Italy's Volcanoes: The Cradle of Volcanology

Etna Decade Volcano, Italy
Eruption update:
7-18 October 1999

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Summit craters map

Sketch map of the summit craters of Etna, based on fieldwork made between 7 September and 1 October by Behncke and others.

WARNING: Access to the summit craters is EXTREMELY DANGEROUS. Activity in the Bocca Nuova and the Voragine is very intense, and bombs are falling to quite some distance beyond the crater rims. Access to the craters themselves is absolutely impossible. Besides this, weather conditions are often unstable, even during the summer; summit visitors may be surprised by snowstorms (as occurred on 24 July 1999) or thunderstorms: one man was killed by lightning at about 2000 m elevation near Piano Provenzana on 30 August. Any person who enters the area beyond the Torre del Filosofo mountain hut (2900 m elevation) or the hut of the guides on the northern flank (Baita delle guide, 3000 m elevation) goes at his/her own risk and is not covered by any insurance in case a rescue operation (e.g., with helicopters) is necessary.

18 October 1999 update. The following information is very preliminary and needs to be confirmed, but its main lines are essentially accurate. Bad weather is preventing visual observations of the activity at the summit craters for most of the time since the early afternoon of 17 October.
During the past five days, eruptive activity has continued with numerous episodes of vigorous lava fountaining at both the Voragine and the Bocca Nuova. On the evening of Saturday 16 October Etna greeted the population of eastern Sicily with the spectacular display of lava fountains jetting from the Bocca Nuova. This was followed, after a few hours of an apparent decline in the activity, by renewed strong explosive activity on the next morning (17 October). Marco Fulle (Trieste Astronomical Observatory) watched the activity of the Bocca Nuova at that time from the dirt road circling around the western side of the summit cone complex and reported that continuous lava jetting to several hundred meters above the crater rim occurred from several vents within that crater, and bombs were dropped onto the outer flanks of the main summit cone, covering about half the distance between the western crater rim and the dirt road. Bombs also fell to the SE, to as far as the saddle between the main summit cone and the Southeast Crater cone. Fulle lost visibility by about 1400 h (local time=GMT+2) due todeteriorating weather conditions, but it appears that thereafter something exceptional happened: lava began to overflow onto the W flank of the main summit cone.
Informations about the exact site of this overflow and the direction of the lava flow are conflicting as of 18 October, early afternoon: while some news reports said that the overflow occurred at the Voragine and was directed towards NW, other sources place the overflow at the W rim of the Bocca Nuova, or even report that a new fracture has opened on the W side of the main summit cone, and that lava is directed westwards. At 1500 h, Marco Fulle telephonically reported from Rifugio Sapienza that local mountain guides visited the western side of the summit area this morning and observed that the western rim of the Bocca Nuova had collapsed, and that lava was moving in a broad river down the W side of the main summit cone, interrupting the dirt road and spilled down the W flank of the mountain, towards the forests of Bronte. The guides furthermore reported that the flow came down a good part of the steep W slope of Etna, but there were no informations available about the extent of the lava. Fulle himself attempted to reach the area this morning but was only able to see very intense lava fountaining at the Bocca Nuova before clouds covered the scene; Fulle did not dare go further due to the high levels of activity and the poor visibility.
From what little can be understood at this time it is clear that Etna is repeating in much detail the events of 1964: in that year, a major summit eruption completely filled the former Central Crater, built a large pyroclastic cone on top of the crater fill, and lava overflowed the crater rim towards NE, NNW, W, SW, S and SE. That eruption also included lava emission from a fissure on the E side of the main summit cone. At the height of the eruption, the SSW rim of the Central Crater collapsed, allowing lava to spill down on that side. The events of this year, with the long-lasting effusive activity near the Southeast Crater cone, and the intense activity in the Voragine and Bocca Nuova, are similar in many respects, but they are notably more intense. The collapse of the W rim of the Bocca Nuova is but the latest of these events; if the activity continues at a similar scale, then lava will travel a few kilometers down on the W flank of Etna.

