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WARNING:
Access to the summit area is DANGEROUS.
Violent eruptive episodes are occurring frequently 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. 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.
Excursions should be made only with the mountain guides who
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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27
April 2000 update.
More detail is emerging about the 26 April eruptive episode at the
SE Crater and its effects, which were more far-reaching than usual.
Additional information was furnished by Charles Rivière and
Robert Clocchiatti, who witnessed the event from close distance, Giuseppe
Scarpinati (Italian delegate of the Association Volcanologique Européenne,
"Lave", seated in Paris; Scarpinati lives in the town of
Acireale on the SE flank of Etna), and other sources.
The first signs of a revival of the activity at the SE Crater were
observed by Scarpinati at around midnight (during the night of 25-26
April) when he noted "a very small incandescent lava extrusion,
which was barely visible" at the N base of the SE Crater cone.
By 0530 h on the 26th, the lava flow had grown significantly and now
was about 500 m long; at its source there was vigorous Strombolian
activity. The next thing that happened was the emission of white vapor
mixed with brown ash plumes at 0615, as observed by Rivière.
Fifteen minutes later Scarpinati, who had returned to sleeping, was
awakened by loud detonations and saw the beginning of strong explosive
activity at the summit vent of the SE Crater. According to Rivière,
the true paroxysmal phase started at 0655 h, when lava fountains rose
hundreds of meters from the crater; a tall eruption column rapidly
rose several kilometers above the summit of the volcano, forming an
impressive dark mushroom of gas and ash. The plume then was carried
to the SE, in the direction of towns like Viagrande (which received
a heavy shower of scoriaceous lapilli) and Acireale, where pea-sized
lapilli fell abundantly. From Catania, the view of the plume passing
just slightly to the north was awe-inspiring; it filled about half
of the sky and blotted out the rising sun.
The strongest activity occurred shortly after 0700 when large bombs
were thrown to more than 1 km distance of the SE Crater summit. Many
bombs up to 0.5 m in diameter fell around the Torre del Filosofo building,
1 km S of the crater. At that time of the day the guided tours of
tourists to the building, which is now the point of arrival of the
tours, had not yet been initiated, so that there very few people in
the area, and no one was hurt. During this phase of activity, a vent
burst open low on the S flank of the SE Crater cone, just above the
saddle which stands between the cone and the newly grown Sudestino.
Lava was emitted from this vent to the SW, forming a short flow; no
lava appears to have flown from there in other directions. Invisible
to observers on the S side of the erupting cone, lava was also emitted
through a large breach on the N side of the cone, where it advanced
for a few hundred meters.
The activity subsided rapidly after 0720 h and was essentially over
five minutes later. However, the lava flow to the SW remained active
for more than one hour afterwards, stopping at the N side of the 1971
"Observatory" cone (indicated as "1971 cone" on
the map above).
It was shortly after the end of the main paroxysmal phase, at 0739
h, when an airbus of the AirEurope, which had departed from the Fontanarossa
international airport of Catania in the direction of Milano, entered
the fallout zone of the plume at an altitude of about 1000 m. Apparently
the aircraft received windshield damage by the violent impact of scoriaceous
lapilli and was forced to return immediately to the airport of Catania.
Windshields were scratched but apparently not broken. Passengers reported
to news reporters that it seemed that the airplane entered a zone
of turbulence, causing it to vibrate strongly, and then it seemed
as though something was scratching one of the side windows, "as
if it were hit by a sharp object". According to some news reports,
some fear was aroused among the passengers, but the pilot soon informed
the passengers about a "technical problem" and told them
everything was under control, and that they were to return to Catania
airport. Other sources report that the passengers did not note anything
unusual until the pilot advised of the return to Catania.
This incident, the first of this kind reported at Etna, underlines
the existence of a hazard that has received relatively little attention
in the past at this volcano. Etna is generally considered a mainly
effusive volcano, for it is essentially known for emission of voluminous
lava flows during flank eruptions, which have a relatively low degree
of explosivity. Summit activity on the other hand is often much more
explosive, and this has been the case particularly during the past
five years, since the current period of intense summit activity has
begun. In this period nearly hundred episodes of powerful explosive
activity generating significant tephra columns have occurred at all
four summit craters, of which 51 have occurred in the last three months
alone at the SE Crater. Etna thus is currently among the most explosively
active volcanoes on Earth.
