Italy's Volcanoes: The Cradle of Volcanology

Etna Decade Volcano, Italy
Eruption update:
25-28 July 1999

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Etna, 24 July 1999

The incredible view of snow on Etna on the evening of 24 July. The building visible in the image is the Torre del Filosofo mountain hut (at about 2900 m elevation). A brilliant rainbow is visible at left; the bay of Catania can be seen in the background.

WARNING: Access to the summit craters is again becoming INCREASINGLY DANGEROUS. Explosive activity has resumed within the Voragine and the Bocca Nuova, and bombs are ejected beyond the crater rim. Magmatic activity is also occurring deep within the active pit of the Northeast Crater which in the past has been the site of violent eruptive episodes. Besides this, weather conditions are often unstable, even during the summer (as experienced just on 24 July 1999). Any person who enters the area beyond the Torre del Filosofo mountain hut (2900 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. The same is true for those who try to get close to the still-active effusive vents on the Valle del Bove slope.

Update on the activity on 28 July 1999. Etna's summit craters were visited today by Boris Behncke, Carmelo Monaco and Angelita Rigano (Dipartimento di Scienze Geologiche, University of Catania) and others. Deep within the central pit of the NE Crater there were near continuous detonations, quite a different sound from the continuous, surf-like sound heard in the same pit early this month. However, no ejecta were thrown to the height of the rim of the pit, but a dense plume heavily charged with sulfur dioxide was emitted, making observations of the pit's interior impossible and rendering the stay on the crater rim highly unpleasant. Within Bocca Nuova, explosive activity occurred deep within the two main vents in the northwestern and southeastern parts of the crater. While no pyroclastics were seen to rise above the rim of the northwestern vent, the southeastern vent produced near continuous emissions of brownish ash which became more forceful when loud roaring explosions occurred at depth. The most impressive activity occurred at the Voragine whose central vent produced powerful explosions and at times prolonged fountains of incandescent bombs, some of them up to one meter across. Some of the explosions were quite violent, ejecting bombs to about 100 m above the crater rim. No ejecta fell outside the crater, and only a few fresh bombs, probably ejected a few days ago, were found on the western crater rim, about 150 m from the active vent. Within the crater, however, bombs had fallen abundantly, especially in the northern part of the crater floor, so that any approach to the vents across the crater floor is absolutely impossible. Many eruptions were accompanied by acute roaring noises indicating high-pressure gas emission from the top of the magma column in the vent, which has risen by tens of meters since last observed directly on 6 July. There was apparently no eruptive activity within the "diaframma vent". No direct observations were made at the SE Cone which is believed to be inactive for the moment.

28 July 1999 photos

28 July 1999 28 July 1999
Left: Small Strombolian explosion in the central vent of the Voragine, photographed from the western rim of the crater.
Right: Ash emission from the southeastern vent of the Bocca Nuova, seen from the northwestern rim of the crater.

At the 4 February fissure, lava emission continues at low rate. One area of effusive activity lies on the northeastern side of a large tumulus that has grown about 100 m downslope from the upper hornito cluster since late June. One narrow (about 0.5-0.8 m) flow issued from a small effusive vent and flowed through a channel with unusually high walls (up to 1 m above the flow surface) while a much larger flow broke through the southern base of the channel wall, feeding a flow 1.5 m wide that extended eastwards.
The observations made today confirm once more that the activity in the summit craters (NE Crater, Voragine and Bocca Nuova) is gradually but steadily increasing while there are no significant changes to the effusive activity at the 4 February fissure. Eruptive activity is definitely taking place in three of the four summit craters, and it is close to the surface in the Voragine. This crater might thus be the one to produce more spectacular activity in the near future, but (unconfirmed) reports about pyroclastic ejections from NE Crater about one week ago may indicate that this crater shows the highest levels of activity since about one year.

