Papers by William Hernández
Land
Before the COVID-19 pandemic, the World Tourism Organization (UNWTO) stated that “sun and beach” ... more 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 contribu...
<p>Tourism is one of the economic activities of reference throughout the wo... more <p>Tourism is one of the economic activities of reference throughout the world despite the consequences of SARS-CoV-2. Within the new tourism products, geotourism is a relatively new modality and alternative to mass tourism in mature destinations. One example of this is the creation and rise of the global and European networks of geoparks. In the case of the Canary Islands, this fact can also be seen in the increase in tourist activities related to volcano tourism as an alternative product to sun and beach tourism. In this sense, the main objective of this study is to identify, inventory, select, characterize and evaluate geomorphosites with geotouristic interest on the Canary Island of La Palma following the methodology proposed by Reynard et al (2007 and 2017), based on the evaluation of scientific and added values. A total of 47 geomorphosites of geotourism interest (Ligts) that host the geodiversity of volcanic and non-volcanic forms and processes of La Palma have been studied. The main results after applying the assessment is that the scientific values ​​(0.53) are above the added values ​​(0.43). Among the first, the paleogeographic interest stands out (0.61) and of the added ones, that of the protection of the site (0.71). All these evaluations show that the geomorphological sites studied are representative of the natural and cultural heritage of La Palma, but also that they are conserved, protected and that they contribute to explain the geological and geomorphological evolution of the island. These aspects are essential to be able in the future to propose itineraries or georoutes of volcano tourist interest.</p>
<p>Cumbre Vieja (220 km<sup>2</sup&amp... more <p>Cumbre Vieja (220 km<sup>2</sup>) is the most active volcano in the Canary Islands. It has been the location of 8 of the 17 historical eruptions in the archipelago during the last 600 years. The establishment of a geochemical monitoring program by our research group for the volcanic surveillance of Cumbre Vieja started in 1997. This program was mainly focused on diffuse degassing monitoring because of the absence of visible volcanic degassing manifestations (fumaroles, plumes, etc.) as well as other obvious geothermal features at Cumbre Vieja up to the 2021 eruption which started on September 19, ended on December 13 and lasted 85 days.</p> <p>The INVOLCAN’s soil degassing monitoring at Cumbre Vieja is carried out by means of a geochemical instrumental permanent network (soil CO<sub>2</sub> efflux, soil gas <sup>222</sup>Rn and soil C isotope ratio) and regular geochemical surveys covering the entire area of Cumbre Vieja (diffuse CO<sub>2</sub>, He and H<sub>2</sub> emissions). Several soil degassing anomalies have been observed and some of them years before the 2021 eruption, which illustrates the importance of diffuse degassing monitoring for volcanic surveillance. The single visible manifestation of volcanic degassing at La Palma is a cold CO2-rich site at Taburiente volcano. Regular helium-3 emission monitoring of this observation site has been carried out since 1991 in collaboration with Tokyo Univ., and provided a clear early warning signal of the 2021 Cumbre Vieja eruption. Because of the registration of seismic swarms, and to strengthen the INVOLCAN geochemical monitoring program of Cumbre Vieja volcano,  regular sampling of groundwater for chemical and isotopic analysis started in October 2017. The results of this hydrogeochemical monitoring also showed significant changes related to the recent volcanic unrest of Cumbre Vieja.</p> <p>Since the 2021 eruption onset, INVOLCAN performed daily observations of SO<sub>2</sub> emissions using a miniDOAS in traverse mode, on terrestrial (car), sea (ship) and air (helicopter) mobile position recording relatively high SO<sub>2</sub> emissions (> 50.000 t/d). Static scanners and satellite instruments were used also to monitoring the SO<sub>2</sub> emission released by this eruption; a task lead by the volcano research group of Manchester University. Additional plume geochemical monitoring was carried out using OP-FTIR spectrometers and UAV, helicopter and ground-base MultiGas units to characterize the chemical composition of the plume degassing in collaboration with scientists from Manchester Univ., Palermo Univ., UCL, INGV, IPGP and Azores Univ.  Carbon isotope analysis of the CO<sub>2</sub> gas plume was also undertaken in collaboration with New Mexico Univ. Analysis of pristine ash leachates has been also performed in collaboration with Durham Univ. and Tokyo Institute of Technology since it is often used to estimate the composition of the gas phase during volcanic eruptions and provides important information on the eruption processes was also performed.</p> <p>The results of these geochemical observations during the inter-eruptive, pre-eruptive, eruptive and post-erupive phases have been tremendously useful to understand the recent magmatic reactivation of Cumbre Vieja volcano.</p> <p> </p>
