Journal of Volcanology and Geothermal Research最新文献

{"title":"The impacts of lulls and peaks in eruption rate on lava flow propagation","authors":"S.I. Peters , A.B. Clarke , E.L. Rader","doi":"10.1016/j.jvolgeores.2024.108099","DOIUrl":"10.1016/j.jvolgeores.2024.108099","url":null,"abstract":"<div><p>Variable effusion rates have been observed during the eruption and emplacement of lava flows which can complicate lava flow predictability. Conventional wisdom suggests that eruption rates decrease exponentially with time, however, this broad trend may also be subject to short-timescale fluctuations. Flow obstructions, changes in source diameter, channel or pond overflow, and changes within the magma reservoir to name a few factors can increase or decrease local flow rates repeatedly during an active eruption and impact the behavior of the flow. Analog experiments are a useful tool for investigating the role of changing effusion rates on flow propagation because they allow reasonably precise control of conditions and detailed documentation of resulting flows. In this work, we address the effects of decreasing and increasing extrusion rates (Q) on flow propagation and four emplacement modes common to lava flows: <em>resurfacing, marginal breakouts, inflation, and lava tubes</em>. We conducted 30 experiments by injecting dyed PEG wax into a chilled bath (∼ 0 °C) on a flat slope. We divided the experiments into two pulsatory extrusion rate patterns, or conditions: stepwise decrease followed by increase in extrusion rate (lull) and stepwise increase then decrease in extrusion rate (peak). We tested a range of flow conditions spanning from flows for which strong crust was favored (low wax temperature; low extrusion rates) and those for which weak crust was favored (high wax temperature; high extrusion rates). We found that a lull in extrusion rates when a strong crust was present promoted flow expansion and thickening via limited resurfacing, localized marginal breakouts, inflation, possible tube formation, with lower rates of flow expansion after the lull. In contrast, a lull and weak crust promoted flow expansion via widespread marginal breakouts, with flow advance rebounding after the lull, and inhibited flow thickening via inflation. A peak in extrusion rates with a strong crust favored flow expansion via widespread marginal breakouts, with flow-advance deceleration after the peak, and possible thickening via inflation. Conversely, a peak in extrusion rate with weak crust promoted flow expansion via widespread marginal breakouts, with flow-advance deceleration after the peak, and inhibited flow thickening via resurfacing and inflation. Our results have implications for pahoehoe flow emplacement and have been used to assess the most appropriate parameters to be used in a probabilistic flow propagation model, MrLavaLoba.</p></div><div><h3>Plain Language Summary</h3><p>Variable effusion rates have been observed during the eruption of lava flows which can complicate lava flow forecasts. In general, lava flow effusion rates decrease with time exponentially although there may be fluctuations in flow rate on short timescales. Flow rates can wax or wane for a variety of reasons, such as flow obstructions, changes in the shape of the erupting sourc","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108099"},"PeriodicalIF":2.9,"publicationDate":"2024-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S037702732400091X/pdfft?md5=6ae5beb33f650e49c12869c027b0836e&pid=1-s2.0-S037702732400091X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141029077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A lower bound on the rheological evolution of magma in the 2021 Fagradalsfjall Fires","authors":"Arianna Soldati ,&nbsp;Donald B. Dingwell ,&nbsp;Thorvaldur Thordarson ,&nbsp;Ármann Höskuldsson ,&nbsp;Ingibjörg Jónsdóttir ,&nbsp;William M. Moreland ,&nbsp;Jóna S. Pálmadóttir ,&nbsp;Catherine R. Gallagher ,&nbsp;Helga K. Torfadóttir ,&nbsp;Jacqueline Grech Licari ,&nbsp;Iðunn Kara Valdimarsdóttir ,&nbsp;Lilja B. Pétursdóttir ,&nbsp;Robert A. Askew","doi":"10.1016/j.jvolgeores.2024.108098","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108098","url":null,"abstract":"<div><p>As magma temperature and composition drift and change, respectively, throughout an eruption, so does its rheology. These changes may span orders of magnitude in magma viscosity and result in orders of magnitude flow velocity changes, as well as transitions in eruptive style. In this study, we present a systematic high precision quantification of the rheological variations that occurred during the 2021 Fagradalsfjall Fires. In the field, we collected a suite of 22 representative samples emplaced between day 2 and 183 of the 2021 eruption. In the laboratory, we measured the melt viscosity of each sample in a concentric cylinder viscometer. Temperatures were initially raised to 1392 °C, and then lowered stepwise to eruptive temperatures as determined through <em>syn</em>-eruptive radiometric measurements. The resulting dataset is analyzed as a time series. An overall trend of viscosity decrease emerges. As the eruption progressed, melt viscosity decreased by 25%, from 40 Pa s to 30 Pa s at a constant temperature of 1200 °C. However, this trend is not monotonous. At least 3 positive spikes in viscosity can be identified, at day 80, 120, and 138 of the eruption. This trend tracks with geochemical variations.