How a West African Lake Killed 1800 People—And How It Could Happen Again (2024)
The evening of August 21, 1986, was like any other night around Lake Nyos, a deep crater lake high on the slopes of the Massif du Mbam mountain range in northwest Cameroon. Some residents of the local villages huddled around their cooking fires, tucking into a late dinner. Many others, tired from a busy day at the market, were already asleep in their grass-roofed huts.
Around 9:30 p.m., those who remained awake heard a strange rumbling noise coming from the direction of Lake Nyos. Within minutes, nearly 1800 people would be dead.
That night, Lake Nyos expelled a jet of water over 300 feet high, releasing with it years' worth of carbon dioxide that had collected in the lake. A cloud of gas rose into the sky before descending over the hilltops and heading toward the unsuspecting villagers. At 160 feet thick and traveling between 12 and 31 miles per hour, there was little chance of escaping it. As it swept past the huts, the hot cloud of carbon dioxide displaced the air, suffocating almost everyone it came into contact with until it eventually dissipated.
Lake Nyos was known by locals as the “good” lake for its clean drinking water. But on that night in 1986, it was responsible for one of the deadliest natural disasters in African history.
Nios, the village closest to the lake, was the worst affected. A man who traveled to Nios on his motorbike the following day discovered it strewn with the bodies of people and animals. He couldn’t find a single person alive.
The man rushed back to his village, Wum, around five miles away. The first survivors had just started to arrive. They later recalled choking on the air before passing out. Some remained unconscious for two days, only to wake up and find that their entire family had died.
As word spread about the disaster, scientists flocked to Cameroon to try to understand what had happened. Tests of the water soon revealed the lake had unusually high levels of carbon dioxide. The carbon dioxide levels were so high that when the scientists tried to pull the water samples to the surface, pressure from the gas caused the containers to burst. They theorized that carbon dioxide had accumulated at the bottom of Lake Nyos until something had disturbed it. That disturbance caused a chain reaction that forced the gas out from the bottom of the lake and into the atmosphere in a rare natural phenomenon called a limnic eruption.
In the following months, U.S. research chemists found that the carbon dioxide levels in Lake Nyos were increasing at an alarming rate. Something had to be done to keep another disaster at bay.
Geologists from the Cameroon Ministry of Mines, Water, and Power proposed installing a pipe system into the lake designed to allow the controlled release of carbon dioxide from its bed up through the surface. Starting with small pipes the diameter of a garden hose, scientists began to test the idea in 1990, swapping them out for progressively larger pipes in the following years. Meanwhile, all villagers within an 18-mile radius of the lake were evacuated. Their villages were destroyed to prevent them from going back.
Though the pipes provided a temporary solution, there were still 5500 tons of carbon dioxide collecting in Lake Nyos every year from the magma chamber deep below the volcanic line the crater lake sits atop. Funding was eventually secured to install the first permanent pipe in 2001, followed by an additional two pipes in 2011. It took another five years for the carbon dioxide to reach safe enough levels for villagers to return and rebuild their communities—three decades after the disaster that had claimed so many of their friends and family.
The Threat of Lethal Lakes
What triggered Lake Nyos's limnic eruption remains unknown. It could have been something as small as a rock falling into the water, or even a strong gust of wind. Once the scientists began figuring out what could have caused the disaster, they began to look for instances of similar eruptions [PDF]. It didn’t take them long to find one.
Just two years earlier in Lake Monoun, 59 miles away from Lake Nyos, nearby villagers heard a loud boom. In the following hours, 37 people mysteriously died. Until then, the strange occurrence hadn't garnered much attention. But in light of the Lake Nyos disaster, it was proof that the problem was greater than anticipated.
Scientists now believe that only three lakes in the world accumulate such deadly levels of carbon dioxide in their depths—Nyos, Monoun, and Lake Kivu on the border of Congo and Rwanda. While Lake Nyos and Lake Monoun have both been declared safe, the same cannot be said for Lake Kivu. Around 2 million people live in the valleys surrounding the lake, which is 1700 times bigger than Lake Nyos and twice as deep. Though Rwanda has begun using methane from Lake Kivu as a source of energy, large scale efforts to completely de-gas the lake have yet to be made. Until that happens, history threatens to repeat itself as danger bubbles silently beneath the surface.
