Uncovering the eruptive patterns of the 2019 double paroxysm eruption crisis of Stromboli volcano

Abstract

In 2019, Stromboli volcano experienced one of the most violent eruptive crises in the last hundred years. Two paroxysmal explosions interrupted the ‘normal’ mild explosive activity during the tourist season. Here we integrate visual and field observations, textural and chemical data of eruptive products, and numerical simulations to analyze the eruptive patterns leading to the paroxysmal explosions. Heralded by 24 days of intensified normal activity and 45 min of lava outpouring, on 3 July a paroxysm ejected ~6 × 107 kg of bombs, lapilli and ash up to 6 km high, damaging the monitoring network and falling towards SW on the inhabited areas. Intensified activity continued until the less energetic, 28 August paroxysm, which dispersed tephra mainly towards NE. We argue that all paroxysms at Stromboli share a common pre-eruptive weeks-to months-long unrest phase, marking the perturbation of the magmatic system. Our analysis points to an urgent implementation of volcanic monitoring at Stromboli to detect such long-term precursors.

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].…”

“…A similar phenomenon occurred on the slope of the Rina Grande collapse depression where the sudden accumulation in the Pizzo area generated a gravel flow that reached 600 m a.s.l. (Figure S10; see also text and supplementary material in Andronico et al [34]). Outside of the studied area, a similar phenomenon occurred throughout the effusive phase on the western sector of the SdF and up to the shoreline, in this case with a different origin: the accumulation of material originating from rockfalls at the lava flow front (Figure S9).…”

“…On 9 June 2019, a more sustained activity resumed with a high HEF, and explosions characterized by a high to very high intensity. This more energetic activity culminated, on 25 June, with a major explosion that involved the central area [33,34].…”

“…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.…”

“…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. Volcanic products from the laterally directed explosions and the collapse of the external crater terrace generated two pyroclastic currents that travelled down the SdF and then advanced on the sea for about 1 km from the coastline, generating a tsunami with a maximum wave height of~40 cm [41].…”