Observations on 24 July 1999. Boris Behncke (Dipartimento di Scienze Geologiche of Catania University) and Giuseppe Scarpinati (L'Association Volcanologique Européenne, Paris) made an attempt to reach the summit craters on the afternoon of 24 July. The visit was severely hampered by adverse weather conditions, and no direct observations of the activity in the craters could be made. When arriving at the Torre del Filosofo mountain hut (which stands about 1 km south of the SE Cone) with a group of about 15 tourists, hail began to fall, followed by severe storms and a true blizzard (this is possible even in July!) accompanied by lightning flashes, so that everybody had to take refuge in the small wooden shack of the mountain guides next to the Torre del Filosofo building. While the tourists were later brought back with the tourist jeeps, Behncke and Scarpinati and a group of the French organization "Aventure et Volcans" stayed at Torre del Filosofo, watching the rare spectacle of a snow fall in July rather than any volcanic activity (a few glimpses of small lava flows on the active flow-field only 500 m away could be obtained anyway). At sunset, the whole landscape of Etna's upper 1000 m was bathed in an eerie gloom, with a strikingly luminous rainbow, Etna's shadow cast onto a dark wall of thunderstorm clouds, near-continuous snow falls, and lightning strokes.

24 July 1999 photos

24 July 1999 24 July 1999
Left: View from the Torre del Filosofo mountain hut (of which a part is visible at left) towards the snow-covered summit cones (the SE Cone is visible at right).
Right: Looking south from Torre del Filosofo towards the Montagnola (the cone visible at the skyline), with a spectacular double rainbow under a heavy cover of ominous dark thunderstorm clouds. Snow covers the relatively flat area in the middle ground (called "Piano del Lago") where lava flows of the 1971 and 1989 show a darker color due to their rough surface. The photo was taken shortly before sunset when the sun was so close to the horizon that its rays passed below the clouds.

Behncke and Scarpinati decided to leave Torre del Filosofo and to return to Acireale, near Catania, when the weather conditions temporarily improved. On their return to the Catania area later that evening, they noted a vivid glow over the summit as the cloud cover had lifted for a brief period, indicating the presence of active lava within either the Bocca Nuova or the Voragine, or both. This is the first time since early February that such a crater glow has been observed, and yet another confirmation that summit activity is increasing, although it is not yet at the levels of last summer.

Update on the activity between 13 and 24 July 1999. There is more evidence that Etna's summit craters are progressively increasing their activity, although this increase is not linear. Lava continues to flow from the 4 February fissure at the southeastern base of the SE Cone, but the amount of lava is relatively small, and short-lived lava flows extend only a few hundred meters downslope (to the east and southeast) before stopping.
The following information is from Charles Rivière
(of Tremblay-en-France, France) who has visited the summit craters repeatedly since early July, and Claude Grandpey (L'Association Volcanologique Européenne, Paris) who visited the summit area on 15 and 16 July. Grandpey reports that on the afternoon of 15 July, at the 4 February fissure, "one lava flow was very active. It was rather narrow (about 30 cm wide) and flowing rather fast. It was coming out of a vent where the lava was fluid with movements up and down so that one got the impression [it] was breathing. Now and then, a bubble appeared that broke open, sending bits of lava around the vent. After 10 meters or so, the lava flow got wider (2-3 m wide) and went further down the slope. In the evening and at night, nothing changed. The darkness [made it possible] to see two more flows some 50 meters downslope, but these were very slow . In the very early morning of Friday 16th, the first-mentioned flow had almost stopped and no other flow was visible. Then, at 12 o'clock or so, 2 new flows had reappeared in the same area."
Grandpey visited the summit craters on 16 July and noted clouds of brownish ash coming out of the NE Crater "with the usual characteristic noise of degassing inside the crater". The two vents in the Voragine were quiet, but Grandpey learned that the "diaframma vent" was active earlier during the week (that is, around 12 or 13 July) with explosions, while lava was visible at the bottom. The northwestern vent inside the Bocca Nuova was quiet, and parts of it had collapsed inside the vent since Grandpey's visit the week before. Strong explosions (with occasional projections of bombs as high as the crater rim (but not out of it) could be heard with a good frequency (every few minutes) in the southeastern eruptive center and this phenomenon had been audible all through the night. Nothing particular was noted at the SE Cone.
Activity was particularly intense in the Voragine on 18 July when Charles Rivière approached and filmed the "diaframma vent" from close-up. Lava had again risen to about 20 m below the rim, and a small, dome-shaped mound of lava produced numerous small explosions. The mound was partly incandescent and was blown to pieces in some of the larger explosions, then rapidly rose again. No information was available about the activity of the central vent in the Voragine. During the days preceding 24 July, however, Rivière observed a diminuition of activity in the Voragine, but there was explosive activity within Bocca Nuova.



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