The 2001 summit and flank eruption

Etna greeted the new millennium with one of its most unusual and complex eruptions recorded during the past 300 years, in July-August 2001. If ever there has been an Etnean eruption in the international mass media, then it was this one: during the dramatic days of late July, dozens of television stations transmitted the spectacular images of the erupting volcano in real time. Very often, unfortunately, the reports were unnecessarily dramaticized, so that the international public received the impression that the town of Nicolosi was doomed, its inhabitants in the grip of fear if not panic, packing their things and some of them already evacuating. Footage of processions held in Nicolosi were a common feature in television reporting, although, seen on location, they rather had quite a different character, and most of the participants were there because they thought "better safe than sorry". As one result of this enhanced media coverage of the dramatic aspects of the events, many people who planned holiday trips to Sicily were worried or cancelled their reservations, others were in fear for their relatives or friends living near Etna or making holidays in Sicily.
Actually, Nicolosi (or any other town) was never at serious risk during the eruption. This was mostly because the main lava flow, emitted from a fissure at about 2100 m elevation, and about 11 km north of the town, was not as vigorously fed as to be capable of covering the whole distance. For this the effusion rate would have had to increase significantly, or the flowing lava would have had to form a stable lava tube, but the eruption ended before any major lava tube system could develop. The population of Nicolosi and surrounding towns and villages can at best be said to have lived through a period of apprehension, but most of the people took the chance to be on a gigantic "Etna Party", with thousands of people walking several kilometers to get as close as possible to the flowing lava, and, if they made it, to the nearest erupting vents. Since car traffic was interrupted by numerous roadblocks around Nicolosi and its neighboring towns, this was a long way to walk, but amazingly enough many did make it through to as far as the area of the famous mountain hut Rifugio Sapienza, which was only a few hundred meters away from the eruptive fissure at 2100 m elevation. The procession of sightseers was continuous, 24 hours a day. During many interviews with the local people, no one ever expressed any true fear to me, although everyone was conscious that if this eruption went well for them, future eruptions could well bring a much more serious threat to their homes.
The photos presented on this page are mostly from newspapers. A gallery with my own photos of this eruption is under construction.

Map of the lava flows of July-August 2001

The following paragraphs summarize the most salient features of the July-August 2001 eruption, which ranks among the medium-sized flank eruptions of Etna, but certainly brought a series of surprises to volcanologists studying and monitoring the volcano. For location of places named in the text see the map above.
Precursory activity and geophysical forerunners. Although there had been no flank eruption at Etna since 1993, eruptive activity had been nearly continuous in the summit area since late July 1995 (see the page about the 1995-2001 summit eruptions). During the first half of 2001, most activity had occurred at the Southeast Crater (SE Crater), starting with very slow lava extrusion from a vent on the NNE flank of its cone in late January. During the following three months the lava emission rate progressively increased, and in late April, weak ejections of lava fragments began to build small spatter cones (also known as hornitos) in the vent area. Strombolian activity resumed at the summit vent of the SE Crater on 7 May and was followed by an episode of vigorous Strombolian activity and lava fountaining two days later.
After this the activity returned to lower levels, but for the next two months the SE Crater was the site of a very picturesque continuous activity, also named persistent activity, with mild, discontinuous Strombolian explosions from the summit vent and vigorous lava emission (at times accompanied by lava spattering) from the NNE flank vent(s). A large, steep-sided cone consisting of overlapping lava flows and spatter began to grow at this place, which was informally named "Levantino" (this cannot be translated literally, but it generally denotes a minor feature located in the direction of the sunrise). Lava flowed toward NE (in the direction of the Valle del Leone), E and SE (in the direction of the Valle del Bove), forming a composite lava field with numerous overlapping and adjacent flow lobes. The longest flows extended up to 2 km from the vent(s). From late May to early June the continuous and relatively harmless activity attracted many visitors, and a tourist path was made between the Piano delle Concazze (on the N flank) and the SE Crater.

Photograph taken on 13 July 2001, shortly after an eruptive episode at the SE Crater (the steep cone visible in the center) with an ash column rising from the Bocca Nuova. At this time the volcano was shaken by thousands of small earthquakes indicating that a flank eruption was imminent. Photograph by Fabrizio Villa

Just when the first tourist groups had been guided to the area of the activity, the SE Crater changed its behavior: the mild, continuous activity was substituted by violent eruptive episodes which occurred at intervals of 2-4 days. The first such paroxysm occurred on 7 June and was mostly confined to lava fountaining at the "Levantino", whereas there was only mild Strombolian activity at the summit vent of the SE Crater. During the following six weeks the vigor of the eruptive episodes gradually increased and at times culminated in true lava fountaining from the summit vent. Fourteen such paroxysms occurred between 7 June and 13 July (7, 9, 11, 13, 15, 17, 19, 22, 24, 27-28 and 30 June, 4, 7 and 13 July), the latest of these, on the early morning of 13 July, was also one of the most violent. Immediately after its cessation, vigorous seismicity began to shake the volcano and its surrounding areas, including shocks that were felt as far as Acireale and Catania. Between the early morning of 13 July and the early morning of 17 July, approximately 2600 tremors, mostly unfelt, were recorded by the seismic networks on the volcano. During this same time interval, severe ground cracking and faulting occurred in various places on the W rim of the Valle del Bove and near the "Cisternazza" pit crater on the Piano del Lago, a flat area at about 2500 m elevation to the north of the Montagnola. Press sources cited local volcanologists saying that magma was rising through a dike and stagnating at about 1 km depth below the surface. Steaming was observed at some of the new fractures, but as of the late evening of 16 July no magma had reached the surface; intense seismicity continued though at a slightly decreased rate. Volcanologists, emergency services and the public were on alert. Even though no explicit forecast of an impending flank eruption was issued, no one ruled this possibility out, and many volcanologists were quite convinced that a flank eruption was indeed due.
Shortly after midnight on 17 July, the lull before the storm ended with yet another paroxysmal eruptive episode at the SE Crater. This was similar to its predecessor on 13 July, with vigorous lava fountaining from the summit vent and the "Levantino". It was the last event that could be considered part of the "prelude" to the main eruption.
Course of events. The eruption lasted nearly 24 days, from early 17 July to late 9 August 2001. It began a few hours after the latest paroxysmal eruptive episode at the SE Crater at about 0700 h (local time=GMT+2) on 17 July, with the opening of an eruptive fissure at the SSE base of the SE Crater, at an elevation of approximately 2950 m. Vigorous lava spattering occurred at a number of vents, while lava flows advanced toward SE, in the direction of the Valle del Bove rim. At 2200 h, another fissure opened at an elevation of about 2700 m, a bit to the W of a panoramic point on the W rim of the Valle del Bove known as "Belvedere", and lava began to extend S from there, across the Piano del Lago, and in the direction of the highly vulnerable area of the cable car and ski lifts that constituted the main ascension route to the upper S flank of Etna.

