Search Results (15)

The eruption of the Tajogaite volcano (Cumbre Vieja) on La Palma Island (Spain) generated a significant amount of volcanic ash (VA). This study evaluates the valorisation of VA, considered a “natural waste,” as a partial substitute for Portland cement or in combination with lime. By using this waste, this study aims to promote its valorisation and contribute to the circular economy on the island and in nearby areas. After the ash undergoes a drying and grinding process, various tests are conducted to assess its physical, mineralogical, and chemical properties. These tests include particle size distribution, powder X-ray diffraction, and field emission electron microscopy, among others. Methods such as the Frattini test, the R³ method, thermogravimetric analysis and calorimetry are used to measure pozzolanic reactivity. The values obtained using the Frattini and R³ methods indicate that VA has low-moderate reactivity. The mechanical properties of mortar specimens based on Portland cement blends and hydrated lime are analysed, where a portion of these binders is replaced with VA. It has been observed that the compressive strengths of the specimens with 15%, 25%, and 35% of cement replaced by VA in cement blends show favourable results after 90 and 365 days of curing. Mortars with a 25% replacement reach compressive strengths exceeding 40 MPa versus 57 MPa of the control after 28 days of curing, which is adequate for many applications in civil engineering. The study highlights the importance of exploring eco-friendly materials and believes that the addition of VA can be a valuable and effective enhancement for mortars. This research marks a significant endeavour in exploring the volcanic ash produced by the Tajogaite Volcano eruption, particularly in relation to its mechanical behaviour in lime-pozzolan mortars. Full article

Volcanic gas emissions, particularly sulfur dioxide (SO₂), are crucial for volcano monitoring. SO₂ has a significant impact on air quality, the climate, and human health, making it a critical component of volcano monitoring programs. Additionally, SO₂ can be used to assess the state of a volcano and the progression of an individual eruption and can serve as a proxy for volcanic ash. The Tajogaite La Palma (Spain) eruption in 2021 emitted large amounts of SO₂ over 85 days, with the plume reaching Central Europe. In this study, we present the results achieved by monitoring Tajogaite SO₂ emissions from 19 September to 31 October 2021 at different acquisition times (i.e., 10:00 UTC, 12:00 UTC, 14:00 UTC, and 16:00 UTC). An optimized configuration of the Robust Satellite Technique (RST) approach, tailored to volcanic SO₂ detection and exploiting the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) channel at an 8.7 µm wavelength, was used. The results, assessed by means of a performance evaluation compared with masks drawn from the EUMETSAT Volcanic Ash RGB, show that the RST product identified volcanic SO₂ plumes on approximately 81% of eruption days, with a very low false-positive rate (2% and 0.3% for the mid/low and high-confidence-level RST products, respectively), a weighted precision of ~79%, and an F1-score of ~54%. In addition, the comparison with the Tropospheric Monitoring Instrument (TROPOMI) S5P Product Algorithm Laboratory (S5P-PAL) L3 grid Daily SO₂ CBR product shows that RST-SEVIRI detections were mostly associated with SO₂ plumes having a column density greater than 0.4 Dobson Units (DU). This study gives rise to some interesting scenarios regarding the near-real-time monitoring of volcanic SO₂ by means of the Flexible Combined Imager (FCI) aboard the Meteosat Third-Generation (MTG) satellites, offering improved instrumental features compared with the SEVIRI. Full article

The 2021 eruption of the Tajogaite volcano (La Palma, Canary Islands) provided a unique opportunity to investigate the early post-eruptive magnetic structure of a newly formed volcanic edifice. Understanding these structures is essential for improving hazard assessment and risk mitigation strategies. In this study, we present the first high-resolution, drone-based aeromagnetic dataset over the Tajogaite volcano, aimed at clarifying its still-uncertain geodynamic framework at shallow depths. We describe the data acquisition and processing workflows for surveying volcanic terrains, providing insights into the challenges encountered and the methodologies applied. The magnetic dataset was analyzed and used to construct a 3D magnetic susceptibility model of the volcanic edifice and its surroundings. Our results revealed very low magnetic susceptibility values at very shallow depths (~50 m below the surface) over the main volcanic edifice, suggesting the presence of a likely vertical, dyke-like structure feeding the eruption. These findings indicate that these materials remain above their Curie temperature around two years after the eruption. Moreover, the magnetic anomalies display patterns that correlate with the previously inferred two-fault systems, which likely played a critical role in channelling magma toward the eruptive vents. An elongated zone of slightly low magnetic susceptibility was identified following the NE-SW Mazo fault orientation, extending toward the eruptive fissure. This feature was associated with a single, fault-controlled magma pathway that remained at high temperatures at the time of the survey, in agreement with studies in other volcanic environments. This study highlights the value of aeromagnetic surveys, particularly those conducted with drones, as effective tools for advancing our understanding of young and dynamic volcanic systems, especially regarding their shallow structures. Full article