15 October 1999 update. Vigorous eruptive activity has continued at the Bocca Nuova since the 12 October summit visit, while the Northeast Crater and the Voragine may have calmed down somewhat. Near continuous ejections of incandescent bombs occur from the Bocca Nuova to a height of several hundred meters above the crater rim. It is assumed that the crater is rapidly filling.
Just as this update is posted, at about 1850 h (local time=GMT+2) on 15 October, vigorous lava fountaining has resumed at the Voragine (or the Northeast Crater? - difficult to recognize from Catania. At the Palazzo delle Scienze, in the center of the city, a distinct, dull rumbling noise is audible. The activity may be the initiation of a new paroxysmal eruptive episode; more detail will be made available in the next few days.

13 October 1999 update: very intense summit activity, and summit visit on 12 October. During the past few days, eruptive activity in the summit craters of Etna has continued at very high levels, mainly at the Bocca Nuova and the Northeast Crater. Sometime around 11 October, explosive activity also resumed in the Voragine which had remained relatively inactive for several weeks.
During the weekend of 9-10 October, numerous persons observed vigorous incandescent ejections from the Bocca Nuova and the Northeast Crater; bombs were frequently thrown far beyond the rims of these craters and rolled down the slopes of their cones. Dark ash-laden plumes commonly rose every few minutes from the Northeast Crater to a height of several hundred meters, due to the almost total absence of wind. The activity reached a climax on 11 October when bombs were ejected from the Bocca Nuova to a distance of several hundred meters, and some bursts rose more than 300 m above the lip of the crater. On the morning of 12 October, Sandro Privitera (Dipartimento di Scienze Geologiche, University of Catania) observed that activity was also occurring from the Voragine; reports in local newspapers indicate that this activity had already occurred on the previous day.
On the afternoon of 12 October, Boris Behncke (Dipartimento di Scienze Geologiche, University of Catania) and Angelo Amara (University of Catania) reached the W flank of the main summit cone, at a distance of about 250 m from the W rim of the Bocca Nuova. Activity within that crater was extremely vigorous (although local mountain guides reported that it had been more intense the day before), and virtually continuous, with ejections of dense jets of bombs to hundreds of meters above the crater rim. About 99 per cent of the bombs fell back into the crater, as the ejections were mainly vertically directed, but occasional larger bursts sent bombs beyond the NW and SW crater rims. Eruptive activity occurred from at least 4 locations within the crater, of which one in the W part of the crater was the most active. This vent may lie in the place where a circular subsidence depression had been observed on 1 October, about 80 m SW of the NW vent which had been the source of the major eruptive episode on 20 September. This latter vent erupted less frequently during the 12 October visit, and produced no activity for about 30 minutes before it reopened violently at 1830 h (local time=GMT+2). At this moment there occurred the first in a series of powerful detonations which ejected abundant lithics along with incandescent bombs, and a tephra-laden plume rose rapidly to about 500 m above the crater rim. Lithics were showered over the NW flank of the main summit cone while bombs fell only to about 50 m below the crater rim. The explosions from this vent initiated about 30 minutes of much more intense activity when broad bursts of countless bombs occurred almost simultaneously from the presumed W vent, the NW vent and still another vent adjacent to the W vent to the S; jets of bombs rose at intervals of less than 1 second. There were some rare ejections of bombs from the area of the SE vents which had been the source of most activity during summit visits by Behncke and others on 1 and 6 October. Much of this activity was accompanied by a surprisingly low noise level, but the explosions at the NW vent produced loud detonations and air concussions.
The Northeast Crater emitted dark ash almost continuously; each emission was announced by a dull rumbling sound followed within a few seconds by the appearance of a dense ash plume at the crater rim. After nightfall it was seen that only about 10 per cent of the emissions were accompanied by ejections of incandescent bombs; however, these were quite powerful and sent bombs over a wide sector of the Northeast Crater cone. Other emissions appeared to eject mainly lithics: while no incandescent pyroclastics were seen to rise over the crater lip, the sound of many large rocks falling onto the crater rim was well audible.
Activity in the Voragine was at relatively low levels. While staying near the front of the 22 July 1998 lava flow on the dirt road which connects the northern and southern ascension routes to the summit, several loud explosions were heard coming from that crater, but no incandescent ejecta rose above the crater rim, indicating that the activity was quite deep-seated.
At about 1945, Behncke and Amara visited the area of effusive activity on the ESE base of the Southeast Crater cone where lava is still issuing quietly, more than 8 months after the beginning of effusive activity in that area. A vigorous lava flow about 2 m wide was fed by a vent lying in a slightly elevated zone made up of slabs of older lava, while a smaller flow (about 0.5 m wide) issued from a vent about 5 m further to the N. The larger of the two flows first moved to the NE and then turned E; incandescence could be seen to a few hundred meters downslope, but it is not known whether that represented the maximum extension of active lava. The effusion rate was estimated at about 1 cubic meter per second; if this value is applied to the past month, then about 2.5 million cubic meters have to be added to the more than 40 million cubic meters of lava emitted between 4 February and early September.
Strong ash emission from the Northeast Crater was visible on the morning of 13 October and is continuing in a pulsating manner as of the early afternoon of this day.