A thick lava flow crosses the Provincial Road 92 at about 1900 m elevation, menacing the Ristorante Corsaro (in the background) on 18 July 2001. This flow was produced by the eruptive fissure at 2100 m elevation which opened on the early morning of the same day. Photograph was published in the 19 July 2001 issue of the newspaper "La Sicilia"

Aerial view of the area of the Rifugio Sapienza (in lower left corner of photograph) with the newly opened eruptive fissure at 2100 m emitting white gas plumes and a strongly steaming lava flow which curves around the N base of the Monte Silvestri Superiore. This flow covered the Provincial Road 92 (visible in the foreground) a few hours after the photo was taken. Cone of Montagnola is visible at upper left. View is to NE. Photograph was taken by Fabrizio Villa and published in the 19 July 2001 issue of "La Sicilia"

At 0120 h on 18 July, a third eruptive fissure became active on the S flank of the Montagnola at about 2100 m elevation, slightly uphill of the Monti Calcarazzi. Activity at this fissure was initially weak, and a sluggish lava flow began to move from the lower end of the fissure toward the Monte Silvestri superiore, a large complex cinder cone formed in 1892. During the day, the activity gradually increased; lava flowed around the W side of the Monte Silvestri Superiore, crossed the Provincial Road 92 (which connected the Rifugio Sapienza-cable car area with the town of Zafferana) and passed uncomfortably close to the "Cappannina", a small souvenir shop, and a large restaurant. While the flow passed the road with a front about 100 m wide, it threatened to enlarge laterally and consume one or both buildings, and desperate efforts were made to protect these structures by spraying water on the side of the flow, and later, by building an earth barrier. In fact both buildings were saved and are now functioning again.
During the remainder of the day and on 19 July, the lava flow fed by the vents at 2100 m elevation continued to advance rapidly down the S flank, passing between numerous older cinder cones along the E margin of the 1983 lava flow-field. By the late evening of 18 July the flow front was at 1800 m elevation. At the same time eruptive activity continued unabated at all eruptive fissures. On that evening a man from Belpasso, a nearby town, who had come with friends to witness the spectacle of the eruption, was seriously injured near the eruptive vents at 2100 m elevation. Eyewitnesses said that he was not hit by a rock fragment ejected from the vents, but that he stumbled and fell while trying to flee from a larger explosion. The man was brought to a hospital in Catania and treated for injuries on his dorsal spine. This incident led the local authorities to close all access roads to Etna to the public; access was granted only to persons who had obtained a special permission - the "pass" as it soon became known.
On the evening of 19 July at about 1900 h, a new vent opened on the Piano del Lago at about 2570 m elevation, about 500 m north of the Montagnola. The activity at this vent was characterized by violent phreatomagmatic explosions which produced a black, ash-laden column and threw out large blocks of older volcanic rocks. This phreatomagmatic activity might have been the result of magma-water interactions at a shallow ground water level (the name of the place, Piano del Lago, the plain of the lake, derives from the fact that frequently during the snow melt in the spring, a small meltwater lake had formed in that area). To observers familiar with footage of the Surtsey (Iceland) eruption in 1963 the steam and ash columns rising from the new vent appeared strikingly similar. After nightfall spectacular lightning flashed through the plume. This was the beginning of heavy ash falls over inhabited area in a wide sector including the NE, E, SE and S sides of the volcano. Close observation of the vent at 2570 m elevation revealed that it was a simple pit whose rims were constantly eroded into older volcanic rocks around it, causing the widening of the pit. Immediately rumors began to spread that the pit would eventually "make the Montagnola cave in" - as a matter of fact, the Montagnola is still standing today.
The front of the lava flow emitted from the fissure at 2100 m elevation was at 1350 m on the late evening of 19 July and still advancing vigorously, though at reduced speed (about 45 m per hour). In this situation, the mayor of Nicolosi gave a dramatic interview in which he accused the outside world of neglecting his town, which was threatened by the lava flow, which might have to be evacuated, and which needed the declaration of the state of emergency. The state of emergency was indeed declared soon after by the President of the Province of Catania.
The risk seemed, at this time, much more serious for the tourist complex at about 1950 m elevation, which lies around the Rifugio Sapienza and the nearby base station of the cable car. Both the Rifugio Sapienza and the cable car had been renovated in the months before and should have been reopened just a few days after the beginning of the eruption. Lava from the fissure at 2700 m elevation had advanced very close to the steep slope that lies between the upper and the base stations of the cable car, and any further advance would seriously threaten the ski lifts in that area and the tourist complex. Efforts were made to erect earth barriers around the upper cable car station and near the lower cable car station in order to contain the feared lava flow.
The eruption was still far from stable. During the night of 19-20 July, the SE Crater reactivated, and lava began to issue from the "Levantino" on its NNE side, forming a small flow that advanced in the direction of the Valle del Bove. On the next morning at about 1100 h, yet another eruptive fissure formed in an area far away from the earlier fissures, below the Pizzi Deneri on the floor of the Valle del Leone, on Etna's NE flank. An impressive arcuate fracture system developed, and lava first issued from its uppermost portion at about 2700 m elevation, then from its eastern extension about 50 m further downslope. Explosive activity at this fissure was very weak and built a small hornito at the lower point of emission. However, it was noted that an extensive fracture system had formed between this northeasternmost fissure and the E side of the summit crater area, and huge gaping fissures up to 1 m wide on the slope between the Bocca Nuova and the SE Crater were emitting dense vapor plumes. The large phreatomagmatic pit crater on the Piano del Lago at 2570 m elevation continued to produce dense, ash-laden plumes, and a heavy rain of ash fell over the area between Zafferana and Acireale.