<p>On 19 September 2021, Cumbre Vieja volcano, La Palma, Canary Islands eru... more <p>On 19 September 2021, Cumbre Vieja volcano, La Palma, Canary Islands erupted after 50 years of quiescence. The eruption lasted 85 days, ending on 13 December. At present, whilst geophysical data may be used to estimate the scale of magma reservoirs (and when combined with the magma output rate can provide a guide to eruption longevity), experience shows that using such techniques to see through activity at crustal levels and quantify deeper magmatic processes during an eruption is not always productive or possible. Success of geophysical techniques is dependent on both the level of instrumentation and the degree to which local magmatic and tectonic environments are understood. Thus, deep magma supply and crustal interactions may be intractable or even invisible, even if they are seismogenic. Simple on-site compositional information (e.g. from handheld XRF) can indicate broad-scale changes in erupted compositions and reflect, for example,  changes in crystallinity or melt composition. However, such bulk data can be ambiguous and therefore insufficiently robust to be useful for decision-makers. In contrast, petrological observations of mineral textures and compositions can provide direct, quantifiable evidence of deep and shallow magmatic processes that, in tandem with upper crustal stress states, ultimately drive magma ascent and eruption. Advancements in the use of precise and automated sample preparation techniques, rapid and high-resolution textural and compositional characterisation, and increasing computing capacity now allows samples to be collected, analysed and interpreted within days rather than months. Measurements of volcanic products include: textures, mineralogy, mineral chemistry (and profiles), whole-rock geochemistry, volatiles, isotope geochemistry and rheology. Petrology combines these data into interpretations of the magmatic system state and evolution, which can inform understanding of the dynamic processes driving eruptions and physical behaviours of tephra and lava. Hence, forecasts of volcanic behaviour underpinned by petrological characterization and trends are more robust. Here we present textural and chemical data from time-resolved samples of lavas and tephras from the eruptive sequence, marking the initiation, duration and cessation of volcanism. These data are used to constrain and trace temperature(s) and pressure(s) of mineral growth and magma storage; mineral-melt equilibrium dynamics; and timescales of magmatic processes through diffusion chronometry. Initial petrographic study has shown the lavas to be hypocrystalline, porphyritic and vesicular. Clinopyroxene is the most common coarse mineral, with olivine and amphibole also present; however, these mineral abundances are not constant through time.<em> </em>This study highlights the importance of time-resolved sampling and shows how both rapid qualitative observations and in situ petrological characterisation can be used to couple volcanic behaviour with subsurface magma dynamics.</p>
<p>La Palma Island (708 km<sup>2</sup&... more <p>La Palma Island (708 km<sup>2</sup>) is located at the north-west and is one of the youngest (~2.0My) of the Canarian Archipelago. On September 19, 2021, a new volcanic eruption occurred at Cumbre Vieja volcanic system at the southern part of the island, the most active basaltic volcano in the Canaries. The erupting fissure (~1.0 km-length) is characterized by lava effusion, strombolian activity, lava fountaining, ash venting and gas jetting. After 85 days of eruption finished on December 13, 2021. We report herein the results of an intensive soil gas study, focused on non-reactive and/or highly mobile gases such as helium (He) and hydrogen (H<sub>2</sub>), in Cumbre Vieja. He has unique characteristics as a geochemical tracer: it is chemically inert and radioactively stable, non-biogenic, highly mobile and relatively insoluble in water. H<sub>2</sub> is one of the most abundant trace species in volcano-hydrothermal systems and is a key participant in many redox reactions occurring in the hydrothermal reservoir gas. Since 2002, soil gas samples were regularly collected at ~40 cm depth using a metallic probe at 600 sites for each survey. He content was analysed by means of a quadrupole mass spectrometer (QMS; Pfeiffer Omnistar 422 and HIDEN QGA) and H<sub>2</sub> concentrations by a micro-gas chromatograph (microGC; VARIAN CP490). Spatial distribution maps have been constructed following the sequential Gaussian simulation (sGs) procedure to quantify the diffuse He and H<sub>2</sub> emission from the studied area. The time series of both diffuse He and H<sub>2</sub> emission show significant increases before and during the occurrence of seismic swarms that took place in the period 2017-2021. During the eruptive period, significant increases in diffuse He and H<sub>2</sub> emission were also observed with good temporal agreement with the increase of the volcanic tremor. These increases in diffuse He and H<sub>2</sub> emission preceded the peak of diffuse CO<sub>2</sub> emission as expected by the characteristics of these gases. The absence of visible volcanic gas emissions (fumaroles, hot springs, etc.) at the surface environment of Cumbre Vieja, makes this type of studies in an essential tool for volcanic surveillance purposes.</p><p> </p>
Volcanica, 2022
How and why magmatic systems reactivate and evolve is a critical question for monitoring and haza... more How and why magmatic systems reactivate and evolve is a critical question for monitoring and hazard mitigation efforts during initial response and ongoing volcanic crisis management. Here we report the first integrated petrological results and interpretation provided to monitoring authorities during the ongoing eruption of Cumbre Vieja, La Palma, Canary Islands, Spain. The first eruptive products comprised simultaneous Strombolian fountain-fed lava flows and tephra fall from near-continuous eruption plumes. From combined field, petrographic and geochemical analyses conducted in the 10 days following sample collection, we infer low percentage mantle melts with a variably equilibrated multimineralic crystal-cargo and compositional fractionation by winnowing during eruptive processes. Hence ‘rapid response’ petrology can untangle complex magmatic and volcanic processes for this eruption, which combined with further study and methodological improvement can increasingly assist in active ...
