17 - Volcanological risk associated with Vesuvius and Campi Flegrei

Abstract

As the eruptive history of Somma–Vesuvius (SV) and Campi Flegrei (CF) gives reasonable reasons to expect eruptions in the future, further analysis of the present delimitation of the Red Zones of both volcanic areas carried out by the Italian Department of Civil Protection (DCP, 1995) is warranted. For SV, the present emergency plan has been devised to protect inhabitants from the possibility of an explosive eruption similar to the ones occurring in the past, such as the 472 CE eruption. However, the new Red Zone (2014) extends up to 7km from the crater, considered as the area of maximum invasion by pyroclastic flows. The peripheral areas of invasion coincide with the administrative limits of the municipalities, which merge, in a questionable way, with sectors that could be invaded by secondary volcanic fall products. Overall, the hazard zone delimitation mostly coincides with the limits of the areas as given in the former 2004 Red Zone delimitation. For CF, the current delimitation of the Red Zone appears overestimated for events of low magnitude, while for a Plinian event (such as the 4.1 ka Agnano–Monte Spina, Volcanic Explosivity Index 4–5 eruption), it is overestimated for pyroclastic flows and underestimated for the pyroclastic fall risk. For CF, it is appropriate to create two distinct risk maps from eruptions of different magnitudes and styles. For risk flows, the only defense for the residential population in the caldera area or at the base and along the slopes of a volcano is to mandate evacuation from the area at greatest risk. Based on this important consideration, we believe that both the models elaborated by DCP should be adjusted to better cope with the levels of risk associated with the next probable worst-case scenario eruptions, both at SV and CF. Finally, the emergency evacuation plan by DCP is completely insufficient, as it is completely missing, both at SV and CF, the building of large escape routes for millions of people to rapidly exit areas at risk. In this extent, there is the misleading message to the population that an eruption could be forecasted in days, if not weeks in advance. The DCP does not explain clearly that this is a possibility, it is not a certainty. In this case, the only way to escape from a catastrophe is, indeed, to have the availability of large escape routes.