Search Results (27)

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

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

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

On 19th September 2021, a protracted eruption of the Cumbre Vieja Volcano on the Canary Island of La Palma commenced and continued for a duration of 12 weeks. Lava flows starting from the rift zone at the mid-western flank of Cumbre Vieja advanced toward the western coast of the island. The eruption was monitored by different remote sensing satellites, including the Copernicus Sentinel missions and DESIS. The Sentinel-2 Copernicus satellites acquired multispectral data from 15th September onward. On September 30th, and with a difference of ∼2 h with respect to Sentinel-2 A, the DESIS hyperspectral sensor also acquired data from the volcano and then again on 15th October 2021. Typically, mid-infrared (around 3.8 $\mathsf{\mu }$m) data are used for the thermal analysis of active lava flows. However, neither Sentinel-2 nor DESIS possesses mid-infrared bands and the Sentinel-2 high-wavelengths bands (∼2 $\mathsf{\mu }$m) have some limitations. Nevertheless, the hyperspectral character of DESIS enables the analysis of active erupting volcanoes in near-infrared wavelengths. The results of this analysis find fluid lava temperatures of about 1100–1200 K but there are problems associated with the high-temperature lava spectral emissivity. 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

On 19 September 2021, La Palma volcano (Canarias Archipelagos) started an eruption that persisted until 13 December 2021. Despite the Volcano Explosive Index (VEI) being estimated equal to 3, corresponding to not so powerful eruption, the long eruption activity posed much scientific interest in this natural hazard event. In this paper, we searched for possible effects of this eruption on the atmosphere and ionosphere, investigating the climatological archive and Swarm magnetic satellite data. In particular, we explored Aerosol, Sulphur Dioxide and Carbon Monoxide concentrations in the atmosphere identifying both the direct emissions from the volcano as well as the plume that drifted toward West-South-West and was reinforced during the eruption period. The vertical profile of temperature from the Saber satellite was analysed to search for the possible presence of acoustic gravity waves induced by volcanic activity. Compared with the year before without eruption in the areas, a lot of Saber profiles present an Energy Potential very much higher than the previous year, proposing the presence of Acoustic Gravity Waves (AGW) induced by volcano eruption activity. We also identified Swarm magnetic disturbances on the day of the eruption and in November. The mechanism of coupling could be different for the latter one, as there is no evidence for AGW. They may be due to a more complex of physical and chemical alterations that propagate from the lower atmosphere to the upper one into the ionosphere. Full article

Climate change may shift species outside of their current climatic tolerances, which can be problematic for oceanic islands with limited options for species migration. Their alpine habitats, which represent islands within islands, are a special concern due to high endemism rates. The Canary Islands have two examples for such fragile ecosystems above 2000 m, on La Palma and Tenerife. This study contributes an assessment of the Canary Islands’ climatic habitat for 47 alpine plant species under observed climate change (1959–1989 versus 1990–2019 periods) as well as for future projections (2041–2060 and 2061–2080 periods). We analyzed the contraction of climatic habitats and migration requirements (biotic velocity) for each species to compensate for observed and predicted climate change. Our results suggest that temporary climate refugia exist on Tenerife but are insufficient on La Palma, where habitat loss due to historical climate change has already created an area of significant concern: the Cumbre Vieja Natural Park. On Tenerife, current alpine species can find suitable climate habitats in the caldera area and on the Teide-Pico Viejo volcano. That said, migration paths toward these refugia are long and complex, and human-assisted migration may be required. Species-specific statistics to support such management interventions are provided in this study. Full article

The signal coming from the artificial satellites of the GNSS system suffers various effects that considerably decrease the precision in solving the positioning problem. To mathematically model these effects, the atmosphere is divided into two main parts, the troposphere and the ionosphere. The troposphere can only be modelled, while the ionospheric effect can be modeled or eliminated depending on the geodetic sophistication of the receivers used. In this way, information is obtained about both layers of the atmosphere. For tropospheric modeling, the parameters of total zenithal delay (ZTD) or precipitable water vapor (PVW) will be taken, and for the ionosphere the total electron content (TEC) will be taken. In this work, statistical and analytical techniques will be applied with the R software; for example, ARMA, ARIMA models, least squares methods, wavelet functions, Kalman techniques, and CATS analysis. With this, the anomalies that occurred in the values of the ZTD and TEC in the case of the 2021 eruption of the Cumbre Vieja volcano on the island of La Palma. Full article

This study used spatiotemporal land gravity data to investigate the 2021 eruption that occurred in the Cumbre Vieja volcano (La Palma, Canary Islands). First, we produced a density model by inverting the local gravity field using data collected in July 2005 and July 2021. This model revealed a low-density body beneath the western flank of the volcano that explains a highly fractured and altered structure related to the active hydrothermal system. Then, we retrieved changes in gravity and GNSS vertical displacements from repeated measurements made in a local network before (July 2021) and after (January 2022) the eruption. After correcting the vertical surface displacements, the gravity changes produced by mass variation during the eruptive process were used to build a forward model of the magmatic feeding system consisting of dikes and sills based on an initial model defined by the paths of the earthquake hypocenters preceding the eruption. Our study provides a final model of the magma plumbing system, which establishes a spatiotemporal framework tracing the path of magma ascent from the crust–mantle boundary to the surface from 11–19 September 2021, where the shallowest magma path was strongly influenced by the low-density body identified in the inversion process. Full article

