Anomalous diffuse CO2 emission from the summit crater of Teide volcano and changes of seismic activity in and around Tenerife, Canary Islands

<p>Tenerife is the largest (2,034 km²) and highest (3,718 m) island of the Canarian archipelago and is the only one hosting an active stratovolcano (Teide-Pico Viejo volcanic system). Its structure is controlled by a volcanotectonic rift-system with NW, NE and NS directions, with the Teide-Pico Viejo volcanic system located in the intersection. The last eruption Teide-Pico Viejo volcanic system occurred in 1798 through an adventive cone. Although Teide volcano shows a weak fumarolic system, volcanic gas emissions observed in the summit cone consist mostly of diffuse CO₂ degassing (Hern&#225;ndez et al., 1998; Mori et al., 2001).</p><p>More than 200 diffuse CO₂ efflux surveys have been performed in the summit crater of Teide Volcano during the period 1999-2023. During each survey, diffuse CO₂emission was estimated in 38 sampling sites, homogeneously distributed inside the crater, by means of a portable non dispersive infrared (NDIR) CO₂ fluxmeter using the accumulation chamber method. CO₂ emission rates was estimated after spatial distribution maps constructed by sequential Gaussian simulation (sGs) algorithm. During 23 years of the studied period, CO₂ emissions ranged from 2.0 to 346 t/d. The most remarkable feature of the temporal evolution of diffuse CO₂ emission rate was an important increase that began few weeks after the occurrence of a seismic swarm of long period events was recorded on Tenerife in 2 October 2, 2016, a followed by a general increase of the seismic activity in and around the island (D&#8217;Auria et al., 2019). Several geochemical parameters showed significant changes during &#8764;June&#8211;August of 2016 and 1&#8211;2 months before the occurrence of the October 2, 2016, long-period seismic swarm (Padr&#243;n et al., 2021). Since then, anomalously high diffuse CO₂ emission rates has remained in the crater of Teide. This change might be explained as an input of magmatic fluids triggered by an injection of fresh magma and convective mixing after the 2 October 2016 seismic swarm (D'Auria et al., 2019; Padr&#243;n et al., 2021). This work reflects how useful are the diffuse studies to understand the behaviour of the volcanic system and to forecast future volcanic activity. Monitoring the diffuse degassing rates has demonstrated to be an essential tool for the prediction of future seismic&#8211;volcanic unrest and has become an important monitoring tool to reduce volcanic risk in Tenerife.</p><p>D'Auria, L., et al. (2019). J. Geophys. Res.124,8739-8752</p><p>Hern&#225;ndez, P., et al. (1998). Geophys. Res. Lett. 25, (17) 3311-3314</p><p>Mori, T., et al. (2001). Chem. Geol. 177, 85&#8211;99</p><p>Padr&#243;n, E., et al. (2021). J. Geophys. Res.126,e2020JB020318</p>