Fieldwork during the first week in June revealed that eruptive activity was mainly concentrated in craters C1 (vent 1) and C3 (vent 4), which fed black plumes no more than 100 m high. Seismicity remained high in June (figure 26), near the 180 events/day reached in the last third of May. A minimum of 108 events was recorded on 24 June. After declining rapidly about 20 May, tremor energy returned to levels characteristic of the period since November 1991.

Figure 26. Seismicity at Stromboli, June 1992. Open bars show the number of recorded events per day, black bars those with ground velocities exceeding 100 mm/s. The curve represents the each day's average of tremor energies on hourly 60-second samples. Courtesy of M. Riuscetti.

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.