7 October 1999 update: reactivation of the Bocca Nuova on 5 October, and summit visit on 6 October. Just as the previous update was posted on this site, on the afternoon of 5 October, vigorous eruptive activity resumed at the Bocca Nuova after about two weeks of relative calm. A few hours later, after nightfall, Giuseppe Scarpinati (Italian correspondent of the French Association Volcanologique Européenne, LAVE) telephonically reported that strong explosions from the Bocca Nuova were visible with the naked eye from his home in Acireale (about 18 km from the summit of Etna) every more or less 10 minutes. Huge incandescent bombs were ejected as far as half way down the southern flank of the main summit cone, and each explosion was accompanied by a loud detonation whose sound arrived about 30 seconds after the visible ejection of the bombs. Furthermore, Scarpinati noted a continuous but fluctuating glow at the Northeast Crater and a slight increase in the effusive activity at the ESE base of the Southeast Crater cone.
The day after (6 October), Boris Behncke (Dipartimento di Scienze Geologiche, University of Catania) and two students of Physical Geography at the University of Trier (Germany) visited the summit area of Etna, making the ascent from the northern side (Piano Provenzana). While staying at Piano Provenzana (about 6.5 km NNE of the summit), at about 1040 h (local time=GMT+2), a very loud detonation at the summit was heard, followed within a few moments by the ascent of a huge "smoke ring" at least 100 m in diameter. During the next 10 minutes or so, a series of loud rumblings and several loud explosions occurred, probably all at the Bocca Nuova, which, according to the local mountain guides, had displayed similar activity during the previous night and the early morning. Ash emissions frequently occurred from the Northeast Crater and less frequently from the Bocca Nuova.
Behncke and his companions arrived at the northeastern base of the Northeast Crater at about 1215 h, and made observations of the eruptive activity for about three hours. During this period, powerful explosions occurred at the Bocca Nuova at intervals of more or less 10 minutes, and minor activity occurred between the explosions. Each explosion initiated with the uprise of large bombs (some of which were several meters across), followed immediately by a loud detonation and the appearance of a bluish-white gas plume. Many bombs were ejected far beyond the crater rim and fell up to 150 m to the S, and SW of the crater rim, and as far N as the base of the Northeast Crater cone. The source of this activity was evidently in the southern part of the crater, probably at the SE eruptive center which was buried under lava on 20-21 September and had been quiet since then. Ash emissions occurred less frequently from the northern part of the crater, it is likely that the source was at the NW vents which had also been silent after 21 September. Due to this activity it was impossible to climb to the crater rim or to the Voragine.
The Northeast Crater produced near continuous Strombolian activity, with jets of lava rising a few tens of meters above the crater rim, and some stronger explosions sent bombs up to 150 m high above the rim. While most lava jets were vertical, and the bombs fell back into the crater, bombs ejected by the larger explosions were scattered over the upper flanks of the Northeast Crater cone and some fell even into the adjacent Voragine. The noise level was generally low, but from an area located just below the NW flank of the cone it could be heard that the activity occurred at quite some depth within the active central pit of the crater. Brownish-gray ash plumes were frequently generated, and some of the Strombolian bursts were densely charged with small bombs. This activity marks the return to the classical "persistent" activity for which the Northeast Crater had become famous in the 1950's to 1970's; similar activity had most recently occurred at this crater in 1996.

It is not without pride that I announce the posting of five unique photographs of the 4 September 1999 Voragine eruption on this web site. To get an impression of the magnitude of that event, go to this page.



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