Battle to degas deadly lakes continues

After nearly a decade, a scheme to suck a deadly build-up of carbon dioxide out of Lake Nyos is nearing its final stages, say project scientists. But two other African lakes may still harbour serious dangers — now or in the future.

Located in a volcanic crater in a remote area of Cameroon, Lake Nyos captured the world's attention in 1986, when an explosive release of CO2 from the lake's depths asphyxiated 1,700 people in the surrounding villages. Gas had been seeping into the lake over decades or possibly centuries from the magma deep below. The dense, gas-filled water had been trapped in a layer near the lake bottom until an event, perhaps a landslide or heavy rainfall, stirred the lake and triggered release of the gas — a limnic eruption. The mass suffocation drew attention to a rare but lethal natural hazard and prompted scientists to consider ways of reducing the risk of it reoccurring.

In 2001, a team led by the physicist and engineer Michel Halbwachs, then of the University of Savoie in Chambéry, France, inserted a long pipe into the middle of Lake Nyos and started to siphon up the gassy water from the lake depths. The siphoned water releases its CO2 as it spews champagne-like from the top of the pipe, then falls harmlessly back onto the lake. In this way, the size of the gas-charged layer below and the risk it poses steadily decrease.

Despite setbacks, the basic strategy is working, says Halbwachs, who is now head of the gas-extraction company Data Environnement, based in Chambéry. But one pipe makes for a slow extraction, leaving villagers at risk. The plan called for more pipes to be installed, but funds were not forthcoming. After campaigning for more than a decade, Halbwachs says that he has secured donations of €1.4 million (US$1.8 million) from the United Nations Development Programme for two more pipes, which he hopes to deploy in Lake Nyos between November 2010 and February 2011. "The long delay is normal with international donors," says Halb­wachs, who estimates that new pipes should make the region around Lake Nyos safe from a limnic eruption within 5 years.

via Battle to degas deadly lakes continues : Nature News.

More on the strange Lake Nyos event:

One survivor, Joseph Nkwain from Subum, described himself when he awoke after the gases had struck:

"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. I was there till nine o'clock in the (Friday) morning . . . until a friend of mine came and knocked at my door . . . I was surprised to see that my trousers were red, had some stains like honey. I saw some . . . starchy mess on my body. My arms had some wounds . . . I didn't really know how I got these wounds . . .I opened the door . . . I wanted to speak, my breath would not come out . . . My daughter was already dead . . . I went into my daughter's bed, thinking that she was still sleeping. I slept till it was 4:30 p.m. in the afternoon . . . on Friday. (Then) I managed to go over to my neighbors' houses. They were all dead . . . I decided to leave . . . . (because) most of my family was in Wum . . . I got my motorcycle . . . A friend whose father had died left with me (for) Wum . . . As I rode . . . through Nyos I didn't see any sign of any living thing . . . (When I got to Wum), I was unable to walk, even to talk . . . my body was completely weak."^[4][10]

Carbon dioxide, being about 1.5 times as dense as air, caused the cloud to "hug" the ground and descend down the valleys where various villages were located. The mass was about 50 metres (164 ft) thick and it traveled downward at a rate of 20–50 kilometres (12–31 mi) per hour. For roughly 23 kilometres (14 mi) the cloud remained condensed and dangerous, suffocating many of the people sleeping in Nyos, Kam, Cha, and Subum.^[4] About 4,000 inhabitants fled the area, and many of these developed respiratory problems, lesions, and paralysis as a result of the gases.^[11]

It is not known what triggered the catastrophic outgassing. Most geologists suspect a landslide, but some believe that a small volcanic eruption may have occurred on the bed of the lake. - wiki