volcanic eruption of Nyiragongo in January 2002 is unique in the annals of vulcanology
because it was caused by tectonic fracture between the active plates of the African
The recent volcano-tectonic crisis of the Nyiragongo
volcano (Democratic Republic of Congo) which destroyed part of the town of Goma
on the 17 January 2002 highlighted a new kind of risk connected to the presence
of dissolved gas in the depths of Lake Kivu.
In its normal state, this highly
stratified lake is stable and not at all dangerous. But an important disturbance,
caused by the volcanic activity of Nyiragongo on the north shore, could cause
a rising up of gas-filled water from the deeps. This water would then release,
either as localised and limited emanations or via a cataclysmic explosion involving
a large part of the lake, a quantity of suffocating gas which would threaten the
safety of local populations.
There are only three lakes in the world containing
large concentrations of dissolved gas. Lake Nyos and Lake Monoun in Cameroon were
the sites of gas explosions which caused 40 deaths in 1984 at Monoun and 1800
in 1986 at Nyos. The third lake is Kivu, which contains a thousand times more
gas than Lake Nyos.
have recently discovered the existence of ancient volcanoes on the lake floor,
right in the middle of those gas-filled layers of water. A new sub-lacustrine
eruption, or a magmatic intrusion at depth would inevitably trigger off, by a
chain reaction, the liberation of an enormous quantity of gas, with probably catastrophic
consequences for the entire region. A population of several millions (Goma, Bukavu,
Gisenyi, even Bujumbura) are living under this threat.