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WARNING:
Access to the summit area is VERY
DANGEROUS. Violent eruptive episodes are occurring
every few days at the Southeast Crater, and heavy showers of
tephra (including clasts tens of centimeters in diameter) may
occur up to several kilometers away. Lava may also arrive rapidly
at up to 1.5 km of distance from the crater on the plain between
Torre del Filosofo, Monte Frumento Supino, and the summit crater
cones. The Torre del Filosofo area, which is familiar to many
excursionists, is presently not a safe place at all. Tourists
are presently not allowed to go beyond 2700 m elevation,
and they should make excursions only with the mountain guides.
Besides this, weather conditions are often unstable. Strong
wind, snow or rain and clouds are occuring frequently in the
summit area, even during the summer, 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, or
(during the summer) at the hotel "Le Betulle" at Piano
Provenzana, on the northern side.
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Simultaneous
eruption at the NE Crater and the SE Crater, 15 May 2000
Photo
by Angelo Nicotra, Catania
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There
are probably very few photos existing of the NE Crater and the
SE Crater erupting simultaneously. Here's one, taken on the
early morning of 15 May from Piano delle Concazze (at about
2600 m elevation on the NE flank of Etna), when Strombolian
activity occurred at the NE Crater (right) and a small lava
flow was extruded from the eruptive fissure on the N flank of
the SE Crater cone. That crater produced a paroxysmal eruptive
episode a few hours later, and yet another on the late evening
of 15 May. This photo was taken by Angelo Nicotra who works
at Piano Provenzana, a privileged position to see eruptive activity
at the summit craters
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NEW:
PHOTOS OF THE 14 JUNE 2000 PAROXYSM
AT THE SE CRATER
NEW:
SOUNDS AND MOVIE CLIPS OF THE
24 JUNE 2000 PAROXYSM AT THE SE CRATER
26 June 2000 update.
The following paragraphs have the detailed description of the latest
paroxysm at the SE Crater, on the late evening of 24 June. The event
was unusually well documented due to the presence of numerous observers
in various places of the mountain: Boris Behncke and David Bryant
at the Pizzi Deneri on the upper NNE flank (about 3 km from the SE
Crater), Marco Fulle at Torre del Filosofo (about 1 km S of the SE
Crater) and Giuseppe Scarpinati at Monte Zoccolaro on the SE flank
(about 5 km from the SE Crater). Behncke and Bryant arrived at their
observation spot at about 1800 h, while Fulle had been at Torre del
Filosofo since earlier that day, and Scarpinati reached his observation
post at about 2300 h.
According to mountain guides, slow lava effusion began from the lowest
vent on the eruptive fissure on the N flank of the SE Crater cone
on the morning of 24 June, sometime after 0800 h. A small lava flow
began to extend eastwards, reaching a length of a few hundred meters
during the following hours. When Behncke and Bryant drove through
the villages of Milo and Fornazzo during the early afternoon, a steaming
streak was distinctly visible extending down the steep slope below
the N flank of the SE Crater cone, and it became clear to them that
the crater had once more entered the buildup phase towards another
paroxysm. After obtaining more information from the mountain guides
at Piano Provenzana, who had observed the effusive activity from the
Pizzi Deneri (a cluster of peaks on the highest part of the "Serra
delle Concazze, the N rim of the Valle del Bove) a few hours earlier,
they decided to climb to the rim of the Valle del Bove to observe
the evolution of the activity. At about 1700 h they arrived at the
crest of the rim above the 1928 eruptive fissure, but the view was
seriously obstructed by a dense plume of gas, which came from the
NE Crater and the Bocca Nuova, and which was pushed down into the
Valle del Bove by a very strong wind, along with weather clouds. Climbing
westwards on the crest of the rim, towards the Pizzi Deneri, they
gradually obtained better views, as lighting conditions improved,
and a brightly incandescent ribbon became visible through gaps in
the gas plume. By 1800 h, when Behncke and Bryant reached the easternmost
peak of the Pizzi Deneri, the lava flow had already extended about
1 km from its source vent, flowing on the steep slope towards the
Valle del Bove. The flow was being fed vigorously, and a dense gas
plume was issuing forcefully from the effusive vent on the lower N
flank of the SE Crater cone. Every now and then the summit of the
cone became visible, and it could be seen that the summit vent was
filled with gas, while no activity of any kind was visible along the
upper part of the fissure on the N flank of the cone.
