On August 21, 1986, Lake Nyos in northwestern Cameroon experienced a rare and devastating limnic eruption, suddenly releasing approximately 1. 6 million tons of carbon dioxide stored in its deep waters. Lake Nyos is a meromictic crater lake situated over a magmatic pocket.
Volcanic carbon dioxide continuously seeps into the bottom water layers at high hydrostatic pressure, dissolving hundreds of meters beneath the surface without mixing into upper layers. In 1986, a trigger—likely a small landslide or localized thermal disturbance—displaced supersaturated bottom water upward. As the water rose, decreased hydrostatic pressure caused dissolved carbon dioxide to rapidly come out of solution, forming bubbles.
These expanding bubbles increased upward buoyancy, driving a self-sustaining chain reaction that violently brought massive amounts of deep water to the surface, bursting forth a massive asphyxiating gas cloud. To permanently mitigate this threat, French and American scientists designed an engineered self-siphoning degassing system installed in 2001. A vertical polyethylene pipe was submerged to the lake bottom.
Water pumped initially from the deep layer causes CO2 bubbles to expand within the tube as pressure drops. The expanding gas creates a low-density fluid mixture that naturally rises rapidly, driving a continuous fountain at the surface without requiring external pumps.