Article by INGV Blog
Starting at 14:46:00 UTC (all times shown are UTC) on July 3, 2019, a paroxysmal sequence occurred that affected the Stromboli crater terrace. The beginning of the phenomenon was preceded by an intensification of Strombolian activity against an eruptive vent active in the central-southern area (S2) and two in the northern area (N1 and N2) and the spattering activity at two mouths located in the central-southern area (S1 and C). At 13:59:00 an explosion from the central-southern area also generates a lava overflow that spills over the upper part of the Sciara del Fuoco. From 14:43:10, the lava overflow begins from all the active mouths inside the crater terrace; in particular at 14:43:10 from the C mouth, at 14:44:20 UTC from the two mouths N1 and N2, at 14:45:00 the overflow begins from the mouth S2. At 14:45:50 UTC there was a more intense explosion from the N1 vent with lava flow. At 14:46:00 the paroxysmal phase begins from the central-southern crater area, followed by two lateral blasts at 14:46:10 and 14:46:20 respectively, presumably from the central-southern area of ​​the crater terrace. At 14:46:40, the main paroxysmal explosion involving the entire crater terrace is recorded. This feeds a lava overflow that sets in place on the Sciara del Fuoco, whose breccia front generates the rolling of incandescent blocks that reach the coastline. INGV personnel in the field observed an eruption column that rose to about 4 km above the summit area. The products generated by the paroxysm and the collapse of the main eruptive column and of the two lateral blast have fallen down along the flanks of the volcano, generating at least two pyroclastic flows with high turbulence, which have taken place along the Sciara del Fuoco reserving itself in the sea. At 14:59:40, there was a resumption of Strombolian activity, with more intense explosions than those ordinarily observed, and the cooling of the relapse products. The lava overflow remained, which formed at least two lava flows.
Today, 4 July 2019, spattering activity is recorded from the central-southern area and an active lava overflow which generates four active flows that propagate in the southern sector of the Sciara del Fuoco reaching the coastline.
Framework of historical activity
The ordinary activity of Stromboli consists of strombolian explosions that occur at an average frequency of 10-20 min from the summit mouths. This typical intensity-varying activity is occasionally interrupted by more energetic explosions or paroxysmal explosions. The latter are discreet violent events that generate eruptive columns that rise for several kilometers above the mouths with the fallout of coarse material that can reach even the inhabited centers of the island and occasionally form pyroclastic flows and lava flows that are put into placed along the slopes of the volcano.
The strongest explosive events can launch bombs and multi-dimensional blocks in the summit area (the Pizzo sopra la Fossa). During the strongest paroxysms, the fallout of incandescent pyroclastic material can cause fires in the vegetation on the outer slopes of the volcano. Among the strongest paroxysms, documented in the last 100 years, there are those of 1919, 1930, 2003 and 2007, of which the eruption column of that of 1930 has generated pyroclastic flows.
Geophysical data
The paroxysmal sequence was visible on the seismic trace, which in addition to the major explosions showed about 20 minor explosive events. Today, the magnitude of the volcanic tremor remains at high levels.
