Italy's Volcanoes: The Cradle of Volcanology

Etna Decade Volcano, Italy
Eruption update:
20-21 October 1999

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Lava flows on W flank

Dramatic shot (taken by press photographer Fabrizio Villa) of lava flows spilling down the W flank of Etna during the night of 17-18 October. This view is from the area near Monte Palestra, located at about 1900 m on the W flank of the volcano.

October 1999 lava flows

Sketch map of the upper W flank and the summit area of Etna, showing the approximate directions of lava flows coming from the Bocca Nuvoa as of 19 October, 2000 h. The true extent of the new lava will be shown in a future map. Dotted line around the summit craters encircles area subjected to heavy falls of large bombs from explosive activity within the Bocca Nuova.

WARNING: Access to the summit craters is EXTREMELY DANGEROUS. Activity in the Bocca Nuova and the Voragine is very intense, and bombs are falling over all of the summit area. 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.

21 October 1999 update. After continuing vigorously until the early morning of 20 October, the activity from the eruptive vents in the W and NW part of the Bocca Nuova ceased, and the overflow of lava through the notch (formed on 17 October) in the W crater rim stopped. Sometime around dawn (0700 h local time=GMT+2), forceful expulsions of ash began from the SE vent in the Bocca Nuova, which had shown little activity in the past week. Later that day weather conditions deteriorated, and visual observations were rendered impossible. However, it was stated this morning that the activity was at low levels throughout the day (communication from Marco Fulle, Osservatorio Astronomico di Trieste, who presently stays at the Rifugio Sapienza and received this information from forest guard personnel). This morning at 0300 h, intense eruptive activity reportedly resumed, with renewed lava overflow from the Bocca Nuova onto the W flank. As of the early afternoon of 21 October, bad weather is preventing visual observations.

