INGV reported a period of intense activity at Stromboli that included spattering, lava overflows from a series of vents along the Sciara del Fuoco, pyroclastic flows, and debris avalanches. During 1-3 July low- to medium-intensity explosive activity at two vents in Area N (one at N1 and one at N2) and in sector S2 (Area C-S) ejected coarse material (bombs and lapilli) less than 150 m above the vents. Explosive activity at S2 decreased and then stopped on 3 July.

A gradual increase in the amplitude of seismic tremor from medium to high levels began at around 1730 on 3 July. A sudden increase in amplitude to very high levels occurred at about 1820 and the amplitude peaked 20 minutes later, concurrent with stronger spattering in Area N at 1835. A series of about 20 collapses at the cone began at around 1845, producing avalanches of incandescent material that rapidly descended the Sciara del Fuoco, reached the coastline, and spread out over the sea. The activity produced ash clouds that drifted over the S and E parts of the island. Spattering and explosive activity followed, and at 1902 lava overflowed Area N, descended the upper part of the Sciara del Fuoco, and produced block avalanches that rolled down the flank. At about 1905 tremor amplitude rapidly decreased but remained at high levels. Lava flows continued to be fed through the night, reaching 550-600 m elevation, but ceased in the morning and cooled.

A period of almost continuous landslides occurred at N2 during the early afternoon of 4 July. At around 1410 on 4 July a lava flow from a new vent at 700 m elevation in Area N descended the Sciara del Fuoco along with a pyroclastic flow. At 1714 the lava branched at around 600-650 m elevation and traveled parallel to the first, reaching the coastline at 1747. At 1818 a new vent with a high lava effusion rate opened at around 510 m elevation. Both the lava flow and a simultaneously generated pyroclastic flow rapidly descended the Sciara del Fuoco to the coastline, where the pyroclastic flow spread over the sea for several hundred meters. An ash plume rose 2 km a.s.l. Numerous additional pyroclastic flows descended the Sciara del Fuoco; the most notable one occurred at 2010 and again spread several hundred meters over the water. At 2000 the Dipartimento della Protezione Civile raised the Alert Level to Red (the highest level on a four-level scale).

Lava flowed down to the coast on 5 July and produced steam-and-ash plumes where it contacted the sea. Tremor amplitude fluctuated between high and very high values and then decreased to average values by 0600. A sequence of pyroclastic flows at 1219, 1227, 1230, and 1233 quickly descended the flank and reached the sea; another descended the Sciara del Fuoco at 1431. By 1536 fresh lava supply to the flow had decreased, and material breaking from the flow front was rolling down the flank. Effusive activity increased at around 2055 based on field observations and a lava flow descended the flank, stopping a few tens of meters from the coastline; effusion again stopped.

Lava effusion restarted by 1321 on 6 July from a vent at 485 m elevation and produced a lava flow that traveled about 285 m. Blocks detached from the flow front and rolled down the flank to the sea. Effusive activity intensified during 6-7 July. Lava from vents at 510 m and 485 m elevation converged and flowed down the flank to the coast, creating a small lava delta and producing ash-and-steam plumes. Incandescent lava blocks rolled down the flanks and caused small phreatic explosions when they reached the sea.

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.

Sources: Sezione di Catania - Osservatorio Etneo (INGV), Dipartimento della Protezione Civile