Lake Nyos sits on the flank of an extinct volcano in Cameroon's remote northwest. It’s a crater lake, 200 meters deep, located along an area of volcanic activity stretching southwest to Mt Cameroon.
The lake is both beloved and feared. Beloved, because of its beauty and because it sits on ancestral land. Feared; because 25 years ago it brought instant death to all the people and livestock within its reach.
On August 21, 1986, Lake Nyos abruptly discharged large clouds of carbon dioxide, killing more than 1,700 people and 35,000 livestock in nearby villages. The mass suffocation came two years after 37 people were killed in similar circumstances at Lake Monoun, 60 miles to the southeast.
Scientists rushed to the scene from across the world. They agreed that the best solution was to install pipes to remove the gases from along the bottom and allow the carbon dioxide to leak out in safe quantities.
Three man-made fountains in the lake are the visible parts of those vent tubes, the last of which was vertically installed in March. The process ended a venture that began in 2001 and proceeded slowly because of funding problems. Scientists say over the next two years, the pipes will pump out some 200 million cubic meters of trapped carbon dioxide.
Michael Halbwachs is the head of the French gas-extraction company DATA Environnement. He says the process will eradicate all lingering dangers of another explosion, leading to a sudden release of carbon dioxide, or CO2.
The French scientist says the system is self-powered and will permanently pump up water heavily saturated with CO2 [carbon dioxide] from the lake bottom. "As the water rises," he says, its pressure drops, implying that higher pressures at the bottom layers will continue to drive the process."
Halbwachs says over long periods, carbon dioxide has been seeping into the bottom layers from underlying magma [or molten rock]. "Over time, the water becomes supersaturated with carbon dioxide which can be detonated by an earthquake, heavy rainfall or rising temperatures," he says.
CO2 is heavier than air, and so once emitted, it sinks to the ground, displacing breathable air upwards. As a result, life forms breathing oxygen for survival are suffocated. Geologists call the phenomenon limnic eruption. They say before a lake is saturated, it behaves like an un-opened carbonated soft drink.
In both cases, the CO2 dissolves much more readily at higher pressure. That’s why bubbles in a can of soda for example, only form after the drink is opened, releasing the pressure and forcing bubbles of carbon dioxide out of the solution.
To date, the phenomenon has been observed only twice in Cameroon. But Lake Kivu, a third body of water bordering the DRC and Rwanda, is known to contain even greater amounts of dissolved CO2. It is 2,000 times larger than Lake Nyos, with more than two million people living along its shores. Scientists say fortunately, Lake Kivu has not attained the level of CO2 saturation needed to provoke an eruption.
Lake Kivy is also a potential source of wealth, holding vast stocks of methane. Halbwachs is at work there, fine-tuning several commercial projects to extract the gas and turn it into useful energy.
Lake Nyos lacks such endowments, but remains a cherished place despite the sad memories. Long before the completion of the project, the few nostalgic survivors of the 1986 disaster had begun resettling their once-abandoned ancestral lands. The successful conclusion of the degassing venture and security guarantees, including an alarm system at the lake gateway, is attracting more farmers and cattle grazers.
But many complain that half a century later, the remoteness of the tourist destination is deterring potential investors. They lament the lack of roads, hospitals and other developmental infrastructure.
There’s another problem. The lake waters are held in place by a natural dam of volcanic rock. Geologists fear that erosion could lead to its collapse in the near future. If it gives way, some 50 million cubic meters of water will sweep downhill, wiping out human settlements inhabited by some 10,000 people both in Cameroon and across the border in Nigeria.
The government has announced plans to artificially reinforce the lake wall with concrete, as well as permanently drain off some of the lake waters to reduce pressure on the wall.
But area resident express concern, saying so far, nothing has been done.