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

Annalisa Cappello,Alexis Hérault,Claudia Corradino,Ciro Del Negro,Giuseppe Bilotta,Gaetana Ganci

doi:10.3389/feart.2019.00213

Annalisa Cappello, Alexis Hérault + Show 4 more

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https://doi.org/10.3389/feart.2019.00213

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Abstract

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 southern flank 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 Pleiades-derived topography updated to 2016, we also present the new hazard map from lava flow inundation in the SEC area, establishing an important basis for mitigation decisions. Our SEC hazard map covers an area of ~15 km2, with lava flows spreading both towards south-west and south-east, reaching the lowest altitude of about 1,500 m a.s.l.

Highlights

Central or composite volcanoes are often characterized by persistent activity at the summit crater
We extend the preliminary statistical analysis and lava flow hazard mapping presented in a previous study related to the 12–13 January 2011 eruption of South-East Crater (SEC) (Vicari et al, 2011b), and revise the catalog of SEC/New Southeast Crater (NSEC) eruptions of the last 20 years (Behncke et al, 2006; Del Negro et al, 2013a; Ganci et al, 2018; Cappello et al, 2019)
From the accurate analysis of the distribution of eruption durations and lava volumes, we identified a time/volume trend associated with different significant periods, and estimated new statistics of occurrence for each class of expected eruptions

Summary

Introduction

Central or composite volcanoes are often characterized by persistent activity at the summit crater. The geological record of some active volcanoes, including calderas (e.g., Sakurajima, Aso, Okmok, Campi Flegrei) and large edifices (e.g., Mauna Loa, Etna) has shown a more complicated eruptive pathway (Rivalta et al, 2019). In particular, has experienced one of the Changing Eruptive Styles at Etna’s SEC best-documented shifts in the location of volcanism in the summit area. Over the last 120 years, the main eruptive activity was initially located at the central crater, migrated to the North-East Crater (NEC) and later to the SouthEast Crater (SEC), as the new summit craters were formed (Cappello et al, 2013). Etna’s summit eruptions are often accompanied by emission of lava flows, which represent the greatest hazard for the touristic facilities located above 1,800 m of elevation (Rifugio Sapienza and Piano Provenzana areas, see Figure 1). Some of them are based on a qualitative analysis of historical eruptions (e.g., Andronico and Lodato, 2005; Behncke et al, 2005), while modern assessment combines geological history with deterministic or probabilistic computational models (e.g., Crisci et al, 2008; Favalli et al, 2011; Connor et al, 2012; Del Negro et al, 2013b)

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