Stromboli erupting from Craters 1 and 3, 12 June 1996

Stromboli volcano, Aeolian Islands (Isole Eolie), Sicily, Italy -- Eruptive history

Stromboli in 1996

(covering the period January-early November 1996)

Two months before the end of the year, it seems that 1996 is a particular period in the recent history of Stromboli (and its residents and visitors). More than ever before, the difficult "relationship" between this volcano and man has demonstrated its complexity, and both tourists and people living from tourism had to face that Stromboli is not a "toy volcano", but that it is potentially dangerous instead.

Activity of Stromboli during the first three months of 1996 generally was similar to that in previous years. Normal explosive Strombolian activity of varying intensity was interrupted once, on the evening of 16 February, by a powerful phreatomagmatic (?) explosion. The event occurred without any evident forerunners, in a manner very similar to events in March 1989, February and October 1993 and on 5 March 1995. Intense seismicity (see the plot created by Roberto Carniel, Udine University) lasted 12 minutes; residents in Stromboli village saw the ejection of incandescent pyroclastics above the summit. This episode was followed by a sudden drop in seismic activity. A few days later, volcanologists from the Istituto Internazionale di Vulcanologia in Catania visited the summit area and found fresh black bombs and Pele's Hair together with blocks of old, altered material to the north of Crater 1, the possible source of the explosion. Further, they observed very weak Strombolian activity.

The explosion seems to have been very similar to the previous events in that it occurred quite suddenly (and therefore had a high danger potential to any people staying in the summit area) and that it occurred during the winter season (most recent explosions of that kind have occurred either during autumn or in February-March). The causes for such explosions and their apparent clustering in certain periods of the year may be interactions of magma with water in the uppermost parts of the mountain, maybe after rainy periods. However, any such relationships would still have to be established and corroborated before taken for valid. In any case, the 16 February 1996 event once more points to the fact that Stromboli can be indeed pose significant danger to visitors of its summit area.

After the 16 February explosion, the seismicity of Stromboli declined dramatically but later gradually increased back to normal values (see the 1996 seismicity graph prepared by Roberto Carniel, Udine). After late February, and through mid-April, the seismicity indicated ongoing normal Strombolian activity with some fluctuations, on levels similar to late 1995.

A notable increase in the number of seismically recorded eruptive events occurred on 16 April (1996 seismicity graph) and was soon confirmed by visual observations, some of them made by Jürg Alean and Roberto Carniel of Stromboli On-Line. The activity was apparently very similar to that of July-October 1994, with tall lava fountains and periods of continuous lava fountaining and spattering. However, this time it appears to have been largely restricted to Crater 1 while in 1994 there was also very intense activity from Crater 3. Photos of this activity have been made available at Stromboli On-Line. There are also a few morphological changes evident. The remainder of the central cone in Crater 1 (partially destroyed by the 5 March 1995 explosion) has completely vanished (see the view of Crater 1 from the summit, taken by Juerg Alean on 28 April 1996), but there is a new, broad feature growing in the same area, evident on a photo taken from a spot south of the crater terrace, below Pizzo sopra la Fossa. The latter shot also shows that parts of the "Gemelli" (twins) cones, formed during the summer 1994 activity, are still remaining, and the more southerly one has a vigorously glowing vent and was the site of occasional eruptions.

Similar activity, with some minor fluctuations, but generally on a very high level, continued through late May. On the late evening of 1 June (at 2350 h), a sudden explosion occurred from Crater 1, surprising a group of mostly German visitors in the summit area. Four of them were slightly injured. Two persons initially reported missing were later found unharmed. A bush fire caused by the fall of hot pyroclastics on the upper slopes was under control a few hours after the explosions. Stromboli On-Line has a spectacular photo taken (by Wolfgang Müller) immediately after the event. A brief summary with several photos has also been prepared by the Istituto Internazionale di Vulcanologia. According to the same institute, another, smaller explosion occurred from Crater 1 on 6 June, this time with less spectacular effects.

Info regarding the activity of Stromboli on 9-12 June 1996 comes from Marco Fulle (Astronomical Observatory of Trieste) which is reproduced here in full length with additional info about activity of Etna. A similar message came from Felicia and Carmelo Monaco in mid-June. Note that the plot of 1996 seismicity shows fluctuating but very vigrous eruptive activity through late June 1996.

Photos taken by Marco Fulle on 9-12 June 1996 show that activity was concentrated on two vents, 1/2 and 3/2, with no eruptions occurring from other vents. While no major morphologic changes (since April 1995) are evident in Craters 2 and 3, the two large explosions of 1 and 6 June 1996 have significantly modified Crater 1. Of the three largest cones formed in the summer of 1994, only part of the southern "Twin" cone remains. No new cones appear to have formed, but the crater floor of Crater 1 seems elevated. Accumulation of pyroclastics on the Sciara side of the crater has led to notable growth of the northwestern crater rim since the mid-1980's.