The circumstances of the 26 April incident are still not clear. It
is not well explainable why the airliner ended up under the plume.
The eruption had been perfectly visible from Catania airport as well
as from all over eastern Sicily, and it occurred quite some time before
the airplane took off. Yet the pilot said that he did not see the
plume ("it was invisible, certainly not a black cloud" -
yet the plume was quite dark as seen from Catania by residents of
the city), and to his knowledge it had been drifting in the opposite
direction (that is, towards W; however, since about one week the wind
had been constantly blowing from W). Certainly an investigation
will follow and hopefully teach an important lesson which will help
avoid similar incidents in the future, as air traffic at Catania is
intensifying with a rapid growth of the tourist flux, and more explosive
eruptions of Etna are to be expected in the near future.
Later on 26 April Boris Behncke (Dipartimento di Scienze Geologiche,
University of Catania) and others visited the summit area of Etna
(as briefly reported in the 26 April update below). Very detailed
observations could be made at the Bocca Nuova and the Voragine, and
good views were obtained of the SE Crater from the platform in the
SE part of what once was the Central Crater of Etna.
The Bocca Nuova, accessible only from SE, S or SW, which in any case
means an agonizing 300 m climb up the steep flank of the main summit
cone, is a most varied, colorful little world on its own. There have
been no remarkable changes at this crater since visits made in the
past three months, and the activity is the same as observed on earlier
occasions: gas emissions from a vent in the E part of the crater,
at times more explosively, but without ejections of any solid material.
The explosions are generally very short, producing sharp reports,
and often resulting in the formation of gas rings.
Little activity is apparently occuring in the second large vent in
the NW part of the crater. This vent is a pit about 150 m in diameter
with vertical, in part even overhanging, walls, from which several
internal avalanches were observed during the stay at the Bocca Nuova.
The interior of this pit is invisible due to a dense, but passive
gas plume.
It was possible to walk around what remains of the NW rim of the Bocca
Nuova to the area where this crater once intersected the SW rim of
the Voragine. Until 1998 the two craters were separated by a thin
wall of rock (which demonstrated a surprising degree of stability),
known as the "diaframma". Now in its place there is a kind
of a saddle separating a knob on the SW rim of the Voragine from the
N side of the partially collapsed cone that had built around the NW
vent in the Bocca Nuova in October-November 1999. The area is cut
by numerous degassing fractures, some up to 1.5 m wide, with beautifully
colorful sublimates on their rims.
The structure of the adjacent Voragine is amazingly simple in comparison
with that of the Bocca Nuova. The crater has a large pit (about 200
m in diameter) in its W part, which was formed during the violent
4 September 1999 eruptive episode. To the N, NW, E and SE this is
surrounded by a very flat terrace up to 150 m wide, which lies some
20 m below the E rim of the crater.
The SE Crater, as seen from the flat area in the SE part of the main
summit cone, shows a deep notch on its N side, which reaches almost
down to its base. The notch and the lavas that had issued at its lower
end (where the effusive vents active before the 26 April paroxysm
are located) were well illuminated by the sun, so that no incandescence
(if there was any) could be perceived there. However, a fan-shaped
field of numerous overlapping lava flows was seen to extend from there
towards NE and E, into the upper reaches of the Valle del Leone and
the Valle del Bove. Only very weak gas emission was seen in some locations
along the N flank notch. The summit of the SE Crater cone consists
of two very sharp crests lying on the E and W sides of the elongate
summit vent area, which are of approximately equal height. The highest
points of the cone stand several meters above the elevation of the
main part of the terrace from where observations were made, that is,
at approximately 3270 m. The highest point of Etna presently lies
at about 3310 m elevation, so that the SE Crater would have to grow
only 40 m to become the new summit of Etna. If the activity continues
at a similar rate to that of the past two years, the cone might reach
that height within one year or two.
Further reading on the internet.