On 20 July, an emergency center named "COM" (Centro operativo misto) was created in a school building in Nicolosi, in order to coordinate the surveillance, communication and emergency measures. On the evening of that day, the front of the lava flow from the fissure at 2100 m elevation had reached an altitude of 1220 m, but it had now reached a gently sloping area and advanced at much reduced speed. Nonetheless, the threat to Nicolosi had become the big news in the international mass media. The main risk from this flow was now that of forest and bush fires. Canadair and military helicopters began to drop large quantities of water onto the burning forest (not onto the lava flow, as was widely reported in the news media). Fortunately, no large forest fire broke out.
On 21 July, the eruption continued with unabated vigor at all eruptive fissures. The main lava flow from the vents at 2100 m reached an elevation of 1050 m late that day, while the lava from the vents at 2700 m had not further advanced on the steep slope above the tourist complex of the Rifugio Sapienza area. On 21 July, Etna gave the people living and working around it a kind of a break.
The next day, 22 July, a shift in the wind direction drove the dense ash plume produced by the phreatomagmatic vent at 2570 m altitude directly over the Catania area, paralyzing the Fontanarossa International Airport of the city, and dropping large amounts of fine, black, sand-sized tephra over streets and buildings. Eruptive activity continued without significant variations at all fissures, although the main lava flow directed toward Nicolosi had slowed down significantly and advanced only a few meters per hour, still 4 km from the outskirts of Nicolosi. On the evening of that day, however, the situation began to appear more serious for the Rifugio Sapienza area and the cable car. Minor, though fast-moving lava tongues fed by the vents at 2700 m elevation spilled down the steep slope above the tourist complex, threatening to overwhelm some of the poles of the cable car and destroying part of the ski lifts. However, none of these flows made it further than about half way down that slope. Vigorous Strombolian activity continued at the fissure at 2100 m elevation, and a cone about 20-30 m high had formed around the largest of its vents, while minor lava spattering from four vents in the lower part of the fissure was building a low spatter rampart. The lava flow from this fissure was moving as a single, broad unit without showing signs of channelizing. Between this flow and the tourist complex at the Rifugio Sapienza, caterpillars were continuously working on ever higher and broader earth barriers, which were hoped to contain any lava flow coming down from the vents at 2700 m elevation.
Throughout 23 July the activity showed little variations. Ash continued to be emitted in large volumes from the large pit crater on the Piano del Lago at 2570 m elevation, and shifting winds carried the plume toward E during the morning, while during the day the plume passed over Catania, causing more ash falls over the city. The vents on the fissure at 2100 m elevation appeared slightly less vigorous than during the previous day, but lava continued to flow unabated from the fissure. Meanwhile the front of this lava flow had essentially ceased advancing, and it did not seem that Nicolosi would soon be reached or overwhelmed by the lava. Almost unnoticed by the public, the SE Crater reactivated on the afternoon of 23 July, with a new fracture opening on the SE flank of its cone that emitted a small lava flow toward the Valle del Bove. On the next morning, lava once more began to issue from the "Levantino", producing a small flow.
On 24 July it became clear that something was changing at the Piano del Lago crater, which until then had displayed only phreatomagmatic activity. More and more incandescent ejecta rose with the ash column, and at nightfall, brilliant incandescent jets rose hundreds of meters into the sky, accompanied by loud roaring noises, much louder than the impressive ash expulsions of the previous days. All eruptive fissures were still erupting on that day, but the vents at 2100 m elevation were clearly less vigorous than during the days before. Some phreatomagmatic activity occurred from the uppermost vents on this fissure, producing gray ash columns that rose in a fountaining manner from the vents. No significant variations were observed at the front of the main lava flow above Nicolosi.
Loud detonations from the Piano del Lago vent greeted the Etna region on the morning of 25 July, as the activity there had now become purely magmatic. The ash column rising from that vent was now much more dilute, although sand-sized ash particles continued to fall on the E flank of the volcano. A broad, low pyroclastic ring began to form around the vent, the initial stage of what was to become the largest cone of the eruption. All eruptive fissures were still erupting, but the new fissure on the SE flank of the SE Crater cone and the "Levantino" showed only very reduced activity. Fresh tongues of lava spilled down the steep slope above the Rifugio Sapienza but stopped about 300 m from the building. So far, damage was limited to the ski lifts and the dirt road that connected the Rifugio Sapienza area with the upper cable car station.

The second lava flow to cover the Provincial Road 92 came from the Piano del Lago cone area and seriously threatened the tourist complex around the Rifugio Sapienza. Ristorante Corsaro is visible in the background. Photograph was taken on 26 July 2001 and published in the newspaper "La Sicilia" one day later.

