In an unprecedented and potentially risky experiment, scientists began venting carbon dioxide-laden water from the bottom of Lake Nyos, a crater lake in Cameroon, on 1 February. The project is intended to prevent a recurrence of a 1986 eruption in Lake Nyos that claimed 1800 lives.
The carbon dioxide seeps from volcanic sediment and underground springs. It stays dissolved at the bottom of the lake, thanks to a combination of high pressure and low temperature. Experts say that about 300 million cubic meters of the gas have accumulated between 50 and 200 meters below the surface. The denser carbon dioxide-laden water remains in a stable layer below the lake's top 50 meters--until something disrupts it. In 1986, an estimated 80 million cubic meters of gas erupted from the lake; no one knows why. The gas flowed over the rim of the crater and down the hillside, smothering residents and livestock.
Hoping to prevent such disasters in the future, a team headed by geologist Michel Halbwachs of Savoie University in Chambéry, France, has floated a 3-meter-wide raft in the middle of the lake with a 200-meter-long polyethylene pipe running to the lake bottom. As the water, pulled by suction, travels upward toward the surface, the carbon dioxide and water separate, releasing 10 liters of carbon dioxide for every liter of water. The result--much like pulling the tab on a shaken-up can of soda--is a 40-meter jet of water that can spurt out of the top of the pipe indefinitely.
"This is a great idea," says Sam Freeth of the Geological Hazards Research Unit at the University of Wales in Swansea, U.K. But he cautions there are "major risks involved" if the experiments are scaled up. Freeth worries that another eruption might be triggered by the movement of dense, degassed water. As for the pilot project, local authorities can turn it off if sensors in the pipe indicate it might be disrupting the lake's layers.