Updates February 1998

Telecamera images of 14-30 January 1998 Upper left shows waning explosive activity and no lava emission at SE Crater on 14 January; top and bottom right frames are zooms on SE Crater on 16 January and bottom left image shows recent and active lava flows on SE Crater on 17 January. Diminishing explosive and absent effusive activity at SE Crater and strong ash emissions from Bocca Nuova caused by internal collapse characterize the activity of Etna's summit craters on 19 January. Note cloud bank over the summit in bottom frames; bottom left frame shows small explosion from SE Crater. Two particular telecamera shots, taken on 22 January (left) after fresh snowfall and on the 27th (right) when steam was apparently issuing from an area near an explosion crater formed during the 1983 eruption. This phenomenon remains unexplained but evidently was no indication of a flank eruption. 28 January: Top frames were taken during the forenoon and show SE Crater with its intracrater cone and fresh lava flows and voluminous steam and ash emissions from Bocca Nuova; bottom frames were taken after nightfall and show intense explosive activity and small lava flows at SE Crater and occasional incandescence at Bocca Nuova. 29 January: Daylight views at top show mildly steaming summit craters, bottom frames taken at dark show very vigorous activity in Bocca Nuova and explosive-effusive activity from SE Crater. Two evening shots on 30 January of SE Crater in vigorous eruption and Bocca Nuova showing fluctuating incandescence.

Telecamera images of 4 February 1998 Top left is a general view of the summit craters, showing recent lava flows on the flanks of SE Crater; top right is a zoom on part of the summit cone and part of SE Crater; bottom left shows SE Crater at sunset, bottom right is a particular of the same situation. Top frames show SE Crater at dusk, with an active lava flow on the southeastern flank. Bottom left is a zoom on Bocca Nuova showing strong incandescence, bottom right shows Bocca Nuova with intense glow and lava emission from SE Crater.

27 February 1998

Bocca Nuova and SE Crater continue to erupt in a quite normal manner. The situation at Etna is reasonably stable. Weather conditions are variable but forecasts for the weekend are good.

26 February 1998

The ash emissions from Bocca Nuova two days ago were followed, that same evening, by vigorous magmatic activity, probably from the southeastern vents, that caused a bright fluctuating glow until daylight yesterday; glow was also visible at the same site last night, although its intensity was less than during the preceding night. SE Crater produced somewhat more vigorous (compared to the previous night) Strombolian activity last night, its southwestern lava flow is continuing and a very minor lava lobe spilled over the southeastern crater rim for a few hours.
An unpleasant piece of news is that again a tourist has lost orientation in Etna's summit area during deteriorating weather conditions. Fortunately he was saved after a night in the cold and after having walked around without orientation in Valle del Bove. This is the most recent of many such incidents during this winter. So whoever decides to visit Etna in these days, don't go up to the craters alone, hire a mountain guide or contact one of us volcanologists in Catania, and especially, don't go when the weather forecasts are other than EXCELLENT. To present some more information about this topic, I will soon add a page to the FAQ section, entitled "Is it safe to climb to the summit?"

24 February 1998

Virtually continuous ash emissions began during the late forenoon at Bocca Nuova, a phenomenon that may have been caused either by internal collapse in that crater (possibly related to subsidence of the magmatic column) or more ash-rich explosions from the southeastern vents. At SE Crater, lava continued to flow down on the southwestern flank at least until daybreak; clouds are preventing visual observations of the summit since early this afternoon.

23 February 1998

The summit eruption continues without significant changes. The lava flow on the southwestern flank of SE Crater is continuing. No details are so far known about its extension, but it appears that is flowing on the northwestern side of the flow emplaced during January in the same area.

22 February 1998

There is continuing eruptive activity at Bocca Nuova and SE Crater, the most striking feature being the long-lived lava flow onto the southwestern flank of the latter. This flow, similar to another one in January, does not stop flowing after about one day but continues for several days, thus allowing a longer extension, beyond the base of the steep SE Crater cone. Explosive activity at the intracrater cone is relatively weak as compared to the activity of about ten days ago.