As darkness began to fall, visibility improved steadily, and at the
same time the lava flow rapidly advanced downslope. The activity was
still completely quiet and non-explosive, there was no spattering
at the active vent, and no eruption noise could be heard, although
low level noise would probably have been masked by the very strong
wind blowing at the observation site.
From the south the effusive activity became evident as darkness fell;
a very bright glow was visible behind the SE Crater cone, but there
was a complete absence of activity at the summit vent, except profuse
gas emission.
By 2200 h the lava flow had doubled in length, its front being about
2 km from the source vent, and advancing at high speed on a steep
slope a few hundred meters above the floor of the Valle del Bove.
Visibility was now excellent, although the powerful wind continued
to push gas emitted from the NE Crater across the Valle del Leone
(a depression lying to the NW of the Valle del Bove, between the Pizzi
Deneri and the summit cone complex). The active lava flow was very
narrow in its uppermost part, where it flowed on the steep lower flank
of the SE Crater cone, but widened and braided at its base. In its
lower part the flow consisted of two or three branches racing towards
the Valle del Bove, and overtaking each other alternatingly. Large
blocks of bright yellow incandescent lava were seen floating on the
flowing lava in the upper part of its course; when coming down through
the channel immediatey below the effusive vent, these blocks moved
at a speed of 30 m per second but slowed to about half that velocity
at the base of the steep flank of the cone. Some blocks foundered
at the slope break, others turned over several times and then continued
to float on the flow surface.
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A
small tornado on the lava flow from the SE Crater paroxysm,
24 June 2000
Photo
captured from video taken by David Bryant
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Sometime
before the eruptive episode of the SE Crater on the evening
of 24 June reached its paroxysmal phase, a small tornado developed
on the lower part of the rapidly advancing lava flow that was
emitted from the crater for many hours before the paroxysmal
phase. This image has been captured from video recorded by David
Bryant; the image has been contrast enhanced to make more features
visible. The lights of Catania can be seen in the upper left
corner of the image
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Still there
was no spattering at the source vent, which remained the only site
of eruptive activity, and no sound except the roaring of the wind
could be heard. A small glowing spot - probably a high temperature
fumarole - was seen on the E rim of the summit vent of the SE Crater,
but otherwise there was no visible activity except at the effusive
vent. There was no glow at the NE Crater, although its gas plume was
at times ejected much more forcefully, and at least one gas ring was
observed to be emitted from that crater, while smaller gas rings were
near continuously produced by the Bocca Nuova. These rings were illuminated
by the yellow-orange glow of the lava flow, which also lighted the
entire upper part of the volcano on its E side. Behncke and Bryant
were able to move around at their observation post without using torches.
At about 2300 h things began to evolve. Behncke and Bryant had built
a makeshift shelter of rocks and pieces of an abandoned seismic station
(which obviously had been vandalized some time ago) to protect themselves
and their equipment (film and still cameras) from the wind, which
often carried centimeter sized pieces of rock with it. Every now and
then rumbling and roaring noises became audible above the wind noise,
even though they were not accompanied by any visible changes in the
activity. The roaring noise became stronger and more continuous, and
at about 2310 h it attained a crashing character, which was immediately
followed by a dramatic increase in the effusion rate at the active
vent; lava overflowed on both sides of the flow channel immediately
below the effusive vent, and a surge of very brightly incandescent
lava spilled downslope on top of the still moving, earlier lava.
For the next 20 minutes the noise level increased steadily as did
the effusion rate, yet there was no explosive activity at the effusive
vent, and no eruptive activity occurred elsewhere.
At about 2325 the noise of degassing once more increased and became
quite spectacular, and this was finally accompanied by the rapid uprise
of an ash column from somewhere in the upper part of the eruptive
fissure on the N flank of the SE Crater cone. From Torre del Filosofo,
Marco Fulle could well observe that at this time the summit vent was
still inactive. The ash emissions were accompanied by jets of thousands
of incandescent lapilli - not bombs or any other large clasts, just
small lapilli. But now things evolved at amazing speed. About 60 seconds
after the first ash puff, a huge lava fountain was seen shooting up
from the summit vent, and in the same moment the lowest vent on the
eruptive fissure, which previously had emitted the lava flow, began
to eject a lava fountain at an almost horizontal angle towards NE,
in the direction of Behncke's and Bryant's observation post. This
fountain, however, was quite small, and bombs did not fall farther
than 200-300 m from the vent. Just when Behncke and Bryant were still
captured by this awesome sight, more fountains roared up from numerous
vents along the entire length of the eruptive fissure, and five or
six tongues of lava appeared on the W side of the eruptive fissure
and very rapidly spilled downslope, towards the Valle del Leone.