Geosciences, 2020
Volcanic areas create spectacular landscapes that contain a great diversity of geoheritage. The s... more Volcanic areas create spectacular landscapes that contain a great diversity of geoheritage. The study of this geoheritage enables us to inventory, characterise, protect and manage its geodiversity. The Canary Islands are a group of subtropical active volcanic oceanic islands with a great variety of magma types and eruption dynamics that give rise to a wide diversity of volcanic features and processes. The aim of this paper is to identify, for the first time, the diversity of volcanic geoheritage of the Canary Islands and to appraise the protection thereof. To this end, a geomorphological classification is proposed, taking into account the features and processes directly related to volcanism, such as those resulting from erosion and sedimentary processes. The main findings demonstrate that the volcanic geoheritage of the Canary Islands is extremely varied and that this geodiversity is safeguarded by regional, national and, international protection and management frameworks. Even so, ...
<p>Tenerife is the second-largest island in the Canarian archipelago with a... more <p>Tenerife is the second-largest island in the Canarian archipelago with an area of 2034 km<sup>2</sup>. It consists of three ancient volcanic massifs (Anaga, Adeje and Teno) located at the edges of the island connected by rift zones to the centre of the island, in correspondence of Las Cañadas caldera. The caldera hosts the most relevant topographic element of Tenerife, the volcanic edifice of Teide – Pico Viejo. Previous studies already suggested the presence of geothermal resources inside and around the caldera. For this reason, in the present study, we have applied the magnetotelluric method (MT) in the central part of the island to better understand subsurface structures in this area.</p><p>The MT method is a useful tool successfully applied to detect conductive and resistive structures located in the subsoil. It is commonly used in volcanic areas to detect volcano-tectonic features and geothermal systems to evaluate exploitable geothermal resources. Furthermore, continuous magnetotelluric measurements can also be employed for volcanic monitoring, allowing tracking temporal changes of the resistivity because of fluid transfer processes in the volcanic system.</p><p>Between 2019 and 2020 we realised a detailed study of Las Cañadas caldera resistivity structure thought 45 magnetotelluric soundings. The instrumentation consisted of four Metronix ADU-08e, equipped with EPF-06 electrodes and MFS-06e magnetic coils, which registered electric and magnetic fields along the N-S and E-W directions. We also installed three remote stations at different times inside the caldera. Depending on the station quality, we obtained the MT response functions for periods of 0.001 – 1000 s. The dimensionality of the data has been analysed using the phase tensor.  The first preliminary results of dimensionality and strike analysis indicate a 1D/2D behaviour for the first layers which present a decreasing resistivity, evolving to a 3D behaviour from 1s and with an increase of resistivity with depth.</p><p>Furthermore, we present some results obtained by a permanent MT station to check the possibility of temporal changes in the electrical resistivity. During the time this station was recording two electrical blackouts which took place on the island. This allowed quantitatively estimating the level of anthropogenic electromagnetic noise in the recorded time series.</p>
The first products of the current Cumbre Vieja eruption comprise simultaneous tephra fall from ne... more The first products of the current Cumbre Vieja eruption comprise simultaneous tephra fall from near-continuous, gas-rich eruption plumes and lava flows. From combined field, petrographic and geochemical analyses we identify: low percentage mantle melts with a variably-equilibrated multimineralic crystal-cargo and compositional fractionation by eruptive processes. Hence petrology can untangle complex magmatic and volcanic processes for this eruption, which through further study can assist in active decision making.
