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Science explodes at African lake

Rachel Strohm

Lake Kivu harbors huge reservoirs of methane and carbon dioxide gas that could power Rwanda and the Democratic Republic of Congo. But gas could also explode, killing everything in and around the lake.

The depths of Africa's Lake Kivu harbor untold quantities of carbon dioxide and methane gases that could provide abundant electricity to millions of Rwandans and Congolese settling along its shores. But those gases could suddenly release, killing everything in and around the lake.

"Understanding whether you can find scenarios that would lead to something like that, a catastrophic release of gas, is of course important," Anthony Vodacek, a remote sensing scientist at the Rochester Institute of Technology in New York, told me on Monday.

He is leading a two-year survey that aims, for the first time, to provide a scientific portrait of the entire lake system. The team consists of seismologists, biologists, remote sensing specialists, and other scientists who will combine their areas of expertise to provide a baseline understanding of the system.

"If you don't know what the starting point is, you don't know what the change is. And so that is part of what we'd like to establish here," Vodacek said.

Methane extraction
The Rwandan government has already built a power plant along the lake's shores which siphons methane from the depths of the lake to generate 3.6 megawatts of electricity, about 4 percent of the country's needs. The aim, eventually, is to generate several hundred megawatts.

Lake Kivu is one three known so-called explosive lakes in the world. The other two are in Cameroon. Lake Nyos experienced an explosive eruption in 1986 that killed 1,500 people. During these so-called overturning scenarios, something triggers the gases trapped in the depths to burst towards the surface.

The gas is trapped at the bottom of the lake because the streams that feed the lake are slightly brackish. Salty water is denser than freshwater and so, it sinks to the bottom, taking all the organic detritus with it that releases carbon dioxide as it decomposes.

In addition, the lake is in a seismically active region. "It is a rift valley lake," Vodacek noted. "The Africa continent is pulling apart … and that means there are fault lines, there are earthquakes, and those can be tied in to potential triggers for what goes with the lake overturning."

It's possible that people extracting the gases to generate electricity will stave off a catastrophic overturning of the lake, though it could also upset the stability of the lake, Vodacek noted. That's one of the questions the team wants answered.

Extraction of the methane to generate electricity could be a huge benefit for development in the region, Vodacek noted. Currently, most of the cooking fuel comes from forests around the lake, the same forests that are home to endangered mountain gorillas.

"Normally, you don't think of development as having positive impacts, but in this you could because it could turn people away from cutting down the forest and subsistence farming on these steep hillsides in the region," he said.

If the lake becomes a source of fuel, then conservationists can focus reforestation efforts in the surrounding hills and help protect the gorillas, Vodacek added.

Explosive history
Team member Robert Hecky, an aquatic biologist at the University of Minnesota, Duluth, performed an analysis of a sediment core from Lake Kivu in the 1970s and found evidence for catastrophic overturns about once every 1,000 years beginning about 5,500 years ago.

This finding corresponds with genetic evidence from cichlids, freshwater fish that first evolved in the lake. Today, only about 15 species are found in the lake, though thousands more species are in other lakes.

People looking at the molecular clock of these fish put two and two together and realized the Lake Kivu fish experienced an extinction about 5,000 years ago, "which coincides with the analysis of the sediment and the overturning of the lake," Vodacek said.

Hecky and other team members will bring advances in the study of lake sediment cores to refine the timeline of the overturning events and perhaps gain insight to the triggers such as landslides or volcanic activity.

Seismologists on the team will embrace advances in GPS sensors to get a detailed read on the rifting process in the valley to understand where fractures and fault lines are located.

Vodacek, who is leading the effort, will take a view from the sky to piece all the data together.

In particular, he is embracing recently released data sets of satellite imagery from NASA that provides nearly 40 years worth of data on the region, showing how the landscape has changed as people settled on the lakeshore and cut down the forests.

"You're always hearing these horror stories of natural resource development without any regard to the environmental impacts of that," he said. "Here's a case where we would like to go in and make sure there's necessary due diligence to make sure that things aren't destroyed as a resource is developed."

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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).