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Is the chain going to wake up?
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La colonne de
poussières d'une éruption vue de la Cathédrale
de Clermont-Ferrand
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 Secretly, the Auvergnat would really like a small
resumption of activity
somewhere in the Chain to complete this fantastic landscape.
Let's admit that it would be unexpected for local volcanology.
The analysis of eruptions
provides many answers to questions about volcanic mechanisms.
But, reasonably, local and national authorities would have
to face an unprecedented situation.
Right from the start, a sudden eruption
can be ruled out. The seismic precursors
of a magmatic uprising will be well captured by the national
monitoring network. The signatures of such a phenomenon are
known, and it will be possible to determine as accurately
as possible, with the help of additional instrumentation,
the perimeter of the exit point.
The problem that specialists still need to solve is the estimation
of the probable date of the eruption. From this will depend
the options chosen by civil authorities who will need to take
the necessary steps to promptly evacuate the area deemed dangerous.
One can imagine the following scenarios:
- Strombolian:
this is the most common model in the Chain. The risks could
be very limited. In the long term, only the lava
flows spreading toward the east would be worrying
for the terraced Clermont habitat.
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Peléan: the effects of past episodes have been,
it seems, very limited. But Peléan activity is unpredictable
because pyroclastic flows
can always develop and destroy the surrounding area.
- Phreatomagmatic: this
is a very plausible scenario because the entire sector of
the chain contains significant water reserves. Explosions
of this type are generally large-scale with projections of
blocks of considerable size.
In addition to eruptive manifestations, water
source pollution by gases, the always possible
gas emissions, and falling
dust plumes in the surroundings
are all effects to consider.
If this were the case, there is no doubt that an entire region
would be disrupted. The displacement of a few thousand people,
due to its social and economic impacts,
would certainly pose a serious logistical problem.
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