In 1986, Lake Nyos, a crater lake in the north west of the country, suffocated almost two thousand people in a single night. Like many other crater lakes, which are formed by subterranean volcanic activity, Lake Nyos contained a high level of carbon dioxide gas.

However, instead of the gas dissipating over time as the water turned over, the lake stored the gas for centuries, making it a ticking time bomb for residents close by.

Once the lake was triggered, an explosion known as a limnic eruption occurred so catastrophic that it released thousands of tons of the toxic gas at a reported speed of 60 miles per hour, annihilating life in a 15-mile radius.

Source: Yahoo News