Tracking magma degassing dynamics during the 2021 Tajogaite eruption using daily OP-FTIR measurements

• MARÍA ASENSIO-RAMOS ^[3] ; ANA PARDO COFRADES ^[1] ; MIKE BURTON ^[1] ; ALESSANDRO LA SPINA ^[2] ; PATRICK ALLARD ^[2] ; JOSÉ BARRANCOS ^[3] ; CATHERINE HAYER ^[1] ; BENJAMIN ESSE ^[1] ; LUCA D'AURIA ^[3] ; PEDRO A. HERNÁNDEZ ^[3] ; ELEAZAR PADRÓN ^[3] ; GLADYS V. MELIÁN ^[3] ; NEMESIO M. PÉREZ ^[3]
  1. [1] University of Manchester

     University of Manchester

     Reino Unido

     
  2. [2] Istituto Nazionale di Geofisica e Vulcanologia

     Istituto Nazionale di Geofisica e Vulcanologia

     Roma Capitale, Italia

     
  3. [3] Instituto Volcanológico de Canarias (INVOLCAN)

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• Localización: Cosmológica, ISSN 2792-7423, Nº. Extra 1 (Conferencia Internacional: Erupción del Tajogaite (Los Llanos de Aridane, noviembre de 2025)), 2025, págs. 289-291
• Idioma: inglés
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  • Between September and December 2021, the Cumbre Vieja volcano on La Palma (Canary Islands) produced an 85 day explosive effusive eruption of basanitic magma after over fifty years of quiescence. Explosive activity was concentrated at the vents of the newly formed Tajogaite cone, where rapid shifts occurred between vigorous lava fountains, Strombolian bursts, and ash rich explosive jets. Simultaneously, lava spattering and effusive flows emerged from lower flank vents. From October 3, 2021, until the end of the eruption, daily measurements of volcanic gas composition were carried out using open path Fourier transform infrared (OP FTIR) spectroscopy, enabling real time tracking of degassing associated with both explosive and effusive activity (Asensio-Ramos et al., 2025). Results revealed a clear compositional dichotomy between the two degassing regimes. Explosive emissions displayed extremely high CO2/SO2 and CO2/HCl molar ratios, which correlated closely with seismic tremor intensity. In contrast, effusive outgassing exhibited much lower CO2/SO2 ratios and relatively higher fractions of H2O, sulfur, and chlorine.

    Ratios of CO/COS/CO2 were consistent with petrological evidence for an oxidized magmatic system, favoring sulfur solubility and late stage SO2 release. Integrating these findings with eruption rates and petrological data indicated gas fractionation at a very shallow conduit branching beneath the Tajogaite cone. Through this system, pre exsolved CO2 rich gases were discharged via the summit vent, while CO2 depleted gases and most of the magma exited through lateral effusive branches...