Etna Decade Volcano, Sicily, Italy
Lava flows spilling down the western side of Valle del Bove, seen from "Belvedere" on the evening of 3 March 1999
Updates 1-10 March 1999
The most recent updates
Etna news archive
6 March 1999
The effusive activity that began on 4 February 1999 from a fissure on the southeastern
base of the SE Cone is continuing, and lava continues to flow into the Valle
del Bove, forming a flow field composed of numerous sub-parallel and overlapping
lobes. The activity was particularly well visible from Catania and other locations
to the east of Etna yesterday evening, the flow field being incandescent over
all its length from the western rim of Valle del Bove down to about 2000 m elevation.
Today, the local newspaper "La Sicilia" has an article with spectacular
photos which were taken by photographer Fabrizio Villa, on the same day I took
the photos presented on this page (above and at right).
On 3 March, the activity was observed by Giovanni Sturiale and Boris Behncke (Istituto di Geologia e Geofisica of the Università di Catania - IGGUC) and Christophe Baudin, a visitor from Belgium. Two of them (Behncke and Baudin) climbed to the summit of the SE Cone and made a survey of its northern flank where effusive activity occurred during the 4 February eruptive episode.
The Southeast Cone. Behncke and Baudin walked around the eastern side of the cone to the lava field emplaced between December 1998 and 4 February 1999 and then climbed towards the notch in the northern rim of the SE crater. During the latest erruptive episodes, lava had flowed through this notch and then turned northeast at the base of the cone. There was no evidence that any of this lava had been produced by any vent other than the SE Cone's summit crater, and the most recent lava, of 4 February, was covered with a thin layer of reddish ash and showed no heat emission from its surface.
The floor of the notch which was inclined upwards towards the crater was a flat channel about 3-5 m wide and covered with rubble, while the width of the notch at its rim was 15-20 m. Dense gas and vapor prevented a close approach to the crater, forcing the visitors to climb the western side of the notch towards the northwestern crater rim. Only a few very brief glimpses were caught of the interior of the crater, but it was evident that at several tens of meters depth there was an inner terrace surrounding a narrow central pit. The width of the crater at its rim was at most 50 m, maybe less. Gas and vapor escaped from several fumarolic areas on the southwestern and eastern crater rims. On the southeastern side of the crater there was a fuming pit about 15-20 m wide (Photo 2 below), possibly formed by collapse during the 4 February eruptive episode when the southeastern side of the cone fractured. Below this pit, on the outer flank of the cone, there was a vigorously steaming fissure segment extending about 100 m downslope, ans below this there was the oval-shaped main vent of the 4 February episode which produced no gas emissions. An irregular crack 0.5-1 m wide extended from the lower end of this vent towards the still-active eruptive fissure, neither was there any gas emission from this crack.
The view from the southern rim of the SE Cone permitted a commanding panoramic view of the active fissure and its lava flows, and besides this created an awesome sensation to a person (Behncke) who had been approximately in the same (geographic) spot tens of times in the past two years - when this spot was still tens of meters lower and much more accessible.
During the visit no sign of eruptive activity at the SE Cone was observed, nor was there any evidence that such activity had occurred recently. There were no fresh ejecta on the crater rim and within the notch on the northern side, and no noises were heard from within the crater.
March 1999 photos
|Photo 1. Panoramic view of the SE Cone with the fracture of the 4 February eruptive episode, and the hornitos at the currently active eruptive fissure (indicated by a red arrow). The main vent of the 4 February episode lies below the steaming upper part of the fissure. View is from near the tourist lookout, about 500 m south of the summit of the SE Cone.||Photo 2. Zoom on the summit area of the SE Cone from south, showing steaming upper part of the 4 February fissure and collapse pit on the crater rim.||Photo 3. Recently formed hornito lying about 70-80 m below the main hornito cluster. Information from various visitors during the preceding days indicate that it began to grow on 28 February and may have ceased erupting on 2 March. The height of the feature is about 2.5 m. Note the fresh lava extending from the base of the hornito.|
|Photo 4. View upslope along the upper part of the active fissure from a point about 100 m below the main hornito cluster (which can be recognized as a couple of yellow spires at the base of the SE Cone in the background). The youngest hornito to form is visible in the foreground, right behind the person who gives a scale.||Photo 5. Main lava river extending downslope, with SE Cone in the background, seen from a spot about 200 m from the main hornito cluster.||Photo 6. One of the uppermost "skylights" of the main lava river.|
|Photo 7. Detail of a "skylight" wall with flowing lava at the bottom. Note that there is no crust on the flowing lava, indicating that the flow is not loosing heat.||Photo 8. Spectacular "skylight" lying slightly below those shown in the previous photos, with the legs of Giovanni Sturiale giving scale. View is downslope.||Photo 9. View from the "Belvedere" (ma che belvedere davvero!), a panoramic view point on the rim of Valle del Bove about 1 km south of the point where lava spills into the Valle. Note that the lava, which is flowing at the surface in the upper part, disappears in a tube and then reappears through numerous ephemeral vents on the western slope of the Valle. The ridge visible in the central background is Pizzi Deneri, the highest point on the northern rim of the Valle.|
|Photo 10. Detail of the lava flows issuing from ephemeral vents on the western slope of Valle del Bove.||Photo 11. Hornitos in the upper part of the eruptive fissure, with Boris Behncke giving scale. Photo by Giovanni Sturiale.||Photo 12. Boris Behncke posing in front of a small overflow from the main lava channel, some 150 m above the Valle del Bove rim. Photo by Giovanni Sturiale.|
The active fissure and the lava flows. Eruptive activity from the short
fissure that opened at a late stage of the 4 February eruptive episode consists
of very weak, and intermittent, ejections of pyroclastics to only few meters
from the vents, and quiet outflow of degassed lava. The explosive activity has
built a cluster of about 10 hornitos at the upper end of the fissure, most of
which were covered all over with sulfur (see photos 1 and 4 above). Relatively
regular observations over the period 27 February-3 March (information from Giuseppe
Scarpinati, Carmelo Monaco and Christophe Baudin) indicate that activity at
the hornitos occurred irregularly. There was relatively vigorous spattering
at one of the main hornitos on 27 February, a new hornito began to grow on the
following day some 70-80 m downslope from the main hornito group (see photo
3), and on 2 March a short-lived lava extrusion occurred from a crack cutting
across the base of one of the uppermost hornitos. On these occasions the hornitos
were the site of high-pressure gas emissions that produced a loud hissing noise.
