Updates September 1998
The most recent updates
Etna news archive
30 September 1998
The "new" SE Crater
Telecamera images taken between 1410 h and 1425 h (local time) today, showing a zoomed view of SE Crater with its rapidly growing intracrater cone. The upper two frames show the emission of dense ash clouds from the Voragine which lies behind SE Crater to the left; in the lower left frame a strong Strombolian burst is visible, in spite of the bright daylight, while the lower right frame is a particularly clear view of the crater. Building in front of SE Crater is the Torre del Filosofo mountain hut, located about 1 km south of the crater, and 300 m lower.
25 September 1998
During the past few days, little changes appear to have occurred in the activity of Etna's summit craters, altough bad weather has prevented visual observations until this evening. Vigorous Strombolian is continuing at SE Crater, which is also emitting lava onto its northeastern flank. The flow is not directly visible in telecamera images transmitted this evening, but the gas plume drifting past SE Crater is brightly illuminated by the incandescence of the flow along much of the slope of the cone, indicating that the flow is of similar dimensions as flows erupted previously at that crater (a few hundred m long). There is also low-level going on in Bocca Nuova.
21 September 1998
Map of Etna's summit craters
Sketch map of Etna's summit craters showing features frequently mentioned in the updates, and approximate extent of recent lava flows (Voragine: 22 July 1998, SE Crater: 15 September 1998 and continuing) as of 20 September 1998. Earlier flows from SE Crater and NE Crater are not indicated.
20 September 1998
SE Crater, 19 September 1998
Sketch drawing showing SE Crater as seen from the northwest on 19 September 1998. The former intracrater cone has been replaced by an explosion crater that contains a small new cone with two erupting vents, and a small, non-eruptive vent lies below the major breach in the crater wall in the left center. Lava that has overflowed the southwestern crater rim until July 1998 is shown in a dark pattern at right.
Evidence of the vigorous activity of SE Crater on 15 September was found mainly on the western and northwestern sides of the crater and, most spectacularly, at the intracrater cone that occupies the northern two thirds of the crater. The explosions of 15 September ejected both lithics and huge fresh bombs which are abundant in the small saddle between SE Crater and the main summit cone. Some of the bombs are up to 5 m across and have flattened upon impact, bombs of these dimensions can be found up to 50 m away from the crater rim. Bombs tens of centimeters in diameter form a continuous deposit on the NW side of the crater, and bombs up to 50 cm in length were found as far as the SE rim of the fomer Central Crater, about 100 m higher and 200 m away from the SE Crater.
Most of the intracrater cone was destroyed during the 15 September explosions, and a new crater about 80 m across formed in its place, whose rims consists of the lower parts of the intracrater cone. A breach in the NW rim of the new crater lies above a small crater that formed on the outer wall of the SE Crater on that side; this vent may have produced much of the bomb deposit that lies plastered against the base of the main summit cone. Vigorous activity on 17 and 18 September ejected further bombs which were described as having been "several meters across" by a group of British geologists led by J.B. Murray working in the area since one week.
A lava flow moved downthe NE flank of the SE Cone in the direction of Valle del Leone. The beginning of this effusive activity is not known but the flow was reported to have been moving at elast on 17-18 September by mountain guides.
During the 19 September visit the SE Crater was erupting less violently than during the preceding days, permitting an approach to the crater rim. Strombolian bursts occurred from two vents in the western part of the 15 September explosion crater around which a small cone had begun to grow. The maximum height of the ejections was 100 m but most explosions sent bombs only a few tehs of meters high. Rarely ejecta fell outside the rim of SE Crater.
Lava emission occurred from a vent high on the outer NE slope of the SE Cone, lying a few meters below a cleft in the rim of the new explosion crater, it was feeding a flow that advanced on top of earlier lava towards Valle del Leone (essentially this is the northwesternmost part of Valle del Bove, a huge collapse depression on Etna's E flank). The newly formed lava lobes appear to be among the longest erupted from SE Crater during the current eruptive period, and no lava effusion from the outer flanks has been observed in this period so far. Apart from these particulars, the activity is equal in style and magnitude to that which had occurred at SE Crater between November 1996 and July 1998, and is considered a continuation of the same eruptive cycle. The six-weeks-long repose period was of unusual lenth in this period, and the violence of the resumption of activity testifies to a notable pressure buildup during the inactivity. The 15 September activity was surely the most significant eruptive event at SE Crater since its reawakening almost two years ago. However, it does not seem to mark a profound change in its current eruptive behavior, like the one that occurred in September 1989 and heralded a series of paroxysmal eruptions from SE Crater and a major flank eruption in Valle del Leone.
The current activity at Etna which is now continuing since more than 3 years is particular for a number of reasons.
All activity is limited to the four summit craters, so that it is to be considered a true Etnean summit eruption. This is important to underline since news media and even the Etnean mountain guides often stress that the current activity is "no eruption". Any event that expels rock from the Earth's interior onto the surface IS an eruption. Although activity at Etna's summit craters occurs commonly also during periods of frequent flank eruptions, this current eruptive cycle is peculiar for the continuity and intensity of the eruptive phenomena, as well as for the, at times simultaneous, involement of all four summit craters.
