A lake in the volcanic crater Iwi at Nyos in Cameroon, where a sudden release of toxic volcanic gas occurred on the night of 21 August 1986. More than 1700 people and all animal life within 14 kilometres of the lake were killed, but plant life was mostly unaffected. Survivors suffered symptoms compatible with an asphyxiant gas like carbon dioxide. Two different explanations have been offered for this extremely rare type of event – that it was the result of a phreatic eruption of groundwater that was exceptionally rich in CO2 or it was a result of overturn of water in the 220 metre deep lake.
Subjects: Environmental Science.