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The Herald of the forthcoming was sent by the Nature. The Rain in Cameroon at 1983 had brought the announcement about forthcoming catastrophes. But the blindness of the people, the reason that the announcement was not be read. The Price of the blindness–the loss 1800 life in 1984 and 1986 on the lakes «Monoun» and «Nyos». In the afterlight of the people – their a salvation.

Nyos: Limnological catastrophe
(Natalija Solodovnika · Anatolijs  Solodovniks )
Riga, Latvia, e-mail: nyos@nyos.lv


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14.08.2006


Limnological catastrophe

The Limnological catastrophe represents the physical phenomenon, at which are included by obligatory constituting part, ruinous for people and for animals, the ejection of gas from open water basin.
The Limnological catastrophe characterize by chemical compound, by mass and origin of  gas, by  duration of the ejection of the gas, by the trigger mechanism of catastrophe.
The Limnological catastrophe occurs since moment of time, when   was switched on the trigger mechanism of catastrophe.
Limnological catastrophe can accompany, occur simultaneously or as a result of beginning of other catastrophes in the water basin or in his vicinity. For instance, at undersea eruption of the vulcan, at penetration of flow of the lava into the water basin and at other disastrous events.  At such events more powerful, relatively of aftermath, catastrophe masks presence not so powerful by which can be of the limnological catastrophe. The Typical example the limnological catastrophes represent the catastrophes in  Cameroon:

  • August 21 1986 on lake Nyos, at which had perished 1700 persons;
  • August 15 1984 on lake Monoun, at which had perished 37 persons.
The Conditions required for the  beginning of  limnological catastrophes, exist in lake Cameroon not only, but also in others the  open water basins of our planet, for instance:

  • on lake Kivu in east Africa;
  • in lakes near mountain Mammoth Mth in USA;
  • in lake Mashu in Japan;
  • in maar Eifel in Germany;
  • in lake Pavin in France.

The Conditions required for begining limnological catastrophes, can be created by leakage of carbon dioxide (CO2), who are swinging to the deep geological structure for long-term storage. The Gas, in the open water basins, can have magmatic origin (Nyos and Monoun), biogenic origin (lake Kivu) or technogenic origin (the gas, which are swinging into deep geological structure for long-term storage).

«The Trigger mechanism»

The Trigger mechanism of limnological catastrophe characterize by composition, by location (the combination) of the forming parts and by the mass transfer.
In composition of the trigger mechanism of limnological catastrophe the parts  can  falls into  varied of combination:   
  • lake's waters, characterize by greater gradients of the temperature, of masses and of concentration of the solutes;
  • earthquake;
  • landslide;
  • mudslide;
  • wind;
  • atmospheric precipitation;
  • underground geological structures.

The Mass transfer

The Mass transfer in trigger mechanism define by composition, by location of the forming parts and by  physico-chemical properties of the flows of substances of these parts.At least one of the flows of the substances in obligatory order contains the  components, which have  ability  are generating the gas.

To Switch on

The parts, forming the trigger mechanism of limnological catastrophe, switch on   the trigger mechanism, when features of parts become critical.

The  Prevention

Blocking of ability   to switch on, of   the  trigger mechanism, prevents from limnological catastrophe.
By The Manner of blocking of ability to switch on, of the trigger mechanism can be:

  • fortification of coasts of the water basin;
  • the degassing of waters of the water basin;
  • increasing or reducing of the level of waters in the water basin;
  • the swinging (or evacuating) of the water and the water solutions into the aquifer;
  • soak of solid stratums, which are  situated under bottom of  water basin, by the watertight substance;
  • by intrusion into the geological structures of the microorganisms , whose products of vital activity reduce porosity of the geological structures.

Monitoring

The Permanent actions on prevention of limnological catastrophes shall be accompanied by  monitoring of  the  state of  "trigger mechanism of" catastrophe.

Nyos

High elevated  (1090 m. above of sea level) the lake Nyos is formed 400 years ago by  surface and underground waters, which have filled the crater of maar, what had   formed as a result of the hydrothermal blast. The Explosion has occurred when the flow of the lava have met with underground water.

The Lake Nyos  (6.44N 10.30E ) is located in Northwest province of  Cameroon on the declivity of the mountain formation belonging to the volcanic  chain , which has  stretched in northeasterly direction  from Atlantic ocean till the  alpine of  Cameroon. On big depth under mountain formation is situated magma, which continuously emits   carbon dioxide (CO2).  Carbon dioxide (CO2) moves upwards (the leakage) and dissolves in underground waters.

The Depth of lake Nyos 209 m., length 1400 m., width 900 m.. In the vicinity of  lake   there are numerous springs , in which water are     carbonated  ( contains  the carbon dioxide  (CO2)).
North coast of lake are confined by natural dam from volcanic rocks, and with height  till 40 m.. Lake's waters via natural spillway on surface of the dam flow down along mountain declivity into river Katsina. The Dam has needs for urgent repair. The Progressing corrosion of the volcanic rocks, which are   forming body of the dam, relaxes the dam and can be by cause her of destruction. The Destruction of the dam will cause the disastrous flood of the adjoining territory of Cameroon and Nigeria, will lower the level of lake's waters and will be disturbing of the ecology of the lake and of the  adjoining territory.

On opposite declivity of the mountain formation at south-east direction on distance 95 km. are located another (  are  cognates with lake Nyos)    lake Monoun (the depth 95 m.) (5.58N 10.95E), which is also formed by the water, which have filled crater of the volcano.

The big mass of carbon dioxide  (CO2), from terrestrial depths, continuously are supplying into (leakage) the lake with the underground waters.

Lake's waters characterize by the positive temperature (practically unchangeable on volume and at time), by high concentration of carbon dioxide (CO2) and by big gradient of this concentrations. Resemblance of the lake Nyos with the lake Monoun are complemented by the unified  (for lakes)  the atmospheric precipitation and by the unified (for lakes)   the source (the magma) of  carbon dioxide (CO2).

Limnological catastrophe

At August 21 1986 on lake Nyos has occurred of the limnological catastrophe, which has carried away the lifes of 1700 mans. Two years before that, at August 15 1984 the similar limnological catastrophe has occurred on lake Monoun in Cameroon, which has carried away the lifes of 37 mans.
In both catastrophe the enormous mass of gaseous carbon dioxide was thrown away from lake's waters during several hours .
The Gas thrown away from the lake Nyos at August 21 1986, was moved quickly   by two flows along mountain declivity, and    all alives on distance till 25 km. from lake was killed by gas.

«The Trigger mechanism»

The Distinguishing features of limnological catastrophes are «Trigger mechanism» and condition for his to switch on. The different variants of the composition «Trigger mechanism», responsible for different variants of  limnological catastrophes on the  lake Nyos, could be  Possible:
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