A lake can look completely peaceful.

But beneath the surface, some lakes can become dangerously saturated with carbon dioxide.

In rare circumstances, that gas can suddenly escape from the water and spread across the surrounding landscape — creating an invisible cloud capable of suffocating people and animals.

In The Lakes That Can Suffocate an Entire Valley, we explore the science behind these extraordinary natural hazards, including the catastrophic events at Lake Nyos and Lake Monoun in Cameroon.

Deep beneath certain volcanic lakes, carbon dioxide can accumulate in enormous quantities.

Or another disturbance can cause deep, gas-rich water to rise.

As the pressure decreases, dissolved carbon dioxide can come out of solution.

The process can accelerate rapidly.

AD BREAK 1 ...