I recently read about a phenomenon known as lake inversion, overturn, or a limnic eruption. This happens in lakes saturated with gas, CO2 for example from decomposing organic material or from volcanic gases building up. When the water reaches a very high saturation of gas, nearby disturbances such as an earthquake or a volcanic eruption can cause all of that gas to come out of solution and rise out of the water, causing a massive eruption and even a tsunami. Think of it like an unopened can of Coke whose bubbles rise to the surface when it is finally cracked open, bringing the gas out of solution.
Once this happens, the gas that is released from the lake then forms a blanket of CO2 over the entire region surrounding the lake and can choke and kill everything from insects to cattle to humans. When Lake Nyos erupted in Cameroon, it brought 80 million cubic meters of CO2 to the surface, killing 1800 people and all animals in a surrounding area of 25km.
Lake Kivu on the border of Rwanda and the DRC is estimated at about 2000 times the size of Lake Nyos and is located in an area with very high population density. An eruption is estimated to kill up to 2 million people.
The good news is that it is possible to de-gassify the lake. Some companies have started removing the CO2 and also some of the methane from the lake in an effort to prevent catastrophe and also to use the methane to generate electricity. Pretty cool idea. Pretty crazy potential for catastrophe. I’m curious what our Earth and Ocean Sciences friends out there have to say on this matter?
It reminds me a lot of the Vancouver earthquake scenario that is expected to occur in the coming decades. While I want to draw some conclusion about how Rwandans are too vulnerable to relocate themselves (which is a silly thing to assume), it seems people in the developed world assume the same level of risk every day living in Vancouver, Seattle, or LA. Fingers crossed for Rwanda and for us.