Updates May 1998
The most recent updates
Etna news archive
SE Crater, early 24 May 1998
Visit to SE Crater, 20 May 1998
View of the central conelet from southwest rim of SE Crater. Note the complex shape of the conelet: the feature at right is a ridge being pushed outwards from the conelet by extruding lava.
Central conelet seen from the south. Erupting vent is at the high point at left. Peak at right is the eastern part of the structure pushing outwards from conelet; extruding lava at the front of this structure is visible as a dark area at lower left flank of conelet, below the erupting vent which is marked by a steam column.
Approaching the central conelet from the south. Erupting vent (ejecting a fountain of bombs not well visible in this low-quality scan from a slide) is at peak at left while peak at right is eastern side of outward-pushing ridge with lava extruding at its front (dark feature at left).
View of central conelet and lava issuing from effusive vent on its eastern base. The flow is rapidly crusting over as it descends across older lava filling the eastern part of SE Crater towards its eastern flank.
Effusive vent seen from a platform of older lava below which the active lava is oozing to the surface. To the left tilted and uplifted slabs of older lava can be seen. View is towards east.
View of the effusive vent from south, flow is from left to right.
View of the effusive vent from north, flow is right to left.
Close-up view of the effusive vent from north, showing rapidly forming rugged crust on the surface of the flow.
Modifications of SE Crater
Comparative views of SE Crater seen from southeastern rim of the former Central Crater, on 11, 16 and 29 July, and on 6 April 1998. The first three frames show rapid growth of the intracrater cone and the first lava overflows (immediately behind the steaming vent of the conelet); the fourth frame shows the enormous amount of infilling that had occurred during eight months prior to 6 April. Lava has overflowed on all sides except the near (western) side where a portion of SE Crater's former rim still stands about 5 m above the intracrater lava field.
Comparative views of SE Crater's central conelet taken from approximately the same point on the SW crater rim on 25 July 1997, 6 April 1998 and 20 May 1998. From the day of the first frame to that of the second, the crater almost entirely filled with lava and the growing conelet; shortly before the second frame was taken, the summit area of the conelet collapsed and its height decreased by more than 10 m. On the third frame, taken only 44 days after the second, regrowth of the conelet is underway, and lava from inside the conelet is pushing the south flank outwards, adding to the complexity of the structure.
SE Crater erupting on the morning of 24 May 1998 (about 0530 h local time), seen from southern rim of Valle del Bove. Two lava flows are descending on the eastern (right) side of the cone and intense explosive activty is occurring from the central conelet. This is a rough scan from a slide, unfortunately the quality is not excitingly good (as in the images taken on 20 May, on the right).
SE Crater, early 24 May 1998
See the photos of the 28 May 1998 visit!
Giovanni Sturiale and Boris Behncke, both of the Istituto di Geologia e Geofisica of Catania University, visited SE Crater yesterday during bad weather conditions; during the brief clear moments the central conelet could be seen to be somewhat higher in the vent area than on 20 May, and more lava had slowly extruded from the southern front of the ridge that had been pushed out of the southern flank of the conelet. The main effusive vent was located at the eastern base of the conelet, and lava was issuing in one narrow stream south of the flow seen active the week before. The new flow spilled over the eastern rim of SE Crater (buried under at least 30 m of lava erupted since July 1997) and descended to the base of the SE Cone, extending no further than other recent lava lobes. All flows appear to arrive at the base of the cone and then stop, followed by the formation of new flows, except on the southwestern side of SE Crater where somewhat longer flows have been observed earlier this year.
Explosive activity was quite vigorous, explosions occurred every 1-2 seconds, dropping bombs exclusively on the northern side of the central conelet. It appears that the activity was close to equal to that observed eight days before, indicating quite a stable eruptive state during this period. The current activity is what is known as Etna's "persistent summit activity" which became famous from descriptions of NE Crater which in the 1950's to 1970's produced the same kind of activity now occurring at SE Crater. It is generally assumed that this activity represents exactly the rate at which magma is being supplied into the volcano from the mantle (estimated at slightly less than one cubic meter per second), unless a more voluminous batch of - possibly more gas-rich - magma rises towards the surface. The latter would be a process that could provoke a flank eruption, an event that has not occurred for more than 5 years on Etna.
25 May 1998
Eruptive activity at Etna's summit craters was observed during the early morning (between 0530 and 0700 local time) of 24 May from the southern rim of Valle del Bove. Vigorous explosive activity occurred from the central conelet of SE Crater, and two active flows were descending on the eastern and ENE slope of the SE Cone. Some explosions ejected incandescent bombs at least 200 m high, and much of the summit area of the SE Cone was covered with bombs; this activity therefore may have been more intense than that observed on 20 May (see preceding update). Loud detonations (not correlating with any explosion from SE Crater) indicated powerful explosive activity at the Voragine (the only other summit vent reported active recently). Detonations occurred in clusters separated by quiet intervals lasting 5-10 minutes. Some were accompanied by the rising of dense volumes of vapor and gas from the Voragine area. Some explosions were well audible on the southern flank of Etna, in the area around Rifugio Sapienza, and even more distinctly in the area of the 1791-92 vents, about 2 km south of the southern rim of Valle del Bove.