During a volcanic eruption, a large volume of pyroclastic material can be deposited on the roads and roofs of the urban areas near volcanoes. The use of volcanic ash as an additive for the manufacture of bricks provides a solution to the disposal of part of this natural residue and reduces the depletion of a non-renewable natural resource, clayey soil, which brings some environmental and economic advantages. The pore system, compactness, uniaxial compression strength, thermal conductivity, color and durability of bricks without and with the addition of volcanic ash were evaluated through hydric tests, mercury intrusion porosimetry, ultrasound, uniaxial compression tests, IR thermography, spectrophotometry and salt crystallization tests. The purpose of this research is to determine the feasibility of adding 10, 20 and 30% by weight of volcanic ash from La Palma (Canary Islands, Spain) in two grain sizes to produce bricks fired at 800, 950 and 1100 °C. The novelty of this study is to use two sizes of volcanic ash and fire the samples at 1100 °C, which is close to the liquidus temperature of basaltic magmas and allows a high degree of interaction between the volcanic ash and the brick matrix. The addition of fine volcanic ash was found to decrease the porosity of the bricks, although the use of high percentages of coarse volcanic ash resulted in bricks with almost the same porosity as the control samples. The volcanic ash acted as a filler, reducing the number of small pores in the bricks. The presence of vesicles in the volcanic ash reduced the compressive strength and the compactness of the bricks with additives. This reduction was more evident in bricks manufactured with 30% of coarse volcanic ash and fired at 800 and 950 °C, although they still reached the minimum resistance required for their use in construction. No significant differences in thermal conductivity were noticed between the bricks with and without volcanic ash additives, which is crucial in terms of energy savings and the construction of sustainable buildings. At 1100 °C the volcanic ash changed in color from black to red. As a result, the additive blended in better with the matrix of bricks fired at 1100 °C than in those fired at 800 and 950 °C. The bricks with and without volcanic ash and fired at 1100 °C remained intact after the salt crystallization tests. Less salt crystallized in the bricks with volcanic ash and fired at 800 and 950 °C than in the samples without additives, although their low compressive strength made them susceptible to decay. Full article

Volcanic eruptions release gases and particulates that may adversely affect human health. The Tajogaite eruption on La Palma provided a unique opportunity to evaluate inorganic pollutant exposure in a directly affected population. As part of the ISVOLCAN study, blood samples from 393 adults residing in the island’s western region were analyzed for 43 inorganic elements using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), including 20 toxic elements identified by the Agency for Toxic Substances and Disease Registry (ATSDR). The median age of participants was 51 years, and 56.7% were female. Higher levels of Hg and Mn were associated with long-term occupational exposure, while smoking was linked to elevated Cd, Pb, and Sr levels. Participants living within 6.5 km of the volcano had significantly higher concentrations of Al and Ti. Ash cleanup activities were associated with increased levels of Ni and Cu, and those spending over five hours outdoors daily showed elevated Se and Pb. This is the first biomonitoring study to assess blood concentrations of inorganic pollutants in a population exposed to volcanic emissions. The findings highlight key exposure factors and underscore the need for continued research to assess long-term health effects and inform public health measures. Full article

Volcanic ashes (VA) ejected by the Tajogaite Volcano were studied to determine their potential as pozzolanic materials for construction applications. A representative number of VA samples (15 in total) were collected from different geolocations and altitudes during and immediately after the volcanic eruption, in order to assess their reactivity as a function of position and environmental exposure. Various analytical techniques—XRD, FTIR, and SEM/EDX—were used to determine the initial microstructural composition of the VA samples. Additionally, saturated lime testing and the Frattini test were performed to evaluate their pozzolanic reactivity for use in historical mortars. The microstructural analyses revealed that the dominant mineral phases are aluminosilicates. The reactivity tests confirmed a good pozzolanic response, with the formation of C-A-S-H gels identified as the main hydration products at the studied curing times. Full article

