A deep volcanic lake can accumulate dissolved carbon dioxide from underground volcanic activity. If the water is disturbed and the gas suddenly comes out of solution, a dense cloud can flow across nearby land and displace breathable air.
Carbon dioxide can build below the surface
Some crater lakes sit above volcanic systems that supply carbon dioxide to deep water. Pressure is higher at depth, allowing more gas to remain dissolved. If the lake is strongly stratified, the gas-rich bottom layer can remain isolated for years.
This is not ordinary evaporation and it is not the lake water turning into a gas. The hazard comes from dissolved CO₂ suddenly forming bubbles and escaping.
An overturn can trigger release
A landslide, volcanic event or major movement of water can disturb the layers. As gas-rich water rises, pressure falls and more carbon dioxide comes out of solution. That can accelerate the overturn, releasing a concentrated cloud above the lake.
Carbon dioxide is invisible and denser than air. Near the ground it can flow into valleys and low areas, where it reduces the oxygen available for breathing.
Why this is rare
The lake needs an unusual combination of deep water, a continuing gas source and long-term stratification. Most lakes do not meet all three conditions. Scientists monitor some volcanic lakes and use pipes or controlled degassing systems where appropriate.
Lake Nyos in Cameroon is the best-known example of a natural limnic eruption. It is evidence for a specific geological hazard, not a reason to treat every deep lake as dangerous.
Monitoring looks for changing layers
Scientists can measure dissolved gas, temperature and water movement at different depths. A warning sign is not simply a lake that is deep or volcanic; it is a combination of gas input, stratification and conditions that could disturb the layers. This is why risk assessment is site-specific rather than a universal rule for all crater lakes.
Sources and evidence
- USGS — The Lake Nyos disaster ↗
Carbon dioxide accumulation and the 1986 limnic eruption.
- Smithsonian Global Volcanism Program — Lake Nyos ↗
Volcanic setting and monitoring context.
Sources consulted: 9 October 2026. Written with AI assistance and checked against the linked references; not independently reviewed by a subject specialist. Sources do not endorse this article. See our editorial policy.
Revision: Distinguished dissolved gas, limnic eruption and ordinary lake evaporation. Added a subject-specific example or limitation to strengthen reader value.