Lake Kivu is one of the largest lakes in Africa and its waters hide methane deposits. If this gas were to emerge, it could cause the deaths of 2 million people living in the area. There are only three such lakes in the world, and all three are African: Kivu and Nyos and Monoun lakes in northwestern Cameroon.
The latter two suffered limnic eruptions in the 1980s and, in the case of Nyos, the lethal potential of this volcanic lake became tragically evident in the eruption of 21 August 1986. Kivu is one of the three African lakes, together with Nyos and Monoun in Cameroon, where a limnic-type eruption occurred.
The analysis of the geological history of the Kivu indicates that there have been episodes of biological extinction in the past millennia. The cause of these phenomena for Kivu is not clear, but it is suspected that it is linked to volcanic activity.
The chemical composition of lakes subject to limnic explosions is specific to each individual case, but in the case of Kivu it seems to be linked to a mixture of carbon dioxide (CO2) and methane, instead of CO2 alone as in the other two cases.
Methane appears to come from the microbial reduction of volcanic CO2. The impact of a massive eruption in the case of the Kivu would be catastrophic, given that around two million people live in the area of its basin.
Lake Kivu: a dive not recommended in the most dangerous lake on the planet
It is hypothesized that a sufficient volcanic interaction with the water of the lake bed characterized by a high concentration of gas, could heat the mass of water, release the methane and trigger an almost simultaneous release of carbon dioxide.
The carbon dioxide released in this way could lead to the death by asphyxiation of a large number of people around the lake, but also trigger a tsunami linked to the explosion of the gas. Coring in the Bukavu Bay area revealed three interspersed layers of deposits of the rare monohydrocalcite mineral with diatom conglomerates in the lake bed, overlying sapropelic sediments with high pyrite content.
It is believed that sapropelic sediments derive from hydrothermal discharge, while diatoms were the result of a flowering that reduced the concentration of carbon dioxide to a level that allowed the precipitation of monohydrocalcite.