A limnic eruption, also known as a lake overturn, is a very rare type of natural disaster in which dissolved carbon dioxide (CO₂) suddenly erupts from deep lake waters, forming a gas cloud capable of suffocating wildlife, livestock, and humans. A limnic eruption may also cause tsunami or seiche as the rising CO₂ displaces water. Scientists believe earthquakes, volcanic activity, and other explosive events can serve as triggers for limnic eruptions. Lakes in which such activity occurs are referred to as limnically active lakes or exploding lakes. Some features of limnically active lakes include:

• CO₂-saturated incoming water
• A cool lake bottom indicating an absence of direct volcanic interaction with lake waters
• An upper and lower thermal layer with differing CO₂ saturations
• Proximity to areas with volcanic activity

Investigations of the Lake Monoun and Lake Nyos casualties led scientists to classify limnic eruptions as a distinct type of disaster event, even though they can be indirectly linked to volcanic eruptions.