Long-term volcanic unrest in Tenerife (Canary Islands): Seismovolcanic signals

Tenerife, the largest and most populated island of the Canary Islands, hosts a complex volcanic system characterized by rift-related activity, long-lived magma reservoirs, and an active hydrothermal system. Although historically characterized by relatively sporadic eruptive activity, the island’s volcanic system remains active, as evidenced by historical eruptions, such as those of Siete Fuentes (1704) and Chinyero (1909), as well as the 2004-2005 unrest. After more than a decade of relative quiescence, the Instituto Geográfico Nacional (IGN) began detecting seismic and geochemical anomalies in 2016 and a continuous slow deformation in 2023, which has persisted to the present.

In this contribution, we analyze the temporal and spatial evolution of seismicity recorded by the IGN seismic network between 2016 and 2025. During this period, at least six seismic swarms have been identified, dominated by deep long-period and hybrid earthquakes. These swarms exhibit significant variability in their frequency content, duration, recurrence, and temporal evolution, indicating changes in the underlying physical processes driving the seismicity. In addition to these swarms, several seismic clusters have been detected, characterized by variations in seismic rate, depth distribution, and migration patterns, and showing a strong spatial correlation with major geological and structural features of the volcanic edifice, as high- and low-density bodies in the island.

The observed seismic patterns show temporal and spatial correlations with independently detected geochemical anomalies (e.g., diffuse gas emissions) and geodetic signals derived from GNSS and InSAR observations. This multi-parameter coherence suggests episodic pressurization processes occurring at different crustal levels beneath the island, likely involving both magmatic and hydrothermal components. The progressive increase in the frequency and persistence of these signals over the last decade indicates an acceleration of the unrest processes, pointing to a dynamically evolving volcanic system rather than isolated or transient perturbations.

The combined seismic, geochemical, and geodetic observations are consistent with the emplacement and accommodation of magmatic intrusions at multiple crustal depths, inducing stress transfer, fluid migration, and sustained seismicity. These results highlight the complex interplay between magma, fluids, and tectonic structures in controlling long-term unrest at intraplate ocean-island volcanoes.

Our findings emphasize the critical role of continuous, high-resolution, multi-parameter monitoring for the early detection and interpretation of subtle changes in Tenerife’s volcanic state. This study contributes to improving the conceptual models of prolonged volcanic unrest and provides valuable insights for hazard assessment and operational volcanic surveillance in similar volcanic settings.