Key Takeaways. On August 21, 1986, Lake Nyos in Cameroon released a large cloud of CO2, suffocating over 1,700 people and countless animals by displacing the oxygen around them. Scientists determined that CO2 had been gradually leaking into the lake, eventually erupting in a deadly release triggered by a rockslide.
What triggered the catastrophic outgassing is not known. Most geologists suspect a landslide, but some believe that a small volcanic eruption may have occurred on the bed of the lake. A third possibility is that cool rainwater falling on one side of the lake triggered the overturn.
Lake Nyos disaster, massive release of carbon dioxide from Lake Nyos in Cameroon on August 21, 1986. The disaster killed between 1,700 and 1,800 people.
Carbon dioxide was blamed for the deaths of around 1700 people in Cameroon, west Africa, in 1986 when a massive release of gas occurred from Lake Nyos, a volcanic crater lake.
The waters of Lake Nyos turn a murky brown because it shoots out toxic gases. In 1986, the lake emitted enough lethal gas to suffocate thousands of people and livestock. Experts discovered that carbon dioxide gases had built at the bottom of the lake for centuries.
The unpredictable and dangerous nature of the lake led scientists from around the world to propose solutions that would prevent another carbon dioxide eruption. In 2001, French scientists installed a degassing instrument—mostly a pipe and fountain that allows gas to escape at a consistent rate.
Once one of Africa's largest lakes, Lake Chad has shrunk by around 90% since the 1960s. This receding water is down to a reduction of precipitation, induced by climate change, as well as development of modern irrigation systems for agriculture and the increasing human demand for freshwater.
The bottom of Lake Kivu, one of the African Great Lakes, contains combustible carbon dioxide and methane that threatens countless communities. Lake Kivu is framed by imposing cliffs, nestled within a verdant valley straddling Rwanda and the Democratic Republic of Congo.
Key Takeaways. On August 21, 1986, Lake Nyos in Cameroon released a large cloud of CO2, suffocating over 1,700 people and countless animals by displacing the oxygen around them. Scientists determined that CO2 had been gradually leaking into the lake, eventually erupting in a deadly release triggered by a rockslide.
Although Nyos is situated within an extinct volcano, magma still exists beneath it. Approximately 80 kilometres (50 mi) directly below the lake resides a pool of magma, which releases carbon dioxide and other gases; the gases then travel upward through the earth.
Precipitation of ferric hydroxide in the oxygenated surface waters caused the lake's reddish-brown color; below 10 m the water was clear. Composition of the bottom water before the event is unknown.
On 21 August 1986, a lethal carbon dioxide (CO2) cloud burst from the bottom waters of Lake Nyos in northwestern Cameroon, killing 1746 people and more than 3000 livestock.
On August 21, 1986, a gas cloud issued from Lake Nyos in Cameroon killed over 1700 people. An Italian technical mission reached the area seven days later and obtained the first field evidences of the catastrophe.
Water from Lake Nyos is discharged over a natural weir which has a free fall of 22.3 m, so although there are fish in the streams and rivers near to the lake they have no direct access into the lake.
An eruption of lethal gas from Lake Nyos in Cameroon kills nearly 2,000 people and wipes out four villages on August 21, 1986. Carbon dioxide, though ubiquitous in Earth's atmosphere, can be deadly in large quantities, as was evident in this disaster.
The normally blue waters of the lake turned a deep red after the outgassing, due to iron-rich water from the deep rising to the surface and being oxidised by the air. The level of the lake dropped by about a metre and trees near the lake were knocked down.
Local mythology suggests that people around Nyos have long been aware that the lake harbored destruction. Indeed, Cameroonian myths reserve a special category for lakes, which are said to be the homes of ancestors and spirits and sometimes a source of death.
'Scientists have found evidence to suggest that volcanic eruptions, landslides, earthquakes and cool rainwater can all trigger limnic eruptions', explains Dr Meriaux, 'but it is also possible for a lake to become unstable on its own.
Introduction: My name is Pres. Carey Rath, I am a faithful, funny, vast, joyous, lively, brave, glamorous person who loves writing and wants to share my knowledge and understanding with you.
We notice you're using an ad blocker
Without advertising income, we can't keep making this site awesome for you.
