Volcanologic prediction

The objectives of the Volcanologie is to include/understand the origin and the operation of the Volcan S and the comparable phenomena in order to establish a diagnosis on the risks and the dangers incurred by the populations and the human activities. The volcanologic predictions require the implementation of knowing of several scientific disciplines.

Methods

The studies and research initially proceed on the ground in order to carry out collections of information in the form of observations, measurements and samplings and in the second time in laboratory in order to analyze and to interpret the data and the samples.

Precursory phenomena

The most typical signs of an imminent eruption are not very major seisms, deformations of ground, an increased volcanic gas exhaust, an increase in intensity and temperatures of the fumerolles, landslides and crumblings minor. The majority of these signs start to be felt months or weeks before the eruption. A few days before the beginning of the eruption, other activities are perceptible like small vapor explosions and the appearance of cracks close to the eruptive chimney.

Tremors

The Seismograph S (at least three to detect the epicentre S) measurement frequencies of the tremors. One can connect the increase in their frequency to the eruptive risks.

Inclinement of the slope

With the approach of the eruption, the ground becomes deformed what causes the crumbling and the landslide. One thus measures, that is to say with a traditional method of land surveying like the statements on the level and the Théodolite, using a total station (by electronic measurement of distance, using an infra-red laser and measures angle precise or as well as using Clinomètre S or even with GPS.

Monitorings of the precursory signs

One supervises normally the temperatures of the Fumerolle S with Thermocouple S and one analyzes water samples to check the abrupt changes of their chemical composition. The emissions great magnitude of volcanic gases are recorded to measure the quantity of Sulfur dioxide. The presence of this gas is a good indication that the Magma is close to surface.

Volcanic risks

The volcanos, by their nature, can generate destruction in many forms which represent an immediate danger or with more or less long run for the man and the animal species and vegetable in general. The type of volcano (hawaïen, Strombolian, Vulcanian, Pelean, plinien or surtseyen) thus influences the risks the consequences volcano. The measures of precaution taken for a volcano with effusive eruptions as the Piton of the Furnace to the Réunion in 2007 is limited to the closing of will caldéra, whereas the inhabitants around the Mont Unzen, a gray Volcan with the Japan, were evacuated on several kilometers.

The volcanic risk is the evaluation of the consequences of an eruption on the human ones and their activities. It can be defined from a probabilistic point of view, like any natural risk, in the following way: Risk = Risk X Vulnerability X Exposure. The risk is the probability of having a volcanic demonstration. The vulnerability represents the damage or the losses which can undergo an activity or built according to the importance of the effect of the risk. The exposure represents the territorial distribution of the activities and the infrastructures. The single manner of reducing the risk is thus to reduce the vulnerability on the one hand and to limit the exposure, other. The risk is quantified by the Volcanologue. Its work is to envisage when the eruption will take place, and which will be its dangerosity.

It should be noted that the human risks related to flow mud caused by the centers and the rain, with the landslides worsened by the presence of water (rains, river or sources) cause much more damage than the lava flows or even as projection of ashes, slags and bombs.

Volcanic risk and prevention

The importance of the energy released at the time of an volcanic eruption makes that the man cannot prevent his arrival and it cannot fight directly against his effects. The only recourse is the forecast of the eruptions as well as the information and the sensitizing of the populations in order to make their evacuation most effective possible.

Using the results of the analyzes and interpretations of the data, the volcanologists can establish a forecast of the next eruption in certain cases and a zoning of the various volcanic risks for thus carrying out a cartography of the zones concerned with these risks. In a preventive way, they can then recommend the evacuation of population to the authorities before an eruption or at the time of an eruption when the risk worsens. Evacuation and alarm systems can be set up like aural signals of alarm, special routes of evacuation, the deployment of the police force, the construction of shelters, the installation of protection measures (port of the helmet, masks with dust, etc).

Monitoring

It is as difficult to envisage the beginning of an eruption as its end. The eruptions can be intermittent besides. The risks can increase or grow blurred then to begin again. It is necessary to preserve at least a certain permanent level of monitoring of the volcanos because of the persistence of the post-eruptive risks during decades.

Observatories

In Canada

To predict which will be the next movement of a volcano is a difficult task, particularly in Canada where the majority of the volcanos are located in distant and inhospitable areas.

In the United States

The geological commission of the the United States ( United States Geological Survey ) supervises closely the American volcanos

In France

The problem arises primarily in the overseas departments in the Antilles and in Martiniques

In Italy

International cooperation

There exists a plan to alert the Canadian authorities in the case of eruptions which would send ashes to Canada.

Exceptional eruptions

Certain exceptional eruptions as that of the Pinatubo in 1991 can modify the world climate. Certain assumptions make activity of a volcano of Deccan one of the causes of the extinction of the dinosaurs.

See too

volcanic Index of explosiveness

External bonds

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