounding villages. Carbon dioxide, being heavier than air, displaced oxygen close to the ground. As a result, people and animals lost consciousness and suffocated, many while asleep.
Official estimates later confirmed that between 1,700 and 1,800 people died, along with around 3,000 cattle. Birds, insects, and other wildlife were also killed. Most victims were found exactly where they had been - in beds, homes, and fields - with no signs of injury or struggle.
What Investigators Found
When international teams from France and the United States arrived at Lake Nyos, they observed unusual damage. The water had turned dark brown, nearby vegetation was flattened, and evidence suggested a powerful wave had surged from the lake's surface.
Scientists soon confirmed that large amounts of carbon dioxide had accumulated under pressure at the bottom of the lake. A trigger - possibly a landslide, a minor earthquake or volcanic activity beneath the lake - caused the gas to erupt upward and spill out into the surrounding valleys.
In certain areas, carbon dioxide levels were estimated to have reached up to 10 per cent. For comparison, normal atmospheric carbon dioxide levels are well below one-tenth of one per cent.
Was This an Isolated Incident?
No. Further research revealed that two years earlier, in 1984, a smaller limnic eruption had occurred at Lake Monoun, another volcanic lake in Cameroon, killing 37 people. The Nyos disaster, however, was far more severe due to the volume of gas released and the surrounding population.
Is Lake Nyos Still Dangerous?
The viral post is partly correct in saying that Lake Nyos has not been forgotten by scientists. Following the disaster, engineers installed controlled degassing pipes beginning in 2001. These pipes safely release carbon dioxide from the lake in small amounts, preventing pressure build-up.
While the risk has been significantly reduced, the lake continues to be monitored closely. It remains a volcanic crater lake, and long-term safety depends on continued maintenance of the degassing systems.
What About Lake Kivu?
Lake Kivu, located on the border of Rwanda and the Democratic Republic of Congo, is indeed much larger and contains vast amounts of dissolved carbon dioxide and methane. Scientists are aware of the potential risks, and the lake is also under constant observation. However, no immediate danger comparable to Lake Nyos has been reported.
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