Explosive activity at the summit craters of Stromboli volcano resumed in early June 2003, before the end of the effusive eruption that finished between 21 and 22 July 2003. Eruptive activity at this volcano is monitored by Istituto Nazionale di Geofisica e Vulcanologia (INGV-CT). They have installed two web cameras at an elevation of 920 m on Il Pizzo Sopra la Fossa and at an elevation of 400 m along the E margin of the Sciara del Fuoco, the depression on the N flank of the volcano. Additionally, a web thermal camera is located at the 400-m elevation site noted above, and a web infrared camera is positioned at Il Pizzo Sopra la Fossa. The 2 cameras (thermal and video) at the 400-m elevation site give important insights when visibility is insufficient at the more distant cameras. The infrared camera at Il Pizzo provides both a continuous view of the activity at the summit craters and a quantification of the energy released by the explosions at the three summit craters through an automated system called VAMOS (Cristaldi and others, 2004).

According to aviation reports from the U.S. Air Force, the web camera at Stromboli captured shots of light ash emissions on 7 and 11 November 2003. In both cases plumes rose to ~ 2.5 km altitude. According to the Toulouse VAAC the Stromboli Web video camera showed a small explosion on 10 December that produced a plume to a height of ~ 1 km above the volcano. No ash was visible on satellite imagery.

According to the INGV-CT, explosive activity at the three summit craters increased after 10 February 2004, leading to a significant growth of the cinder cones inside the craters. Several powerful explosions, especially from crater 1 (the NE-crater) and crater 3 (the SW-crater) carried scoriae 200 m above the craters. These explosions led to fallout of fresh bombs and lapilli on Il Pizzo Sopra la Fossa (the top of the volcano, ~ 100 m above the crater terrace) in early March. Samples of lapilli and scoriae collected on Stromboli by local guides have been analyzed with the scanning electron microscope and microanalysis instruments of INGV-CT (Corsaro and others, 2004). Measurements of glass compositions indicated that products erupted until 25 February 2004 are related to the black scoriaceous volcanics normally erupted during Strombolian activity. Golden basaltic pumices were absent from available samples; such pumices at this volcano have been generally associated with paroxysmal explosive events (Bertagnini and others, 1999) such as that of 5 April 2003. Analysis of components carried out on several ash samples allowed scientists at INGV-CT to recognize sideromelane and tachylite as the main components, making up ~ 80% of the erupted ash (Andronico and others, 2004). The activity of this volcano as of 8 March 2004 can be described, fittingly, as Strombolian with variations in the number and frequency of explosions within normally observed limits, and intensity of explosions at the higher limit of commonly observed activity.

References. Andronico, D., Caruso, S., Cristaldi, A., and Del Carlo, P., 2004, Caratterizzazione delle ceneri emesse dallo Stromboli nel Gennaio-Febbraio 2004: INGV-CT Internal Report, Prot. int. n° UFVG2004/034.

Corsaro, R.A., Miraglia, L., and Zanon, V., 2004, Caratterizzazione dei vetri presenti nei prodotti emessi dallo Stromboli durante il mese di febbraio: 2004 INGV-CT Internal Report, Prot. int. UFVG2004/033.

Cristaldi, A., Contelli, M., and Mangiagli, S., 2004, Rapporto settimanale sull'attivit eruttiva dello Stromboli: 22-29 Febbraio 2004. INGV-CT Internal Report, Prot. int. n° UFVG2004/031 [download at http://www.ct.ingv.it/].

Bertagnini, A., Coltelli, M., Landi, P., Pompilio, M., and Rosi, M., 1999, Violent explosions yield new insights into dynamics of Stromboli volcano. Eos, American Geophysical Union Transactions, 80, 52: 633-636.

Geological Summary. Spectacular incandescent nighttime explosions at Stromboli have long attracted visitors to the "Lighthouse of the Mediterranean" in the NE Aeolian Islands. This volcano 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 took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent scarp that formed about 5,000 years ago due to a series of slope failures which extends 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.

Information Contacts: Sonia Calvari, Istituto Nazionale di Geofisica e Vulcanologia, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/); Charles Holliday, Air Force Weather Agency (AFWA), Satellite Applications Branch, Offutt AFB, NE 68113-4039, USA.