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Sept.-Dec. 2003:
Since the activity remained fairly stable during this
period, comparable to the latest updates, only a new photo page has been
posted documenting activity as observed during a summit visit in Sep.
2003. It is found
here.
12 August 2003: Update - end of flank
eruption, strombolian activity with near-continuous spattering at NE
crater
As reported by INGV, the flank eruption on Stromboli
volcano finished on 22 July 2003.
At the same time, strombolian activity from the NE crater became
gradually more frequent and almost continuous in July, with spatter often
falling outside the crater rim. The SW crater showed mainly degassing and
sporadic ash emissions during July, with occasional strombolian
explosions during the second half of the month.
As on 9 August, strombolian activity from the NE crater continues,
accompanied by weak near-continuous spattering from a small intracrater
cone. Occasionally, lava bombs are ejected beyond the crater rim. In
addition to the active intracrater cone, 4 small vents inside the NE
crater are present. At the SW crater, strombolian activity produced ash-rich plumes, some up to 200 m high, and
occasionally spatter was thrown out of the crater rim.
Source: INGV
9 July 2003: Update - reappearance of
strombolian activity/ end of effusive eruption?
After repeated visits to Stromboli
during our recent expedition (see details on
travel.stromboli.net) the
following summary is given: it appeares that the
effusive eruption is about to come or perhaps
already has come to an end.
While the lava emission from 2 or 3 vents at around 500-600 m was
fluctuating in intensity throughout May and most of June, it was
essentially a continuous event. A small number of alternating or
simultaneous lava flows, usually 2 or 3, were active on the Sciara del
Fuoco during all times, reaching elevations that varied between 200 and
400 m a.s.l.; incandescent blocks tumbling down from their fronts and from
the surfaces of the flows, spectacular during the night, were frequent.
They produced a near-continuous heavy-rain-like sound, accompanied by the
deeper rumblings of occasional minor landslides and the more frequent
small rockfalls from what is left of the W rim of the 30 Dec. 2002
landslide scar. The depression that had formed by the 30 Dec. landslide
has largely been filled by the recent flows and the loose debris of lava
blocks discharged from their fronts.
On around 4 July, the lava emission
decreased significantly. On late 7 July, only a tiny small incandescent
lobe from one vent was still visible at night. At the same time, the SE
crater had started to display small and medium-sized strombolian
explosions (50-150 m high), occurring about every 20 minutes during the
night of 6-7 July. On 7 July, the SW crater (towards Ginostra) displayed
frequent and impressive emissions of brown, probably older ash, some of
which rose as billowing clouds to about 300 m above the summit. During the
night of 7-8 July, no incandescent strombolian explosions could be
observed during about 2 hours of observation, while the ash emission
continued. It is therefore likely that the internal magma column had
dropped sharply at some time on 7 July and caused internal collapses
within the conduits, that resulted in the emission of huge amounts of
older ash.
It is so far unclear weather this
heralds the definitive end of the effusive eruption, but this seems
likely. Once the lateral vents are shut down because of the lack of
alimentation, the most probable future scenario would be that the summit
craters will come back to life as the only active vents, when the magma
column rises again. That this change has already partially taken place,
was clearly demonstrated by the beautiful strombolian activity of the SE
crater that reappeared during early July, particularly when observed
during the night of 6-7 July.
Photos of the recent activity are now
available at this link.
19 May: Update
The effusive eruption is still continuing at low levels. INGV
reports several small lava flows that extend and overlap each other on the
upper flatter part of the Sciara del Fuoco, reaching down to elevations
around 550 m a.s.l. Occasional ash emissions without corresponding seismic
explosion signals are observed at the NW crater (towards Ginostra),
these are probably related to internal failures of the conduit walls. Incandescent
rock-falls from the lava flows are occurring frequently and spectacular at
night-time. In the meantime, new
regulations to visit the area and amazing photos of the 5 April
eruption as well as of the recent lava-flows have become available on my
colleagues' website www.stromboli.net.
9 April: Update/ report on 5 April explosion
INGV reports that the
effusive eruption from 4 small vents at 590 m asl. is still ongoing after
the paroxysm on 5 April. In the meantime, a dramatic report of that
particular event, based on eyewitnesses who were on a surveillance
flight during the eruption, has been published and is here given in its
full length:
-----
"From: Sonia Calvari <calvari@ct.ingv.it>
Stromboli eruption update: 8 April 2003
The effusive eruption from a vent along the Sciara del Fuoco is still
going on as on 8 April 2003. Effusion of lava takes place from 4 vents at
590 m a.s.l., with effusion rate decreasing since early March. Thermal
mapping of the lava flow field and of the craters interior revealed on
early April a talus of debris partially obstructing the summit craters
bottom. Frequent inner collapses and lithic ash emission increased the
possibility of sudden gas explosions, which eventually happened on 3rd
April 2003. Lithic angular blocks up to 50 cm wide have been expulsed from
crater 3 (the SW crater), falling mainly on the north flank of the cone up
to 300 m distance.
