On This Day – August 21 : Over 1,700 people died when a huge carbon dioxide cloud erupted from a volcanic lake in Cameroon on this day in 1986

The cloud travelled as far as 25 km from the lake and was moving fast enough to flatten vegetation, including trees. The cloud reached the deep, iron-rich waters of the lake causing a dramatic change of colour from blue to red as the iron (Fe) oxidised.

Related resources:

• Iron podcast
• Periodic table