Monitoring the morphological changes associated with the 3 July 2019 paroxysmal eruption at Stromboli volcano (Italy) using UAVs

Resolving morphological changes through time using accurate high-resolution digital elevation models (DEMs) is key to understanding active volcanic processes.

UAVs have recently become a powerful platform for aerial data acquisition of DEMs. They permit a rapidly-deployable, low-cost alternative to classical manned aerial photogrammetry, which is especially useful for large-to-medium-scale landscape reconstruction or detailed 3D surveying of features of interests. In addition, the use of UAVs reduces the exposure of operators to volcanic hazards.

We used Unmanned Aerial Vehicles (UAVs) to monitor morphological changes of the Stromboli volcanic edifice following the paroxysmal eruption occurred on 3 July 2019. Specifically, we focussed on the crater terrace area, the Sciara del Fuoco (SdF) slope and the lava flows. At present, end of July 2019, five high-resolution UAV survey campaigns have been performed since May 2019.

Using Structure-from-Motion (SfM) techniques we generated orthophotos and DEMs of the crater terrace area, as well as of the SdF slope. The obtained DEMs and orthophotos have a resolution of 0.2 m. Additional DEMs were extracted from available tri-stereo Pleiades satellite imagery. Furthermore, thermal orthophotos were generated based on UAV surveys with a thermal camera.

The comparison of the multi-temporal DEMs allowed for the evaluation of the height and volume variations due to the 3 July 2019 paroxysmal eruption and to the following strombolian activity and lava flows. The high-resolution orthophotos also proved useful to constrain the distribution of the volcanic deposits emplaced during the 3 July 2019 eruptive activity, while thermal orthophotos can highlight active vents and lava flows.

The combined use of UAVs and SfM techniques are crucial for improved capabilities to collect frequent and low-cost measures on landscape changes associated with dynamic volcanoes. The data collected during these field efforts and the temporal comparisons of the DEMs and orthophotos represent a fundamental contribution to both volcanic hazard assessment and risk mitigation, and can be used to support civil protection operations.