In 1986, a mysterious gas cloud escaped from Lake Nyos in Cameroon, silently killing people as they slept. An invisible cloud travelled 25 km, wiping out entire villages and killing more than 1,700 people overnight

In August 1986, Lake Nyos in Cameroon suddenly released a huge cloud of carbon dioxide that moved silently through nearby valleys while people slept. The invisible gas displaced oxygen in the air, killing more than 1,700 people and thousands of animals. Scientists later uncovered what had caused the deadly lake disaster.