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WARNING:
Access to the summit area is DANGEROUS.
Explosive activity is occurring at the Bocca Nuova, and at times
bombs are thrown beyond the crater rims. Lava is also flowing
from a vent on the NNE flank of the Southeast Crater cone, but
this vent is virtually inaccessible due to its remote location
and the hostile terrain around it. Guided excursions on the
south flank that end at the Torre del Filosofo, at about 2900
m elevation, have resumed in mid-March. Tourists
should make excursions only with the mountain guides,
even though this will not satisfy the wish to see what's going
on at close range. Besides this, weather conditions are often
unstable: strong wind, snow or rain and clouds are occuring
frequently in the summit area, and one can get easily lost.
The mountain guides can be contacted at the cable car (near
the Rifugio Sapienza) on the southern side of Etna (phone: 095-914141),
or (during the summer) at the hotel "Le Betulle" at
Piano Provenzana, on the northern side (phone: 095-643430).
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26 March 2001 update.
On 25
March, Boris Behncke (Dipartimento di Scienze Geologiche of the University
of Catania) and Giuseppe Scarpinati (Italian delegate of the "Association
Volcanologique Européenne" based in Paris, France) visited
the summit craters of Etna for the first time since 25 October 2000.
It was a welcome escape from the unusual heat of the Catanese lowlands
(on 24 and 25 March, the thermometer struck 37° C) and a long-awaited
return to the "fiery lover", which had remained, in Behncke's
case, a distant landmark throughout the period of PhD completion.
The volcano greeted them with splendid, though relatively modest,
activity at the Bocca Nuova and the effusive vents low on the NNE
flank of the Southeast Crater cone.
The Bocca Nuova, from a morphological point of view, was very much
like last autumn, with two large pits in its NW and E parts. Both
pits were erupting, but in quite different manner. The E pit, about
100 m wide and no more than 25 m deep, had four closely spaced vents
on its floor, of which one was the site of continuous Strombolian
activity. This activity varied from relatively weak spattering to
fairly strong bursts which produced jets densely charged with incandescent
fragments rising at times up to 100 m above the lip of the pit. The
fragments fell mostly on the SE and E sides of the pit, and so it
was possible to peer into the pit from its S and SW rims. The active
vent, located in the NW part of the pit's floor, was 5-10 m across,
the other (inactive) vents had similar diameters and were mildly fuming.
The activity in this pit was purely magmatic, with virtually no vapor
generation.
The NW pit, which has a diameter of about 150 m, showed a strikingly
different, and far more dangerous, behavior. During a brief glimpse
into that pit from its SW side it was possible to ascertain that it
was quite shallow as well - 30 m or so below the lowest point of its
(S) rim. Its floor was occupied by a broad, low pyroclastic cone with
an active vent in its SE part. This vent would produce low pitched
hissing noises every few seconds, and for certain periods it emitted
dense, white steam plumes indicative of a high degree of humidity
within the conduit (relative air humidity was exceptionally low at
that time). Then, a dull, muffled, roaring noise would come from the
vent, accompanied by the rapid ascent of a jet of grayish-brown ash.
Through the rising puff of ash thousands of dark rock fragments would
shoot considerably higher, and these often fell outside the pit in
all directions. After dodging some falling fragments, Behncke and
Scarpinati noted that some of these were fresh scoriae, up to 10 cm
long, while others were dense lithic blocks which were quite hot to
the touch and emitting wisps of vapor. One block which fell about
8 m from Behncke was about 6 cm across. Dense projectiles of this
size can cause serious injury if falling on a person's head.
Most ejecta, however, fell back into the vent and onto the adjacent
walls of the pit, triggering rockslides into the vent. This seems
to have been the principal mechanism of the activity in this pit:
the sliding material clogged the vent until a new burst would temporarily
clear its throat. Evidently much of this material was moist, causing
abundant evaporation once it had slid into the hot conduit. The activity
was phreatomagmatic, but fortunately it was mild - in 1979 a significantly
larger phreatic explosion in the Bocca Nuova caused the death of 9
people and injured more than 20 others.