20 February 1998

Bocca Nuova and SE Crater are in continuous eruption, although the activity appears to be less vigorous than last week. Lava is overflowing onto the southwestern flank of SE Crater, possibly following the track of a flow emplaced during the first half of January. Activity in Bocca Nuova is characterized by low-level bomb ejections with occasional larger jets of bombs. If the local weather continues to be as good as in the past ten days, I will make another summit visit on this weekend.

18 February 1998

The third visit to Etna's summit craters (better say, two of them) within eight days was made yesterday. At SE Crater, Strombolian activity from the intracrater cone was intermittent, and phases of noisy degassing alternated with vigorous bomb ejections while a lava flow slowly moved down the south-southeastern flank of the SE Crater cone until reaching the base. New vigorous lava flows issued from the effusive vent at the southeastern flank of the intracrater cone, covering about one-fourth of the crater floor, and a new lava lobe began spilling down the outer flank of SE Crater adjacent to the still-active south-southeastern flow at about 1830. Bocca Nuova was erupting from its northern and southwestern eruptive centers, although less vigorously than on 11 February. One vent was erupting in the southern part of the collapse crater on the summit of the southeastern eruptive center, ejecting continuous lava fountains and occasional large jets to above the crater rim, but no bombs fell outside the crater. The vent had a diameter of 30-35 m and the level of the degassing magma stood at least 10 m below its rim, below the limit of visibility. The northern eruptive center had a small new eruptive vent in the central part of the collapsed cone, which was the site of continuous very narrow incandescent fountains, and a small lava flow issued from near this vent towards the deepest part of the collapse structure. Occasional violent explosions occurred from the vent on the southern rim of the collapse structure which had been the most active vent in this area one week earlier, these explosions ejected bombs and ash high above the rim of Bocca Nuova, and bombs fell outside the crater on its western side.
These observations confirm that the situation at Etna is presently stable, and there are no indications of an immediately impending flank eruption although civil protection services and authorities are maintaining the state of alert declared one month ago after the intense seismic activity on the upper western flank. In the long term, a flank eruption will inevitably occur on Etna but there are at present no means to determine exactly where and when it will take place.

15 February 1998

The summit eruption in Bocca Nuova and SE Crater is continuing without significant modifications; lava flows are moving down the southwestern and southeastern flanks of SE Crater, and there are vigorous bomb ejections from the two active areas in Bocca Nuova, many of which are dropping bombs on the outer slopes of the main summit cone. Further growth appears to have taken place on the summit of SE Crater's central cone. New summit visits are planned for the forthcoming days as weather in the Etna area is unusually stable.