20 October 1999 update. During the past ten days or so, vigorous episodic activity within the Bocca Nuova gradually filled the crater (its depth was about 30 m below the lowest point of the crater rim, on the W side, when observed on 1 October), and on the late evening of 17 October, a section of the W crater rim about 25 m wide collapsed, and lava rapidly spilled through the newly formed breach onto the W flank of the main summit cone, covered the dirt road which connects the northern and southern ascent routes over a width of several tens of meters, and then flowed down the W flank of Etna in at least four main branches. By the early morning of 18 October, the farthest flow front was at about 2000 m elevation, in an area located roughly between Monte Nunziata and Monte Palestra, just above the tree line, and only a few hundred meters from the Forest Guard road (Forestale road).
At the time of the overflow, spectacular lava fountaining occurred from two main vents located in the W and NW part of the crater. This activity apparently diminished during the late forenoon of 18 October, but resumed during the following night. Lava was reported to flow vigorously through the newly formed breach on the W side of the Bocca Nuova on the evening of 18 October (oral information from the mountain guides at Piano Provenzana on the N flank of Etna).
At about noon on 19 October, Boris Behncke (Dipartimento di Scienze Geologiche, University of Catania) and Giuseppe Scarpinati (Italian correspondent of the French Association Volcanologique Européenne) reached the western side of the summit area, coming from Piano Provenzana with some of the mountain guides. At the time of their arrival near-continuous explosive activity ejected large bombs high above the rim of the Bocca Nuova (many bombs fell far beyond the crater rim), but movement of the lava flow had slowed significantly, and only the central portion of the flow moved at a speed of no more than 10 cm per minute. The flow overflowed from the crater through a deep channel; below this the lava field emplaced since late 17 October widened, with many overlapping and adjacent flow units which had a total width of about 100 m at the interrupted summit dirt road. Between 1200 and 1230 h (local time=GMT+2) the activity of the Bocca Nuova increased significantly, until fountaining from the more southerly of the two vents became virtually continuous, and frequent large blasts occurred from the other vent, dropping bombs up to 150 m beyond the crater rim.
A short time later, the rate of lava overflowing into the channel below the Bocca Nuova rim increased dramatically, and a new flow with a front about 3 m high advanced rapidly through the central flow channel, on top of the still-moving, earlier lava. At the elevation of the interrupted dirt road the flow front was seen to advance about 100 m in 5 minutes; below this elevation the flow split into several branches and slowed, but when arriving at the steep W slope of Etna, movement of the flow fronts became much faster again. Among the notable features of this newly advancing lava was the little sound it made, probably due to its high fluidity.
Behncke and Scarpinati observed the activity until about 1500 h; during this period lava fountaining continued with some fluctuations, and several particularly powerful explosions from the more northerly vent sent bombs to as far as the central part of the adjacent Voragine. From certain points along the N margin of the new lava field the summit of a sizeable pyroclastic cone growing within the Bocca Nuova could be seen rising high above the crater rim. Occasionally large glowing blocks of lava appeared on the crater rim to the S of the overflow channel and tumbled down the SW side of the main summit cone. It is probable that the level of lava filling the crater was almost as high as the rim on this side, and the continuous addition of lava caused its margins to extend over the lower parts of the crater rim, although no true overflow occurred besides the one on the W side.
After returning to Piano Provenzana in the mid-afternoon, Behncke and Scarpinati drove towards Bronte on the lower W flank of Etna; while driving towards this town it was noted that explosive activity at the Bocca Nuova had apparently diminished, and only a few ash-rich emissions occurred between 1630 and 1730 h. Flowing lava was distinctly visible on the W flank, the fronts of the new lava flows initiated at about 1230 h had extended about half way down the steep W flank of Etna and were at about 2400-2500 m elevation; the flows emplaced during the previous day were stagnating. Behncke and Scarpinati climbed the cone of Monte Ruvolo, an old flank crater on the W flank of Etna, about 7 km from the summit, from where they had a spectacular view of the scene of the current activity. After sunset (about 1830 h), the active flows were brightly incandescent over all of their length, and the activity of the Bocca Nuova increased again, producing awesome bursts of huge incandescent bombs every 2-10 seconds. Bombs were sprayed over most of the summit area, arriving even at the summit of the Northeast Crater. As before, two vents were erupting within the Bocca Nuova. As time passed, the lava fronts on the W slope of Etna slowed, but two new branches of lava began to descend from below the Bocca Nuova, one following in the central part of the new lava flow-field, the other much further to the south, and by 2030, these branches began to spill down the steep W flank. Near continous powerful bursts of huge bombs continued by 2100 when Behncke and Scarpinati drove back to Catania.
This new phase of activity is very similar to a phase of the 1964 eruption when lava overflowed from the Central Crater (now replaced by the two craters Voragine and Bocca Nuova) onto the W flank of Etna, following essentially the same path as the new lava, and later lava broke through the SSW crater rim and spilled down the flank of the main summit cone, forming a 4 km-long flow on the SSW flank which narrowly missed the building of the former Etna Observatory (this was eventually destroyed by an eruption in 1971). The activity in the past ten days or so is clearly episodic, and the overflow of lava from the Bocca Nuova is not continous, but rather consists of surges which last several hours, emplacing numerous flow units on top and aside each other. For this reason it is unlikely that any lava on the W flank will proceed much further than the farthest flow fronts of 17/18 October, and the only risk is that the lava will destroy some forest, bury a portion of the Forestale road and endanger a mountain hut near Monte Palestra.
On the other hand, it is extremely dangerous to get close to the summit area, especially during phases of violent Strombolian activity as observed during the evening of 19 October. This activity is launching thousands of meter-sized bombs to places such as the Northeast and Southeast Craters, and any person who desires to see the ongoing activity should consult the local mountain guides at the Rifugio Sapienza (or the cable car station) on the S flank of Etna or those at Piano Provenzana on the N flank. The former can be reached by car from Nicolosi while the latter is best reached from Linguaglossa (driving uphill on the "Mareneve" road). A spectacular view of the eruption and the lava flowing down the W flank can be obtained from Bronte - there is a small country road leading from this town about 5 km further upslope to a gate at the margin of the inner zone of the Etna Natural Park, where in these days numerous spectators assemble to witness the unique natural display. Lava flows on that side of the mountain were last seen in 1964 and during a small flank eruption in 1974. If the eruption follows the same pattern as the 1964 activity, then the activity may last for weeks to months, with further overflows of lava from the summit craters.

To learn more about the 1964 eruption, visit this page.

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Page set up on 27 May 1997, last modified on 21 October 1999

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