During our 3 March visit, all hornitos were unusually quiet. High-pressure gas emission occurred from a few locations some 50-80 m downslope. No flowing lava was visible in this area, but a row of "skylights" (that is, holes in the roof of a lava tube) lay between 100 and 150 m downslope from the hornitos, marking the course of the main lava river which had roofed over in its upper part (photos 6-8). It was not until another 100 m or so downslope that the lava appeared at the surface to continue its course in a well-defined flow channel (photo 5). Several other lava flows were slowly moving across the surface of the lava field, but the overall impression was that much less lava was active at the surface than during previous visits by Behncke (see the February 1999 updates). At the rim of the Valle del Bove there was one main flow that spilled into this vast depression, forming a pronounced ridge where it disappeared in yet another lava tube. Lava resurfaced a few hundred meters further downslope through numerous ephemeral vents (photos 9 and 10), forming narrow flows that extended to the floor of the Valle. The farthest active lava was at about 2000 me elevation, above the Monti Centenari (a cluster of cinder cones formed in 1852-1853, of which only the summits protrude from lavas erupted in recent decades).
The multitude of active lava flows in the Valle del Bove indicates that there is actually more lava flowing through tubes than may seem from the lava visible in the upper part of the flow field. It is also probable that the effusion rate undergoes minor fluctuations. The mean output is still several cubic meters per second, and thus the volume of lava produced in one month of activity is between 5 and 10 million cubic meters. Although this is a very rough estimate, with an error of about 50 per cent, it indicates that this activity is more productive than other long-lived effusive eruptions in the summit area in the past, which had effusion rates of less than 1 cubic meter per second.
Outlook. The effusive activity initiated on 4 February has shown a remarkable regularity during its first month, and there are no signs that it is diminishing significantly. Based on the record of similar eruptions near the Northeast Crater in the mid-1970's, this activity may well continue for many months, or even years. As long as it continues, the probability of renewed vigorous activity from the SE Cone is low. However, this cone will probably return to life if the magma path to the eruptive fissure gets blocked. The more probable scenario is that the rate of lava emission from the fissure will slowly decrease and eventually stop as magma is draining away from the central conduit system. In that case a brief repose period may be followed by renewed vigorous activity from the SE Cone or vents nearby.
Little prediction or forecasting is possible in the case of the other summit craters. Although in recent months the SE Cone area appears to have acted as the main "safety valve" for the whole summit area, the summit craters are known to behave quite independently, and so their activity may not be too much influenced by the activity of the SE Cone in the future. For the moment all or most magma that rises to the surface within the central conduit system appears to erupt through the presently active fissure, there is remarkably little activity in the other craters, and the brief flurry of activity within the Bocca Nuova shortly before the events of 4 February indicates that magma pressure was increasing and was eventually discharged through the SE Cone and the new fissure. Whatever the outcome, even once the current effusive activity ends, further activity can be expected shortly afterwards in the summit area.
Public response. A final word about the attitude of local residents, tourists and the mass media. The ongoing activity generates much interest in the more educated part of the local population, especially of Catania, and many people express their wish to see the activity and the lava close-up although in the end only few of them really go there. The local newspapers and television stations have reports at irregular intervals, most of them very pragmatic and non-sensationalistic, and close to the real facts. This is not so with the mass media outside Sicily. Every few days, the Italian RAI television has services with spectacular footage of the activity which often are bought by foreign companies and transmitted all over the world. It is there that a vivid phantasy determines the style of reporting, and for this reason much false or exaggerated information about Etna's activity circles the globe. This is arousing interest both in tourists and other mass media, and my colleagues and I myself receive frequent questions regarding "the imminent great eruption of Etna" and "the effects of the current activity on tourism". Some people worry for their relatives living near Etna (this is especially the case for Amercian military personnel stationed at the Sigonella base south of Catania), others wonder if they need to cancel their vacations in Sicily, and one person even feared the possible effects of Etna's activity in Malta, hundreds of kilometers to the south!
While many individuals are planning to visit Etna in the near future, the expected stream of tourists to the volcano is still a trickle. During my three visits to the active fissure in the past four weeks, the visitors were mainly television teams and mountain guides.
2 March 1999
While effusive activity from the 4 February fissure continues since 26 days, this morning there are also renewed ash emissions from the southeastern vent in Bocca Nuova. Since there is no wind today in the summit area, a huge gas plume is rising majestically from the volcano. A group of geologists from Istituto di Geologia e Geofisica of Catania University is due to visit the summit of Etna tomorrow, and more information about the activity as well as a new map will be provided afterwards. See photo at right for an impression of the view of the volcano from Catania on the evening of 2 March.
Page set up on 15 March 1999