Vigorous activity continued through late August, and included a brief episode of lava effusion from vent 3/1 into the depression of Crater 3 on 16-17 August. Just a few days after that event, a tourist was injured on his head by a falling bomb while sleeping only about 80 m from the rim of Crater 3. Appartently, the tourist group to which the unfortunate man was belonging had been guided to the summit by a guide from Roma who had chosen the site for sleeping. While staying in Catania and on the Isole Eolie in September-October 1996, I was unable to get reliable information about the outcome of the event. About half of the persons I asked told me that the man had died after being brought to a hospital in Messina while the other 50% maintained that he survived.

During the last days of August, the eruptive activity of Stromboli declined abruptly. Another look on the plot of 1996 seismicity of Stromboli On-Line shows a dramatic decrease in the number of seismically recorded events. While activity was still at very low levels, a powerful explosion occurred without any warning at 1345 GMT (1545 local summer time), launching incandescent tephra towards the northern side of the summit area. The source of the explosion may have been Crater 1 although no details are available up to now. Tourists staying at the crater lookout on the upper N flank were caught in a shower of tephra, and six or seven of them were injured. The fall of incandescent tephra onto the outer slopes of the volcano caused bushfires in some places (see photo below), but these fires were extinguished soon after. Access to the volcano was closed by the mayor of the town of Lipari (of which Stromboli is a part) on the following day, after a recommendation by the provincial authorities of Messina. Volcanologists of the Istituto Internazionale di Vulcanologia, Catania, had previously declared that the volcanic activity did not present any danger to the inhabitants of the island.

The explosion of Stromboli, 4 September 1996
This photo was taken a few minutes after the explosion and shows bushfires on the upper slopes of the mountain. The eruption plume (upper left) is rapidly dissipating as no further major eruptive activity is occurring. The site from which the photo was taken is in the San Vincenzo fraction of Stromboli village (the "bunker" hosting an observation post of volcanologists from Firenze, Italy, is visible on the lower slope to the right). Photo taken by Antonio Di Sarno, Napoli.

During the following weeks, a difficult situation developed on Stromboli. The denial of access to the summit was maintained through mid-October (and possibly thereafter), depriving local tourist guides of their main income and causing considerable discontentment among them. At the same time, hundreds of tourists continued to climb the volcano. During the few hours when the main paths to the volcano were controlled by local carabinieri, people trying to access the closed area were detained and fined. At the same time, the volcano's activity prevailed at extremely low levels. Matthias Hort and Ralf Seyfried, both of Geomar, Kiel (Germany), visited the volcano from 30 September to 2 October and observed small eruptions from Crater 3 (vent 2) while Craters 1 and 2 were inactive. On 30 September, Crater 1 made "terriffic noises" but did not show any visible activity, and during the next two days, even the noises from this crater had disappeared. The overall level of activity showed a gradual decline from 30 September to 2 October. According to Hort, the most spectacular event during the entire observation period was an ash emission that produced a plume to 100 m above the craters. There were periods of up to 2 hours without any eruptive event.

View of Crater 1 during an eruption, late September 1996
This is a typical view from Pizzo sopra la Fossa into Crater 3 during an eruption in late September 1996. Incandescent lava fragments are barely visible at Vent 2, remaining deep in the crater. According to Matthias Hort (who took this photo on 30 September 1996), few eruptions during the observation period (30 September until 2 October) were stronger than this one.

Crater 3, 30 September 1996
Another view of Crater 3 during a small eruption, 30 September 1996. A complex conelet at vent 3/1 is visible at the extreme right; this conelet grew during the intense activity of August 1996 and was only degassing in late September 1996. Photo by Matthias Hort, Geomar.

Stromboli was active when Giada Giuntoli and I passed the island while travelling on the ferry ship from Lipari to Napoli on the evening of 10 October. While approaching the island from south, two lava fountains shot up from Crater 3 during a 5 minute interval, reaching 80-100 m above the vent (to the height of Pizzo sopra la Fossa). Each fountain lasted about 20 seconds. About 10 minutes after the second fountain, an eruption apparently occurred at Crater 1 (or Crater 2, but this is unlikely). When travelling north after stopping at Stromboli village, a faint red glow could be seen once but clouds had begun to cover the summit, and no details were visible.

Roberto Carniel reports the lowest levels of activity recorded in a long time on 25 October with only 27 recorded seismic events, and a 7-hour period without any seismically recorded eruption. Overall, the seismic graph shows that Stromboli's activity was at very low levels during all of October.