On the next day, 26 July, the new cone forming on the former Piano del Lago showed impressive levels of activity. Like on the previous day, it produced near continuous explosions accompanied by loud detonations that could be heard to tens of kilometers away. The cone grew rapidly by the accumulation of the enormous volumes of huge bombs ejected from at least three vents within it. The shift from phreatomagmatic to magmatic activity at this cone had serious consequences: lava was now flowing from vents on its southern and northern sides. These new flows rapidly spilled around the N and NW sides of the Montagnola and down the steep slope on the W side of that cone toward the Rifugio Sapienza area. On 26 July four of the poles of the cable car were overwhelmed by this new lava before the flow passed on the E side of the lower cable car station, covered another portion of the Provincial Road 92 and advanced a few hundred meters further. The upper cable car station was surrounded by the same flow further upslope but remained intact for another few days. Desperate efforts were made to reinforce the earth barriers which until now had prevented the flow from directly invading the tourist complex at the Rifugio Sapienza, but it seemed that the battle was all but lost. Vigorous eruptive activity continued on that day at the eruptive fissure at 2950 m elevation while the fissure at 2700 m elevation continued to emit lava but pyroclastic activity there had ended. Weak activity continued at the Valle del Leone fissure, with lava flowing toward Monte Simone (in the N part of the Valle del Bove), and the fissure at 2100 m elevation showed no significant changes in its activity with respect to the previous days.
27-30 July were the most dramatic days of the eruption in terms of the impact on human structures. While the fissure in the Valle del Leone showed ever lower levels of activity and the fissures at 2900, 2700 and 2100 m elevation continued to erupt in a manner almost identical to the previous days, the new-born cone at the former Piano del Lago and several nearby vents not only provided an awesome show, but vents located on its N and S flanks delivered vigorous lava flows that spilled down the steep slope to the W of the Montagnola in surges, presenting a continuous threat to the Rifugio Sapienza area. These days were characterized by frantic attempts to contain the lava, to keep it away from the lower cable car station and the Rifugio Sapienza, and the souvenir shops around them. Yet on the last of these days, on the evening of 30 July, the eruption claimed its most prominent victim. Before the eyes of the operators of the cable car and the lenses of television cameras from all over the world the upper cable car station burst in flames as a tongue of lava had invaded its interior. Behind it, the rapidly growing cone of the Piano del Lago sent its lava fountains hundreds of meters into the sky, producing ground-shaking detonations. Never during the entire eruption was the atmosphere as apocalyptic as on that evening. Yet this culmination was the end of the worst.

Spectacular night view (from near Torre del Filosofo) of the erupting vents at 2700 m elevation (left) and lava fountain at the Piano del Lago cone (right), probably taken on 30 July 2001. Lights of towns between Acireale and Giarre in the background. Photo was published in the 1 August 2001 issue of "La Sicilia"

During the following days, the rate of lava emission in the direction of the Rifugio Sapienza area diminished as a new vent opened on the S side of the Piano del Lago cone, from which a lava flow spilled over the crest of the Valle del Bove and arrived on the bottom of the Valle, covering a portion of lava erupted in 1991-1993. The Valle del Leone fissure ceased emitting lava. The large cone (which was now informally named "Montagnola 2", "Monte del Lago" or "Cono del Laghetto") again shifted from magmatic to phreatomagmatic activity. Although the level of activity at this cone was decreasing, huge columns of ash were produced once more, and the wind carried the ash again in the direction of Catania, forcing the closure of the Fontanarossa airport. Vigorous eruptive activity continued during the first days of August at the fissure at 2100 m elevation, but the lava effusion rate had dropped, and only the central portion of the original flow remained active, feeding a flow that advanced on top of the larger earlier flow from the same fissure. Strong phreatomagmatic explosions occurred from time to time at the upper vents on this fissure, making any approach highly dangerous. Lava also continued to pour from the fissure at 2700 m elevation, and numerous active flow lobes extended SE toward Monte Nero degli Zappini.
From 3 August on the activity at the fissure at 2100 m elevation showed a marked decrease. During the last week of the eruption (4-10 August) lava continued to flow from that fissure at a rapidly diminshing rate, explosive activity ended, and the fissures at 2950 and 2700 m elevation ceased erupting. Ash emission from the Piano del Lago cone ceased around 6 August. Lava was last seen flowing from the fissure at 2100 m elevation on late 9 or early 10 August. The eruption ended after almost 24 days, much earlier than its vigorous onset had suggested.
Products of the eruption and morphological changes. The July-August 2001 eruption emitted at least 8 distinct lava flows which mostly affected the S and SSW flanks of Etna. The largest flows were produced by the fissures at 2100 and 2700 m elevation, though the most damaging flows came from vents near the Piano del Lago cone at 2570 m elevation. This latter cone produced most of the pyroclastic material, of which the most fine-grained portion (ash) caused widespread distress.
