When the UN contract in Haiti came to an end a little over a year ago, we headed to Goma in the Democratic Republic of Congo to fly for Monusco, the UN Peacekeeping Mission that has been trying to separate Congo’s warring factions for the last twenty years.
Our job is the same; the destinations are different. Instead of Port-au-Prince, Cap Hatïen and Santo Domingo, we shuttle to Kalemi, Kisangani, and Entebbe in Uganda. Occasionally we fly to Beni, about two hundred kilometres north of here, where sporadic attacks by an Islamic militia hamper international efforts to contain the Ebola outbreak.
Goma huddles up against Gisenyi in Rwanda, on the shore of Lake Kivu. To the north, Mount Nyiragongo, an active volcano, smokes ominously, a constant reminder of the 2002 eruption that drove a swathe of molten lava through Goma and into the lake.
The city is five-thousand feet above sea level. Daily downpours in the rainy season wash away the film of sulfurous ash and keep the air cool. When the sun dips toward the horizon, it dapples the clouds crimson and the mountains guarding the edges of the lake fade to purple.
One of the best places to watch the sunset is from the bar of Hotel Linda. Fishing boats venture out for the evening catch: three boats tied together side-by-side with long poles protruding from their flanks, like the antennae of an enormous insect. It’s a tranquil scene, but danger lurks under the still surface of the lake.
You’d think that a volcano, armed rebels and the threat of Ebola would be enough for one region. But the three of them are dwarfed by the biggest danger of all, the lake itself.
Lake Kivu is part of the Rift Valley that tries to cleave the eastern third of Africa from the rest of the continent. The lake has an average depth of eight hundred feet, and a surface area of one thousand square miles.
Brackish springs deep within the lake release water rich in carbon dioxide. Because the water is saline, it’s heavier than the fresh water above, so it stays at the bottom. Pressures of over forty atmospheres ensure that the carbon dioxide remains dissolved in the water. In some places the bacteria that live at the bottom of the lake feed on the carbon dioxide, turning it into methane.
To the south-east, near the Rwandan shore, there’s a white structure that looks a bit like an oil rig. Rwanda is extracting methane from the water for power production. But the volume of methane is increasing faster than it is being used, and the water can only hold so much methane. When the pressure of the gas equals the pressure of the water, the dissolved gas will bubble and surge to the surface, forming a toxic blanket, displacing all the oxygen.
In 1986 something similar happened to Lake Nyos in Cameroon. The lake released a large cloud of carbon dioxide from its depths, suffocating almost two thousand people, and more than three-thousand cattle. Lake Nyos is a fraction of the size of Lake Kivu.
There, a solution was found to prevent it from happening again. Vents were installed to allow the gas to bubble out of the lake at a controlled rate. But a similar project for Lake Kivu might run into tens of millions of dollars, money that the Congo and Rwanda don’t have to spare.
A major disturbance, like a volcanic eruption, might trigger an overturn, with all the gas effervescing out at once, possibly causing a tsunami.
As in 2002, the volcanic eruption would send people fleeing to the lake shore. Those that avoid the lava, and don’t drown, will be suffocated in a gigantic gas cloud. Two million people might die.
Fortunately, it only happens every thousand years, or so. But the last overturn was about a thousand years ago. It’s almost due for another one. Scientists predict that the next overturn will only happen towards the end of this century… or when the volcano erupts. And nobody’s quite sure when that’s going to happen.