Update on the activity of Etna and Stromboli, 5 July 2011

Etna

During the forenoon of 4 July 2011, explosion sounds were heard coming from the crater that lies on the eastern flank of the Southeast Crater cone. On the evening of the same day, a faint glow was intermittently visible at the same crater. From 02:00 GMT on 5 July, the Schiena dell'Asino monitoring camera of the INGV-Catania, on the southeast flank of Etna, started recording small Strombolian explosions. These explosions occurred at intervals varying from a few minutes to several tens of minutes, launching incandescent pyroclastics up to a few tens of meters above the crater rim.

Similar activity has preceded, always by a few days, at least three of the four paroxysmal eruptive episodes that have taken place at the same crater between January and May 2011; therefore the current activity might be a first precursor of a new paroxysmal episode.

During the past few days, ash emissions from the Bocca Nuova have continued. During a visit by INGV staff on 30 June, measurements made with a thermal camera showed that hot material deposited around the active vents had a temperature of about 150°C, whereas more elevated values (up to 300°C) were encountered in intensely fractured zones along the walls and on the floor of the Bocca Nuova. One ash emission, at 19:28 GMT on 1 July, was accompanied by a thermal anomaly (as recorded by the Montagnola thermal camera of the INGV-Catania), caused by the emission of material that was hotter than that emitted previously. Finally, on 5 July, some ash emissions from the Bocca Nuova produced darker material than that emitted during the ash emissions since 14 June.

Video frames recorded by the thermal camera of the INGV-Catania on the Pizzo sopra la Fossa (SPT), showing three different moments during the strong explosion of Stromboli that occurred at 02:45 GMT on 5 July 2011. The interval between the first and the third frames is 14 seconds. Note the abundant fall of hot pyroclastic material in the immediate vicinity of the camera

Stromboli

At 02:45 GMT on 5 July 2011, a powerful explosion took place in the southern portion of the crater terrace of Stromboli, which produced a tall pyroclastic jet and caused heavy fall of coarse-grained pyroclastic material onto the Pizzo sopra la Fossa and onto the upper outer flank of the volcano. The seismic trace indicates a prolonged sequence of explosions, which ended at 03:02 GMT.