Petrographically, the lavas fall into two main groups, one of which is essentially similar to the historical products of Etna (porphyric hawaiites with phenocrysts of plagioclase, clinopyroxene and olivine), while the other shows characteristics not seen in any Etnean lavas during the past millennia: these are alcalic basalts with abundant clinopyroxene megacrysts up to 0.5 cm in diameter; clinopyroxene is also present as phenocrysts along with plagioclase, olivine and 1-2% amphibole. Lavas of the first group were erupted from the eruptive fissures in the Valle del Leone, and on the upper S flank at 2950 and 2700 m elevation. These fissures were apparently closely associated with the central conduit system. The vents at 2570 (Piano del Lago) and 2100 m elevation, however, produced the amphibole-bearing alcalic basalts, which furthermore contained abundant xenoliths derived from the sedimentary basement of Etna (Numidian Flysch). Most of these xenoliths are several centimeters in diameter, but some are 10-15 cm across. More rarely, schists occur as xenoliths in the same lavas, and cumulates have been observed in a few samples. According to an information bulletin issued on 31 July 2001 by the INGV, "a high ratio of femic minerals-plagioclase is typical of the products of "eccentric" eruptions (such as 1763 and 1974, among the most recent), which are generally fed by conduits not closely related to the central conduits. The presence of amphibole, in the form of inclusions with dimensions of a few tens of microns, has been observed in the products of the 1991-1993 eruption; relics of amphibole of similar dimensions have been also noted in the products of the Plinian eruption of 122 BC. In the past, significant amounts of this mineral have been observed only in the initial (>35 ka, with hawaiitic-mugearitic compositions) and final (15 ka, with benmoreitic-trachytic compositions) products of the Ellittico volcano. (...) These preliminary data, if confirmed by more mineralogic and geochemical studies on the future products of the volcano, indicate that an important change is under way."
Several major pyroclastic edifices grew during the eruption. The largest, the Piano del Lago cone at about 2570 m elevation, is a nearly symmetrical cone, about 80 m high, which grew mostly between 25 and 31 July. It is crowned by a large crater about 150 m across and 50-60 m deep with near vertical walls. During a visit on 30 August a few fumaroles located on the S and SE crater walls emitted vapor and gas without forming a visible plume. A spectacular dike is exposed at the base of the E crater wall, another, less conspicuous dike is visible at the base of the WNW crater wall. Furthermore there are several faults or groups of faults visible in the E and NE crater walls; a narrow graben developed on top of the conspicuous dike in the E crater wall.
The second largest pyroclastic edifice lies in the upper part of the fissure at 2100 m altitude. Here a horseshoe-shaped cone open to the S was formed around the most vigorously active vent, which is about 70 m high above its S base but only about 5-10 m high above its N base. In its upper part lies the main explosive vent of the fissure, which is about 25 m wide, funnel-shaped, and has a narrow (about 3-5 m) bottomless hole in its floor. Fumaroles are still active along more or less circumferential subsidence cracks on the NW and NE sides of the crater rim, while gas emission from the narrow pit on the vent floor decreased markedly between visits on 29 August and 13 September. On the southern side the cone is cut by a deep fissure from which the main lava flow issued. This fissure presents a number of interesting features that merit a discussion for their own, which will be included in a photo essay to be posted later on this site.
Minor pyroclastic edifices formed at the vents at 2700 m elevation (a main cone about 20 m high and a steep-sided hornito about 6 m high), at 2950 m elevation (several hornitos up to 8 m high and a lower spatter rampart) and in the Valle del Leone (a single symmetrical hornito 8-10 m high). Among the most interesting minor features are several vents that were active on the S side of the Piano del Lago during the last days of July. These consist of various hummocks, two effusive vents, and two small craters, all apparently formed in a zone of essentially effusive activity. The latest of these vents to erupt lies in a small depression between the Piano del Lago cone and the Montagnola; it produced the lava flow of 27 July 2001. The vent itself is hidden under a "cake" of lava that built up at the source of the flow. A nearby vent which produced powerful explosions on 28 July was clogged by a small lava dome toward the end of its activity, which was perforated by a last explosive gasp leaving a small pit (3-5 m across) in the center of the dome.
Extensive (non-eruptive) fracture systems formed between the various eruptive fissures. Some of them began to form before the eruption, others developed during its first week. Many of these fractures are arranged in an "en echelon" pattern, which is especially notable in the Valle del Leone, between the northeastern (2600 m) vents and the SE Crater. Other spectacular fractures opened between the Piano del Lago cone and the eruptive fissure at 2100 m elevation. However, the most impressive fractures developed on the E side of the former Central Crater (now occupied by the Voragine and the Bocca Nuova), where they attained widths of more than 1 m. These fractures were vigorously steaming when visited in late-August and mid-September 2001. Fracturing also affected the southern face of the SE Crater cone.
About 5.5 square kilometers of Etna's upper and middle slopes were covered with new lava (compared to 7.6 square kilometers in the 1991-1993 flank eruption). The total volume of lavas and pyroclastics emitted during the eruption is approximately 40 million cubic meters (21 million cubic meters of lava and less than 20 million cubic meters of pyroclastics, the whole corresponding to no more than 30 million cubic meters of dense rock), which makes this eruption a relatively modest-sized one for Etna (the 1991-1993 eruption had produced about 235 million cubic meters of lava). Yet the fairly high proportion of pyroclastic material distinguishes this eruption from most other recent Etnean flank eruptions. The most productive vents were those at 2100 m elevation, which produced the longest (about 7 km) and most voluminous (slightly less than 14 million cubic meters) single lava flow. The mean eruption rate at all vents for the entire duration of the eruption is about 15 cubic meters per second, which is not exceptionally high. It is assumed that much of the magma that accumulated in one or more reservoirs below the base of the volcano in the years preceding the eruption was not erupted and remains available for future eruptions. A new eruption did in fact begin in late October 2002 and lasted until late January 2003 (see below).