The 24 May excursion led to vents and lava flows on the southern flank of Etna (1536, 1766, 1780, 1791-92, 1892, 1910, 1983, 1985, and several prehistoric cones). Of the many photographs taken during this journey, some will appear soon on the Etna pages to form the nucleus of what is intended to become a "virtual Etna" with links to places of interest on the volcano. This will offer maps, photos and descriptions of eruptions and notable features of Etna.
21 May 1998
Vigorous explosive and continuous effusive activity as well as morphological changes were observed at SE Crater during a 3 hours visit with students from North Dakota State University. The active central conelet was observed at very close range, and the main effusive vent could be approached amidst a rain of light scoriae.
Strombolian activity occurred from a single vent about 10-15 m in diameter on the top of a mound growing in the northwestern summit area of SE Crater's central conelet. This mound was only a few meters higher than the same place in early April, indicating that in spite of continuous vigorous explosive activity no significant cone growth had taken place. Explosions occurred incessantly, at times more than one per second, and many were very strong, ejecting bombs more than 200 m above the vent. The fountains were clearly inclined northwards, no bombs fell farther than some 20 m south of the vent while they fell copiously on the northern, northwestern and northeastern sides of SE Crater, up to more than 100 m away. As on many other occasions, a distinct periodicity could be noted in the activity, each cycle culminating in a series of powerful Strombolian blasts heavily charged with meter-sized bombs. The first blast of each series would be very noisy and eject strongly fragmented and therefore small bombs in broad jets 150-200 m high; this would be followed within 10-20 seconds by a much less noisy blast which carried abundant huge bombs in a dense fountain equally high. The succeeding explosions would be almost noiseless, but some of them could be even more voluminous (in terms of ejected pyroclastics) than the second blast of the series.
Due to the northward directed nature of the explosions, the southern side of the cone could be approached and climbed to within about 20 m of the active vent at relatively low risk. Thia area was morphologically highly complex; a low hill with an elongate summit depression resembling a horseshoe-shaped crater had developed, at the downhill side of which a very small volume of bulbuous lava had been squeezed out/ This lava still showed incandescent cracks and was interpreted as very recent, maybe only a few hours old. The entire structure presumably formed as a part of the southern flank of the central conelet was pushed outwards by lava intruding below the flank; as the lava began to extrude from the front of this structure, a graben-like depression formed on its top. The walls of the outward-pushing structure were in part oversteepened and constantly crumbling, indicating that slow outward movement was continuing. While climbing the slope of this advancing feature, made of pyroclastics of all grain sizes, an intense heat was felt through the hiking boots, and it is assumed that a few tens of centimeters below the surface there was a temperature of several hundred centigrades. Lava had also issued from the southern base of the central conelet after 6 April (in an area where continuous effusive activity had occurred from December 1997 until late March 1998), but this lava was deeply covered with bombs and scoriae indicating that effusion occurred some time, possibly several weeks, ago.
The effusive vent(s) that had formed on the eastern side of the central conelet on or shortly before 6 April continued to produce narrow channellized flows at a low effusion rate (0.1-0.2 cubic m per second). The emission of numerous overlapping flow lobes since then had built a low shield in this area, and the depression which had formed at the onset of effusive activity on the E base of the central conelet was completely filled. Lava oozed out from below a very smooth-surfaced platform of recent lava between two ridges of tilted slabs of older lava (see photo at top of this page). At times there was high-pressure gas emission at the point where the lava was extruding, but this was not accompanied by any visible fluctuation in the effusion rate. As the lava flowed away from the vent, it rapidly crusted over and moved in a channel about 1.5 m wide towards the eastern side of the SE Cone where it overflowed onto the cone's flank.
Unstable weather conditions and very dense gas plumes prevented a visit to the other summit craters, but loud detonations were frequently heard from the Voragine whose southwestern vent had been recently observed in eruption. The local mountain guides at Torre del Filosofo reported that there had been no recent activity at Bocca Nuova and NE Crater.
15 May 1998
A visit to Etna's summit was made yesterday by scientists of the Istituto Internazionale di Vulcanologia. They reported vigorous activity from the vent in the southwestern part of the Voragine and numerous fresh bombs that had been ejected onto the southwestern to western rim of the Voragine from that vent. This is the first occasion on which bombs have been ejected outside the Voragine during the current summit eruption. No significant cone appears to have built around the vent. Meanwhile, SE Crater continues to produce Strombolian explosions (about 1 to 5 per minute yesterday night) and occasional small overflows of lava.
14 May 1998
Eruptive activity at SE Crater is continuing. Like in previous months, lava is overflowing onto the flanks of the SE Cone, forming small lobes that rarely extend beyond its base, and Strombolian activity occurs from the summit of the growing central conelet within the SE Crater. Images transmitted by the live-cam of the Istituto Internazionale di Vulcanologia have failed to document this activity at night due to a malfunction of the infrared filter. This filter renders incandescence visible in night images whereas no incandescence can be viewed without it. The lack of "the red stuff" in recent nights is therefore not due to a lack of eruptive activity.
Weather conditions in the Etnean area are still variable, there were frequent snowfalls on the volcano through early May, but by now almost all snow has melted (there was no accumulation of deep snow this winter like two years ago when there were still four meters of snow thickness at Torre del Filosofo in mid-May). Arrival of a new bad weather front is anticipated for this weekend.