Lake Nyos: The Invisible Disaster That Killed 1,700 People

On the night of August 21, 1986, communities near Lake Nyos in Cameroon were struck by an invisible mass of carbon dioxide. The disaster caused the deaths of about 1,700 people and approximately 3,500 head of cattle as they slept.

How Lake Nyos accumulated so much carbon dioxide

Carbon dioxide of magmatic origin reaches the lake from underground and dissolves in the deep waters, where pressure allows it to remain trapped. The strong stratification of the waters prevents regular circulation between the bottom and the surface, favoring the progressive accumulation of the gas. For years, carbon dioxide accumulated in the depths of the lake, trapped under more than 200 meters of water.

The moment of the limnic eruption

On the night of August 21, 1986, Lake Nyos suddenly released a massive cloud of carbon dioxide that spread through the nearby valleys and villages. Researchers believe that a landslide may have triggered the release of the gas by disturbing the carbon dioxide-rich waters at the bottom of the lake. This rare phenomenon is known as a limnic eruption, in which deep, gas-rich waters suddenly rise to the surface and release the dissolved gases.

Why the gas was lethal

Carbon dioxide is harmless in normal atmospheric concentrations, but at high levels, it acts as an asphyxiant, displacing oxygen from the air. Because it is heavier than air, the gas flowed down the slopes toward the villages, where many residents died in their sleep before even realizing something was wrong. The Smithsonian estimates that about one cubic kilometer of carbon dioxide was emitted.

Degassing tubes and current safety

In the following years, engineers installed degassing pipes in Lake Nyos to gradually release the carbon dioxide trapped in the depths. In March 2001, a degassing system went into operation using a vertical pipe to channel the gas-rich water to lower-pressure levels. Today, experts say the lake no longer contains enough dissolved carbon dioxide to cause another tragedy, although the gas continues to enter the lake through the underground volcanic system.

With information from G1, SAPO, Olhar Digital.