María Asensio-Ramos1, Gladys V. Melián1,2, Daniel Di Nardo1, Germán D. Padilla1,2, Carla Méndez-Pérez1, Sttefany Cartaya-Arteaga1,2, Pedro A. Hernández1,2, Eleazar Padrón1,2 and Nemesio M. Pérez1,2
¹Instituto Volcanológico de Canarias (INVOLCAN), 38400 Puerto de la Cruz, Tenerife,
Canary Islands, Spain
2Instituto Tecnológico y de Energías Renovables (ITER), 38600 Granadilla de Abona, Tenerife, Canary Islands, Spain
Abstract: Tenerife (2,034 km²), the largest of the Canary Islands, is characterized by a complex volcanic structure controlled by a volcano-tectonic rift system with dominant NW, NE, and NS trends. The intersection of these rifts hosts the Teide-Pico Viejo volcanic complex, which culminates at 3,718 m a.s.l. Teide volcano last erupted in 1798 through an adventive vent of the Teide-Pico Viejo system. Its summit area is affected by persistent visible and diffuse activity, with diffuse degassing representing the main pathway for gas and heat release to the atmosphere. Since 2007 and continuing into 2026, a long-term monitoring program has been carried out at the summit crater of Teide volcano, based on repeated diffuse gas emission surveys (254). This study provides a robust and consistent dataset to evaluate the spatial and temporal variability of the volcanic-hydrothermal system.
Diffuse CO2 and H2S emission rates were directly estimated from field measurements using the accumulation chamber method, and total emission rates were calculated using sequential Gaussian simulations. Concurrently, thermal release was monitored via surface heat flux estimations. During the 2007–2026 study period, diffuse CO2 emissions ranged between 2 and 1257 t·d⁻¹, while H2S emissions fluctuated between 0 and 31 kg·d⁻¹. Surface heat flux values varied from 0.002 to 1.06 MW. From 2007 until late 2016, diffuse degassing and thermal parameters remained low and relatively stable, with CO2 emissions averaging approximately 20 t·d⁻¹. However, from late 2016 onwards, the system experienced a major shift. An initial geochemical anomaly coincided with a prominent hybrid seismic swarm on October 2, 2016, triggering a sustained, multi-year increase in gas discharge and thermal flux that continues to the present. Since 2021, baseline low-emission values are no longer observed. A historical series maximum for CO2 was recorded in September 2023 (1257 t·d⁻¹), followed by a massive escalation in monthly seismic events during February–March 2026, exceeding 1,100 events per month. Variations in diffuse H2S emissions show a nearly synchronous behaviour with CO2, while fluctuations in the CO2/H2S and molar ratios reflect episodic fluid injections and magmatic-hydrothermal interactions closely linked to successive hybrid seismic swarms in 2019, 2022, 2024, 2025, and 2026.
Temporal variations in diffuse CO2, H2S, and surface heat flux provide valuable insights into structural changes and pressure updates within the Teide volcanic system, serving as an effective tool for tracking volcanic unrest. Continuous monitoring of these diffuse parameters has proven essential for improving the understanding of deeper magmatic mechanisms and contributes significantly to volcanic risk assessment and mitigation on Tenerife.
Keywords: Teide volcano; Tenerife; diffuse degassing; carbon dioxide; hydrogen sulphide; surface heat flux; volcanic unrest; hybrid seismic swarms.
Author Profile (first or corresponding author):
Nemesio M. Pérez, INVOLCAN’s Scientist-in-charge, mainly engaged in geochemical research applied to volcano monitoring, surface geothermal exploration, groundwater studies and environmental issues, etc.
E-mail: nperez@iter.es
