Mt Etna volcano (Italy) typically generates lava fountains and Strombolian eruptions
from the summit craters, producing significant emissions of tephra which may cause
moderate to high impact both in the atmosphere and on the ground. However, we have also
witnessed a number of minor ash emissions that, although far less powerful, may pose
considerable volcanic hazards. In this paper, we deal with three ash emissions occurring in
2010 (8 April at Southeast Crater, 25 August at Bocca Nuova, and 14β15 November at
Northeast Crater), correlating their volcanological features with the associated seismoacoustic
signals. We provide details regarding the chronology, eruption column, dispersal
of the deposit, and texture (grain size, componentry and morphology) of the emitted ash.
Each eruptive episode has also been characterized by means of seismo-acoustic analyses
evaluating the volcanic acoustic-seismic ratio (VASR). Furthermore, the source of volcanic
tremor recorded from March to December 2010 was localized. The joint volcanological
and seismo-acoustic analyses allowed distinguishing two main kinds of ash emissions:
types a (8 April and 25 August) and b (14β15 November). Regarding the former, the
accumulation of gas below a dense cap rock obstructing the conduit vent, giving rise, with
the uncorking, to impulsive explosivity, was hypothesized. The latter type instead is
characterized by a longer-lasting and less explosivity, likely due to the existence of open
conduit conditions. Therefore, type b ash emissions are less hazardous than type a. This
simple model, regarding minor explosive activity, may constitute a starting point to assess
the volcanic risk from unexpected explosions