Etna activity, 26 May 1996
Etna activity, 30-31 May 1996
Etna activity, 1 June 1996
Etna activity, 3 June 1996
Morphology of NE Crater in May-June 1996
Stromboli activity, 9 June 1996
Stromboli activity, 12 June 1996
All times are local = UT + 2 hr
1. Etna
Activity on 26 May 1996 (8 h observations from 1400 to 2200)
Observations from W rim of Bocca Nuova
Bocca Nuova: Vent filled by thick steam. From 1500 to 1600 strongly increased activity, with many explosion. During moments of good visibility, a vent with a lava pond on the flat bottom of the crater was well visible, ejecting meter sized lava clots 20 m high. On the SE side of the crater, another vent was ejecting steam jets every minute with strong roars. Thanks to the darkness, the vent on the crater bottom was observed in the dense steam from 1930 to 2030: the level of the lava pond was clearly varying, so that every minute the vent (active lava) disappeared, and then reappeared. When the lava pond was close to the crater bottom (highest), Strombolian explosions 50 m high occurred.
NE Crater: At 1800 eruptions of thin ash and black bombs started. From 2100 to 2200 weak regular Strombolian explosions every 10-50 sec threw a few bombs towards the E rim (strong W wind), sometimes reaching 50 m high over the rim, but no bombs fell outside the crater.
Activity on 30-31 May 1996 (18 h observations from 1700 to 1100)
Observations from Pizzi Deneri and W rim of NE Crater
Bocca Nuova: Not observed.
NE Crater: Strong explosions with ejection of black bombs observed during the long path around the "Ellittico" crater (a prehistoric caldera in Etna's summit region). NE Crater was then observed from Pizzi Deneri from 2100 of 30 May to 0600 on the 31st. Large Strombolian explosions lasting 1 - 2 sec ejected bombs 100 - 200 m high over the rim every 1-40 sec. On 31 May at 0800 we were about 200 m away from the W rim. Many meter sized bombs, red glowing in the daylight, were ejected well outside the SW rim of the crater (strong wind from NE), reaching apparent elevations in the sky of more than 60°, thus making any approach to the crater rim imprudent. The explosions produced many characteristic steam rings. At 0830, the activity abruptly changed, with voluminous emission of ash, but no more explosions of bombs, thus allowing us to reach the W rim at 0900. The view of the new "caldera" was impressive, at least two times larger than the former crater, and with the active vent south of the center. The intensity of the ash eruptions increased, giant lava clots were ejected all over the "caldera", and the intensity of the Strombolian explosions increased, with dark bombs more than 60° high in the sky, so that we were forced to leave the rim at 1000, when the activity returned to its characteristics displayed before 0830 (many bombs, strong explosions, no ash).
Activity on 1 June 1996 (2 h observations from 1900 to 2100)
Observations from W rim of Bocca Nuova and Voragine
Bocca Nuova: Perfect visibility without steam. Two vents with active lava ponds were well visible on the bottom of the crater, aligned N-S. The N vent produced Strombolian explosions every 10-30 min, 50 m high, towards south. The S vent produced Strombolian explosions 10-30 m high every 5-20 sec. A third vent in the SE side of the crater produced steam eruptions every 2-10 min with visible incandescence during the steam ejections. At 1930 we observed the Voragine, half filled in its northern part by the new growing slope of NE Crater, with steam jets every sec.
NE Crater: Inactive.
Activity on 3 June 1996 (5 h observations from 1700 to 2200)
Observations from West rim of NE Crater
Bocca Nuova: Not observed.
NE Crater: From 1800 to 2000, we observed the NE Crater from a distance of 200 m from the W rim. Strong Strombolian explosions every 2-50 sec, 100 - 200 m high over the rim, with bombs up to the N rim of the crater (strong wind from SSW). From 2000 to 2100, we observed the explosions from the W rim. Impressive explosions, with bombs ejected with a velocity as high as being visible as red straight lines 50 m long. The vent was 300 m distant from the rim, and the bombs reached heights in the sky of more than 60°, but the strong wind dragged all of them inside the "caldera" up to the N rim, falling at least 100 m from the W rim. During the explosions, blue gas was ejected with the bombs. From 2100 to 2200 similar explosions were observed from the edge of the "Ellittico" crater.
Morphology of NE Crater during late May-early June 1996
The following is summarized from a separate message by Marco Fulle, 20 June 1996.
