Changing Eruptive Styles at the South-East Crater of Mount Etna: Implications for Assessing Lava Flow Hazards

The formation of new craters or cones in active volcanoes can influence the style
and frequency of eruptions and may also significantly affect volcanic hazard. Here, we
explore how the lava flow hazard changed on Mount Etna in the past 20 years, while
continuous shifts in the location of volcanism in the summit area were experienced.
The summit area of Mount Etna has undergone large morphological variations since the
formation of the South-East Crater (SEC) in 1971 and New Southeast Crater (NSEC)
in 2007, which have also marked a notable change in the eruptive activity of the
volcano. Indeed, in less than 50 years, the SEC area has been the source of more than
two hundreds of eruptions characterized by the emission of lava fountains, pyroclastic
material, and short-lasting lava flows, which are the greatest hazard presented to the
tourist facilities on the flanks of Etna. Here we statistically analyze the main quantitative
parameters (i.e., duration and lava volume) of 154 well-documented eruptive events
occurred since 1998 with the aim of characterizing the time-volume evolution of the
SEC activity. From 1998 to 2018, we find a cumulative volume of 135 millions of
cubic meters that gives a long-term output rate of 0.21 m3/s, with a remarkable
change in the eruptive style (longer and more voluminous events) starting from 2011.
Taking advantage of this analysis and lava flow simulations run on a Pléiades-derived
topography updated to 2016, we also present the new hazard map from lava flow
inundation in the SEC area, which is quite different from the hazard map produced in
2011, covering an area of 15 km2 and reaching the lowest altitude of about 1,500 m
a.s.l. This map establishes an important basis for mitigation decisions and long-term
territorial planning, allowing key at risk areas to be rapidly and appropriately identified.