In the Canary Islands and in other parts of the world where it can be found in its natural state, basaltic tephra, or “Picón” as it is known locally, is commonly used as a soilless substrate for crops. The aim of this study is to learn more about the physical properties of the Canary Islands’ tuff, and to find a simple method to predict the hydraulic behaviour of these substrates due to their heterogeneity. To accomplish this, 32 tuff samples were collected from all the quarries on the island of Tenerife (Canary Islands) that were authorised for the study. The tuffs had hydraulic properties that were highly influenced by the particle size. Coarse tuffs had an aeration capacity greater than 35% v/v and easily available water of less than 5% (v/v), while fine tuffs had aeration capacities below 20% v/v and elevated water retention (20 to 26% v/v). The intermediate tuffs had characteristics that varied between those of the two previous groups. Particle size fractions of less than 1 mm demonstrated the best correlation to common air:water ratios and present the best predictive capacity to relations involving air. By focusing on air:water ratios and the previous assumption, an attempt was made to predict the suitability of new pyroclastic material samples emitted by the La Palma Volcano as growing substrates for vegetables. 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 the Cumbre Vieja volcano on 19 September 2021, resulted in the deposition of large quantities of volcanic ash (VA), causing a great impact on the citizens. This work aims to study the properties of this volcanic ash as pozzolanic raw materials to establish their potential use in the development of sustainable cement. Results of chemical and technical characterization are presented. To achieve this goal, Ordinary Portland Cement (OPC) was replaced with standardized percentages of OPC/VA: 10, 25, and 40%. Characterization studies were carried out using chemical analysis of X-ray fluorescence (XRF), chemical quality analysis (QCA), pozzolanicity test (PT) at 8 and 15 days, as well as determining the mechanical strength (MS) at 7, 28, and 90 days. The results obtained by XRF and QCA established that the chemical composition of the VA corresponds to that of the natural pozzolan typical of pyroclastic genesis. The PT test showed that the analyzed samples have a marked pozzolanic nature, both at 8 and 15 days, showing a significant increase in their hydraulic reactivity. Likewise, the MS tests confirmed a continuous increase in mechanical compressive strength, which increased significantly from 7 to 90 days of curing, reaching more than 58 MPa. On the other hand, mechanical tests showed that the three types of dosages used OPC/VA: 10, 25, and 40% were equally effective, with OPC/VA formulations: 10–25% being the most effective. The results obtained in this research could be used by local industries as a guide for the correct use of the volcanic materials of this island, both for the manufacture of construction materials, such as aggregates, and to produce pozzolanic cement with low CO₂ emissions, thus having a positive impact on the environment. Finally, the great natural availability of natural VAs in the surrounding areas of La Palma could cover part of the needs for materials used in the construction and restoration of houses and infrastructures damaged during the volcanic eruption. Full article

On 19 September 2021, a volcanic eruption began on the island of La Palma (Canary Islands, Spain). The eruption has allowed the assessment of an unprecedented multidisciplinary study on the effects of the volcanic plume. This work presents the estimation of the spectral direct radiative forcing ($\Delta$F) and efficiency ($\Delta$F${}^{Eff}$) from solar radiation measurements at the Izaña Observatory (IZO) located on the island of Tenerife (∼140 km from the volcano). During the eruption, the IZO was affected by different types of aerosols: volcanic, Saharan mineral dust, and a mixture of volcanic and dust aerosols. Three case studies were identified using ground-based (lidar) data, satellite-based (Sentinel-5P Tropospheric Monitoring Instrument, TROPOMI) data, reanalysis data (Modern-Era Retrospective Analysis for Research and Applications, version 2, MERRA-2), and backward trajectories (Flexible Trajectories, FLEXTRA), and subsequently characterised in terms of optical and micro-physical properties using ground-based sun-photometry measurements. Despite the $\Delta$F of the volcanic aerosols being greater than that of the dust events (associated with the larger aerosol load present), the $\Delta$F${}^{Eff}$ was found to be lower. The spectral $\Delta$F${}^{Eff}$ values at 440 nm ranged between −1.9 and −2.6 Wm${}^{-2}$nm${}^{-1}$AOD${}^{-1}$ for the mineral dust and mixed volcanic and dust particles, and between −1.6 and −3.3 Wm${}^{-2}$nm${}^{-1}$AOD${}^{-1}$ for the volcanic aerosols, considering solar zenith angles between 30${}^{\circ }$ and 70${}^{\circ }$, respectively. 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