In geology, a mazuku (Swahili for "evil wind") is a pocket of carbon dioxide-rich air that can be lethal to any human or animal life inside.^[1] Mazuku is created when carbon dioxide accumulates in pockets low to the ground.^[2] CO₂ is denser than air, which causes it to flow downhill, hugging the ground like a low fog, and is also undetectable by human olfactory or visual senses in most conditions.

Mazukus can be related to volcanic activity or a natural disaster known as a limnic eruption. In the first case, noxious gases are released from the Earth's crust into the atmosphere, whereas in the second case, the gases originate deep in a lake and boil rapidly to the surface. Because of their nature as sporadic and subtle events, few mazukus have been recorded, but there is a growing understanding of them based on historical and fossil evidence.

Effects

Mazukus can cause a variety of effects on flora and fauna in the regions in which they occur depending on the composition and concentration of the gases that they consist of. Massive clouds of CO₂, such as those released from lakes in the 1980s, can cause widespread devastation of human and wildlife populations. However, they may have little or no effect on local vegetation. If the concentration of CO₂ is high enough and maintained in a prolonged outgassing event, even vegetation can succumb to the mazuku, as is the case on Mammoth Mountain in California, United States, where deforestation has occurred as well as CO₂ poisonings, including the deaths of two skiers, one in 1995 and one in 1998.^[3]

Related events such as pyroclastic flows or limnic eruptions can cause the temperature of a mazuku to vary considerably from the natural environment. Reports of frostbite, condensation, and other temperature changes can occur.^[4] Because they are often accompanied by other cataclysmic events such as volcanic eruptions, landslides, and tsunamis, mazukus are not easy to identify as potential dangers in their own right.

In some cases, mazukus are large enough to cause a localized extinction event that is documented in the fossil record. Lake Kivu, on the border between the Democratic Republic of the Congo and Rwanda, is a very large lake that has a sediment record of repeated and regular massive lake turnover events that include methane explosions, tsunamis and mazukus. The Messel pit in Germany contains a fossilized extinction pattern that could be related to a mazuku event there during the Eocene epoch.