Long-term volcanic unrest in Tenerife (Canary Islands): Ground deformations 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 characterised 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.The IGN currently operates a geodetic monitoring network on Tenerife consisting of 16 continuous GNSS (cGNSS) stations, the first installed in 2007, together with other geodetic instrumentation used continuously for the monitoring of ground deformation associated with volcanic activity. These ground-based observations are complemented by the analysis of InSAR data, allowing the detection of spatially distributed deformation patterns. Analysis of the geodetic data reveals the onset of slow, low-magnitude ground deformation affecting the central sector of the island since mid-2023. This deformation pattern had not been observed in previous years and coincides in time with the seismic and geochemical anomalies detected by the IGN, suggesting a common magmatic origin. Time series derived primarily from cGNSS and InSAR analysis indicate an extensional deformation affecting the central part of Tenerife, with horizontal velocities of the order of a few millimeters per year. Focusing on the central sector of the island, and considering a NW–SE-oriented axis, stations located to the north of this axis show northwestward horizontal displacements, whereas those to the south exhibit southeastward movements, consistent with a regional extension pattern. To date, no significant vertical deformation associated with the observed horizontal displacements has been identified. This absence may be explained by several factors, including the higher noise level of the vertical component due to atmospheric effects and/or the influence of the island’s aquifer system, as well as the possible influence of the island’s geological structures on the observed deformation, which may locally modify or redistribute strain. The analysis of the deformation processes developed since 2023, together with their temporal evolution, provides essential constraints for monitoring the ongoing volcanic unrest on Tenerife.