Two photos showing the last stages of the eruption at the 2100 m eruptive vents: they were taken on the evening of 8 August 2001, when explosive activity had already ceased, and people began to approach the last remaining active effusive vent (see photo at right). One day later flowing lava was observed for the last time in this eruption. Photos courtesy of Paul and Monique Schilders, The Netherlands (see their web site)

Effects of the eruption. A) Damage. As noted in the previous paragraphs, the July-August 2001 eruption caused serious damage, though it did not reach truly disastrous proportions. The tourist area on the S flank suffered a severe blow, especially with the partial destruction of the cable car, one of the biggest sources of income in the region and a major tourist destination. One building, the upper cable car station which contained also a bar, was completely burned and rendered useless. Several poles of the cable car were buried by the lava, and most of the ski lifts were destroyed. On the Montagola, the hut which had contained the monitoring live-cam of the INGV (formerly Poseidon) was shattered and burned to its foundations by the rain of bombs from the Piano del Lago cone and vents at its southern base; the transmission antenna were blown to smithereens. The camera and associated equipment had been saved before the hut was destroyed. Nearby poles of the uppermost ski lift show further dramatic evidence of the violence of the fiery bombardment.
The scenic ruin of the "Piccolo Rifugio" (a small mountain hut that stood near the upper cable car station at about 2500 m elevation; this hut had been severely damaged by the 1983 and 1985 eruptions) vanished under new lavas as did the much-visited hornitos of the 1985 eruption. During a visit to the area on 28 July, all that could be recognized of these features was a leveed lava flow channel of the 1985 eruption behind which rose a steep wall of fresh lava 5 m high.
A large portion of the dirt road connecting the Rifugio Sapienza area with the summit area was interrupted by lavas from the fissure at 2700 m and from the Piano del Lago cone. A hut of the mountain guides in the lower part of the valley to the W of the Montagnola was mostly buried by the lava but not crushed. In the Rifugio Sapienza area, a building of the Provincial Tourist Agency was surrounded on two sides by a lava flow but remained intact. All other buildings in the area (except a small wooden shack) escaped unharmed. The Provincial Road 92 was interrupted by the two parallel lava flows from the fissure at 2100 m and from the Piano del Lago cone, on 18 and 26 July, over a width of about 500 m. In the area of the most advanced lava front at about 1050 m elevation, fruit gardens and forest were buried by the lava as well as several dirt roads of the forest guard. As of early October 2001, reopening of the Provincial Road 92 and of the dirt road leading from the Rifugio Sapienza to the upper part of the mountain is under way.
B) Disruption of traffic, nuisance by tephra falls. By far the most widespread effect of the eruption was the disruption of traffic (mostly air traffic) and nuisance to the population caused by the frequent heavy ash rains over densely urbanized areas. The Fontanarossa International Airport of Catania had to be closed repeatedly and for entire days due to the presence of ash, causing a major chaos in touristic flights during the high season in Sicily. Flights had to be rerouted to Palermo, Reggio Calabria and Trapani, and many passengers had to live through many hours of waiting. To the residents of Catania and surrounding towns the ash falls brought different problems. The ash entered everywhere, depositing a black film on everything in every home. Since the weather was very hot at the time, one had to let fresh air come in at least during the night, and that allowed much larger quantities of ash to come into one's home as well. Cleaning efforts cost the city of Catania at least 2 billion Lire (about 0.8 million US$), while the activity of the caterpillars for the construction of protective barriers against the lava flows was reported to cost about 100 million Lire (about 400,000 US$) per day. These sums probably constitute only a very small fraction of the total economic damage caused by the eruption.
C) Reaction of the public and authorities. While the eruption had been expected at least since four days before its onset (anybody who lives on Etna is commonly aware that flank eruptions occur at intervals of several years), its onset and complex evolution made local authorities, emergency services and civil protection staff face a serious challenge. First of all, spectators had to be kept away from the immediate vicinity of the eruptive fissures, a need that was dramatically underlined when a man was seriously injured on the evening of 18 July near the vents at 2100 m elevation. Second, the opening of new fractures, the shifting of vents in limited areas and the changes in the character of the eruptive activity with corresponding changes in the direction of lava flows during the first two weeks of the eruption often caused confusion and forced scientists and administrations to work with ever changing scenarios. Third, the public had to be informed about what was going on, and information provided was at times contrasting or confusing, to which unfounded rumors added significantly (e.g. that the Montagnola would "cave in" or that the Piano del Lago cone could become a new permanent vent on Etna). The mass media (especially those from countries other than Italy) distributed vastly exaggerated descriptions of an apocalyptic situation with numerous residents of threatened villages preparing for flight, life in a state of fear or even panic, and many people praying for a miracle. Inside Italy, the news media avidly concentrated on a public conflict between the director of the Civil Protection agency, Franco Barberi (who was released from his duties shortly afterwards, but rather for political reasons), and the president of the INGV (National Institute of Geophysics and Volcanology), Enzo Boschi, who had contrasting opinions about the degree of risk during the eruption, as well as about the dynamics of the eruption itself.
The local population did indeed follow the events with some apprehension since it was well visible that the eruption was powerful and affected a vast sector of the volcano. Yet it was mostly the elderly population who participated in mass celebrations, and people were mostly annoyed by the tephra falls, but all persons I spoke to remarked that they were not particularly worried for their homes and lives, even though they admitted that sooner or later they might live a far more dangerous situation. The most amazing reaction of the local population was the never-ending pilgrimage to the accessible eruption areas, such as the lava front on the plain above the town of Nicolosi. Rather than having their usual weekend picnic in the forests, families went to "see the lava". Each evening thousands of young people walked kilometers to get as close as possible to the eruption sites on the S flank, wearing their newest dresses and costumes, but surely nothing suitable for a major excursion to an active volcano.

First section of the paper by Schiano et al. as it appeared in the 30 August 2001 issue of "Nature". Offprints can be requested from the authors