Satellite imagery provides a rich source of information that serves as a comprehensive and synoptic tool for the continuous monitoring of active volcanoes, including those in remote and inaccessible areas. The huge influx of such data requires the development of automated systems for efficient processing and interpretation. Early warning systems, designed to process satellite imagery to identify signs of impending eruptions and monitor eruptive activity in near real-time, are essential for hazard assessment and risk mitigation. Here, we propose a machine learning approach for the automatic classification of pixels in SEVIRI images to detect and characterize the eruptive activity of a volcano. In particular, we exploit a semi-supervised GAN (SGAN) model that retrieves the presence of thermal anomalies, volcanic ash plumes, and meteorological clouds in each SEVIRI pixel, allowing time series plots to be obtained showing the evolution of volcanic activity. The SGAN model was trained and tested using the huge amount of data available on Mount Etna (Italy). Then, it was applied to other volcanoes, specifically, Stromboli (Italy), Tajogaite (Spain), and Nyiragongo (Democratic Republic of the Congo), to assess the model’s ability to generalize. The validation of the model was performed through a visual comparison between the classification results and the corresponding SEVIRI images. Moreover, we evaluate the model performance by calculating three different metrics, namely the precision (correctness of positive predictions), the recall (ability to find all the positive instances), and the F1-score (general model’s accuracy), finding an average accuracy of 0.9. Our approach can be extended to other geostationary satellite data and applied worldwide to characterize volcanic activity, allowing the monitoring of even remote volcanoes that are difficult to reach from the ground. Full article

The Tajogaite Volcano erupted on the western slope of the Cumbre Vieja mountain range on La Palma Island in the Canary Islands, Spain, in 2021. As one of the multiple consequences of this eruption, a layer of tephra was deposited, to a variable extent, over a large part of the island. Tephra deposits affect all aspects of vegetation recovery, the water cycle, and the long-term availability of volcanic nutrients. Protozoa, including free-living amoeba (FLA), are known to be among the first microorganisms capable of colonizing harsh environments. In the present study, the presence of FLA has been evaluated in the Tajogaite Volcano deposits. Samples of the tephra were collected and incubated at 26 °C on 2% non-nutrient agar plates with a layer of heat-killed E. coli. Morphological features, as well as the DF3 region sequence of the 18S rDNA, confirmed the presence of a T4 genotype strain of Acanthamoeba. Thermotolerance and osmotolerance assays were used to evaluate the strain’s pathogenic potential. This strain was considered thermotolerant but poorly osmotolerant. To the best of our knowledge, this is the first report of Acanthamoeba being isolated from a recently erupted volcano. Full article

The objectives of this article are (i) to identify the most challenging ethical dilemmas and questions arising from the experiences of communities and professionals affected by or involved in volcanic eruptions, including risk management, the dissemination of information, and tourism; and (ii) to provide arguments for intercultural ethics to address these dilemmas. Intercultural ethics provide invaluable resources to disaster ethics across all three phases of the complete disaster management cycle. In this article, intercultural ethics is viewed as an ethics grounded in ongoing dialogue, facilitating the examination and establishment of norms and a critical reflection on values and their evolution. This approach recognizes power dynamics that may influence fair participation in dialogues and aims to address them, while also integrating elements of deliberative ethics to ensure that dialogues genuinely contribute to legitimizing decisions. Intercultural sensibility helps bridge the gap between experts and non-experts in both directions (a) by emphasizing the duty of transferring scientific knowledge (for experts) and the responsibility of acquiring scientific literacy (for citizens); and (b) by highlighting the importance of a ‘knowledge dialogue’ that acknowledges the non-scientific knowledge of citizens, rooted in their cultural background and experiences of dealing with past disasters, and shaping life in volcanic territories. Full article

