The latest effusive eruption at Stromboli ended between 21 and 22 July (BGVN 28:07), when active lava flows on the upper Sciara del Fuoco were no longer visible. Since then explosive Strombolian activity became more common at both summit craters. Four active vents were observed within Crater 1 (the NE crater), and there was one funnel-shaped incandescent depression within Crater 3 (the SW crater). Strombolian activity during the first half of August was very intense at Crater 1, causing a spatter cone to form on the crater floor and incandescent bombs to fall on the outer flanks. Explosive activity at Crater 3 was apparently deeper, and was often accompanied by ash emission.

During the first half of August, thermal images of the apparently inactive lava flow field revealed thermal signatures within cracks on the upper flow field, and within skylights along two lava tubes in the upper Sciara del Fuoco, at ~550 m elevation. Temperatures of over 300°C, and incandescence of these hot spots, suggest endogenous growth. Incandescence and thermal signatures at these sites were not observed between 22 and 31 July.

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/).