Outlook: Is Etna becoming more explosive? About three weeks after the end of the eruption, Etna returned into the news. News agencies reported that a team of French and Italian scientists had announced that the volcano was changing character, that it was transforming from a hot-spot (mantle-plume) volcano to a subduction-zone volcano, and this meant that its future activity would become more explosive and thus dangerous. This news, which obviously was broadly covered in the national and local press, provoked apprehensive reactions among residents and somewhat annoyed comments by Italian geoscientists, such as Eugenio Privitera and Enzo Boschi of the INGV. Indeed, the internationally renowned journal Nature had a spectacular photo (taken by Charles Rivière during a paroxysm at the SE Crater in June 2000) on the front page of its 30 August 2001 issue, and the same issue had an article entitled "Transition of Mount Etna lavas from a mantle-plume to an island-arc magmatic source", which was written by P. Schiano, R. Clocchiatti, L. Ottolini and T. Busà. The article was based on a study of small blobs of magmatic glass that appear as inclusions within crystals in lavas erupted at various times during the geological evolution of Etna. Such blobs, called melt inclusions, give precious information about the original composition of a magma before it arrives at the surface. The authors had observed that in time the original composition of Etnean magmas had changed and attained a more calc-alkaline character. Calc-alkaline magmas are typical of volcanoes that form near subduction zones, such as those of Indonesia, the Philippines, Japan, the western coast of the Americas, and also the volcanoes of the Aeolian Islands in Italy, which lie only about 100 km north of Etna. These volcanoes are commonly highly explosive, and the observed increase of the calc-alkaline component in more recent Etnean magmas was interpreted by Schiano and his collaborators as a sign that Etna was becoming more similar to those volcanoes. This implication was necessarily to be put into a framework of geological times, which are considerably longer than a human lifespan. Yet, according to the authors, some of this geodynamic and compositional change had already produced visible results: since 1970, they remark, Etna is more active, with a "higher frequency of eruption and higher effusion rates" (in fact, a notable increase in the output rate, or "productivity", of Etna, has been observed for the past 50 years, but this has been more dramatic since the 1970s, with frequent strongly explosive eruptive episodes at the summit craters).
What could cause such a change in character, what process could lead to the appearance of a more calc-alkaline signature in Etnean lavas? Schiano and his co-authors propose two explanations. One is that "subduction-related magmas originate from the nearby Aeolian island arc and migrate along tectonic features, such as the northwest-southeast Tindari-Giardini-Etna-Malta fault system to interact with Etnean plume-related magmas", but alternatively "the southwestern lateral limit of the Ionian slab [the subducted segment of the Ionian lithospheric plate] beneath Mount Etna is progressively shifting [closer to the volcano]".
On the same day the article was published in "Nature", the Catania-based newspaper "La Sicilia" had a lengthy discussion of the article and cited the immediate reactions of two Italian geoscientists, Eugenio Privitera (who works in the data acquisition center of the Catania section of the INGV), and Enzo Boschi, president of the INGV. "[This is] a partial interpretation of the phenomena which alone is not sufficient to develop such a radical hypothesis on the evolution of a volcano", said Privitera. "First of all it is impossible to say that a volcano is changing its [eruptive behavior] based on nothing else than the analysis of the composition of its lavas. Such a hypothesis would need to be supported by [the studies carried out in] many other disciplines... Secondly, during human history, no volcano has ever been seen, and thus studied, which has changed the style of its behavior. One needs to go back many thousands of years to find [evidence of] large-scale explosive phenomena." Futhermore Privitera described the evident increase in the activity of Etna as a purely "physiological" phenomenon: "Etna remains an effusive volcano, and the major risks are those of invasion by lava flows that could threaten cultivated, and, possibly, inhabited areas, but surely not the lives of those who live on the flanks of Etna."
In the same issue of "La Sicilia", Boschi described the hypothesis of Schiano and his collaborators as "certainly fascinating, but based on partial considerations". "Until now no [research] has ever been conducted which has allowed to observe changes of such a kind in a volcano (...) because no one knows the mechanisms which could bring about a tranformation in the activity of a volcano." The observations made by Schiano's team could be interpreted in many other ways. In the end, remarked Boschi, it seemed likely that Nature had used the article as some kind of "scoop" in order to acquire a more favorable position in the competition with other scientific journals. Indeed the publication date of the article so shortly after the much publicized eruption is notable; however, it had been written and submitted before July 2001 (submitted 5 February, accepted 5 July 2001, is written at the end of the paper) and thus does not include data from the July-August 2001 eruption.
Yet this eruption showed a number of characteristics that one could interpret as a confirmation of what Schiano and his co-authors believe. In an interview with the German newspaper "Süddeutsche Zeitung" on 13 August (more than two weeks before the Nature article became known), Sonia Calvari of the Catania section of the INGV commented on the presence of amphibole crystals in some of the newly erupted magmas. "No lavas of such chemical composition have been emitted from Etna for 15,000 years", is said there. The presence of amphibole, which contains water in its crystal structure, indicates that this kind of melt is more explosive, and more of it could be erupted in the near future in unusually violent eruptions. Much of the explosivity (and tephra generation) of the 2001 eruption, however, was due to the interaction of the uprising magma with groundwater, mostly at the Piano del Lago cone.
On 7 September, "La Sicilia" extensively reproduced a letter by the second author of the Nature paper, Clocchiatti, which was a reaction to the comments by Privitera and Boschi cited above. "[They] certainly had no possibility to know the article at that time since it was not yet available, and thus relied on what was reported by the news agencies." He and his research team had observed that the early Etnean magmas (between 500,000 and 100,000 years old) were compositionally similar to those of the Monti Iblei. "As we went on with our studies, we have noted that a compositional change in the magmas of Etna had taken place between 100,000 and 7000 years ago. ...the recent and modern primitive lavas of Etna have compositions that fall between those of the ancient Etna and those of [Vulcano and Stromboli]." Furthermore, "[the analysis of] the composition of a lava, like an analysis of a blood sample, has nothing to do with speculation, but reveals facts and clear evidence." As for the possibility of future explosive volcanism at Etna, Clocchiatti writes: "[The press has surely exaggerated when focusing on the fact] that the dynamics of Etna are becoming more violent. This is nothing new, but it has already happened before: ...the Sicilian volcano has had violent [eruptive] manifestations in the past, such as the [pyroclastic flow] of Biancavilla, 15,000 years ago. But one has to remember that that eruption was the result of a maturation process that lasted several millennia. So, my Sicilian friends, you may sleep quietly, Etna will not become a Pinatubo tomorrow."

Aftermath. Only fourteen months and 17 days after the end of the 2001 eruption, Etna erupted again. It did so much more violently, and much more destructively than in 2001, during the night of 26-27 October 2002. That new eruption led to the total devastation of the Piano Provenzana tourist facilities on the northeastern flank, where one of two eruptive fissures opened. The second eruptive fissure formed on the upper southern flank, where the activity was strikingly explosive; lava was emitted at this site only during the first few days and then again from mid-November 2002. Serious damage occurred in the tourist complex around the Rifugio Sapienza. The 2002-2003 eruption emitted about twice as much magma as the 2001 eruption. As of October 2003, the volcano appears quiet, but in reality the preparation for yet another flank eruption is already under way. More on the 2002-2003 eruption

References

Two years after the 2001 eruption, an impressive number of publications dealing with that event has already appeared. They cover a wide range of aspects, mostly geophysical (Bonaccorso et al., Lundgren et al., Patanè et al.), geochemical (Aiuppa et al., Caracausi et al. a and b, Pompilio et al., Taddeucci et al.) and structural (Acocella and Neri, Billi et al., Lanzafame et al.). Others deal with the magmatic plumbing system in a more general sense (Patanè et al.) and with protective measures taken against lava flow damage to the Rifugio Sapienza tourist complex (Barberi et al.), while Behncke and Neri give an overview of the eruption chronology and describe some of its more peculiar features such as eccentric and phreatomagmatic activity.

Acocella V and Neri M (2003) What makes flank eruptions? The 2001 Mount Etna eruption and its possible triggering mechanisms. Bulletin of Volcanology 65: 517-529, DOI: 10.1007/s00445-003-0280-3

Aiuppa A, Federico C, Paonita A, Pecoraino G and Valenza M (2002) S, Cl and F degassing as an indicator of volcanic dynamics: The 2001 eruption of Mount Etna. Geophysical Research Letters 29, DOI: 10.1029/2002GL015032

Barberi F, Brondi F, Carapezza ML, Cavarra L and Murgia C (2003) Earthen barriers to control lava flows in the 2001 eruption of Mt. Etna. Journal of Volcanology and Geothermal Research 123: 231-243, DOI: 10.1016/S0377-0273(03)00038-6

Behncke B and Neri M (2003) The July-August 2001 eruption of Mt. Etna (Sicily). Bulletin of Volcanology 65: 461-476; DOI: 10.1007/s00445-003-0274-1, (download pdf of the full article)

Billi A, Acocella V, Funiciello R, Giordano G, Lanzafame G and Neri M (2003) Mechanisms for ground-surface fracturing and incipient slope failure associated to the July-August 2001 eruption of Mt. Etna, Italy: analysis of ephemeral field data. Journal of Volcanology and Geothermal Research 122: 281-294, DOI:10.1016/S0377-0273(02)00507-3

Bonaccorso A, Aloisi M and Mattia M (2002) Dike emplacement forerunning the Etna July 2001 eruption modeled through continuous tilt and GPS data. Geophysical Research Letters 29, DOI: 10.1029/2001GL014397

Caracausi A, Favara R, Giammanco S, Italiano F, Paonita A, Pecoraino G, Rizzo A and Nuccio PM (2003) Mount Etna: Geochemical signals of magma ascent and unusually extensive plumbing system. Geophysical Research Letters 30, DOI: 10.1029/2002GL015463.