On 5 April, at 9:12 am local time, scientists from INGV-CT
were doing a helicopter flight for the daily surveys with a portable
thermal camera. We surveyed the active lava flow field expanding on the
upper sector of the Sciara del Fuoco, above a flat zone at the base of the
28 December 2002 eruptive fissure. Three vents along this surface were
feeding small lava flows, and the
summit craters of the volcano were producing a very diluted gas cloud. A
few minutes after the start of the survey, the gas plume coming out from
the craters and moved west by the strong wind was suddenly crossed by a
reddish ash emission, that we interpreted as further collapses within the
craters. However, the red ash was soon substituted by juvenile, darker
material coming out from
crater 1 (the NE crater). This formed a hot jet with cauliflower shape
rapidly growing above the crater. Two-three seconds later, also crater 3
produced a hot jet of juvenile material. The eruptive process then evolved
very rapidly, with jets from craters 1 and 3 joining together. A very
powerful explosion took place, which pushed the helicopter away from the
crater, suddenly increasing
its velocity of 30 knots/hour. A mushroom-shaped dark cloud rised from the
craters, expanding vertically up to an elevation of about 2 km a.s.l., 1
km above the volcano's summit. The eruptive cloud was surrounded at its
base by a dark-grey cloud similar to a base-surge, while it was still
expanding vertically and assuming the mushroom shape. Bombs, ash and
blocks fell on the
NE flank of the volcano above 400 m elevation, causing burning of the
vegetation. Most of the ejecta were brought by the wind westward, falling
on Ginostra and damaging two houses. No people have been injured by the
event.
Continuing the helicopter survey after the paroxysm, we could observe that
the lava flow field on the upper Sciara del Fuoco was completely covered
by a brown carpet of debris ejected from crater 1 during the initial phase
of the event. A very thick steam cloud was rising from this site,
suggesting vaporisation of wet material above the still active lava flows.
In the meanwhile, several
alternating black and reddish pulses were taking place, mainly from crater
3. Several fingers of light-brown debris were expanding from the NW flank
of crater 1 along the middle part of the Sciara del Fuoco. The upper part
of the volcano above 700 m elevation was completely covered by a
continuous carpet of pyroclastic products. Il Pizzo Sopra La Fossa, a hill
standing above the summit
craters, showed on the north flank a number of new fractures concave
towards north and extending between the summit of the volcano and the
south base of crater 1. The presence of these fractures makes it possible
that new landslides can occur on the summit of the volcano. Within a few
minutes from the start of the paroxysm, the upper Sciara del Fuoco showed
active flows emerging from the
carpet of debris covering the lava flow field. The explosive event caused
abundant emission of the so-called "golden pumice" mixed with little brown
scoria. The golden pumice comprised little crystals and was very
vesiculated. Often surrounded lithic blocks of crystalline, angular
material with light grey groundmass and centimetre-sized crystals of
pyroxene.
A helicopter survey carried out on 8 April showed four active vents
pouring out lava on the upper Sciara del Fuoco at 590 m a.s.l.. Two of the
flows were expanding along the middle Sciara del Fuoco, causing detachment
of blocks from the flow front and little rock falls reaching the sea.
Within the summit craters a thick carpet of debris has accumulated
following the paroxysm of 5 April. This has reduced the craters depth of
about 50 m thickness, causing partial obstruction.
Photos of the 5 April paroxysm can be found at the INGV-CT webpage
www.ct.ingv.it. "
-----
5 April: Special event: large explosion
INGV and
Stromboli on Line report an
exceptionally strong explosion at Stromboli, presumably from one of the
summit craters that occurred earlier today. This event is likely to herald
the beginning of a new phase of summit activity. A spectacular shot and
further details on a
special page
of Stromboli on Line.
Press photo released by INGV showing the ash cloud of the eruption.
According to INGV, the explosion took place at the NE
crater at 7.12 GMT on 5 April. It produced a spectacular mushroom cloud of
about 500 m height, but judged from the photograph on Stromboli On Line,
it is likely to be much higher. During the explosion, the onset of the
eruption was dominated by the ejection of lithic fragments, which can be
interpreted as effectively cleaning the crater followed by fluid spatter.
This is confirmed by distance measurements during the eruption, indicating
a rapid enlargement of the conduit diameter. In the second phase of the
eruption, it was observed (?) that fresh, hot lava was thrown out as
spatter. Some of the ejected bombs and blocks have reached the lower
slopes of the island, apparently some larger blocks have hit houses in the
village of Ginostra and others caused a number of smaller bush fires on
the vegetation of Stromboli's upper slopes. No impacts are reported from
the village of Stromboli.