The current eruptive cycle is characterized by an unprecedented variety of eruptive events in the summit area, with each of the four summit crater being the site of intense activity. Even the most recent cycle of prolonged summit activity (1955-1971) did not involve as many as four summit craters, and activity was commonly occurring at only one crater at any given time.
What clearly results from these facts is that Etna is much more stable than during the preceding >20 years, and if it has been capable of withstanding the enormous pressure of magma within its central conduit system without fracturing, it may still be so for some time to come. There are currently no indications of a flank eruption in the near future.
18 September 1998
SE Crater remains active, providing again the spectacular display of its rhythmic Strombolian explosions, possibly accompanied by renewed lava emission. This activity appears to be very similar to that which had occurred at that crater between early November 1996 and late July 1998. Bad weather, however, is preventing good observations of Etna's summit. Yesterday there were increases in the seismic activity registered by the Osservatorio Sismologico di Acireale indicating flurries in the eruptive activity although the location of this activity was not known. After nightfall yesterday, Strombolian activity at SE Crater appeared on images of the IIV telecamera. Some more images registered by the telecamera on early 15 September have been posted below at the 16 September update.
<17 September 1998
While there are no further informations regarding the activity of SE Crater since its violent reawakening on 15 September, ash emissions from the Voragine and/or Bocca Nuova were observed by us (Boris Behncke and Giovanni Sturiale of IGGUC) today during fieldwork in the Monti Iblei. It is possible that SE Crater has resumed its moderately strong Strombolian activity, similar to the activity prior to late July 1998 which was not easily detectable during daylight from a distance.
16 September 1998
The reawakening of SE Crater
Telecamera images (from IIV) showing Etna's summit before the reawakening of SE Crater (the cone at right - note also the ash emission from the Bocca Nuova in the central part of the image) on 26 August (top left frame), a view at about 0340 h (local time) on 15 September showing a brightly incandescent fountain at the crater (top right frame), an ash-rich explosion and steam rising from the southern slope of the SE Crater cone (building at the base of the crater is Rifugio Torre del Filosofo) at about 0712 h (bottom left frame) and a view similar to the first one, taken on 16 September 1998, which shows that the activity of the previous day has destroyed the top of the intracrater cone (bottom right frame).
Brief glimpses of the summit craters today (by the telecamera of the Istituto Internazionale di Vulcanologia, IIV) have permitted a good view of SE Crater this morning. The large intracrater cone that had grown within this crater since late 1996 has been almost completely destroyed by the explosions of yesterday. IGGUC geologists are intending to visit the summit craters later this week, and scientists of the IIV may reach the area today.
10 September 1998
Activity at Etna's summit craters has declined since the beginning of September but is continuing in the Voragine and Bocca Nuova. A visit to the summit by Boris Behncke and Giovanni Sturiale of the Istituto di Geologia e Geofisica of Catania University (IGGUC) on 9 September revealed continuos moderately strong Strombolian activity from a vent in the southwestern part of the Voragine, somewhat to the north of another vent immediately above the "diaframma" (the wall that separates the Voragine from neighboring Bocca Nuova) and sporadic, more vigorous explosive activity from the latter which sent bombs over the crater rim to the W and S. At least three other vents were quietly degassing in the southern and central parts of the crater whose floor was only a few meters below the low northwestern crater rim. In the Bocca Nuova one single vent at the summit of the northwestern cone was the site of Strombolian bursts alternating with bomb and ash emissions. This vent had widened significantly since last seen (by Behncke) on 20 August, and the overall impression of the activity was that the magma level at this cone had lowered. There were four smaller vents on the flanks on the cone which were only weakly degassing. Continuous but weak Strombolian activity occurred from two vents in the southeastern part of the Bocca Nuova where a small cone was growing in a larger depression left after the series of collapses earlier this year. No activity occurred at SE Crater and NE Crater was only strongly degassing.
Intense activity in both the Voragine and Bocca Nuova had continued through the end of August, as indicated by information kindly submitted by members of the French volcanological association L.A.V.E.. Among the most spectacular features of that activity was the growth of a small cone at the vent located immediately above the "diaframma" which culminated in the fracturing of this cone and a cascade of lava down the "diaframma" wall into the Bocca Nuova, an event that was filmed on video. Vigorous activity in the Voragine and Bocca Nuova was also observed by Carmel Monaco, Luigi Tortorici (both of IGGUC) and others during a visit on 29 August. One week later, the activity was significantly weaker. Etna guides at Rifugio Sapienza reported during our visit yesterday that the levels of activity began to drop "about 10 days ago". However, there have been flurries of more intense activity, such as on 6 September when bombs fell abundantly on the outer western slope of the Voragine and on 7 September when ash emission occurred almost continuosly throughout the day. More details of the recent activity will be provided in the next few days.