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We present first results on the continuous monitoring of the 2021 La Palma volcanic eruption (Canary Islands, Spain), from September 2021 to December 2021. During the eruption we installed a 8 level 3-component geophone string and 15 m spacing between geophones in Las Manchas within the restricted area and less than 2 km away of the volcanic edifice. The string was installed on the ground surface, in a straight line pointing towards the volcano. The 24 channels were sampled at 250 Hz, and data acquisition was performed in real-time and continuously till the end of the eruption with occasional minor gaps. The resulting seismoacoustic dataset is a sample of elastic energy propagating in both the subsurface and the atmosphere, allowing us to improve our understanding of the eruptive subsurface and subaerial processes. We use these seismoacoustic records to identify and characterize the different phases and signals of the volcanic activity. For the first analysis of the dataset we performed the calculation and graphing of spectrograms during the acquisition. We identify eruptive signals and correlate them with different events that can be directly observed on the basis of frequency content and relative timing. Explosive events like those derived from destruction of conduit plugs and ash-rich plumes emission, ash-rich explosions, volcanic lightning and degassing events are being analysed.Finally, we study the correlation of seismic and seismoacoustic records for the same event by comparing with seismic data recorded on land stations. Results show that a good correlation exists between seismic and seismo-acoustic data for the main activity observed in the surface: the activity at the various vents and events like episodes of ash emission and bursts, indicating that this methodology can be successfully applied to monitor remote eruptions. Coupled seismoacoustic observations have turned out to be useful because they provide a comprehensive record of subsurface and subaerial eruptive activity.

In 2017, La Palma Island entered a state of volcanic unrest, with nine pre-eruptive seismic swarms detected by the seismic monitoring network of the Instituto Geográfico Nacional (IGN) up to 2021, most of the events occurring at depths of 20-35 km. During this period, the IGN geochemical network detected significant changes in deep gas emissions. On 11 September 2021, the last and most energetic pre-eruptive unrest began with more than 1500 earthquakes located at 10-15 km depth and migrating upwards, accompanied by ground deformation with up to ~20 cm vertical inflation detected by the IGN deformation network (GNSS, Insar, tiltmeters). On 19 September 2021 at 15:08 UTC, a volcanic eruption began on the western flank of Cumbre Vieja in El Paso village. This was the first eruption in the island after 50 years of quiescence.The 2021 eruption has lasted almost three months, ending on 13-14 December 2021 (last activity at the time of this writing). It began as a SE-NW fissural eruption and rapidly evolved to construct a main volcanic edifice up to ~200 m high, with several craters partially overlapping in a SE-NW direction, and later it constructed a secondary cone with a horseshoe shape open to the NE. The eruptive activity has been both strombolian and effusive, sometimes alternating and many times simultaneous with different behaviour at different emission points, a typical situation being strong degassing and strombolian jet and ash emission from an upper crater simultaneous to emission of fluid lavas and lava lake formation and periodical overflowing from a lower crater. Significant volcanic plumes have reached up to 8500 masl (typical value of 3000-3500 masl), and a large set of successive basanitic lava flows has been emitted to the west, developing a volcanic lava-fan covering ~12 km2 (~3000 buildings) and reaching the sea at several points along the western coast of La Palma.During the eruption, the IGN geochemical monitoring network included four stations measuring diffuse radon/thoron in soil, one station measuring diffuse CO2 flux in soil, an infrared thermal camera coupled with a visual camera and six water sampling points, regularly sampled for water composition, dissolved radon content, total and isotopic composition of dissolved gas (5 points) and free gas (1 point). Physical-chemical parameters (pH, Eh, T, EC, alkalinity) were also regularly measured in situ at these points. In this work we present the obtained dataset and first results. Changes in dissolved gas, mainly H2 and He, were recorded before and during the eruption. In two radon/thoron stations, abrupt increases in both gaseous species related to the eruptive process were also detected. Changes in dissolved radon in water were also observed at some of the sampling points. Finally, the analysis of the thermal image set can be used to monitor the surface volcanic activity in correlation with visual images and geophysical signals (volcanic tremor).

