Rapid geomorphological changes on Stromboli volcano monitored by multi-platform remote sensing data

Abstract

Steep-slopes volcanoes are susceptible to rapid geomorphological changes resulting from frequent eruptive activity, leading to non-equilibrium slope conditions. Stromboli, among other volcanoes, undergoes significant geomorphological alterations within short time frames (days to months) due to the accumulation of eruptive deposits, lava flows, and various processes including erosion, transportation, and re-sedimentation of volcaniclastic material. These changes are activated by mass-flows and exogenous phenomena, primarily the action of sea waves. To comprehend the complex interplay between eruptive activity and the morphological response of the volcanic slope, a comprehensive investigation was conducted on events occurring at Stromboli between October and December 2022. This study employed a range of methodologies, including multiplatform remote sensing data, bathymetric surveys, geophysical-volcanological monitoring data, slope stability modeling, and direct observations. The remote sensing data encompassed satellite imagery, airborne single-pass Interferometric Synthetic Aperture Radar (InSAR) data, and Unmanned Aerial System (UAS) topographic data, complemented by ground-based and spaceborne InSAR displacement measurements, and very-high-resolution visible optical orthophotographs. The primary objective of this study is to elucidate the mutual influences between eruptive activity and the morphological response of the volcano slope. Stromboli, with its persistent eruptive activity and dynamic, steep-slope volcanic flank, serves as an ideal case for such investigations. The findings of this study illustrate how the inherent characteristics of the material comprising the slope (a heterogeneous accumulation of volcanic deposits and thin lava flows), along with the steep slope angle, constitute crucial factors affecting slope stability, particularly in coastal regions. The impact of overloading from lava flows and mass-flows, combined with undercutting effects resulting from erosion, especially along the coast, acts as triggers for mass-flow phenomena. The formation of mixtures between lava flows and volcaniclastic deposits plays a role in generating glowing mass-flows, attributing them to what is commonly known as deposit-derived Pyroclastic Density Currents (PDCs). The findings aim to enhance our understanding of the mechanisms leading to the instability of volcaniclastic deposits, resulting from the interaction between erosive phenomena and the overloading of slopes by lava flows and mass-flows. The obtained results can be helpful in estimating the hazard induced by geomorphological processes in contexts like Stromboli, including the potential triggering of landslides and deposit-derived PDCs that may, in turn, lead to tsunamis.