Montait une nuée...; elle ressemblait
très exactement à un pin. ...laissée seule ou vaincue par
son propre poids, s'évanouissait en s'élargissant.
La colonne de poussières
d'une éruption vue de la Cathédrale de Clermont-Ferrand
the "Chaîne" awake ?
Secretly, Auvergnat would wish well a small renewal
of activity some where in the Chain to supplement
this fantastic landscape. Let us acknowledge that it would be
unhoped for local volcanology. The analysis
of the eruptions gives many answers to the questions
about the volcanic mechanisms. But, reasonably the local and
national persons in charge would have to face a situation
From the start one draws aside a sudden
eruption. The seismic first steps
of a magmatic increase will be well collected by the inspection
network in place. The signatures of such a phenomenon are known
and one will be able to determine as well as possible, with
a complementary instrumentation, the perimeter
of the exit point. The problem to be solved by the
specialists remains the evaluation of the probable date of the
eruption. From there will depend the options retained by the
civil authorities which will have to do what is necessary to
evacuate without delaying,
the zone considered to be dangerous. The nonexplosive character
(Plinian) of the volcanos of the Chain makes it possible to
circumscribe a sector of only a few tens of kilometers. We can
imagine these cases :
- Strombolian " only ": it is the model most present
in the Chain. The risks could be very limited. With term, only
the lava flows being propagated
with dimensions East will be worrying for the Clermont-Ferrand
- Pelean or trachytic: the effects of the last episodes
apparently were very limited. But Pelean operation is unforeseeable
bus of the volcanic clouds
can always develop and devastate the neighbours.
Phréatomagmatic: it is a very possible scenario because
all the sector of the Chain comprises significant water reserves. The
explosions of this type are generally of great width with projections
of blocks to impressive dimensions.
In addition to the eruptive demonstrations, water
the pollution of sources, the always possible
gas emissions, the plumes
of dust falling down neighbourhoods, are as many
effects to consider.
If it were the case, there is no doubt that
it would be a whole area which would be upset. The displacement of some five hundred
miles people, by its social and economic impacts,
would pose surely a serious problem of logistics.
It is interesting to see what it would occur through
observations brought back by médias
such a significant event. Here in a local newspaper
the kind of informationhat we could find, in a context with the limited consequences.
It is supposed of course that the daily newspaper is printed elsewhere than in
Clermont- Ferrand. (English version of newspaper)
The volcanic activity
last volcanos died out 6500 years ago (Pavin system). Since there no were recognized
demonstrations. This time is too short to
conclude that the Chain of Puys is definitively deadened. The
probability of a renewal of activity is not negligible. But where?
Search does not make it possible to answer this question immediately. It is necessary
to have more precise localization of the magmatic tanks
and a thorough knowledge of the structure of the base. With the obviousness certain
hot sources of the various thermal spas Auvergnates, such as "Chaudes-Aigues",
are indication of latent volcanic situation.
The seismic activity
It is significant and primarily tectonics, in connection
with the push of the Alps.
Contained in low values, it appears sometimes with the inhabitants
of the area. Example the numerous events of August, 2003 (see
the usual page), with a shock of magnitude 3.6, and the
epicentres of which extended of the sector of Ancizes-Comps
until the Gour de Tazenat
(RENASS source). This seismic episode, fortunately without
consequence, was more intense as usual.
At left a
photograph simulating the western horizon
of the Clermont-Ferrand plain. The permanent reddish glow of the craters projecting
of incandescent slags is an always extraordinary and attractive night spectacle.
The prehistoric men of the area surely observed
these phenomena, without being able to give them explanations. Today, an event
of this type, by its social and economic repercussions, would have very an other
width, in spite of the scientific and tourist
interest which it would get.
This picture is Etna in strong Strombolian
activity (Christmas 1997) seen live-camplaced on Montagnola (animation
of the site of the General Council pointed at the puy of Dome
from Clermont-Ferrand will allow you, for lack of assiter
in a possible event directly,
to appreciate the remarkable landscape