Meanwhile the lava fountain at the summit vent continued to grow vertically.
The fountain consisted of pulses following each other in rapid succession,
and each rose higher than its predecessor, until the fountain roared
to about 1000 m above the summit of the cone. Myriads of glowing bombs
and scoriae were seen rising and falling in an incredibly turbulent
manner, and within one or two minutes the entire cone was covered
by incandescent material. At some of the vents on the eruptive fissure
on the N flank of the cone, lava fountaining alternated with emission
of black plumes of ash. The lowest vent no longer produced an inclined
jet of lava, but the lava in this vent was now splashing and exploding.
The main lava flow, on the E side of the cone, had increased enormously,
and a voluminous surge of fresh lava raced downslope on top of the
earlier lava, which was still advancing rapidly towards the floor
of the Valle del Bove.
At the height of the paroxysm, a vent opened high on the S flank of
the SE Crater cone, in the same place where small lava fountains had
occurred during the most recent paroxysms, and a small volume of lava
was emitted there, forming a flow that split into two branches at
the base of the cone. One of these branches flowed W while the other
took a more southwesterly course, in the direction of the 1971 "Observatory"
cone.
At about 2340 h, the entire scene was shrouded in dense gas and falling
pyroclastics, so that only the lowermost of the lava fountains on
the eruptive fissure could be seen, but after some time it became
evident that the main lava fountain was rapidly dying out. Strangely
enough, at the same time the noise level went up in an incredible
manner. The air was filled with a tremendous roaring and thundering
din, which went through numerous phases of waxing and waning. The
noise of the wind seemed almost absent compared to that sound, although
the wind had not the least diminished. The spectacle of sound eventually
culminated with a profound and extremely loud roar and a series of
cannon shot-like detonations, caused by supersonic gas jets in the
conduit where the degassing magma was subsiding. This phase of activity
was accompanied by the forceful emissions of a very dense column of
black ash, which rose more than 1 km high. The detonations were heard
overe a vast area in E Sicily, causing some apprehension among people
living in villages on the volcano's slopes, who had already been impressed
by the violence of the lava fountains and the unusually long lava
flow on the E flank.
At his observation point on Monte Zoccolaro Giuseppe Scarpinati found
himself under a rain of scoriae, some of walnut size, which forced
him to retreat under a tree. The view from there of the erupting crater
was hampered by the gas and tephra plume, but the advancing main lava
flow could be seen better from there than from anywhere else. The
front had now reached the bottom of the Valle del Bove at the base
of its steep W slope, in an area between the cinder cones of the Monti
Centenari (1852-1853 eruption) and Monte Lepre, almost 3 km from the
SE Crater. On the flat ground the lava began to fan out, but still
it advanced at a speed of about 0.5 m per second. The flow front was
5-10 m thick with many large incandescent boulders rolling from its
sides and to quite some distance away from the flow, only to be buried
by the advancing flow front a few seconds later.
After the impressive detonations, the noise level rapidly declined,
and the wind noise again became dominant at the Pizzi Deneri where
Behncke and Bryant were just beginning to realize what had happened
during the previous 15 minutes. Small lava fountains were still playing
intermittently at several vents in the lowest part of the eruptive
fissure, but feeding of the lava flows towards the Valle del Leone
had stopped, and also the main lava flow towards the Valle del Bove
received less and less fresh lava. The 64th paroxysmal eruptive episode
at the SE Crater in 5 months was over.
Just as the eruptive activity waned, thousands of inhabitants of the
Etna region who had seen the lava fountains and the long lava flow
jumped into their cars, called their friends and neighbors on their
cell phones and began to speed towards the Rifugio Citelli on the
NE flank, and towards the Monte Zoccolaro area on the SE flank. More
and more cars were seen racing up the "Mareneve" road which
leads from Fornazzo to the Rifugio Citelli and further on to Piano
Provenzana, and up the road leading from Zafferana to Monte Zoccolaro,
and on to the Rifugio Sapienza. Within about 20 minutes these roads
were completely jammed, and the situation became even worse as many
cars who had arrived earlier began to return downslope when people
recognized that the eruption was over, and the lava flow could not
be seen from the Rifugio Citelli. Nonetheless many people remained
to stay and chat with others in a strange outdoor party atmosphere.
Cars were still driving up towards the mountain at about 0200 h on
25 June, although by that time the lava flow was cooling rapidly and
thus lost incandescence.
