Analysing how the properties of tephra from the 2021 Tajogaite eruption affected the environment in La Palma, Canary Islands

The 2021 Tajogaite eruption on La Palma was the most destructive volcanic event in recent Canary Islands history, lasting 85 days and producing extensive lava flows and tephra deposits. Beyond its immediate impacts on infrastructure and air quality, the eruption raised critical questions about how tephra properties influence environmental hazards and public health. Fine ash particles (<10 µm) pose respiratory risks, while soluble salts and trace elements leached from lapilli and ash-sized pyroclastic material can affect water and soil quality. Understanding these processes is essential for volcanic risk management and environmental protection.

To address these issues, we collected and analysed tephra samples throughout the eruption, applying dynamic image analysis (DIA), scanning electron microscopy (SEM), X-ray diffraction, and batch leaching tests. DIA proved highly effective compared to laser diffraction for detecting ultrafine particles relevant to health hazards. SEM revealed diverse morphologies, including fluidal shards and Pele’s hairs, and identified salts such as fluorides and sulfates on particle surfaces. Leaching experiments showed the rapid release of sulfates, chlorides, fluorides, and nitrates, with potential implications for groundwater and ecosystems. multivariate statistical analysis linked these soluble phases to magmatic volatiles and eruptive dynamics, which evolved through six stages marked by lava compositional changes and intermittent phreatomagmatic activity.

Our findings show that tephra from mafic eruptions, though less explosive than silicic events, can have a significant environmental impact. These results inform hazard assessments, guide civil protection strategies, and highlight the need for continuous monitoring of water quality and air pollution during and after eruptions. Ultimately, this research supports better preparedness for future volcanic crises and contributes to safeguarding public health and ecosystems.

This research was supported by the Canary Islands Smart Specialisation Strategy (RIS3 Extended 2021–2027) through the NEVA2 project (ProID2024010012), funded by the Canary Islands Agency for Research, Innovation and Information Society (ACIISI) and co-funded by the European Union under the Canary Islands ERDF Programme 2021–2027. Additional support was provided by the MESVOL Project (SD RD 1078/2021 LA PALMA) funded by the Spanish Ministry of Science and Innovation, the LAJIAL Project (PGC2018‑101027‑B‑I00; MCIN/AEI/10.13039/501100011033 and ERDF “A way of making Europe”), Project PID2022‑139990NB‑I00 (MCIU), and a pre‑doctoral fellowship (FPU20/05157). Institutional support was provided by the GEOVOL research group  (iUNAT, ULPGC) and Structure and Dynamics of the Earth (Generalitat de Catalunya, 2021 SGR 00413).