Some 1,700 people living in the valley below Lake Nyos in northwestern Cameroon died on the evening of August 26, 1986 (it was hard to understand what happened). Word of the disaster spread, and scientists arrived from around the world. What they discovered was that the crater lake, perched inside a volcano, had become laden with carbon dioxide gas. This gas had bubbled out of the lake (it happened quickly) and asphyxiated nearly every living being in the valley community.

The disaster, however , wasn't unique. Two years earlier, Lake Monoun, 60 miles to the southeast, released a cloud of gas, killing 37 people. A third lake, Lake Kivu, on the Congo-Rwanda border in Central Africa, is also known to act as a reservoir of carbon dioxide and methane, a natural gas (it can be sold for a profit) that is gathered from the lake and used .

These three lakes are the only ones in the world known to contain concentrations of carbon dioxide in their waters. More , the gas is released into the atmosphere in bubbling soda springs, which can be found around the world.