This study addresses the in situ mobility of fluoride and aluminum in two different ashfall deposits accumulated during the 2021 eruption of the Tajogaite volcano (La Palma, Canary Islands, Spain), which were exposed to contrasting conditions of ambient humidity and precipitation. We selected one site to the east of the volcanic emission center, located near the top of Cumbre Vieja Ridge and exposed to continuous humidity and rain, and another site to the west of the volcano situated in a lowland and characterized by much drier conditions. The mobility of fluoride and aluminum is markedly different at both sites, with the first sequence suggesting a downwards migration of Al and F, and the second sequence showing no sign of mobility. The migration of aluminum and fluorine results from the dissolution of different fluoride salts (mostly AlF₃ and CaF₂, as suggested by scanning electron microscopy) followed by vertical transport as ionic complexes (AlF₃, AlF₂⁺, AlF₄⁻) during the percolation of rainwater through the ashfall deposits. Geochemical calculations suggest that the mobility of fluorine at neutral to alkaline conditions (pH 7.0–9.0) is likely limited by the solubility of fluorite (CaF₂), whereas at slightly acidic conditions (pH < 6.5), the aqueous concentration of aluminum seems to be controlled by the solubility of gibbsite (Al(OH)₃). This study demonstrates that aluminum and fluoride can be transported from volcanic ash to the underlying soil or groundwater, which is an environmental concern that should be followed in the future. Full article

The present work evaluates the feasibility of using volcanic fly ash (VFA) generated by the eruption of the Tajogaite volcano on the island of La Palma (Spain) in 2021, as a precursor in the preparation of cementitious materials with different Portland cement (PC) replacement levels (0%, 30%, 70% and 100%), in the absence (Blended Cement, BC) and presence of an alkaline activator (Hybrid Alkaline Cement, HAC, and Alkaline Cements, AC). Hydration kinetics (isothermal conduction calorimetry), paste mechanical strengths and reaction products were characterised by XRD, FTIR, TG/DTG and BSEM/EDX. The results obtained indicate that the strengths developed by the hybrid alkaline cements (HAC) are higher than those of the blended cements (BC), especially at the age of 2 days, where 25 MPa were obtained with the replacement of 70% PC by VFA. Alkaline cements (AC, 100% VFA) that were prepared with 8 M NaOH solution as the activator reached 40 MPa after 2 days. It was observed that in all the binders, depending on the initial composition of the binder mixture and the percentage of replacement and/or activator, VFA reacts to form cementitious gels, C-A-S-H and N-A-S-H type, which supports its use as a mineral addition to blended cement or as a precursor in the preparation of alkaline and hybrid alkaline cements. Full article

Geology, as a basic science within the natural sciences, is one of the key areas of knowledge for students in both primary and secondary education. However, when teaching the areas related to geology, many doubts arise both for teachers and students. In the case of students from the Canary Islands, who live literally on volcanic islands, geology becomes even more important and its teaching becomes mandatory. Geological concepts and processes form part of their environment, their heritage, and they are also relevant in terms of the exploitation of natural resources and ecosystems around them. During the 2021–2022 academic year, and within the educational project “Ciencia a lo Grande” (“Science in a Big Way”), several practical workshops on volcanoes have been developed in 9 primary schools in Tenerife, with the target audience being students and teachers, who also received specific training to continue the activities on their own in the following years. The workshops were very successful, and the results were very positive, partly due to the interest around all the information surrounding the last eruption that took place in the Canary Islands archipelago, as well as the Tajogaite volcano in the neighboring island of La Palma. For this reason, there was great motivation with regards to the interactions between teachers and students. The workshops have been focused on the activation of perception and awareness of our environment, highlighting the volcanic structures that each school has around it and their morphological characteristics, differentiating them from other prominent volcanoes in the Canary Islands and all around the world. Full article

