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Diffuse He/CO2 and H2/CO2 from Cumbre Vieja volcano during the Tajogaite eruption, La Palma, Canary Islands

Gladys V. Melián 1,2,  María Asensio-Ramos1, Eleazar Padrón 1,2, Germán D. Padilla1,2,  Ana Girones1,2, Daniela Taño Ramos1, Laura Trujillo Vargas1, Claudia Ramos Delgado1, Sttefany Cartaya1,2, Mónica Arencibia1,2, Pedro A. Hernández1,2, Nemesio M. Pérez1,2

  • Affiliations: 1Instituto Volcanológico de Canarias (INVOLCAN), Puerto de la Cruz, Tenerife, Canary Islands, Spain.   2Instituto Tecnológico y de Energías Renovables (ITER), Granadilla de Abona, Tenerife, Canary Islands, Spain. 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 235

  • Programme No: 1.6.12

  • Theme 1 > Session 6

Abstract

La Palma (708 km²), located northwest of the Canary Archipelago, is one of the youngest islands (~2.0 Ma) and the most volcanically active according to historical records. On September 19, 2021, a volcanic eruption occurred in the southwestern sector of the Cumbre Vieja rift zone, the most active basaltic volcano in the Canaries. The eruption is considered as a basaltic fissure type, dominated by strombolian activity and with episodic phreatomagmatic pulses, concluding on December 13, 2021. This study focuses on the diffuse emissions of He, H2 and CO2 from the soil atmosphere of Cumbre Vieja, emphasizing the He/CO2 and H₂/CO2 ratios, considering that He and H2 are highly mobile gases. He is chemically inert, radiologically stable, non-biogenic, highly mobile and poorly soluble in water, while H₂ is abundant in volcanic and hydrothermal systems and a key participant in redox reactions within hydrothermal reservoirs. Since 2002, and at each survey, soil gas samples have been regularly collected at ~40 cm depth using a metal probe at 600 sites. He was analyzed using a QMS-type spectrometer, while H₂ and CO2 were measured with a micro gas chromatograph. Spatial distribution maps constructed by sequential Gaussian simulation showed significant increases in He/CO2 and H₂/CO2 ratios before and during seismic swarms (2017-2021). During the eruption, these ratios also increased with the occurrence of volcanic tremor and preceded the peak of diffuse CO₂ emissions. In the absence of visible gas emissions (e.g. fumaroles, plumes), diffuse degassing surveys are essential geochemical tools for volcanic monitoring purposes.