Small-scale slope instability on the submarine flanks of insular volcanoes: the case-study of the Sciara del Fuoco slope
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ORIGINAL PAPER
Small‑scale slope instability on the submarine flanks of insular volcanoes: the case‑study of the Sciara del Fuoco slope (Stromboli) Daniele Casalbore1 · Flavio Passeri1 · Paolo Tommasi1 · Luca Verrucci2 · Alessandro Bosman1 · Claudia Romagnoli3 · Francesco Latino Chiocci4 Received: 30 September 2019 / Accepted: 14 March 2020 © Geologische Vereinigung e.V. (GV) 2020
Abstract Small-scale landslides affecting insular and coastal volcanoes are a relevant geohazard for the surrounding infrastructures and communities, because they can directly impact them or generate local but devastating tsunamis, as demonstrated by several historical accounts. Here, a review of such landslides and associated predisposing/triggering mechanisms is presented, with particular reference to the submarine volcanic flanks. We take into account, as a case study, the instability phenomena occurring on the Sciara del Fuoco (SdF, hereafter), a 2-km wide subaerial-submarine collapse scar filled by volcaniclastic products, which form the NW flank of the Stromboli volcano. Because of its steepness (> 30°) and the high amount of loose volcanic material funneled from the summit crater towards the sea, the submarine part of the SdF is prone to instability phenomena recurring at different spatial and temporal scale. Particularly, landsides with a volume of some millions of cubic meters, as the 2002 tsunamigenic landslide, can repeatedly affect the submarine slope. Based on the integration of 11 years (2002–2013) of morpho-bathymetric monitoring of the SdF with geotechnical characterization of volcaniclastic and lava flow materials, stability analyses of the subaerial and submarine slope and previous literature studies, we analyze the role of different triggering mechanisms in controlling the occurrence and size of submarine slope failures at the SdF, such as dykes intrusion as occurred in 2002 or the emplacement of a large delta as occurred in 2007. Keywords Multibeam bathymetry · Slope stability · Tsunamigenic landslide · Lava delta · Time-lapse surveys · Stromboli · Geotechnical modelling
Introduction Volcanic eruptions, landslides and associated tsunamis are recognized as one of the main geohazards on insular volcanoes, and a source of risk for surrounding areas. Several natural disasters (with more than 40,000 casualties only in the last few centuries) have been the direct or indirect result of landslides affecting volcanic flanks, as observed * Daniele Casalbore [email protected] 1
Institute of Environmental Geology and Geo‑Engineering, National Research Council, Rome, Italy
2
Department of Structural and Geotechnical Engineering, Sapienza University, Rome, Italy
3
Department of Biological, Geological and Environmental Sciences, University of Bologna, Bologna, Italy
4
Department of Earth Sciences, Sapienza University, Rome, Italy
at Oshima–Oshima in 1741 and Unzen Volcano in 1792 (Japan) (Satake and Kato 2001; Satake 2007; Brantley and Scott 1993; Sassa et al. 2016), Krakatau in 1883 and Anak Krakatau
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