The eruption of Cumbre Vieja (also known as Tajogaite volcano, 19 September–13 December 2021, Spain) is an example of successful emergency management. The lessons learnt are yet to be fully disclosed as is whether the response can be further improved. The latter may include tools to predict lava flow inundation rheological characteristics, amongst other issues related to volcanic eruptions (i.e., ash fall and gas emission). The aim of this study was to explore if a scientific open-source, readily available, lava-flow-modelling code (VolcFlow) would suffice for lava emplacement forecasting, focusing on the first seven days of the eruption. We only the open data that were released during the crisis and previously available data sets. The rheology of the lava, as well as the emission rate, are of utmost relevance when modelling lava flow, and these data were not readily available. Satellite lava extent analysis allowed us to preliminarily estimate its velocity, the average flow emitted, and flow viscosity. These estimates were numerically adjusted by maximising the Jaccard morphometric index and comparing the area flooded by the lava for a simulated seven-day advance with the real advance of the lava in the same timescale. The manual search for the solution to this optimization problem achieved morphometric matches of 85% and 60%. We obtained an estimated discharge rate of about 140 m³/s of lava flow during the first 24 h of the eruption. We found the emission rate then asymptotically decreased to 60 m³/s. Viscosity varied from 8 × 10⁶ Pa s, or a yield strength of 42 × 10³ Pa, in the first hours, to 4 × 10⁷ Pa s and 35 × 10³ Pa, respectively, during the remainder of the seven days. The simulations of the lava emplacement up to 27 September showed an acceptable distribution of lava thickness compared with the observations and an excellent geometrical fit. The calculations of the calibrated model required less time than the simulated time span; hence, flow modelling can be used for emergency management. However, both speed and accuracy can be improved with some extra developments and guidance on the data to be collected. Moreover, the available time for management, once the model is ready, quasi-linearly increases as the forecasting time is extended. This suggests that a predictive response during an emergency with similar characteristics is achievable, provided that an adequate rheological description of the lava is available. Full article

Magma-filled dikes may feed erupting fissures that lead to alignments of craters developing at the surface, yet the details of activity and migrating eruptions at the crater row are difficult to monitor and are hardly understood. The 2021 Tajogaite eruption at the Cumbre Vieja, La Palma (Spain), lasted 85 days and developed a pronounced alignment of craters that may be related to changes within the volcano edifice. Here, we use COSMO-SkyMed satellite radar data and ground-based time-lapse photographs, offering a high-resolution dataset to explore the locations and characteristics of evolving craters. Our results show that the craters evolve both gradually and suddenly and can be divided into three main phases. Phase 1, lasting the first 6 weeks of the eruption, was characterized by a NW–SE linear evolution of up to seven craters emerging on the growing cone. Following two partial collapses of the cone to the northwest and a seismicity increase at depth, Phase 2 started and caused a propagation of the main activity toward the southeastern side, together with the presence of up to 11 craters along this main NW–SE trend. Associated with strong deep and shallow earthquakes, Phase 3 was initiated and continued for the final 2 weeks of the eruption, expressed by the development of up to 18 craters, which became dominant and clustered in the southeastern sector in early December 2021. In Phase 3, a second and oblique alignment and surface fracture was identified. Our findings that crater and eruption changes coincide together with an increase in seismic activity at depth point to a deep driver leading to crater and morphology changes at the surface. These also suggest that crater distributions might allow for improved monitoring of changes occurring at depth, and vice versa, such that strong seismicity changes at depth may herald the migration and new formation of craters, which have major implications for the assessment of tephra and lava flow hazards on volcanoes. Full article

Before the COVID-19 pandemic, the World Tourism Organization (UNWTO) stated that “sun and beach” tourist destinations needed to direct more resources towards innovation, sustainability and accessibility. This is related to the crisis that many sun and beach tourist destinations are experiencing. In the Canary Islands, changes to legislation together with urban and tourist products have been made in accordance with UNWTO proposals. For many years the island of La Palma has been offering tourists hiking, stargazing and volcano tourism besides “sun and beach holidays”. However, the 2021 eruption of Tajogaite, Cumbre Vieja aggravated the island’s tourism crisis and caused very negative effects on the economy. This work identifies, selects and characterizes places of interest for geotourism development in the two largest population centers (Santa Cruz de La Palma and Los Llanos de Aridane). Santa Cruz de La Palma has 20 points of interest; Los Llanos de Aridane has 14. All sites contribute to showcasing the diversity of the natural and cultural volcanic and non-volcanic heritage of the regions. The geotourism product in La Palma is relatively new and exploits the topography present, including natural outcrops (cinder cones, lava fields, ravines, cliffs, sedimentary deposits or beaches), and also the cultural heritage (religious and civil architecture, streets or town planning, planes). These proposals for urban geotourism take advantage of the volcanic geoheritage of La Palma and increase the breadth and quality of tourism on offer. Full article