The Bocca Nuova floor surrounding the two active pits was littered
both with scoriaceous and dense bombs. The largest among them (up
to 3 m in diameter) were clearly older, probably from the period of
intense activity in October-November 2000, but some fresh clasts lying
as far as 50 m from the NW pit were up to 0.5 m across.
The second target of the visit was the active lava flow issuing from
a vent (or to say more precisely, a cluster of vents) low on the NNE
flank of the Southeast Crater cone. Of all places on Etna where an
effusive vent could be located, this is probably one of the least
accessible, and it lies in a precarious position near the Southeast
Crater whose violently explosive potential has been unleashed 66 times
in 2000. To say it in a few clear words, getting to that vent is a
BIG pain in the neck. Either descending from the E side of the main
summit cone or struggling one's way across the lower E side of the
Southeast Crater cone, one encounters a highly hostile environment,
and above this looms, with its tantalizing steepness, the Southeast
Crater cone, presently quiet but who knows for how long.
In return for the tremendous struggle to reach the effusive vents,
the place where the lava reaches the surface is a relatively bland
affair. On 25 March, from the top of a wmall knob (or tumulus) there
oozed two narrow rivers of lava, one to the E, the other to the W,
the latter turning N at 2-3 m from the source. There was no kind of
explosive activity at the source of the two flows, neither could any
high-pressure degassing be observed.
The most striking thing about this effusive activity was how similar
it was to the lava emission on the SE side of the Southeast Crater
cone two years earlier, especially in its quieter moments. Both flows
issued at a combined effusion rate of less than 1 cubic meter per
second, but smaller flows issued from a few points on the lower W
and N flanks of the tumulus, so that the overall effusion rate may
have been as much as one cubic meter per second. Several active flows
were seen moving NE and E to a distance of 250-300 m from the summit
of the tumulus, amidst stagnant older lobes of lava. A fan-shaped
compound lava field spanning a sector from NNE to ESE and consisting
of numerous leveed flow lobes had formed during the preceding more
than 2 months of effusive activity.
Surely enough any visitor to Etna should decline from the idea to
visit the flowing lava on the NNE side of the Southeast Crater cone.
Exept to experienced conoisseurs of Etna, it is virtually inaccessible.
A dense, sulfur dioxide-rich plume from the Bocca Nuova frequently
passes directly over the area, making breathing difficult. The terrain
immediately around the tumulus consists of sharply edged, loose, unstably
placed blocks, and the risk of stumbling and falling on this material
is high. The (rather inexistent) path around the E side of the Southeast
Crater cone is covered with countless blocks, with diameters of tens
of centimeters, which have fallen down the oversteepened E face of
the cone. Rockfalls were frequent during Behncke's and Scarpinati's
return passage through that area. Furthermore, in the case of a sudden
reactivation of the Southeast Crater or of an intensification of activity
at the effusive vents, there is hardly any escape route.
Last week local newspapers and television reported on the lava flow
for the first time since its initiation (20 January), and surprisingly
it was this media coverage which finally aroused the interest of locals.
Due to its modest extension, and because it frequently hides behind
the ridge formed in 2000 at the lower end of the eruptive fracture
on the NNE side of the Southeast Crater cone, the flowing lava has
been almost invisible for the naked eye from the larger populated
centers on the lower E, SE and S flanks of Etna.
6 April 2001 update.
Fine weather
has returned to Sicily earlier this week, and Etna has been visible
most of the time. Snow that had fallen over the weekend rapidly melted,
and the mountain, as viewed from south, is practically snow-free,
unusually early this year. During a two day-long excursion with students
from Bern, Switzerland, Etna was observed over long periods, and it
seems that the activity at its summit craters has somewhat decreased
lately. There is still lava flowing from a vent low on the NNE flank
of the Southeast Crater cone, much the same way it has done since
about 20 January, but the Bocca Nuova has calmed down to produce only
sporadic ash emissions. No night glow has been seen at that crater
throughout this week.
Yet the excursion was a great event to everyone who participated.
