Paroxysmal Explosions, Lava Fountains and Ash Plumes at Etna Volcano: Eruptive Processes and Hazard Implications

Abstract

Lava fountains have a major impact on the local population since they cause ash plumes that spread several kilometers above and hundreds of kilometers away from the crater. Ash fallout is responsible for disrupting airports and traffic on the motorways well beyond the area of the volcano itself, as well as affecting the stability of buildings and causing public health issues. It is thus a primary scientific target to forecast the impact of this activity on local communities on the basis of parameters recorded by the monitoring network. Between 2011 and 2015, 49 paroxysmal explosive episodes occurred at two of Mt Etna's five summit craters: the New South-East Crater (NSEC) and the Voragine (VOR). In this paper, we examine the features of the 40 episodes occurring at the NSEC during 2011-2013, and of the 4 events at VOR in December 2015. We study these paroxysms using geophysical monitoring data, characterize the episodes, and analyse all available data statistically. Our main results are two empirical relationships allowing us to forecast the maximum elevation of the ash plume from the average height of the lava fountain, useful for hazard assessment and risk mitigation. For Etna, and using the examples described in this paper, we can infer that wind speed <10 m s −1 generally results in strong to intermediate plumes rising vertically above the crater, whereas wind speed >10 m s −1 is normally associated with weak plumes, bent-over along the wind direction and reaching lower elevations.

Eruption frequency patterns through time for the current (1999–2018) activity cycle at Volcán de Fuego derived from remote sensing data: Evidence for an accelerating cycle of explosive paroxysms and potential implications of eruptive activity

“…Factors causing the rise in monthly VAAC reports from Fuego since 2015 could include increased reporting from INSIVUMEH and/or pilots to the VAAC, and more frequent imagery available since the launch of GOES-16 in November 2016. -1996(Allard et al, 2006 and (Viccaro et al, 2015Calvari et al, 2018;Giacomoni et al, 2018) also bear some comparison to Fuego's recent activity. In the days before a paroxysmal eruption, the increase of summit explosive activity produces a satellite-detectable increase of thermal anomalies at Fuego's summit (in terms of both intensity and frequency).…”

The VEI 2 Christmas 2018 Etna Eruption: A Small But Intense Eruptive Event or the Starting Phase of a Larger One?

“…It is an open-conduit volcano displaying an almost persistent mild explosive activity from the four summit craters: Bocca Nuova (BN), Voragine (VOR), NE Crater (NEC), and New SE Crater (NSEC; Figure 1). This quiet and low magma output is sometimes interrupted by either frequent, small-volume lava fountaining events [5][6][7][8], or by less frequent but volumetrically more important lava flows from the summit craters or from flank fissures [4,9], with the last flank eruption in 2008-09 [10,11]. The volcano was of interest since early November 2018 due to weak Strombolian activity and small ash emissions from the summit craters of BN, NEC, and NSEC [12], accompanied by an almost constant rate of inflation [13].…”

The Relationship Between Lava Fountaining and Vent Morphology for the 2014–2015 Holuhraun Eruption, Iceland, Analyzed by Video Monitoring and Topographic Mapping

“…At these fissures, a large number of vents may lead to lava fountaining and are thought to be closely related to the geometry and pressure fluctuations at the underlying feeder dike (Witt and Walter, 2017). A lava fountain is a mixture of magmatic gases and fragmented lava, which erupt vertically from a vent as a jet (Calvari et al, 2018). A vent is the surface feature from which the lava fountain occurs (see Figure 1C).…”

“…A vent is the surface feature from which the lava fountain occurs (see Figure 1C). The lava fountain is formed when large amounts of volatiles are rapidly released from the magma while the magma is ascending and the pressure is reducing within the conduit (Calvari et al, 2018).…”