The expedition of scientists has completed the investigation of the case that occurred August 21, 1985. On this day over the North shores of lake Nyos in Western Cameroon held a suffocating cloud of gas that left the victims 1746. In the village of Nyos, Soboma, Cha and Fang almost did not remain of the inhabitants, killed all livestock, poultry and even insects.

Since this lake is situated in the crater of a volcano, considered dormant, many researchers, who arrived here shortly after the tragedy, suggested that the volcano came to life and ejected by the eruption of poisonous gas, passing through water, poison on everything in its path alive.

The survey, carried out by expeditions from Italy, France, Japan, Nigeria, Switzerland, the USA and the UK, found that damaged vegetation along the banks of the lake. The foliage was covered with a brown film. In some places the leaves were black and shrivelled, as from cold. The conclusion was: it is a consequence of the fact that gas emitted from the depths of the lake, extending, cooled and iced foliage. It is known that the selection of dissolved carbon dioxide CO2 is the absorption of energy and therefore causes cooling. In this case cooling could be 10 degrees. The first attempts to take chemical samples of deep water were unsuccessful: when lifting vessels burst due to high pressure gases contained therein. Managed it only slowed the rise of blood vessels with an open valve. A site survey showed that 99.6 per cent of the dissolved gases represented by carbon dioxide, in addition, the samples contained methane and a small amount of helium.

Made in the laboratory by German scientists, the analysis allowed to conclude: immediately after the disaster in the waters of the lake contained about 250 million cubic meters of CO2. The isotopic composition of oxygen and carbon confirms that gases entered here, seeping from the depths of the earth. New measurements, made in April 1992, say that CO2 continues to enter the lake — about five million cubic meters a year.

All this, however, contradicts the testimony of survivors of the inhabitants, claiming that at the moment of disaster they felt the smell of rotten eggs or gunpowder, and allegedly heard the sound of an explosion. Such phenomena could accompany volcanic eruption of the explosive type. But it would have caused disturbance of the thick layer of bottom sedimentary rocks that are deposited very slowly. At the same time, none of the water samples taken did not contain precipitation and sulfur gases was not.

It is believed that carbon dioxide has no odor, but has a slight acidic taste in the mouth, it forms carbonic acid. The English researchers noted that in all six of the languages spoken by the inhabitants of the environs of lake Nyos, separate words for the concept of “smell” and “taste” is not. Therefore, when translating (often double) of these sensations could be transferred by the same word “smell”. Moreover, it is difficult to explain why some residents of the village of Soboma located 10.4 kilometres from the lake, say they simultaneously heard the roar of the explosion and felt “bad smell”, though the gas cloud could cover this distance in half an hour, and the sound for 32 seconds.

The burying of the dead was in mass graves very quickly, without an autopsy. Doctors, even native Cameroonians living in the capital of the country, local languages do not possess and symptoms suffered tragedy describe only approximately. It is noted, however, that some of the victims body were blisters. Volcanologists took it for evidence of acid or exposure to the hot gases ejected by the eruption. But live they were only superficial and healed quickly.

At 548 hospitalized and 297 individuals who received outpatient treatment, the symptoms were similar to those that come with the effects of asphyxiant gases, such as carbon dioxide. All admitted to hospital was unconscious, many of them within a few hours, which also indicates a high concentration of CO2.

All taken together led the researchers to the following conclusion. Obviously, by August 1985 water and sediment in the lake Nyos were saturated with carbon dioxide. In the rainy season (the peak falls on this month) numerous streams and rivers flowing from the South, joined the lake water, which formed a separate surface layer. It was slightly colder and denser than the lower layers. Gradually new top layer spread over the entire surface. At the same time the deep percolation of water through the very porous rocks has led to the fact that the power of the upper cold layer is increased. Usually this resolves stratifikatsiya as surface water in the late rainy season get warm.

However, on the evening of 21 August 1985, something shattered the calm of lake Nyos. Deep water rich in CO2, in the North-Eastern parts of went upstairs. It is known that in this time of year is dominated by North-easterly winds; it is possible that this time they were stronger and harder than ever, and shifted the cold surface water in the southern part of the area. It was enough to slightly denser waters to concentrate there, where they have lost a stable state, submerged and universally replaced the “soda” water from the depths to the top.

Rising water, coming closer to the surface, started to emit bubbles of gas, and since they have the buoyancy, facilitated the process of raising deep-seated masses with their own gas. All this led to the cooling water, as discussed above.

Missionaries on the surface of giant bubbles of gas generated powerful waves, stopusa the lowlands on the South shore. This gas and accompanying moisture is turned into fine mist, which formed a cold mist, which the cloud flowed through the valleys surrounding the lake, where the population is concentrated. This model does not contradict any of the facts.

It remains to determine how likely the recurrence of such a tragedy. That lake has already accumulated more than a sufficient amount of gas, no doubt. However, if the model is correct, then the gas can come again in motion, but only if a new powerful external effects, allowing deep wave closer to the surface. Such major violations of the normal state is a rare phenomenon, and perhaps the person has time to find ways to reduce the CO2 content in the water, expresses the hope journal “new scientist”.

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