We first got up to about 2500 m elevation with the cable-car on the
southern flank and then climbed to the summit of the Montagnola, a
large cinder cone formed during an eruption in 1763, from where there
is a marvellous view over the summit area of the volcano, and eastwards
into the spectacular Valle del Bove, a huge depression (caldera) formed
when the eastern flank of the volcano collapsed about 8000 years ago.
The second part of the escursion led to an area about 2 km to the
west of the Rifugio Sapienza, at about 1800 m elevation on the south-southwestern
flank, which has beautiful forests, cut by various generations of
lava flows (1537, 1780, and 1985, all of which have a thin cover of
scoriaceous lapilly erupted in 2000). On the second day the group
was guided to the Monti Rossi, one of Etna's largest flank craters,
which erupted in 1669 and produced a lava flow which eventually reached
the outskirts of Catania, after annihilating 15 villages. This crater
lies about half way between the summit and the city of Catania, and
a visit to this site gives an impression of the sheer dimensions of
Etna. The final stop was the area where the 1669 lava flow reached
the sea south of Catania. Outcrops of the lava are present in a few
locations at what at the time were the western and southern margins
of the city.
27 April 2001 update.
During
the three weeks since the previous update, activity at the summit
craters of Etna has continued, at a decreased rate first, but in a
progressively increasing manner since about 20 April. Lava effusion
from a vent on the lower NNE flank of the Southeast Crater cone has
continued unabated, and an increase in the effusion rate has become
evident on 26 April. Descriptions of summit visits by Charles Rivière
and others can be found (in French language) on the web site "Etna
volcan sicilien". Seismic activity in the Etna area, more
vigorous than in previous months, is reported in detail in the 16-22
April bulletin of the Poseidon monitoring network (now part of
the National Institute of Geophysics and Volcanology INGV). The following
is based on direct observations made by Behncke and Scarpinati on
25-27 April.
When returning from a visit to Lipari on 25 April, Behncke noted ash
emissions from the Bocca Nuova and light gas emissions from the effusive
vent on the NNE flank of the Southeast Crater cone. The following
day at nightfall, Scarpinati noted that the active lava flow from
that vent had lengthened significantly and was well visible with the
naked eye. Scarpinati estimated the length of the incandescent flow
at at least 600 m.
During daylight on 27 April, dense gas emissions (not forceful, though)
were visible at the summit vent of the Southeast Crater. These emissions
were considerably denser than during recent weeks and their concomitance
with the increased lava output at the effusive vent might indicate
a higher magma flux towards that crater, which last erupted vigorously
in late August 2000. Increased activity at that same vent in February
2001 culminated in a brief episode of Strombolian activity, but was
not followed by paroxysmal lava fountaining, tephra emission and production
of voluminous lava flows.
Several
other web pages covering the recent and ongoing eruptions of the Southeast
Crater are now available; these contain photos and movie clips of
some of the most spectacular moments of that period.
Etna
in 2000 - a list of all paroxysms at the SE Crater since 26 January
and photos (this site)
Etna
in 2000 - various pages at Stromboli On-line with photos and movie
clips of SE Crater paroxysms and Bocca Nuova gas rings: most photos
are of Marco Fulle, the artist photographer among us
Extremely
spectacular video clips, taken by British cameraman and film maker
David Bryant on 15 February 2000
At
"Italy's Volcanoes" -
At Stromboli On-line
An
interview with Boris Behncke, made in late February 2000 by a BBC
team
and a video
clip (RealPlayer)
Photos
of the eruptive activity, 15-23 February 2000, by Tom Pfeiffer (University
of Arhus, Denmark) - scroll to bottom of page
Photos
of an eruptive episode on 13 February 2000, posted on the web site
of the Association Volcanologique Européenne, Paris, France
Thorsten
Boeckel's web site (Germany) with photos and movie clips of several
paroxysm of the SE Crater in February, April and June 2000
A
small web page reporting on Etna's current activity - and check what
happens to your cursor on that page...
Charles
Rivière's Etna home page, with many photos and video clips
(the most recent of the paroxysm of 5 May 2000), frequent updates,
and other, highly interesting items (in French and English)