On 10 October 2011, a submarine volcanic eruption began 2 km south of the island of El Hierro (Canary Islands, Spain). It was the first eruption after 40 years of quiescence in the Canarian archipelago. Since mid-July 2011, a multiparametric network has been deployed by the Instituto Geográfico Nacional (hereinafter IGN)to monitor volcanic processes. The data recorded by five stations, measuring the air and soil temperature, CO and radon concentration in the air inside four galleries and one well, are the focus of the present paper. Two important anomalies were found that improve comprehension of the volcanic process. First, a clear increase in CO concentration in one gallery (from 825 ± 19 to 2305 ± 35 ppm)which seems to be mainly controlled by ground deformation measured during the unrest period preceding the eruption. Second, a relationship between radon concentration in air in a well located in the northern side of the island with seismic energy release (several peaks with up to 115% increase), and ground deformation (50% growth in background level), also before the eruption onset. Lastly, changes in radon concentration during eruptive period seem to be modulated by seismic activity (increases up to 233%), which in turn is likely related to variations in magma rheology.

Monogenetic eruptions are the most common volcanic activity in the world. However, unrest monitoring data are scarce due to the long intervening quiescence periods. This study analyzes unrest signals recorded in one of the largest monogenetic fields in the Canary Islands, Cumbre Vieja (La Palma). Two seismic swarms were registered in October 2017 and February 2018 with b-values of 1.6 ± 0.1 and 2.3 ± 0.2 respectively suggesting an intense magmatic fluids contribution, gas and/or magma. Both swarms were linked to changes in gas emissions. Increases in hydrogen concentration, and (R/Ra)c up to 7.52 ± 0.05, were recorded before the first swarm, at the sampling point closest to where seismicity was located, indicating a deep gas input. After the second swarm, increases in (R/Ra)c and thoron soil concentration were recorded at two locations. This dataset is compatible with a stalled magmatic intrusion at ca. 25 km depth, with an estimated volume between 5.5·10−4 km3 and 3·10−2 km3.

In Tenerife there are a vast number of sub-horizontal blind water mines, called “galleries”. Seven air and soil temperatures and CO2 concentration profiles in air were carried out inside the Río de Guía gallery (hereinafter RdG). An anomalous stable maximum temperature point (hereinafter MTP) was found around 2000 m from the entrance. During the warm period, a clear CO2 stagnation was detected before MTP, showing concentrations up to 14,000 ppm. In order to study gas emission and its dynamics inside the gallery, four stations were deployed around MTP. All stations recorded air and soil temperatures, and CO2 and Rn concentration in air from November 2009 to January 2011. After analyzing this dataset, it was possible to characterize the influence of MTP. This thermal anomaly divided the gallery into two sections. In the cold period, the outer section located outwards from MTP became colder while the inner section warmed up owing to a less heat transfer into the deepest part of the gallery. There were several short periods when variations in barometric pressure created an advection movement that was able to temporally change the gas behavior inside the gallery. Two soil gas samples were taken around MTP and their δ13C (CO2) ratios suggested a magmatic origin. All data were combined to create a model for the gas and thermal dynamics inside the gallery. This model, together with identification of background levels in each parameter, allows to identify any anomalous signal that could be elated with changes in volcanic activity., This study was funded by the Instituto Geográfico Nacional (Ministerio de Fomento, Spanish Government).

In this paper we present low-power seismic acquisition equipment for long-range telemetry, developed as a compact system for easy transportation. This acquisition system has been developed to detect the seismic activity of volcanoes, and represents the achievement of joint work from different scientific and technological disciplines such as geophysics, electronics, communications, mechanics, and information technology. The paper includes the laboratory validation results by means of automated measuring systems and calibration procedures, and the final validation results of different measurement campaigns on the El Hierro and Tenerife islands (Canary Islands). The seismic acquisition equipment includes an on board signal processing system developed to reduce the size of seismic data transmitted and to increase the autonomy of the equipment. Moreover, the seismic acquisition equipment has been designed based on a low cost electromagnetic sensor, which has been conditioned to achieve our goals. In a volcanic seismic survey, a series of seismic acquisition systems are placed near the area under study, where they record the natural seismic activity of volcanoes., The authors would like to acknowledge the financial support of “Spanish Ministry of Economy and Competitiveness” in “Interoperability and implementation of autonomous marine platforms for seismic monitoring” (INTMARSIS) CGL2013-42557-R and in “Instrumentation and Applied Technology for the Study, Characterization and Sustainable Exploration of Marine Environment” (MarInTech) CTM2015-68804-REDT.

