ORCID

Abstract

This study analyses the morphological changes induced by eruptive activity at Stromboli volcano (Italy) during and after events occurring during July–August 2019. This period was characterized by intense eruptive activity (two paroxysmal explosions, a two-month-long lava emission, and more intense and frequent “ordinary” explosive activity) that produced significant changes within the region known as Sciara del Fuoco, located on the most unstable, north-western flank of the volcano. Since September 2019, the eruptive activity waned but remained intense, and erosive phenomena continued to contribute to the re-shaping of the Sciara del Fuoco. The morphological changes described here were documented by integrating topographic (PLÉIADES satellite tri-stereo Digital Elevation Models) and multibeam bathymetric data, acquired before, during, and after the paroxysmal events. This allowed the study of the cumulative effect of the different processes and the characterization of the different phases of accumulation/emplacement, erosion, remobilization and re-sedimentation of the volcaniclastic materials.Data acquired at several periods between September 2018 and April 2020, allowed a comparison of the subaerial and submarine effects of the 2019 events. We find evidence of localized, significant erosion following the two pyroclastic density currents triggered by the paroxysmal explosion of the 3 July 2019. We interpret this erosion as being caused by submarine and subaerial landslides triggered by the propagation of pyroclastic density currents down the Sciara del Fuoco slope. Immediately after the explosion, a lava field accumulated on the sub-aerial slope, produced by effusive activity which lasted about two months. Subsequently, the newly emplaced lava, and in particular its breccia, was eroded, with the transfer of material onto the submarine slope. This work demonstrates how repeated topo-bathymetric surveys allowed identification of the slope processes that were triggered in response to the rapid geomorphological variations due to the eruptive activity. The surveys also allowed distinction of whether estimated volumetric losses were the result of single mass-flows or gradual erosive processes, with implications on the related geohazard. Furthermore, this work highlights how submarine slope failures can be triggered by the entry into the water of pyroclastic density currents, even of modest size. These results are important for the development and improvement of an early warning system for tsunami-induced by mass flows, both in Stromboli and for island-based and coastal volcanoes elsewhere, where landslides and pyroclastic density currents can trigger significant, potentially destructive, tsunami waves.

Publication Date

2022-03-01

Publication Title

Geomorphology

Volume

400

ISSN

0169-555X

Acceptance Date

2021-12-20

Deposit Date

2022-11-01

Embargo Period

2022-12-30

Funding

This research was funded by the “Presidenza del Consiglio dei Ministri–Dipartimento della Protezione Civile” (Presidency of the Council of Ministers–Department of Civil Protection), through the UniFi-DPC 2019-2021 agreement (Scientific Responsibility: N.C.) and the CNR-IGAG – DPC agreement 2019-2022 (Scientific responsibility: F.L.C). The contents of this paper represent the authors' ideas and do not necessarily correspond to the official opinion and policies of the “Presidenza del Consiglio dei Ministri–Dipartimento della Protezione Civile” (Presidency of the Council of Ministers–Department of Civil Protection). This research was also funded by the NERC Project “Tsunamigenic mass flows at Stromboli Volcano- analysis and modelling after the 3rd of July events” (NE/T009438/1; Scientific Responsibility: I.M.). The authors are grateful to the editor for managing the publication, to the reviewers for the comments that have improved the manuscript.

Keywords

Digital Elevation Models, PLÉIADES, Repeated bathymetric surveys, Volcano geomorphology, Submarine morphology, Stromboli, Active volcano, Aeolian Archipelago

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