Diffuse CO2 emission from NERZ and NWRZ Tenerife volcanic systems, Canary Islands

Tenerife (2,034 km²), the largest island of the Canarian archipelago, is characterized by three volcanic rifts NW-SE, NE-SW and N-S oriented, with a central volcanic structure, Las Cañadas caldera, hosting Teide-Pico Viejo volcanic complex. The North-West volcanic Rift Zone (NWRZ, 72 km²) is one of the youngest and most active volcanic systems of the island, where three historical eruptions (Boca Cangrejo in the 16th Century, Arenas Negras in 1706 and Chinyero in 1909) have occurred. The North-East volcanic Rift Zone (NERZ, 210 km²) has showed one historical eruptive activity during 1704 and 1705 across 13 km of fissuraleruption (Siete Fuentes-Arafo-Fasnia eruption). As part of the volcano monitoring program of NWRZ and NERZ, diffuse CO₂ degassing surveys have been carried out yearly since 2000 at the NWRZ and since 2001 at the NERZ. In-situ measurements of CO₂ efflux from the surface environment were performed according to the accumulation chamber method using a portable non-dispersive infrared (NDIR) sensor. Soil CO₂ efflux contour maps were constructed to identify spatial-temporal anomalies and to quantify the total CO₂ emission using the sequential Gaussian simulation (sGs) interpolation method. Previous studies in the NWRZ has shown a temporal correlation between long-term variations in the diffuse CO₂ output with the occurrence of a seismic unrest in 2004 and the 2016 seismic swarm (Hernández et al., 2017). The last diffuse CO2 emission survey performed in the survey in the NWRZ in 2022 showed values between non-detectable ones and 32.1 g·m^-2·d^-1, with an average value of 5.6 g·m^-2·d^-1 for NWRZ. In the case of the NERZ, the last diffuse CO₂ emission survey performed in 2022 showed values ranging between non-detectable values and 59.1 g·m2·d^-1, with an average value of 6.7 g·m^-2·d-1. Diffuse CO₂ emission rate were estimated in 360 ± 15 t·d^-1 for NWRZ and 1,444 ± 42 t·d^-1 NERZ were obtained in the 2022 surveys. The normalized CO₂ emission value by area was estimated in 5 t·d^-1·km^-2 for NWRZ and in 6.9 t·d^-1·km^-2 for NERZ. Temporal evolution of diffuse CO₂ emission at both NWRZ and NERZ of Tenerife shows a clear relationship with the volcano seismic activity in and around Tenerife Island. These geochemical observations are clear evidence of changes of processes operating deep in the hydrothermal-magmatic system of Tenerife.

Hernández et al. (2017). Bull Volcanol, 79:30, DOI 10.1007/s00445-017-1109-9.