Monitoring diffuse CO2 emissions by means of an automatic geochemical station at Cumbre Vieja volcano, La Palma, Canary Islands.

La Palma Island (708.3 km²) is located at the north-west and is one of the youngest (~2.0My) of the Canarian Archipelago. Volcanic activity has taken place exclusively at the southern part of the island, where Cumbre Vieja volcano, the most active basaltic volcano in the Canaries, has been constructed in the last 123 ky. Cumbre Vieja has suffered seven eruptions in the last 500 years, being the last in 1971 (Teneguía volcano). Since the last eruptive episode, Cumbre Vieja volcano has remained in a relative seismic calm that was interrupted on October 7th and 13rd, 2017, by two remarkable seismic swarms with earthquakes located beneath Cumbre Vieja volcano at depths ranging between 14 and 28 km with a maximum magnitude of 2.7. The frequency of these seismic episodes increased in 2020 with the occurrence of five more seismic swarms

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 has changed after 2017 as an increasing trend in being observed in a good temporal agreement with the increase of seismic activity recorded. The observed diffuse CO₂ emissions trend in the LPA04 geochemical station support the occurrence of an upward magma migration towards a subcrustal magma reservoir beneath La Palma island.

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