Pyroclastic flows with lightning and devastation
by strong ash fall
Mt. Sinabung volcano landscape
At the beginning our
observations at the 12/13th
of January a weak activity was detected by smaller
pyroclastic flows (=> short PFs) and rock fall. Did we
come too late? No! - During our
observations from the 13th
to the 15th the activity
increased to a most highly peak since weeks. Therefore
it was possible to observe the glowing fronts of the
PFs which are seldom and only visible by night. The
special situation was, - the PFs were accompanied by
fearsome flashing while sliding down soundless over
the plain up to four kilometers.
1
2
3 
4
Single photos
1,3,4: The glowing front
of the pyroclastic flows are only visible by night.
Photo 2 upper right is a composite of 5 photos
Glowing trace of the pyroclastic flows
The
pyroclastic flows
are following
like a 'given' trace
in
the plain which seem to appear
however
aslope . Why
the PFs are not shooting straigt down is unknown.
Tornados
The heat of the
pyroclastic flows
and the wide dispensation of the front convert
the plain into a roasting
panel sheet. Due to the different heat potentials of the
fresh air currency strong tornados developes itself. May
they have the strenght of an F ?.
The whole scene in a
wide angle objective
Night impressions
of downsliding pyroclastic flows.
Like a Rolling
Stones tongue, the volcano shows the lava flow by good
weather condition.
Observing the
volcano intensively outside the exlusion zone without loosing a good
activity phase. Middle: Ashfall of 5 minutes shown on a
tripod.
By visiting the
first village we got impressed what immense mass of
falling ash covered every facillity.
The mechanism of a
pyroclastic flow generator
Now, the actual and different situation to the 1rst of
February which killed a couple of local people was a
nearly 800m lava loaf (tongue) which was maybe crushing
down at the huge front. Hence the direction could not be
determined like the “mechanism of the pyroclastic flow
generator” two weeks before.
Here, the tongue was laying like a big cake in the
active summit fracture. The forward moving material gets
weakened in its static consistency and
broke away
in the approx. first third. Now the 'target mechanism'
gets effective. This means that a narrow rock gash gives
the dynamic direction of the forward moving material to
the first plateau which is situated approx. in the half
altitude of the volcano. The PFs are now finding their
way pinpointing downward the flow field again and again.
The volcano seems to vary in its activity. One day only
smaller flows appeared, and in the next activity period
the flows run down every ten minutes.
Than the PF is plunging
down a steep rock wall on the first plateau which is
situated apprx. in
the half altitude of the volcano.
The PF is now finding its way pinpointing downward the
flow field.
The volcano seems
to vary in its activity. One day only smaller flows
appeared, and in the next activity
period the flows run down every ten minutes.
Ash devastation
On the 16th of
January we observed the villages lain in the northern
part of the
volcano. While passing the western areal strong ash
rain turns the scene in an acherontic place of
destruction.
We got impressed strongly
what immense mass of falling ash covered nearly every
facility.
Roofs and satellite bowls
broke down under the heavy load of an up to 10cm
compressed ash layer, which came down three weeks
before.
The whole harvest seems to be
destroyed. Would this ash mass came down during the
monsoon time the plants would have maybe cleaned by
rainfalls. But the ash rich eruptions happened during
the dry season. The most problem
prevailed, that the plants could not practice
photosynthesis what means the surely exodus.
Like cement the ash
enclose coffee beans and whole bushes got
irrecogniseable
on the plantages.
The volcanic ash
destruction make no stop before sanctuaries like
graves and a mosque. Here a roof crushed down because
of the heavy weight of the ash layer.
New plants urging through the hard ash plating.
,
An evacuation
center in the village of Berestagi. Althought in the state of emergency life
goes on in a patient way.
Of corse the people want to
get back to the villages but the situation of
the
active
volcano an the predictions of the volcanologists
let dominate precaution.
An
couple before the volcano outside
the exclusion zone seemed not to be frightended at
all. Also a farmer wife with her son appeared in a
hopeful manner.
All in all it was one of the most impressive
performance of a volcano with its seldom variation of
eruption. But, we had not one minute of a safety
feeling while staying at the
closer lain
observation points.
More at
ALPE
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