Conclusions
Impact on everyday life related to mid-intensity explosive activity can be incredibly large, and this type of activity poses major problems at Italian volcanoes - especially for those with eruptive vents near inhabited areas. The extensive case history presented in this paper gives account of the wide variability of eruptive processes involved in this class of eruption and of the spectrum of events which can occur at Italian volcanoes. Looking at the past history of the main Italian volcanoes, however, this spectrum can be even larger. Hazards posed by these eruptions are extremely variable - ranging from scattered ballistic fallout over proximal areas, to extensive ash fallout over very large areas, to the proximal dispersal of PDCs, to the possible emission of lava flows. Consequently, expected damage could be extremely high due to the high exposure and vulnerability of the affected areas.
A special feature of mid-intensity explosive eruptions, which heavily reflects in their impact on environment and everyday life, is the general long duration of these events. In fact, while large scale, catastrophic eruptions generally exhaust their destructive power within a few days, mid-intensity events can last for periods of weeks to several months, alternating phases of intense activity to periods of reduced activity. This behavior, together with the proximity of Italian volcanoes to largely inhabited areas, can produce a dreadful mix in terms of the response of population and authorities living under their shadow.
In the assessment of volcanic hazard and risk, both a long-term and a short-term perspective should be considered. Assessment over a long-term perspective should consider the whole range and probability of occurrence of possible hazards (and risks) related to each type of expected eruptions at a given volcano in a given point. The results can be very useful - especially for territorial planning. Planning the response to a volcanic event is a matter of short-term hazard (and risk) assessment. In this case, defining the eruption scenario in terms of the different types of activity, geographic area and their expected temporal evolution in the course of the eruption, is the basis for effective emergency management - immediately before, during and in the aftermath of an eruption. The study of the different types of eruptions that have occurred in the past for a given volcano like those described in this paper, both on the basis of geological information or of direct observations, is fundamental for this type of analysis.