The Lake Nyos gas disaster

Abstract

The Lake Nyos disaster, in Cameroon, killed an estimated 1250 people on the 21 August, 1986, was caused by the release of a toxic aerosol of water and carbon dioxide. Lake Nyos is stable, under normal circumstances, despite being highly charged with carbon dioxide, as it was both before and, to a lesser extent, after the disaster. Raising carbon dioxide rich water started to relase gas as the hydrostatic pressure decreased. As the exsolved bubbles rose, they increased the convective flow and helped to drag more gas oversaturated water towards the surface. The sequence fed on itself and led rapidly to a runaway degassing of part of the lake. At the surface the vigorous release of gas generated a wave of water which swept into the valleys to the south. The gas itself was not only cold, when it was released, but some of the water accompanying it was transformed into a fine mist, thus generating the cold dense aerosol of water and carbon dioxide which swept down the valley to the north, through Nyos and on to Subum, Cha and Fang, leaving death and devastation in its wake. -from Author