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Volcano monitoring of El Hierro island (Canary Islands, Spain) through diffuse CO2 degassing surveys

Héctor de los Ríos 1,2, Gladys V. Melián1,2, Alba Fernández1, Patricia Hernández1, Daniel Di Nardo1, Eleazar Padrón1,2, María Asensio-Ramos1, Germán D. Padilla1,2, Victoria J. Leal1,2, 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: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 257

  • Programme No: 3.17.31

  • Theme 3 > Session 17

Abstract

El Hierro (278 Km²), the youngest and westernmost island of the Canary archipelago, sits on an ocean floor 3.5 km deep and rises 1.5 km above sea level. Formed ~1.12 million years ago through rapid constructive and destructive volcanic processes, the island experienced a submarine eruption 2 km off the southern part of the island from October 2011 to March 2012, being the first volcanic eruption fully monitored from its onset in the Canary Islands. Diffuse degassing studies have been an important volcano monitoring tool at El Hierro, since there are no current visible volcanic gas emissions on the surface. Annual surveys of diffuse CO₂ emissions began in 1998 and were intensified during the 2011--2012 unrest. Each survey involves 600 sampling sites where soil CO₂ efflux is measured using the accumulation chamber method, and soil gas samples are collected at 40 cm depth for chemical and isotopic analysis of CO₂. During the preeruptive and eruptive periods, the diffuse CO2 emission released by the whole island experienced two significant increases: 2 weeks before the onset of the submarine eruption and several days before an increment in the amplitude of the tremor signal. In the latest survey (summer 2024), CO₂ values ranged from non-detectable to 44 g·m⁻²·d⁻¹. the diffuse CO₂ emission was estimated in 699 ± 32 t·d⁻¹, slightly higher than the background average of 410 t·d⁻¹. These findings highlight the importance of discrete CO₂ monitoring for enhancing early warning systems in volcanic surveillance programs.