Nobody can say exactly what triggered these deadly disasters, but scientists may have learned enough to keep them from happening again. Last month experts from Cameroon, Japan, France and the United States watched as the supreme local authority, Sultan Njoya, poured libations on the water of Lake Monoun to placate the spirits. “The gods of the land, we are here to appease you with oil and wine from your children you left in my hands,” he chanted. Then it was the scientists’ turn. The villagers in their flowing robes stood ready to take to their heels, dead silent, as a pumping jet began to pull CO2-rich water from the lake bed. Before long, a 25-foot geyser of water and gas was spurting from a pipe sticking out of the lake. The experts were accomplishing their goal: to gradually burp Lake Monoun.
That geyser may signal the end of a unique scientific journey. At first, researchers believed that gas within the two lakes was released during a volcanic eruption. Surveys of other volcanic lakes in Cameroon and as far away as Lake Kivu in eastern Congo helped eliminate this theory–Nyos and Monoun were alone in having such high CO2 concentrations. That left a second theory: that the gas eruptions had something to do with the nature of water that enters the lake from underground springs.
After studying the bottoms of the lakes, scientists came up with a partial explanation. Water flowing through underground passageways comes into contact with magma, picks up high concentrations of carbon dioxide and minerals, and makes its way into the lakes, where it settles to the bottom. Because of a geological quirk, the CO2 concentrations become extremely high. Like other deep volcanic lakes in the region, Nyos and Monoun are heavily stratified–the layers of water don’t easily mix. When they do, it triggers a massive release of gas.
This partial explanation was enough for the Cameroon government to formulate a plan–to gently destratify the lakes before another violent release of gas. First, to protect local residents, solar-powered monitoring stations at the lakesides were designed to keep tabs on the levels of CO2; above safe levels, red lights flash and a siren sounds. The government then began laying pipes deep into the lakes to pump gas-rich water to the lake surface, where CO2 bubbles off harmlessly into the atmosphere. The aim is to release gas faster than it flows in from underground. In two years, the gas level at Lake Monoun should reach normal.
Not everybody is sold on this solution. “The gods of Lake Nyos were angry” in 1986, says Ghong Gabriel, 50, a traditional healer who survived the disaster. They could grow enraged again, he speculates. In reply, Joseph Metuk Nnange of Cameroon’s Ministry of Technical and Scientific Research simply gestures at an instrument raft in Lake Monoun that monitors the ongoing release of gas. Its meters give ample evidence of the calming of the lake’s unsettled spirits.
