Lake Nyos CO2 eruption

I had never heard of the Lake Nyos disaster that occurred in 1986. Scientists aren't sure of the cause (this was an unknown phenomenon), but apparently a magma pocket beneath the lake had been leaching carbon dioxide into the deep water of the lake over a long time. At the lake depths the co2 disolves into the water and builds up under high pressure. Apparently something disturbed the water, perhaps a landslide or something churning the water, causing the c02 to de-pressurize, and explode violently. After the eruption the huge cloud of C02 gas released surged into the surrounding valleys, killing over 1700 people and thousands of livestock. The story really has the felling of a biblical disaster.

A reporter who visited the site after the disaster describes what he learned and saw. From his telling:

Survivors of the disaster recounted that at about 9pm on Thursday August 21, 1986, there was a powerful explosion in the lake after villagers had complained it had been boiling for five days. About three minutes after explosion, a violent wind started blowing from the lake to the south, invading the village of Fang, Chah, lower Nyos and Subum. The gas they said, was too hot and suffocated all living things. All those affected had burns on their bodies.

Here are some survivor stories from the Smithsonian Magazine.

scattered about lay the bodies of Suley’s children, 31 other members of her family and their 400 cattle. Suley kept trying to shake her lifeless father awake. “On that day there were no flies on the dead,” says Che. The flies were dead too.

Here's the Wikipedia article.