No further eruptive activity occurred at the summit craters since
that paroxysm, but numerous gas rings were emitted from the Bocca
Nuova.
A few summarizing remarks concerning the 24 June paroxysm should be
mde here. First, this event came after the longest period of repose
between two paroxysms that has been recorded in the current series
of such events. Some people had already speculated that this spectacular
phase of activity at the SE Crater, initiated on 26 January, had finally
come to an end. Surely this type of activity will not go on forever;
yet the paroxysm of 24 June has shown that the SE Crater is still
vigorously alive. Yet this paroxysm was unusually short, with a full
duration of 17 minutes, as recorded by Fulle from Torre del Filosofo.
And although it was of stunning violence, the tephra falls, which
were concentrated in a narrow sector on the SE flank, were less extensive
than during many earlier paroxysms. At Zafferana, which lies in the
center of the fallout sector, the deposit was less than 1 cm thick,
and the largest clasts were only 1 cm in diameter. The area subjected
to falls of large bombs was restricted to the immediate vicinity of
the SE Crater cone - which itself was entirely covered with incandescent
pyroclastics. Observers at Torre del Filosofo initially feared that
bombs might fall there, as has occurred on many occasions in the past
few months, but the nearest impacts on 24 June were hundreds of meters
away.
It remains an open question what causes the sudden transition from
quiet effusive activity to the paroxysmal phases of high lava fountaining.
One hypothesis is that the effusive activity represents the extrusion
of degassed magma from the upper part of the conduit as fresh, gas-rich
magma pushes it from below once a hypothetical storage area below
the crater is recharged with fresh magma to a critical value. The
quantity of degassed magma above the deeper gas-rich magma prevents
the decompression of the latter and the growth of gas bubbles for
some time, but once enough degassed magma has been evacuated from
the top of the magma column, the gas-rich magma begins to foam in
a manner very similar to a bottle of champaign that has been shaken
and then is uncorked. This occurs in a stunningly rapid manner during
many paroxysms, although in some cases - like on 8 and 14 June - the
transition has been more gradual, with Strombolian bursts preceding
the phase of vigorous lava fountaining.
The sudden onset of lava fountaining in many paroxysms may furthermore
be triggered by some very minor rifting along the eruptive fissure
that cuts the cone from its lower N flank to the upper S flank, over
a length of about 500 m. It may be assumed that each time (or nearly
so) that magma rises into that fissure, it pushes its sides apart
and thus causing slight extension over a limited area. The displacement
of the E side of the cone - if its takes place in a very short period
- would lead to the decompression of the magma in the conduit and
thus trigger the phase of violent lava fountaining. Such a mechanism
would also explain the observed broadening of the SE Crater cone in
E-W direction over the past few months, which appears too great to
be only caused by the accumulation of pyroclastics. Furthermore, if
minor rifting occurs during all or most eruptive episodes, this would
imply a high hazard for the area lying below the cone to the E, which
is the steep W slope of the Valle del Bove. What if the E side of
the cone - and the ground on which it is sitting - collapses, exposing
a part of the conduit below the SE Crater? It is known that the W
headwall of the Valle del Bove is structurally unstable, and it is
also assumed that at least part of the Valle formed as a large block
on the upper E flank underwent a gravity slide, similar to some degree
to the giant rockslide on the N flank of Mount St Helens in May 1980.
These thoughts are not even to be called a hypothesis, but they should
surely be tested by whatever means, because if they do hold a bit
of truth, this would mean that a high risk exists in the area below
the SE Crater to the E, and the sudden collapse of a part of the cone
and the block lying below could trigger a much more violent explosive
eruption than those observed in the summit area so far.
25 June 2000 update.
After ten and a half days of quiet, the SE Crater finally produced
its 64th paroxysmal eruptive episode in five months, and this was
one of the most violent, although the main paroxysmal phase lasted
only about 15 minutes. An unusually long lava flow was emitted for
many hours before and during the paroxysm, this flow extended eastwards
and reached the bottom of the Valle del Bove at about 1700 m elevation.
This is the longest flow from the SE Crater of the current series
of eruptive episodes.
Lava fountaining at the summit vent started immediately before 2330
h and continued until about 2345 h. Almost simultaneously the entire
fissure on the N flank of the SE Crater cone became active. Very high
lava fountains were ejected from the summit vent, at times reaching
a height of 1000 m. The fountaining phase ended with very loud degassing
and copious ash emission. In some moments the gas jet was expelled
at supersonic velocity, producing ground-shaking detonations.
A more detailed description based on observations by Behncke, Bryant
and Fulle will appear in this place later today.
