Multi-sensor UAS surveys for rapid volume estimation and geomorphological mapping: the July 2024 eruptive crisis at Stromboli volcano

The July 4–12, 2024 eruption of Stromboli volcano produced significant effusive activity, pyroclastic density currents and a paroxysmal explosion on July 11, resulting in rapid and substantial morphological changes along the Sciara del Fuoco slope and the summit crater terrace. In this work, we present a quantitative assessment of erupted volumes and associated geomorphological modifications derived from multi-temporal Unmanned Aircraft System (UAS) surveys acquired before, during and after the eruptive sequence.

High-resolution Digital Surface Models (DSMs) and co-registered visible and thermal infrared (TIR) orthomosaics, collected between October 2022 and July 2024, were analysed to reconstruct the evolution of lava flows, erosional features and collapse structures. The integration of TIR data proved essential for identifying active eruptive vents and discriminating cooling lava flows from the complex background of the Sciara del Fuoco. Lava volumes were estimated through a combination of DSM differencing and cross-sectional analyses along the main lava channel, integrating pre-eruptive (May 2024), syn-eruptive (11 July 2024) and post-eruptive (18 July 2024) datasets. TIR surveys provided the thermal constraints necessary to isolate distinct contributions from multiple eruptive vents were quantified, allowing a precise separation of early short-lived lava flows from sustained effusive activity preceding and following the paroxysmal explosion.

Results indicate a total subaerial lava volume of approximately 1.3 × 10⁶ m³ (±20%), with the largest contribution associated with lava emitted from vents located within the central channel. A substantial fraction of this volume formed a lava delta at the coastline, implying the presence of an equivalent or larger submerged deposit. DSM comparisons and thermal anomalies also reveal major erosional processes, including the re-excavation of a pre-existing canyon with an estimated material removal of up to ~5 × 10⁶ m³, and a summit area collapse producing a depression of 70–90 m and a missing volume of ~1.9 × 10⁶ m³.

These results highlight the effectiveness of rapid multi-sensor UAS-based surveying for near-real-time volume estimation and morphodynamic analysis during volcanic crises. This approach provides key constraints for mass balance assessments, hazard evaluation and coastal instability monitoring at active volcanoes such as Stromboli.