Drone-based aeromagnetics combined with magnetotellurics to investigate volcanic structures at the Tajogaite volcano, La Palma Island.

Our regional aeromagnetic study of La Palma Island (Canary Islands), based on conventional airborne data, successfully imaged the island's large-scale magnetic structure. While the magnetic data provided a robust regional framework, they lacked the spatial resolution required to investigate shallow volcanic structures and post-eruptive thermal anomalies following the 2021 eruption. Therefore, a high-resolution, drone-based aeromagnetic survey was conducted over the Tajogaite volcano, targeting the area most affected by the eruption.

The survey was carried out in June 2024 and March 2025 using the DJI Matrice 210 RTK and DJI Matrice 300 RTK with a dual-sensor fluxgate magnetometer system sampling at 200 Hz. Constant-altitude flights covered an area of ~7 km², with N-S-oriented survey lines spaced 30–60 m apart and tie lines spaced 150–200 m in the perpendicular direction. The drone flew in a lawnmower pattern, and we acquired high-altitude calibration flights in low magnetic gradient conditions to quantify and correct the magnetic measurements.

Data curation involved several processing stages, including removing inconsistent flight tracks and compensating for platform-induced noise using the calibration data. The total magnetic intensity map and anomaly were obtained by applying gridding and smoothing to the signal and then removing the IGRF model.

The resulting high-resolution magnetic anomaly map provides critical detail of the shallow magnetic structure of the Tajogaite volcanic edifice, allowing the identification of fault-controlled anomalies, low-susceptibility zones (after the 3D modelling of the data) related to high temperatures, and a potential shallow magma pathway.

Additionally, we acquired new magnetotelluric data along a North-South oriented profile, perpendicular to the inferred still-hot dyke direction. This enabled us to construct a 3D electrical resistivity model that correlates with the magnetic model to further analyse this area, which is likely to be related to the final stage of magma ascension.

This multidisciplinary research emphasises the importance of drone-based surveys in investigating active volcanic environments and post-eruptive dynamics on a local scale.