21 June 2000 update.
No further eruptive activity has occurred at the SE Crater since its
latest paroxysmal eruptive episode on 14 June, although a new paroxysm
may be expected within the next few days. When seen on 20 June during
a summit visit made by Behncke, Bryant and others, the crater was
completely quiet. A thin gas plume was emitted from a group of fumaroles
located on the high E rim of the crater. The eruptive fissure that
extends from the summit vent down the N flank of the SE Crater cone
was quiet as well, with only very weak gas emission from two vents
in the lower part of the fissure. The fissure was for the first time
observed very well, it is curved towards NE in its lower part, and
there are several small craters located on it. Numerous tongues of
lava have extended from the fissure, building a curved ridge on the
lower N flank of the cone.
Tephra from the latest two eruptive episodes of the SE Crater was
present in two stretches extending to the NNW and to the N. The latter,
more recent of these had stricken the area around the village of Solicchiata,
damaging vineyards and fruit gardens. Scoria clasts up to 10 cm in
diameter, ejected during the 14 June episode, were found along the
dirt road leading to the summit area from Piano delle Concazze. Larger
clasts (up to 50 cm in diameter) formed a continuous cover on the
NE Crater.
During the visit, Behncke and his companions made observations at
the NE Crater and at the Voragine, which had been visited infrequently
in the past few months. The NE Crater had changed little since last
visited by Behncke in late September 1999. The northern part of the
crater floor consists of a flat terrace surrounded by a crescent shaped
ledge. The southern half of the crater is occupied by a tremendous,
bottomless pit with near vertical and in places overhanging walls.
This pit was the site of extremely loud explosive activity, probably
taking place at a depth of several hundred meters. Many explosions
generated strong pressure waves that were painful to the ears when
standing on the rim of the pit. The sound of falling rocks could be
heard at depth, but no rock fragments were seen in the range of visibility.
A pulsating gas plume rose from the pit, which contained small amounts
of fine ash. No fresh looking bombs or scoriae were found around the
pit, and it seems that the most recent ejecta on the NE Crater are
the scoriae ejected on 14 June from the SE Crater.
The visit to the adjacent Voragine brought a surprise. This crater
has been quiet since October 1999, with only weak fumarolic activity
occurring from the bottom of a large pit formed in the W half of the
crater on 4 September 1999. No changes had been seen during Behncke's
last visit to the crater on 26 April. On 20 June, a new vent, which
emitted gas at high pressure, was discovered on the SW wall of the
4 September 1999 pit. This vent was about 5 m in diameter. Gas emission
was pulsating, and at times small explosions occurred, which, however,
did not eject any rock fragments. Mountain guides at Piano Provenzana
on the N flank of Etna reported that the vent had probably formed
about two weeks earlier when an explosion reportedly ejected blocks
of old rock. Some blocks up to 30 cm in diameter were found within
a range of 30 m around the vent when Behncke approached it to a distance
of about 20 m.
The opening of this new vent in the Voragine may be a forerunner of
renewed eruptive activity from this crater in the near future. Similar
events have heralded periods of heightened activity in the past two
years; each culminated in very powerful explosive eruptive paroxysms
(on 22 July 1998 and 4 September 1999). It will be interesting to
see the behavior of that vent in the next few weeks. Fresh magma may
be nearing the surface in the central conduit system, as indicated
by an increase in the gas output at the summit craters in recent weeks.
Activity in the Bocca Nuova was observed directly only for a short
moment while exiting the Voragine along the former "diaframma"
(the wall that once separated that crater from the Bocca Nuova). As
during the previous months, the activity consisted of intense gas
emission from a vent in the E part of the Bocca Nuova, which generated
beautifully shaped gas rings at intervals of a few minutes. The pit
in the NW part of the crater was filled with gas, preventing a view
of its interior, but no noise was heard from this pit.
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Activity
at the NE Crater
on 23 May 2000
Photos
by Boris Behncke
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Ash
emissions from the NE Crater on 23 May, photographed from Piano
delle Concazze (photos above) and from the dirt road leading
from there to the summit craters (photo at left). Note blackening
of the snow below the crater in upper left photo
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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)
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)
Photos
of an eruptive episode on 13 February 2000, posted on the web site
of the Association Volcanologique Européenne, Paris, France
Photos
of the 15 February 2000 paroxysm of the SE Crater, by Thorsten Boeckel,
Germany
Photos
by Marco Fulle, 15-20 February 2000, at Stromboli On-line - very high
quality, as usual
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)