<p>The Canary Islands are one of the main “sun and beach&#822... more <p>The Canary Islands are one of the main “sun and beach” tourist destinations in the world. As an example, Tenerife received in 2018 more than five million tourists. Even so, on the island there are some destinations that are experiencing a decrease in the touristic afflux. With the aim of avoiding the decline of these destinations initiatives have been raised to promote new touristic products and experiences as result of diversify the leisure offer of the island. Within the variety of new products, urban geotourism is one of those new and alternative modalities that may increase the touristic offer of Tenerife. Urban geotourism aims at exploiting the geographical and natural elements (volcanoes, cliffs, beaches, ravines, etc.), that have not been wiped out by the urban growth and transformation processes. Urban geotourism involves also cultural heritage (churches, hermitages, cemeteries, houses, squares, etc.) and the urban layout itself.</p><p> </p><p>The aim of this work is to propose an urban geotourism itinerary through the historical centre of Santiago del Teide (Tenerife, Canary Islands, Spain). For this purpose, we selected places and elements that are directly or indirectly associated with the monogenic basaltic eruptions of the Chinyero (1909 AD) and the Bilma Mountain volcano (3,000 years BC). Santiago del Teide is a municipality located at the west of Tenerife with an area of 52.21 km<sup>2</sup> and a population of 10,755 inhabitants. The municipality can be divided into two large areas: the coast dedicated to “sun and beach tourism” and mid-elevation areas dedicated mainly to agricultural activities and hiking tourism associated with flowering almond trees. The documented methodology consists of making an inventory of the land forms and processes related to the geomorphological features present in the historical centre and its surroundings. This inventory comprises also natural elements visible in the architecture of the town and allowed classifying and estimating the valuable element of the geoheritage. This identification and selection are based on the variety of inventoried resources, on the possibilities it offers and on its geographical distribution. Twelve places of natural heritage (Way of the Virgin of Lourdes and Mountain Bilma) and cultural relevance (Church of San Francisco Rey, Hermitage of Santiago Apostle, El Calvario, Casona del Patio, CEI Chinyero, Alley of the Virgin, Eras of Rodríguez Guanche Street, Crescent Square, San Francisco Cemetery and Cemetery Road, Queen's Street, Santiago del Teide City Hall, La Grama Quarry, Vicente Febles PR and the Arribas Valley) of the city were selected to design a geotouristic itinerary with a length of about 8 km and requiring about 5 hours walking.</p>
<p>... more <p>During a volcanic eruption, one of the most relevant threat for civil aviation is the dispersion of volcanic ash in the atmosphere. All the aircraft are susceptible to suffer damages from volcanic ash even at low concentrations. The economy of Canary Islands (Spain) strongly depends on tourism, so it is of fundamental importance to estimate the consequences of a possible eruptive scenario of the air traffic in the archipelago and consequently on the tourism. We made an exhaustive study about the impact of volcanic ashes on aviation for one of the most important islands in the archipelago: Tenerife.</p><p>We developed a large set of numerical simulations of small-magnitude eruptions in Tenerife, which are the most probable eruptive scenario in this island. Our main goal is to develop a probabilistic approach to evaluate the airports most affected by dispersion and fallout of volcanic ash. We carried out more than a thousand simulations with the software FALL3D using supercomputing facilities of Teide-HPC from the Instituto Tecnológico y de Energías Renovables (ITER). In order to model the small-magnitude eruptions, we calculated datasets of total mass of volcanic ash erupted and eruption lengths using a bivariate empirical probability density function obtained using Kernel Density Estimation (KDE) from data of historical eruptions in Tenerife. The vent positions were selected following the density of vents related to Holocene eruptions. Granulometries were chosen following Bi-Gaussian distribution of particle size ranging from Φ=-1 to Φ=12, where Φ=-log<sub>2</sub>d (diameter in mm). The number of eruptive phases within each eruption is selected randomly. We have split equally the total eruptive duration into these eruptive phases and we set a gaussian distribution in the centre of each division. After that, the intersection between each eruptive phase is chosen taking into account these gaussian distributions to have eruptive phases with different duration.</p><p>All the simulations are coupled with ERA-Interim meteorological reanalysis data from the European Centre for Medium-Range Weather Forecasts (ECMWF). We have implemented a probabilistic procedure to map in 3D the hazard associated to volcanic ash. For this purpose, we calculated concentration percentiles (P<sub>25</sub>, P<sub>50</sub> and P<sub>75</sub>) and time intervals of high concentrations of volcanic ash to evaluate the hazard of suspended ash in the volume surrounding the major airports in Tenerife.</p>
Updates in Volcanology - Transdisciplinary Nature of Volcano Science, 2021
Volcanic landscapes offer a multitude of resources to the communities that live within them. Howe... more Volcanic landscapes offer a multitude of resources to the communities that live within them. However, the main attraction that volcanoes offer is associated with volcanic heritage and geotourism. The scope of this project is to create and promote emerging geotouristic products through the empowerment of volcano tourism and thus contribute to strengthening the economic and business fabric of the volcanic island of Tenerife (Spain). In Tenerife, this great geodiversity includes the stravolcanoes, shield volcanoes, calderas, cinder cones, maars, tuff cones and rings, and lava fields, all exposed beautifully in cliffs, ravines, beaches, deposits, etc. The main activities of the project associated with the documentation and quantification of the conservation values of the volcanic heritage are the following: production of a documentary on the volcanic geoheritage of Teide volcano, selection of the top 50 sites of geotouristic interest, creation of urban geotourism itineraries, recreation...
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Papers by William Hernández