Daily summit observations revealed frequent weak explosions and vigorous fumarolic activity in July and August. Tremor amplitude was constant, and seismic activity was slightly above average. Tremor amplitude, measured with hourly 60-second samples, generally averaged 0.4-0.6 v, with one day >0.7 v (3 July). There were >100 recorded seismic events per day throughout the period; 16 days had >200 events (4 August and 15-29 August); 16 and 26 August had >250. The last two weeks in August also had more strong shocks (ground velocities >100 mm/s), but no more than 50/day.

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: M. Riuscetti, Univ di Udine.