Data collected over nearly a decade reveal active hydrothermal fluid circulation at the Enmedio submarine volcano in the Canary Islands. This activity does not correspond to a volcanic eruption and is unrelated to the seismic swarms recorded in recent weeks. The findings provide key insights into its impact on the biogeochemistry of the deep ocean. The study involved researchers from Geosciences Barcelona (GEO3BCN-CSIC) and the Institut de Ciències del Mar (ICM-CSIC), both CSIC research centres based in Catalonia.
A scientific team from the Spanish Institute of Oceanography (IEO-CSIC), part of the Spanish National Research Council (CSIC), an institution attached to the Spanish Ministry of Science, Innovation and Universities, has obtained the first multidisciplinary evidence of hydrothermal activity at the Enmedio submarine volcano, located at depths exceeding 1,600 metres between Tenerife and Gran Canaria.
Based on geological, geophysical, geochemical and oceanographic data collected over nearly a decade, the results published in the journal Bulletin of Volcanology do not indicate a volcanic eruption, but rather the circulation of hydrothermal fluids. These findings contribute to a better understanding of submarine volcanism in the Canary Islands and its influence on the functioning of the deep ocean.
The Enmedio submarine volcano takes its name from its location between the islands of Tenerife and Gran Canaria, approximately 25 kilometres from the former and 36 kilometres from the latter. Its conical structure forms a seamount whose base, with a diameter of approximately 3.5 kilometres, lies at depths between 2,140 and 2,350 metres, while its summit is located around 1,600 metres below sea level. The study also reveals a significant fracture crossing the volcano from north to south, as well as a large depression on one of its flanks. These geological structures facilitate the release of hot fluids from the interior of the volcano into the surrounding marine environment.
The results, obtained in collaboration with Geosciences Barcelona (GEO3BCN-CSIC), the Institut de Ciències del Mar (ICM-CSIC), the University of Salamanca (USAL) and the University of La Laguna (ULL), confirm that this deep-sea volcano exhibits active hydrothermal fluid circulation. This process occurs when seawater infiltrates fractures in the Earth’s crust, comes into contact with the planet’s internal heat, and subsequently emerges as an extremely hot, mineral-rich solution. “Although this process commonly occurs on the ocean floor, it had barely been studied in the case of the Enmedio volcano,” explains Eugenio Fraile, researcher at IEO-CSIC and lead author of the study.
These emissions not only alter the volcanic substrate but also generate anomalies in the water column, affecting both its chemical composition and the microbial communities inhabiting the deep ocean. For instance, researchers observed that the water column above the summit of the volcano is approximately half a degree Celsius warmer than the surrounding ocean waters.
Furthermore, “rock samples collected during several oceanographic campaigns show alterations rich in iron oxides and filamentous microstructures associated with biological processes, typical of low-temperature hydrothermal environments. These indications are reinforced by high-resolution seismic and bathymetric data, which point to intense alteration of the volcanic substrate in fractured zones,” explains Adelina Geyer, researcher at GEO3BCN-CSIC.
Oceanographic observations conducted over the volcano revealed several anomalies linked to hydrothermal fluid emissions. On the one hand, anomalous temperature and turbidity were detected in the water column between depths of 1,600 and 2,200 metres. On the other hand, researchers observed an increase in microbial abundance and an enrichment of dissolved inorganic nutrients in the water, particularly ammonium, whose concentrations reached four times the normal values.
“The results indicate that hydrothermal activity directly influences the biogeochemical processes of the deep ocean in this area of the archipelago,” states Rafael Bartolomé, researcher at the Institut de Ciències del Mar (ICM-CSIC).
The authors emphasise that the recorded activity does not correspond to a volcanic eruption and is unrelated to the seismic swarms recorded last week in the Las Cañadas del Teide area. The significance of the study lies in the detection of hydrothermal activity at the Enmedio volcano, providing key information for understanding submarine volcanism in the Canary Islands and its interaction with the ocean. “Volcanoes of this type, which represent the majority of volcanism on the planet, play a relevant role in global nutrient cycles, marine biodiversity and the functioning of the deep ocean,” the researchers conclude.
The study was carried out within the framework of several scientific projects led by the Spanish Institute of Oceanography (IEO-CSIC) and is based on data obtained during oceanographic campaigns conducted aboard the research vessels RV Ángeles Alvariño and RV Sarmiento de Gamboa.