Caracausi A, Italiano F, Paonita A, Rizzo A and Nuccio PM (2003) Evidence of deep magma degassing and ascent by geochemistry of peripheral gas emissions at Mount Etna (Italy): Assessment of the magmatic reservoir pressure. Journal of Geophysical Research 198, DOI: 10.1029/2002JB002095

Lanzafame G, Neri M, Acocella V, Billi A, Funiciello R and Giordano G (2003) Structural features of the July-August 2001 Mount Etna eruption: evidence for a complex magmatic system. Journal of the Geological Society of London 160: 531-544, DOI: 10.1144/0016-764902-151

Lundgren P, Rosen PA (2003) Source model for the 2001 flank eruption of Mt. Etna volcano. Geophysical Research Letters 30, DOI: 10.1029/2002GL016774

Patanè D, De Gori P, Chiarabba C and Bonaccorso A (2003) Magma ascent and the pressurization of Mount Etna’s volcanic system. Science 299: 2061-2063, DOI: 10.1126/science.1080653

Pompilio M and Rutherford MJ (2002) Pre-eruption conditions and magma dynamics of recent amphibole-bearing Etna basalt (abs.) Eos Transactions of the American Geophysical Union 83 (47) Fall Meeting Supplement: F1419

Taddeucci J, Pompilio M and Scarlato P (2002) Monitoring the explosive activity of the July-August 2001 eruption of Mt. Etna (Italy) by ash characterization. Geophysical Research Letters 29: 71-1 - 71-4, DOI: 10.1029/2001GL014372

The July-August 2001 eruption and its precursors (the spectacular paroxysmal eruptive episodes at the Southeast Crater in June-July 2001) are featured on many web pages that contain additional information, highly spectacular images, and video clips. Some of the earlier posted links have disappeared and are not reproduced here. Others need to be controled and will be removed if they are no longer active.

The most instructive web page on the 2001 eruption (but in Italian only), created by Lisetta Giacomelli and Roberto Scandone

The "official" Etna 2001 eruption web site at the Catania section of the National Institute of Geophysics and Volcanology (INGV), contains a preliminary map of the lava flows

Photos of the eruption at the Roma section of the National Institute of Geophysics and Volcanology (INGV)

Etna eruption 2001: a page produced by the GNV (National Group for Volcanology) and hosted by Vulcanoesplorazioni.com, with photos, maps and movie clips

"Emergenza Etna" - the Etna emergency, presented by the Italian Department of Civil Protection (includes simulations of the lava flows)

Charles Rivière's Etna home page, with frequent updates, photos, video clips: Rivière was at Etna almost continuously during the 2001 eruption

Davide Corsaro's (of the Hotel Corsaro) "Etna FAQ", a nice and entertaining resource with many references to this Etna News page (grazie Davide!)

Tom Pfeiffer (University of Arhus, Denmark) has stunning photos of:
the precursory activity at the SE Crater in the spring of 2001 and of the July-August 2001 eruption (scroll down to "Etna photos")

Alain Catt� (Association Volcanologique Europ�enne) is currently working on a page on the 2001 eruption (we went together to see the incredibly spectacular activity at the "Monte del Lago" (also called "cono del laghetto") one evening during the eruption)

Thorsten Boeckel's web site (Germany) contains various pages with photos and video clips of the SE Crater activity in the spring of 2001 and of the July-August 2001 eruption

Henk Bisschop from The Netherlands, whom I met personally during the 2001 eruption and again in September 2003 describes his impressions of the later phase of the 2001 eruption with numerous photos and video clips. One of these (the first one) has the only existing authentic sound recording of the impressive explosions at the newly formed crater on the former Piano del Lago

www.vulkane.net, a German homepage about volcanoes made by my former colleagues (at the University of Bochum) Marc Szeglat and Daniela Szcze

Jean Louis Piette from Belgium, who visits Etna every year, and who always has something good to drink when we meet on the volcano, presents his impressions of the July-August 2001 eruption

Alain Melchior, also from Belgium and partner in crime of Jean-Louis Piette, has set up his Etna 2001 page, with nice 3D animations and digital elevation models of Etna and photos, video clips and other items are planned to appear on this site soon

Eurimage has spectacular satellite (Landsat, ERS) views of the July-August 2001 eruption

www.vulcanoetna.com, a web site maintained by Andrea Fiore, has impressive photos and videos of the eruption

Photos taken during the eruption on 20 July 2001 at www.sicilian.net

A brief summary of the 2001 eruption (in Spanish), with a few photos (the second one shows the 4 September 1999 lava fountain at the Voragine, the third and seventh show the Piano del Lago cone, and the other photos are of the vents at 2950 m elevation), from the Instituto Andaluz de Geofísica (University of Granada, Spain)

"Etna 2000" is an Italian home page made by Simone Genovese, with general information on Etna, and has a special section on the 2001 eruption with photos and video clips

A small selection of photos of the 2001 eruption (mainly of the lava flow from the vents at 2100 m elevation), by Giovanni Grasso and Antonio Guarnera (at Acitrezza On-line)

Photos (2 galleries) of the 2001 eruption (including a spectacular aerial view) by Alexander Gerst (in German)

Photos and reports on a field trip with OUGS-ME (Open University Geological Society - Mainland Europe) in May 2001, with a visit to the erupting SE Crater

Continue with
THE 2002-2003 ERUPTION OF ETNA

Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"