14 February 1998

During the past few days, vigorous activity has continued at Bocca Nuova and SE Crater, being at the highest levels since early January; this activity triggered heightened interest among people observing the telecamera, but it is fully normal in the framework of the current eruption.
The following summarizes the observations made during two summit visits on 10 and 11 February.
The 10 February summit visit. During this visit, all craters except NE Crater were visited. The Voragine was found inactive. Since the previous visit on 8 January, only little eruptive activity appears to have taken place at the cone in the center of the crater floor which was found only mildly steaming. The only significant change was the regrowth of a crater rim on its southeastern side , healing the breach formed by the most recent lava outflow from this cone, probably in late December 1997. The vent at the base of the southwestern crater wall did not produce any emissions.
On 10 February, the cone at SE Crater was the site of continuous powerful Strombolian explosions that frequently dropped bombs and scoriae beyond the crater rims. Although one single crater was present at the cone's summit, it evidently had two erupting vents, thus maintaining the configuration already established in early January. As during the 8 January visit, activity alternated between the two vents, only one erupting at any given time. The southern vent produced fountains inclined towards south, showering the whole southern sector of SE Crater with bombs. When this vent resumed erupting after a period of activity from the other one, adjacent to the north, it frequently ejected jets of bombs mixed with ash. The northern vent sent vertical fountains of bombs up to 200 m high, and bombs fell abundantly on the western and northern sides of the cone and even far beyond the old crater rims of SE Crater in those directions. Some bombs that fell on the western crater rim were up to 30 cm long. Smaller projectiles even fell at the lower slope of the main cone, some 50 m from the rim of SE Crater and 100 m from the erupting vent. Growth of the intracrater cone appears to have occurred mostly in its outhern aummit area where a "shoulder" had developed over a vent that had already ceased erupting when seen on 8 January. The northeastern flank had almost merged with the outer flwnk of SE Crater on that sinde, largely obliterating the gap in the former crater rim.
Lava emissions occurred from a vent on the southeastern side of the intracrater cone, in the same general area where it had occurred on 8 January. A lava flow with well-developed lateral levees moved northwards around the base of the cone to turn eastward when reaching the remainder of the northeastern crater rim, now almost submerged below the adjacent crater-filling lava field. A rapidly moving lava tongue spilled over the crater rim on its east-northeastern side, feeding several narrow lava flow lobes, one of which had arrived at the base of the SE Crater cone. Other recent lava tongues were seen to have extended only little beyond the base of the cone; the longest flow towards east-southeast (produced in mid-December 1997) had advanced to within about 50 m of the western rim of Valle del Bove. No flow erupted from SE Crater in the current eruptive period has arrived at the rim of Valle del Bove or spilled into it.
The only significant remainder of SE Crater's former rim is on the western and northwestern side ("Fortino" area) where it stands some 15 m above the lava field surrounding the central cone. In all other areas the crater is completely filled and has overflowed in many places. The appearance of the crater's interior is that of a low lava shield topped by the intracrater cone that rises some 30-40 m over the lava field.
The overall appearance of Bocca Nuova on 10 February was surprisingly similar to that observed 33 days earlier, before the episodes of internal collapse that accompanied the seismic crises on the western flank of Etna. The collapse had affected only the summit areas of the two large complex cones in the northern and southeastern parts of Bocca Nuova, and the whole northern cone had subsided by several meters along concentric fractures. Activity had resumed at both cones and resembled that observed in early-late August 1997. The southeastern vents produced frequent explosions, accompanied by cannon-shot like detonations, but occasionally there were longer-lasting eruptions. Jets of bombs, at times mixed with ash, rose tens of meters above the vents, occasional explosions ejected bombs high above the crater rim, but few fresh ejecta were found to have fallen outside the crater near these vents.
Eruptive activity from the northern cone had resumed at a new vent which lay on the southern rim of the partly collapsed cone, very close to the center of Bocca Nuova. A vent in the deepest part of the ca. 150 m wide crater of the cone was vigorously degassing but not erupting. A third vent lay between the former two and very rarely produced spectacular emissions of ash. The main eruptive vent (on the south rim of the cone) was in constant eruption, with powerful bomb ejections occurring about every 2 seconds. Many ejections rose higher than the western rim of Bocca Nuova, which now stands at least 70-80 m above the vent. Every 5-10 minutes, this vent would produce much larger eruptions, ejecting continuous fountains mixed with ash for some 10-15 seconds to considerable height above the Bocca Nuova rim. Such eruptions caused the fall of ash and lapilli on the western and southern crater rims. On several occasions, the activity of the vent stopped completely for some 2-3 minutes, followed by brief but extremely violent explosions that sprayed large bombs and blobs of lava all over the crater floor and high into the air, many of these projectiles falling outside Bocca Nuova. Observers on the crater rim were shaken by strong pressure waves. After such explosions, ejection of bombs would resume in a "normal" manner.
Some collapse had occurred at the remainder of the 1964 cone, above the southeastern vents, and its still-standing vertical face was highly fractured and vigorously steaming. No significant changes were observed at the "diaframma", the septum between Bocca Nuova and Voragine.
The 11 February summit visit. Activity in Bocca Nuova had increased notably on this day and no views of its interior could be obtained due to the frequent ejections of sizeable bombs beyond the crater rims. It was evident that activity was continuous at both cones, the southeastern one being the more more violent. During the afternoon, there were periods of near-continuous ash emissions from this latter area; these emissions were accompanied by powerful explosions and thus were not related to internal collapse. At night, both eruptive areas produced intense continuous glow that was probably caused by persistent low fountaining or bursts that followed each other in rapid succession. Occasional larger explosions (at time twice per minute) ejected bombs up to 150 m above the southeastern rim of Bocca Nuova, many of which fell on the outer southern slopes of the main summit cone.
At SE Crater, growth had taken place on the northwestern side of the intracrater cone, raising its summit by at least one meter since the day before. Two vents were active in its summit crater, and for the first time these were seen to erupt simultaneously on a few occasions. The vigor of the activity was initially similar to that of the day before but increased notably after 1930 h local time, when jets of bombs frequently rose much higher than Etna's summit (the top of what remains of the 1964 cone), maybe up to 250 m above the vent. These vertical jets were very narrow, and few bombs fell on the western rim of SE Crater. Lava issued from the effusive vent on the southeastern base of the intracrater cone, feeding a sluggish flow on the east-southeastern flank of SE Crater; a new vigorous flow lobe rapidly covered the southeastern sector of the crater floor and began to spill down the upper outher flank of SE Crater at about 1900 h. By 2000 h, it had already extended some 50-100 m downslope.
Activity continued at similar levels during the next three days, and is vigorous at the time of writing (2130 h local time).

