1,700 people living in the valley below Lake Nyos in northwestern
Cameroon mysteriously died on the evening of August 26, 1986.
Word of the disaster spread, and scientists arrived from around
the world. What they discovered was that the crater lake, perched
inside a dormant volcano, had become laden with carbon dioxide
gas. This gas had suddenly bubbled out of the lake and asphyxiated
nearly every living being in the surrounding valley community.
however odd, wasn't unique. Two years earlier, Lake Monoun,
60 miles to the southeast, released a heavy cloud of toxic gas,
killing 37 people. A third lake, Lake Kivu, on the Congo-Rwanda
border in Central Africa, is also known to act as a reservoir
of carbon dioxide and methane, a valuable natural gas that is
gathered from the lake and used locally.
These three lakes are the only ones in the world known to contain
high concentrations of carbon dioxide in their waters. More
typically, the gas is released into the atmosphere in harmlessly
bubbling soda springs, which can be found around the world.
behind the disaster is fairly simple. Lake Nyos is a deep pool
of water sitting in the throat of a dormant volcano. The real
culprit is a pool of hot magma,
laying almost 50 miles below the lake. The magma releases the
carbon dioxide and other gases, which travel upward through
the earth. The gases gets trapped in natural spring water, which
eventually rises toward the surface and feed into the crater
The carbon dioxide, instead of being released
harmlessly into the atmosphere, collects in the cold water at
the bottom of the lake. The amount of gas that can be dissolved
in the water is dependent on water temperature and pressure.
The greater the pressure, the more gas can be trapped. None
of this would be particularly hazardous if the water at the
bottom of the lake were to regularly rise to the surface, where
the gas could be safely released. The problem is that the waters
of Lake Nyos, like many tropical lakes, are steady and still,
with little annual mixing of the water layers.
Over time, the lowest levels of the lake become
more and more saturated with gas. And eventually, when they
reach 100% saturation, the gas can bubble spontaneously out
of the lake, creating a foaming column of carbonated water.
This eruption, or release, can be triggered even before saturation
is reached by a landslide, earthquake, violent storm, or other
disturbance of the waters.
The eruption itself isn't dangerous, but the
suddenly released gas cloud can be fatal. Carbon dioxide is
heavier than air, and when released, it pours over the rim of
the crater and slides down into the surrounding low-lying valley.
Carbon dioxide normally makes up 0.03% of air, and concentrations
of more than 10% can be fatal. The unfortunate villagers around
Lake Nyos literally suffocated under the heavy poisonous cloud
Lake Nyos and Lake Monoun contain more gas than was released
during the last disasters. At the very greatest depths, Lake
Nyos is about 60% saturated with carbon dioxide, and the waters
of Lake Monoun are 83% saturated. Recent scientific studies
show that the gas concentrations in both lakes is increasing
rapidly, and that another lethal gas release is inevitable.
an effort to side-step another catastrophe, an international
team of scientists, supported by the U.S. Office of Foreign
Disaster Assistance, have developed a plan to try to remove
the gas from the lakes. The plan is to place large pipes in
Lakes Nyos and Monoun. These pipes, each about five inches in
diameter, will be placed on a floating platform and sent down
to the lowest layers of water, creating a vent to the surface.
Water will be pumped from the bottom of the lake, and the gas-water
fountain that results releases the carbon dioxide harmlessly
into the atmosphere.
Currently, there is funding to place one pipe
in Lake Monoun, which will slowly remove the gas stored in the
lake over the next five years. A pipe will also be placed in
Lake Nyos, which should be sufficient to prevent the further
build up of carbon dioxide, but since this lake is considerably
bigger than Monoun, six to ten pipes will eventually be needed
to remove all the gas stored in the lake.
The vent pipes should be placed in September
2000, just after the next rainy season. Since this plan is novel,
and results a little uncertain, the scientists installing the
pipes will evacuate everyone from the area while the work is
-- By Micah Fink