Truely, Cameroon lies along a fault-line, but why is it that after the fatal Lake Nyos gas explosion in (1982)? there has been no consensus amongst the scientists as to the origin of this unusual volcanic activity.? A lot of folks (back in Cameroon) are still to be convinced that this was a natural disaster, due to this lack of any scientific explanation.

rocky Adolphus

Hi Adolphus,

Camaroon isn't necessarily along a fault line. Geologists are not certain whether the "Camaroon line" of volcanoes is a hotspot trace or perhaps a leaky transform fault from the mid Atlantic ridge. The former explanation makes more sense to me. Regarding the volcanoes though, it doesn't really matter what the underlying tectonics are if you are dealing with trying to reduce the hazards at a volcano.

I think there is a pretty good consensus as to what happened at Lake Nyos (in 1986, by the way). A few folks disagree on the details, but the main event was the sudden release of a large cloud of carbon dioxide gas from the lake. Lake Nyos is a water-filled throat of an old volcano and it is deep and funnel-shaped. Although no longer erupting, there is still gas being released by the old plumbing system under the lake. Carbon dioxide gas was released directly into the deepest waters of the lake, where it could remain in solution (the way that carbon dioxide stays in solution in an un-opened soda or beer). In this situation the lake could build up a large amount of carbon dioxide dissolved in the deeper water. This was a stable situation. The carbon-dioxide charged water was slightly denser than the normal water in the upper levels of the lake, and the weight of the overlying water kept the carbon dioxide in solution in the deeper parts of the lake.

However, nature decided to unbalance the situation. This is where the disagreement among volcanologists comes in. It is agreed that somehow some of that carbon dioxide-rich water was displaced upward into shallower depths to the point where the overlying water pressure was lower and carbon dioxide bubbles could start to form (like when you lower the pressure on a soda by opening the bottle and suddenly bubbles start to form). At Lake Nyos, once these bubbles started to form they wanted to rise to the top, this brought up more carbon dioxide-rich water which then also started to develop bubbles, and pretty soon there was a big rush of carbon dioxide bubbles to the surface. What people don't agree on is what the trigger for this unbalancing event was. Most people, I think, feel that there was some sort of landslide into the lake that stirred up the water. There are a few volcanologists who think there was some type of eruption in the deeper part of the lake, but they are in the minority. That detail is't really too important.

Once all this carbon dioxide reached the surface, it splashed some lake water out of the lake, like a big bubble bursting. Carbon dioxide is denser than air, so it hugged the ground and flowed down the stream valley that leads away from the lake. Unfortunately many homes and at least one town are also along this valley and the inhabitants were caught by this cloud of ground-hugging gas. Carbon dioxide usually kills people by displacing the air that they need to breathe, but in high-enough concentrations it is poisonous as well.

So you see that although volcanologists might disagree on the tectonic details underlying Camaroon and might even disagree on the triggering mechanism for the 1986 disaster, but the danger is pretty well understood. Obviously one way to minimize the chances of this happening again is to prevent the deep lake waters from becoming gas-charged. A program was started to have a pump running that brought up the deep water (in a small controlled way), where it was pumped into the air like a fountain. This allowed smaller amounts of deep water to lose their carbon dioxide gradually rather than having the potential of a big bubble occurring again. Another worry is that the lake walls themselves are not very strong (they are constructed of tuff, partially solidified ash). The problem is that there is this lake at an elevation higher than the main towns nearby, and if for any reason the walls of the lake were breached there would be a flood of water that could be just as dangerous as a flood of carbon dioxide. I'm not sure but I think there were plans to pump water out of the lake to try and keep the level and pressure down.

This has been kind of a long-winded explanation. One of the most important things that volcanologists need to do is to make sure the folks who are actually living in danger understand the dangers. Perhaps this has not happened in Camaroon. Often scientists are very good at talking amongst themselves in technical language but are not so good at explaining things to normal people. It is often a good idea to have local teachers, writers, and artists helping to prepare materials for educating the public.

Sincerely,

Scott Rowland 

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