To control and preventing volcanic risk, are used different devices where many parameters are monitored that provide insight into the state of a volcano. This paper presents the design of system for monitoring the volcano seismicity. This system is composed of the module of acquisition data, the power module, the peripherals for communicate remotely and GPS to get time synchronization. This system is proposed to have a quick deployment in case of volcanic crisis, with a low cost of construction and maintenance. At the same time the equipment is built inside a watertight box, which allows installation of the system in adverse conditions and in remote locations with difficult access. The graph that can be seen in the results section shows a correct system operation.

This paper describes the development of a low-cost multiparameter acquisition system for volcanic monitoring that is applicable to gravimetry and geodesy, as well as to the visual monitoring of volcanic activity. The acquisition system was developed using a System on a Chip (SoC) Broadcom BCM2835 Linux operating system (based on DebianTM) that allows for the construction of a complete monitoring system offering multiple possibilities for storage, data-processing, configuration, and the real-time monitoring of volcanic activity. This multiparametric acquisition system was developed with a software environment, as well as with different hardware modules designed for each parameter to be monitored. The device presented here has been used and validated under different scenarios for monitoring ocean tides, ground deformation, and gravity, as well as for monitoring with images the island of Tenerife and ground deformation on the island of El Hierro.

An extensive self-potential survey was carried out in the central volcanic complex of Tenerife Island (Canary Islands, Spain). A total amount of ~. 237. km of profiles with 20. m spacing between measurements was completed, including radial profiles extending from the summits of Teide and Pico Viejo, and circular profiles inside and around Las Cañadas caldera and the northern slopes of Teide and Pico Viejo. One of the main results of this mapping is the detection of well-developed hydrothermal systems within the edifices of Teide and Pico Viejo, and also associated with the flank satellite M. Blanca and M. Rajada volcanoes. A strong structural control of the surface manifestation of these hydrothermal systems is deduced from the data, pointing to the subdivision of Teide and Pico Viejo hydrothermal systems in three zones: summit crater, upper and lower hydrothermal systems. Self-potential maxima related to hydrothermal activity are absent from the proximal parts of the NE and NW rift zones as well as from at least two of the mafic historical eruptions (Chinyero and Siete Fuentes), indicating that long-lived hydrothermal systems have developed exclusively over relatively shallow felsic magma reservoirs. Towards Las Cañadas caldera floor and walls, the influence of the central hydrothermal systems disappears and the self-potential signal is controlled by the topography, the distance to the water table of Las Cañadas aquifer and its geometry. Nevertheless, fossil or remanent hydrothermal activity at some points along the Caldera wall, especially around the Roques de García area, is also suggested by the data. Self-potential data indicate the existence of independent groundwater systems in the three calderas of Ucanca, Guajara and Diego Hernández, with a funnel shaped negative anomaly in the Diego Hernández caldera floor related to the subsurface topography of the caldera bottom. Two other important self-potential features are detected: positive values towards the northwestern Santiago rift, possibly due to the relatively high altitude of the water-table in this area; and a linear set of minima to the west of Pico Viejo, aligned with the northwestern rift and related to meteoric water infiltration along its fracture system. © 2014 Elsevier B.V., This work has been funded by the Instituto Geográfico Nacional (Ministerio de Fomento, Gobierno de España). S. Barde-Cabusson was funded by JAE-Doc Program (JAEDoc 09 01319).

[1] On 10 October 2011, a submarine volcanic eruption started 2 km south from El Hierro Island (Spain). Since July 2011 a dense multiparametric monitoring network was deployed all over the island by Instituto Geografico Nacional (IGN). By the time the eruption started, almost 10000 earthquakes had been located and the deformation analyses showed a maximum deformation of more than 5 cm. Earthquake migration from the north to the south of the island and acceleration of seismicity are in good correlation with changes in the deformation pattern as well as with some anomalies in geochemical and geomagnetic parameters. An earthquake of local magnitude 4.3 at 12 km depth (8 October 2011) and shallower seismicity a day after, preceded the onset of the eruption. This is the first time that a volcanic eruption is fully monitored in the Canary Islands. Data recorded during this unrest episode at El Hierro will contribute to understand reawakening of volcanic activity in this region and others of similar characteristics.