Ash plume generated by the explosion at 09.31 h (local time) on 29 August 2010, seen a few minutes after the event from Viagrande, on the southeast flank of Etna

Ash emission from the Bocca Nuova at 16.18 h (local time) on 28 August 2010, seen from the western flank of the Montagnola, about 3.5 km south of the Bocca Nuova. The large cone to the right is Monte Barbagallo, formed during the flank eruption of 2002-2003

Ash emission from the Bocca Nuova at 09.31 h (local time) on 29 August 2010, seen from Trecastagni, on the southeast flank of Etna

From 25 to 29 August 2010, numerous explosions, internal collapse, and ash emissions have occurred at the Bocca Nuova, the westernmost of the four summit craters of Etna. In particular, there have been 7 more significant events, though considerably smaller than the first explosion on 25 August. These events occurred at 19.29 h (local time) on 25 August, at 01.25 on 26 August, 11.29 on 27 August, 11.15 and 16.18 on 28 August, and 07.40 and 09.31 on 29 August. All emissions occurred from the western pit  (BN-1) of the Bocca Nuova.

During a field inspection on the morning of 26 August it was observed that the main ash emission event  at 15.09 h (local time) on 25 August had caused the collapse of a portion of the western crater rim of the BN-1 pit. The remaining part of the crater rim is extremely unstable and shows numerous fractures; rockfalls were heard continuously during the field inspection. The visit revealed the absence of any coarse-grained lithic or juvenile material on the crater terrace next to the pit.

However, the 25 August explosion caused light ash falls over populated areas in the southeastern sector of the volcano to as far as Catania. This ash is constituted mostly of lithic material, although a small fraction (~2 %) of juvenile material is present.

In contrast, all ash emitted by the events of the following days is lithic, and no emission of hot material (pyroclastic or gas) has been recorded by the thermal surveillance camera on the Montagnola.