Dramatic morphological changes have taken place at NE Crater since the onset of magmatic activity in the summer of 1995. The diameter is estimated at 400-500 m (it takes three photographs taken with a 28 mm lens to cover all of it when seen from the rim). The N rim seems to have changed least and is the highest point of the crater. Towards S, the crater appears much enlarged, with the outer slope growing deeply into the Voragine pit, reaching as far as the actively degassing conduit in its center. The cone of NE Crater is best accessible from its W side, but the vast gap present in the W rim until November has been completely filled and the new tephra wall is almost as high as the N rim. Another morphological high is on the SW rim of the cone where intense fumarolic activity is occurring (similar to recent years). From the W rim, the S and E rims appear fairly uniform in height.
The crater floor is now about 50 m below the rim and is relatively flat, however with many small-scale undulations. It is covered with "an incredible variety of pyroclastics of all colors" and lots of bombs tens of meters in diameter. There may be up to two active vents, one of them being the source of the eruptions described above which lies about 50 m south of the center of the crater, and the other (inactive one) maybe 50 m north of the center. There are no cones around the vents, they are mere holes about 30-50 m in diameter.
"The surroundings of the crater are equally spectacular, in particular on the W and N sides of the cone. One walks upon layers of ash which cover snow that in turn overlies ash and so on, with a total thickness of several meters. (...) Seen from above, the area seems a bombing field. (...) The tracks to the craters are not as they were before. It is now impossible to reach NE Crater from Bocca Nuova because of a still-steaming lava flow emplaced during one of this winter's eruptive paroxysms. You have now to surround this flow at the base of the cones."
Stromboli Activity on 9 Jun 1996 (6 h observations from 0050 to 0650)
Observations from Pizzo sopra la Fossa
Vent 1/2: continuous fountaining 50 m high with a pulse every sec, larger pulses every 5-10 min with ejection of meter sized lava clots (red even in the daylight) lasting 20-60 sec. Strongly glowing vent. Superimposed to this activity, the vent produced 35 large explosions lasting 1-2 sec, 100-200 m high, with bombs over the Sciara and the terrace up to crater 2, with meter sized lava clots falling inside crater 1.
Log of large explosions of vent 1/2:
0058, 0059, 0110, 0119, 0123, 0132, 0149, 0211, 0214, 0226, 0243, 0258, 0308, 0316, 0317, 0330, 0331, 0351, 0423, 0425, 0431, 0433, 0435, 0454, 0505, 0511, 0530, 0557, 0603, 0613, 0618, 0629, 0630, 0638, 0645
Vent 3/1: Completely inactive (the first time since 1992)
Vent 3/2: 20 explosions lasting 2-10 sec 50 m high with abundant ash and bombs ejected inside the crater. No glow between explosions.
Log of explosions of vent 3/2:
0147, 0157, 0218, 0247, 0322, 0326, 0355, 0408, 0418, 0419, 0434, 0444, 0509, 0529, 0531, 0536, 0553, 0556, 0633, 0642
Activity on 12 June 1996 (6 h observations from 0040 to 0640)
Observations from Pizzo sopra la Fossa
Vent 1/2: continuous fountaining 50 m high with a pulse every sec. Strongly glowing vent. Superimposed to this activity, the vent produced 46 big explosions lasting 1-2 sec, 100-200 m high, with bombs over the Sciara and the terrace up to all crater 3, with meter sized lava clots (incandescent even in the daylight) inside crater 1.
Log of large explosions of vent 1/2:
0054, 0106, 0110, 0112, 0118, 0127, 0134, 0140, 0155, 0206, 0210, 0224, 0226, 0235, 0246, 0255, 0303, 0319, 0320, 0332, 0337, 0344, 0405, 0414, 0427, 0430, 0433, 0448, 0455, 0456, 0458, 0500, 0506, 0511, 0512, 0514, 0533, 0541, 0551, 0616, 0622, 0628, 0635, 0638, 0639, 0640
Vent 3/1: Completely inactive.
Vent 3/2: 37 explosions with big noise, lasting 2-10 sec, 100-250 m high (well above the horizon) with little ash. Red fountaining during the explosions even in the daylight. West-Vertical jets of bombs falling south of the crater rim (almost reaching the protective S "stone castles") and over all vent 3/1. The active vent was well visible on the N flank of the crater, from a point located just slightly above the south crater rim, strongly glowing during all the observation time, with brighter glow every 10-30 min.
Log of explosions of vent 3/2:
0040, 0054, 0106, 0110, 0124, 0134, 0152, 0158, 0221, 0237, 0253, 0257, 0303, 0305, 0313, 0317, 0344, 0352, 0357, 0408, 0421, 0430, 0433, 0436, 0452, 0506, 0514, 0520, 0521, 0531, 0540, 0547, 0556, 0620, 0624, 0627, 0636