Shallow conduit dynamics fuel the unexpected paroxysms of Stromboli volcano during the summer 2019

Abstract

Open conduit basaltic volcanoes can be potentially hazardous as the eruptive activity may turn suddenly from a steady state to highly explosive. Unexpected changes in explosion intensity are recurrent at Stromboli volcano, where major explosions and large-scale paroxysms sometimes break off the ordinary, Strombolian activity with little or no warning. Two powerful paroxysmal eruptions took place at Stromboli volcano during the summer 2019, causing widespread fires, consistent damages across the island, injuries and one fatality. Prediction of similar events is really challenging for the modern volcanology, though models propaedeutic to early-warning monitoring systems are not properly assessed yet in many volcanoes worldwide. Here, we present a multi-parametric study that combines petrological and geophysical data to investigate processes generating the two paroxysms. The time information derived by Li enrichments in plagioclase crystals correlates with tilt time series derived by seismometers installed on the island, highlighting the dominant role of shallow conduit processes in triggering the 2019 paroxysmal activity. Our dataset conceives a mechanism of gas slug formation and fast upward migration that finally triggered the eruptions in very limited times. The proposed model questions our capability to forecast such kind of paroxysms in times that are rapid enough to allow mitigation of the associated risk.

Characterising vent and crater shape changes at Stromboli: implications for risk areas

“…Stromboli, Italy; Villarica, Chile; Whakaari/White Island, New Zealand; Yasur, Vanuatu) are famous for the accessibility of observational points but infamous for unheralded strongly explosive events [e.g. Dempsey et al 2020;Giordano and De Astis 2021;Viccaro et al 2021]. Depending on eruption frequency, recurrent up-close surveys of the active crater area can reveal high(er) temporal resolution information on changes.…”

Unoccupied Aircraft Systems (UASs) Reveal the Morphological Changes at Stromboli Volcano (Italy) before, between, and after the 3 July and 28 August 2019 Paroxysmal Eruptions

“…The differences mentioned above could be the results of structural changes that occurred in the shallower portion of the central conduits after the 2007 eruption [32]. However, analyzing the magmatic and structural processes involved in the 2019 eruptions and leading to further interpretations is beyond the scope of this paper and the reader is referred to the recent literature for additional details [27,34,38,39,68,69].…”

“…The activity maintained very high frequency and intensity levels until, a few days later, the first paroxysm (3 July 2019) deeply disrupted the crater terrace and part of the upper portion of the SdF (Figure 1). This event involved both the north (hereafter N) and the central-south (hereafter CS) crater areas [27,[34][35][36][37][38][39]. The paroxysmal eruption generated an eruptive plume rising 6-8 km above the island's summit (924 m a.s.l., Vancori peak) [34,38], while the incandescent pyroclasts set fire to vegetation on the flanks of the volcano, resulting in a fire-damaged area of 39% of the total area of the island [40] and about 70% of the vegetated areas.…”

“…On 28 August 2019, the second paroxysmal eruption occurred, again modifying the morphology of the summit area and producing an eruptive column estimated up to 6 km above the summit [27,38,39,[43][44][45]. Pyroclasts from the eruption and debris from the collapsed rim of the CS area contributed to the generation of a pyroclastic current that again travelled down the SdF and out to sea.…”

Using dense seismo-acoustic network to provide timely warning of the 2019 paroxysmal Stromboli eruptions

“…Unexpected changes in explosion intensity at Stromboli are due to the dominant role of shallow conduit processes triggering paroxysmal activity 21 . On July 3rd and August 28th 2019, the volcano produced such paroxysms, followed by intense explosive and intermittent effusive activity.…”