Continuous monitoring of diffuse CO2 emission from Cumbre Vieja volcano: early evidences of magmatic CO2 surface arrival

Cumbre Vieja volcano is the last stage in the geological evolution of La Palma Island (Canarian Archipelago, Spain). The volcanic activity of La Palma has taken place exclusively in Cumbre Vieja in the last 123 ka, and has remained in volcanic quiescence in the last 50 years. After the occurrence of several seismic seismic swarms since 2017, a volcanic eruption began at Cumbre Vieja volcano on September 19, 2021, and resulted in the longest volcanic event since data are available on the island. The eruption lasted for 85 days and 8 hours and lava flows covered 1,219 hectares. As part of the volcano monitoring program of Cumbre Vieja, diffuse degassing of CO₂ has been continuously monitored since 2005 at the southernmost part of Cumbre Vieja according to the accumulation chamber method. The monitoring site (LPA04) was selected because it shows anomalous diffuse CO₂ degassing emission values with respect to the background values that had been measured in different surveys (Padrón et al., 2015). Meteorological and soil physical variables are also measured in an hourly basis and transmitted to ITER facilities about 150 Km far away. Since its installation, CO₂ emissions ranged from non-detectable (<1.5 gm^-2d^-1) to 1,464.0 gm^-2d^-1. The time series was characterized by a strong variability in the measured values that are modulated mainly by the atmospheric and soil parameters. Soil moisture is the monitored parameter that explains the highest variability of the data, being the dry season (spring y summer) the period with the highest observed diffuse emission values. This behavior in the time series changed after 2017 as an increasing trend was observed in a good temporal agreement with the increase of seismic activity recorded. Diffuse CO₂ emission values showed a sustained increase reaching maximum values (up to 890 gm^-2d^-1) before de eruption onset. The observed diffuse CO₂ emissions trend in the LPA04 geochemical station was useful to record the arrival of magmatic CO₂ due to the occurrence of an upward magma migration beneath La Palma Island that caused the 2021 eruptive event.

Padrón et al., (2015). Bull Volcanol 77:28. DOI 10.1007/s00445-015-0914-2