Diffuse CO2 and H2S degassing monitoring at the summit crater of Teide volcano, Tenerife, Canary Islands

Tenerife, the largest and highest island in the Canarian archipelago, houses the active Teide-Pico Viejo volcanic system. Its structure is shaped by a rift-system with various directions intersecting at this volcanic system. The system’s last eruption in 1798 expelled approximately 12 million m³ of lava across a three-month period, resulting in the formation of a distinct black surface that contrasts sharply with the surrounding. While Teide volcano exhibits a faint fumarolic system, the observed volcanic gas emissions mainly consist of diffuse CO2 degassing.Spanning from 1999 to 2024, over 200 surveys meticulously assessed CO2 and H2S emissions across 38 strategic sites within the Teide Volcano's summit crater. Portable fluxmeters, equipped with CO2 and H2S sensors, estimated emission rates via the accumulation chamber method. These rates fluctuated between 2.0 and 1,257 tons per day over a 25-year span. Following a seismic swarm in October 2016, there was a general marked escalation in CO2 and H2S emissions, aligning with heightened seismic activity. This shift led to relatively high CO2 emissions, possibly attributed to fresh magma injection and convective mixing catalyzed by the seismic swarm.It is pertinent to note a distinct event in the latter half of 2023, marked by a notable surge in CO2 and H2S emissions (ranging between 222 and up to 1,257 tons/day for CO2, and 40 to 270 tons/day for H2S), despite a relatively unchanged seismic activity compared to preceding years.This study highlights the value of examining diffuse degassing in understanding volcanic behavior and forecasting potential volcanic activity. Monitoring these emissions has become a crucial tool in predicting seismic and volcanic unrest, contributing significantly to mitigating volcanic risks in Tenerife.