Unusual eruptions

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1.4.2003

The lava flows continue to issue from a variable number of vents located below NE crater. The lava branches fill a lava field located at about 600 m a.m.s.l. From the side of this small lava plain, moderate-sized landslides, mainly involving the rolling of (cold and hot) blocks affect the slope of Sciara del Fuoco. Sometimes the landslides descend with an interestingly slow movement, like gravel sliding, producing a peculiar sound similar to a degassing episode. From the logistical point of view, it is now possible for non-residents to land on the island, but NOT to climb the mountain up to the Pizzo. However, the access limit was fixed by Civil Defense at the end of the "mulattiera" climbing from Semaforo Labronzo, at 273 m a.m.s.l. altitude. From this point one has already a good view of the Sciara slope and of the landslides, many of them incandescent at night, that descend the slope itself.

4.1.2003 to 23.1.2003

The lava flows continue to descend the slope of Sciara del Fuoco, inside the scar left by the big 30 December 2002 landslide. As time passes, there are different branches issued by vents located at different heights, but always at least several tens of metres below the crateric area. In the last few days, there is an active vent at about 500 m a.m.s.l. This, together with the absence of thermal anomalies in the crater terrace, suggests that the magma level is quite low in the conduit. Therefore, the explosive activity that is still recorded instrumentally, does not manage to produce the classical strombolian eruptions visible from Pizzo sopra la Fossa. On the Sciara slope, highly unstable after the big 30 December landslide, moderate sized rockfalls and landslides continue to be observed and recorded by the seismic stations.

28.12.2002 al 3.1.2003

Explanations follow below the maps and images.

Click the small images for larger versions. Steam and ash cloud after the descent of the avalanches on Sciara del Fuoco as seen from Stromboli village on 30. December 2002. Courtesy Sergio Ballarò	(4 images) We received these four photos from Gianfranco Cincotta (thanks!) but we don't know who is the photographer. For their interest we decided to publish them anyway, but we ask the author to contact us so we can properly credit him.	(3 images) Cloud caused by the landslide, people running away from the tsunami. Photos copyright Philippe Guillemin. Philippe reports that two waves arrived in a 20 second interval; there was no sound and, therefore, no previous warning.

Active lava flows on 30. December 2002 at 11h30 local time (red) and on 31. December 2002 (purple). Drawn after maps published by INGV-Catania.

Landslides which descended from Sciara del Fuoco on 30. December 2002 at 13:15 and 13:22. Drawn after maps published by INGV-Catania.

Illustration showing the spreading tsunami after the landslides entered the sea. Note that the drawing is not a computer simulation but only an estimation of how the waves might have propagated.

The following summarizes developments on Stromboli since the 29.12.2002. It is mainly an abbreviated version of a report by Dr. Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, 95123 Catania:

The effusive eruption from the base of NE Crater started on 28 December and finished the following day. A survey performed on 29 Dec. with the helicopter of the Civil Protection using a thermal camera revealed three lava flows spread in the eastern Sciara del Fuoco, which have reached the sea within 30 minutes. The flows were together up to 300 m wide along the coast, and were no longer fed on 29 December.

A small lava flow up to 200 m long formed again on 30 Dec. was spreading in the upper Sciara del Fuoco in a small depression when observed at 11:30. Suddenly, at 13:15 and 13:22 local time on 30 December, two landslides formed along the Sciara del Fuoco. They reached the sea, and have been accompanied by fine ash fallout on the SE flank of the island. Ash fallout was not caused by explosive activity, but by crashing of rocks during rock fall. The first landslide was about 600,000 m3, the second about 5,000,000 m3 of rock, detaching the 28 December lava from the slope together with a large portion of the ground below.

Upon entering the sea the landslides caused two tsunamis that, on the island of Stromboli, caused sea regression first, and then two waves several meters high that spread on the villages of Stromboli and Ginostra causing damages to buildings and boats, and injuring a few people. Large waves have been reported up to Milazzo, on the northern coast of Sicily, at a distance of 60 km south of Stromboli.

The summit craters of Stromboli show no explosive activity at all since the start of the eruption. No large explosions occurred on the volcano, and no earthquakes have been recorded by our seismic network. Previously tsunamis at Stromboli volcano occurred on 1930, 1944 and 1954. These have been related to paroxysmal eruptive activity, to landslides along the Sciara del Fuoco, or to pyroclastic flows, but not to lava flow emplacement. A thin lava flow is still expanding along the Sciara del Fuoco as on January 1st, 2003.

	Press photos from Corriere della Sera, Villa, AP-Photos. Top Damage caused by the tsunami along the coast of Scari, Stromboli. Left Lava flow entering the sea below Sciara del Fuoco. Undated photo.

Further details reported by Klaus Jäger, Tom Pfeiffer and volcano guides Antonio Famularo and Nino Zerilli: By now the major part of the population has been evacuated also from Stromboli village. Panic was caused in the population of Stromboli village when, on 31.12.2002 wet ash fell which seemed to indicate a large summit eruption. However the wet ash fall was produced by the landslides in Sciara del Fuoco, wind transport and rain, and clearly not by a summit eruption.

28. December 2002

Abbreviated from report by Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, via VOLCANO listserv: "On 28 December the height of ejecta reached 200 m above NE Crater, and the shape of explosions suggested magma very close to the crater rim. This activity climaxed at 18:30 with a strong explosion that caused ash fallout on the village of Stromboli, accompanied by the opening of an eruptive fissure trending NE-SW. The fissure opened at the NE base of NE Crater. A lava flow came out from the base of the fissure, and formed three lava branches spreading within the Sciara del Fuoco. Within 30 minutes the flows reached the sea, about 1 km away. The lava flows were up to 300 m wide at the shore line, but very narrow along the steep slope of Sciara del Fuoco."

Livecam image (INGV) showing the reflection of the lava flow's glow in the low clouds (above) and steam from the craters (center and right). Image brightness enhanced.