Many Italian newspapers with on-line versions carry the news of the
26 April eruptive episode and the airplane incident. Note that many
of these links will probably remain on-line only for the next few
days, and all are in Italian.
La Sicilia,
the most widely read newspaper in Catania, has an article entitled
"Etna
wakes up in the morning" and another one with the
header "Debris
against the airbus". The print edition contains a
third article on the fall of ash and lapilli on towns to the SE of
the volcano. It furthermore contains numerous photographs of photographer
Fabrizio Villa (who is faithfully documenting as many of the eruptive
events of the volcano as possible).
The Giornale di
Sicilia has the following on the event: "Cloud
of dust and ash from Etna - Airplane forced to return",
and a short interview with L. Villari, director of the Poseidon monitoring
network: "Black
rain of sand and lapilli - No reason for alarm, says volcanologist".
The third newspaper focused on Sicily (and Calabria) is the Gazzetta
del Sud, which reports "Airbus
in an ash cloud - A disaster narrowly avoided".
The national newspaper La
Repubblica tells of "Fear
during flight over Etna, airplane hit by lapilli".
The Corriere
della Sera of Milano has three articles on the event. The
first is headed "Etna:
a cloud of lapilli hits jet plane - Terror on flight Catania-Milano";
the second is under the header "Storm
of lava; Etna stops airplane", while the third, "Volcanologist
says, the only countermeasure is to modify the airline routes",
has an interview with one of the scientists of the Poseidon monitoring
network, R. Azzarro.
At Yahoo,
a search option allows to find news
containing the word "volcano". It also has a
link to press
photos about volcanoes. For the next few days you will
find there some of the photos by press photographer Fabrizio Villa
of the damaged airplane and of the eruption column of 26 April.
26
April 2000 update.
Almost ten days have passed between the 50th and eruptive episode
at the SE Crater on 16 April and the next episode on the morning of
26 April. At around 0630 h the crater finally erupted again violently,
producing a gas and ash plume which is drifting over Catania right
as this update is posted on the web. The activity could be well observed
from Catania during perfectly clear weather. It seems that this eruptive
episode - the 51st in precisely 3 months - lasted shorter than its
predecessor and maybe it was slightly less violent. The main phase
of the activity lasted about fifty minutes and was characterized by
lava fountaining, the generation of a tall eruption column, and some
lava emission.
During the hours preceding the Giuseppe Scarpinati (Acireale) observed
the slow resumption of lava effusion at the vents at the N base of
the SE Crater cone. This activity gradually increased with Strombolian
bursts from one of the vents. At the same time no lava emission occurred
at the S side of the cone, but mountain guides had observed increased
fuming late on 25 April. The eruptive episode was thus announced like
most of its predecessors by a gradual increase of the activity at
vents located on its flanks.
Interestingly the Sudestino, which had emitted lava for about 18 hours
prior to the onset of paroxysmal activity during the preceding episode
on 16 April, did not show any activity during the 26 April event.
Instead, towards the end of the paroxysmal activity, lava was emitted
from a vent located in the saddle between the Sudestino and the SE
Crater cone. One lava flow, which moved from there to the SW, advanced
only about 200 m to near the 1971 "Observatory" cone; other
lava may have descended to the SE, but no information is available
about the dimensions of flows in that area. Some fresh lava forming
a short flow was also observed during the afternoon on the N side
of the cone. Other flows from recent eruptive episodes had advanced
significantly farther into the Valle del Leone.
This is the second consecutive time that the repose period between
two eruptive episodes has lasted ten days; the latest two repose periods
have been the longest so far in the current series of paroxysms at
the SE Crater.
During a visit to the summit area a few hours after the end of the
paroxysm on 26 April, Behncke and others saw no further movement at
the SW lava flow, and the SE Crater and the Sudestino were perfectly
quiet. The Bocca Nuova was equal to how it had been seen by Behncke
during previous visits in early February and late March. The Voragine
was also quiet, with only some gas issuing from the bottom of the
large pit formed in its W part on 4 September 1999.
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 (the most recent
of the paroxysm of 16 April 2000), updates, and other, highly interesting
items (in French and English)