It appears that the explosion has severely damaged a number of
surveillance instruments placed around the crater region, since no signals
from many instruments have arrived since the event. It looks as if no
distinct precursors have been registered enabling anyone to predict the
eruption. More details are available and even more expected to be posted
very soon on the website of the INGV.
29 March 2003: Update
As of 29 March, the lava flow is still active on the Sciara del Fuoco, but does no longer reach the sea. The active vent at
about 600 m asl. is feeding a small flow that divides into a number of
branches with the most advanced fronts being at about 500 m asl.
Incandescent rockfalls from the flow fronts are frequent as well as minor
rockfalls from the walls of the crater and the landslide scar.
Explosive activity seems to have resumed at at least one
of the craters (the NE crater towards Stromboli village) with 10-20 heard
explosions every hour, some of which are accompanied with ash emission.
In the meanwhile, the island has been reopened, but access
anywhere close to the eruptive theater is -obviously- still officially
forbidden or at least heavily restricted by the local authorities.
Detailed reports (in Italian) can be found at the INGV-CT
website www.ct.ingv.it.
1 March 2003: Update
Eruptive activity:
As of 26 February, the lateral effusive eruption at the Sciara del Fuoco
is still continuing at a low rate. After a gradual
decrease, the main effusive vent at ca. 500 m elevation has remained
inactive since15 February. Since then, the previously sporadically active vent at ca. 600 m
appears to have been the site of all lava emission. The low effusion rate,
however, did not allow to create a major lava flow extending to the sea, but
rather built up a field of small, overlapping lava lobes on the relatively
modestly gently steeping slope below the base of the NE crater.
On the summit, no explosive activity has been visibly observed at the craters,
but it is likely that weak, deep-seated strombolian activity has been
continuing, as is indicated both by seismic signals and occasionally
audited loud explosion sounds. Rare episodes of emission of brown ash from
the craters are
interpreted as caused by collapses of the inner crater walls.
On the Sciara, frequent minor rockfalls and small landslides have slowly been
eating and widening the W side of the huge scar
left by the 30 December 2002 landslide. By the same process, the
base and W wall of the NE crater is being eroded significantly. As a
result, all those, who have climbed Stromboli in the past and will
hopefully be able to do again so in the near future can expect to find
themselves facing a significantly changed scenery. Recent studies of the
submarine part of the Sciara have confirmed that a significant part of the
landslide on 30 Dec. took place underwater, resulting in a total volume of
at least 10-20 million cubic meters (ca. 1/50th of a cubic kilometer).
Detailed reports (in Italian) can be found at the INGV-CT
website www.ct.ingv.it.
(summarized from a report by S. Calvari, INGV)
Access to Stromboli:
As authorities are praising themselves for their efforts to 'protect' the
population, claiming that the Eolian island are now among the
best-monitored (and thus 'safest' ) areas on the planet, the Sicilian
newspaper "La Sicilia" announced on
27 February, that within a few days, the effective blocking of all
non-residents to the island should be suspended and free access granted to
everybody. No big surprise,- the tourist season is approaching.
1 February 2003: Update
As of 1 February, Stromboli is still erupting small, but
very beautiful lava flows on the Sciara del Fuoco from 2 vents at around
500 m elevation and a recently opened vent at ca. 600 m. Thus, lava
emission has been continuous with some fluctuation continually since 28
December. At the same time, smaller rockfalls and minor landslides are
occurring frequently on the
instable walls of the breached Sciara del Fuoco. On short visits on 23 and
24 January, the
emission rate from the vents around 500 m was very low, and no active flows reached the sea.
During that visit it became clear that the continued lava effusion had
already partly filled the channel formed by the landslide.
The strict access rules to Stromboli, maybe
questionable, are still being enforced by civil authorities. As far as information is
publicly
available, however, there is no indication that a major volcanic disaster
(such as a large explosive eruption or another large or even catastrophic
landslide triggering another tsunami) can be expected in the near future.
More intensely than the eruption, an immense amount of work is being done
by combined efforts of volcanologists, trained
mountain engineers, civil protection, military and other authorities to
monitor the eruption and install a number of modern monitoring
devices. In the future, Stromboli will probably be
one of the best monitored volcanoes around. Advanced GPS devices, tiltmeters and a stationary radioinferometer are among the critical
instrumentation that should detect any significant ground deformation as
well as larger rockfalls and landslides that could trigger tsunamis.
In an interview, the Civil Protection announced that the works should be
terminated within the next weeks, to "guarantee complete safety for
everybody on the island", and free access to Stromboli would again be
given to everybody. For the future, regular emergency evacuation exercises
are planned.
Sources:
INGV,
La Sicilia
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