Report on Stromboli (Italy) — 9 April-15 April 2003
Smithsonian / US Geological Survey Weekly Volcanic Activity Report, 9 April-15 April 2003
Managing Editor: Gari Mayberry
Please cite this report as:
Global Volcanism Program, 2003. Report on Stromboli (Italy). In: Mayberry, G (ed.), Weekly Volcanic Activity Report, 9 April-15 April 2003. Smithsonian Institution and US Geological Survey.
38.789°N, 15.213°E; summit elev. 924 m
All times are local (unless otherwise noted)
INGV-CT reported that the effusive eruption at Stromboli, which started on 28 December 2002, continued through 8 April 2003 from vents at 600 m a.s.l. On 5 April scientists from INGV-CT observing the volcano from a helicopter saw lava flowing from three vents at 600 m and a diluted gas plume emanating from the summit craters. A few minutes after the survey began the gas plume suddenly became red and soon after juvenile, darker material was emitted from Crater 1 (the NE crater). A hot, cauliflower-shaped jet rapidly grew above the crater. Around 2-3 seconds later Crater 3 (the SW crater) emitted a hot jet of juvenile material and soon after the two jets joined together. Then a very powerful explosion occurred at 0912 that pushed the helicopter away from the crater. A mushroom-shaped dark cloud rose to ~1 km above Stromboli's summit. The base of the cloud was surrounded by a dark gray cloud similar to a base surge. Bombs, blocks, and ash fell on the volcano's NE flank above 400 m elevation, burning vegetation. Most ejecta drifted W, falling on the town of Ginostra, about 1.5 km away, and destroyed two houses.
Observations after the eruption revealed that the lava-flow field on the upper Sciara del Fuoco (a horseshoe-shaped scarp) at 600 m elevation was completely covered by a carpet of brown debris ejected from Crater 1 during the initial phase of the event. A thick steam cloud rose above the debris carpet, formed by vaporization of wet debris above the hot lava flows. Alternating pulses of black and red ash emissions rose mainly above Crater 3. The upper part of the volcano (above 700 m elevation) was completely covered by a continuous carpet of pyroclastic products. Within a few minutes after the eruption, lava flows were active again on the Sciara del Fuoco at 600 m elevation, emerging through the debris carpet. On 8 April INGV-CT scientists saw lava flowing from four vents on the Sciara del Fuoco. Two flows traveled in the middle of the scarp and blocks detaching from the lava-flow fronts generated small rockfalls that reached the sea. News about the eruption (in Italian) and photos are available on the INGV-CT website.
Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period from about 13,000 to 5000 years ago was followed by formation of the modern edifice. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5000 years ago as a result of the most recent of a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.