9 February 1998

SE Crater is continuing in explosive activity while small lava flows are moving down its southeastern flank; magma is again withdrawing from Bocca Nuova (as indicated by internal collapse) and possibly draining into a fracture under Etna's western flank. Mild seismic activity was occurring again in the Monte Palestra area (western flank at around 2000 m) on the weekend, in the same area that has been affected repeatedly by seismic activity since late December. The sinking of the magmatic column in Bocca Nuova and the seismic activity are possible indicators of an impending flank eruption, but the timing, location and character of such an event cannot be predicted at this moment, and it is by no means sure that it will occur in the near future.
Today, collapse in Bocca Nuova ended and was followed by a rapid and vigorous rise of the magmatic column. Telecamera images during the day showed only white gas plumes issuing from the crater. There were some meltwater flows recognizable on the southwestern flank on the main cone which probably were generated as the strong northeasterly wind drove the hot gas plume down over that side of the cone. At nightfall, bright incandescence is visible at Bocca Nuova while activity at SE Crater is continuing as before.

8 February 1998

Etna's summit activity is continuing without significant changes; there are at times emissions of dark ash from Bocca Nuova indicating collapse of the crater walls.

6 February 1998

Seismic and eruptive activity at Etna are at stable levels. Explosive and effusive activity from SE Crater continued through at least Wednesday night (4 February) and is assumed to go on as of today. Intense glow was visible at Bocca Nuova on Wednesday evening, indicating vigorous intracrater activity from the two eruptive areas that have been intermittently active during the past months.

4 February 1998

Clear weather allows perfect views of Etna's summit today, revealing fresh lava flows on the southern and east-southeastern flanks of SE Crater. The activity from the summit craters is assumed to continue in unchanged manner; no significant seismicity has been reported since last Sunday.

3 February 1998

Weather conditions prevent visual observations of Etna today, but it is assumed that the activity of the summit craters is continuing without significant changes. A light earthquake was felt last night at Catania; its relationship with the eruptive activity is not clear.

2 February 1998

The eruptive activity of Etna's summit craters continued over the past weekend without significant variations. After about two weeks of relative seismic quiet, earthquakes occurred again below the Monte Palestra area (on the western flank) on Saturday (31 January) and below the summit craters yesterday. In statements by scientists from the Istituto Internazionale di Vulcanologia this seismicity was described as a normal phenomenon in the context of the current activity of the volcano.