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108098"},"PeriodicalIF":2.9,"publicationDate":"2024-05-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140947471","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Time scales of olivine storage and transport as revealed by diffusion chronometry at Waitomokia Volcanic Complex, Auckland Volcanic Field, New Zealand","authors":"Rosa Didonna ,&nbsp;Heather Handley ,&nbsp;Helena Albert ,&nbsp;Fidel Costa","doi":"10.1016/j.jvolgeores.2024.108094","DOIUrl":"10.1016/j.jvolgeores.2024.108094","url":null,"abstract":"<div><p>Detailed knowledge of the pre-eruptive time scales associated with magma storage and transport is vital to improve volcanic hazard forecasting in active volcanic regions. However, quantification of the timescales of volcanic processes at mafic volcanic centres in continental intraplate settings is challenging, despite them being a source of significant hazards for human populations and infrastructure due to their limited predictability in space and time. We conducted a detailed petrological study to investigate the time scales of olivine storage and transfer throughout the eruption sequence of Waitomokia Volcanic Complex, a tuff ring and scoria cone complex in the Auckland Volcanic Field. Olivine crystal textures and compositions were determined from stratigraphically-constrained samples of the volcanic complex, from the initial phreatomagmatic phase to the final magmatic phase. Olivine crystals are typically &lt;300 μm in length and characterised by skeletal morphologies, displaying chemical zoning in forsterite (Fo = 100*Mg/[Mg + Fe]; mol%), CaO, MnO and NiO wt% contents. We classified olivine into three major groups based on their Fo core compositions: (1) normally zoned crystals with high Fo content (Fo &gt; 85), (2) crystals with intermediate Fo contents (84–81), and (3) reversely zoned crystals with lower Fo core content (&lt;80). Olivine chemical zoning (diffusion) profiles were modelled in the context of a specific magmatic environment linked with changes in thermodynamic variables during storage (temperature, pressure, and oxygen fugacity). We propose that the normally zoned olivine crystals grew in one magmatic environment (ME1), which subsequently intruded into a more evolved (lower MgO) environment (ME2), where they interacted and were stored for up to 135 days before their eruption. During magma ascent to the surface, a second magma mixing event occurred between ME2 and magma within a third magmatic environment (ME3), forming reversely-zoned olivine crystals yielding notably shorter ascent times of approximately a few days. The rocks from the opening phreatomagmatic phase of the eruption show a larger range in olivine group types compared to the final magmatic phase, where those from the deeper ME1 are more abundant. The short time scales of magma transport obtained in our study, on the order of days to months, should be informative of the warning times that may be encountered between the onset of volcanic unrest and an eruption in the Auckland Volcanic Field.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108094"},"PeriodicalIF":2.9,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000866/pdfft?md5=3a5095b94a81ab9cc9a12af244064f55&pid=1-s2.0-S0377027324000866-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141033308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The spatial distribution and evolution of volcanic vents in monogenetic fields in active extensional tectonic setting: Examples from the northern Main Ethiopian Rift (Ethiopia)","authors":"Francesco Mazzarini,&nbsp;Ilaria Isola","doi":"10.1016/j.jvolgeores.2024.108093","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108093","url":null,"abstract":"<div><p>Monogenetic volcanic fields are present in different geo-tectonic settings (subduction, divergence and intraplate settings) consisting of tens to hundreds of volcanic constructs (cones, maars, fissures, small shields) that are the physical expression of distributed volcanism.</p><p>Notably, the spatial distribution of the volcanic constructs in volcanic fields often shows a spatial clustering that is thought to be linked to shallow (i.e., crustal strain, structural inheritance) and deep processes (i.e., magma input, composition and rheology). Noteworthy, the spatial distribution of vents (cones, maars, fissures, small shields) is the final frame of the history of the volcanic field and does not provide information about its time-evolution.</p><p>Consequently, when a vent spatial clustering is assessed for a particular volcanic field two questions remain unanswered: i) have the vents always been clustered during the life of the volcanic field? ii) If not, when did the clustering of vents begin? To answer these questions, the spatial distributions of vents along with their morphologic classification have been applied to volcanic fields located in an active tectonic and volcanic area. The northern Main Ethiopian Rift, being its geo-tectonic setting and its geologic evolution well known, is the locale where the time evolution of vent spatial clustering can be investigated. Spatial distribution and morphometric analysis of vents have been applied to three well known monogenetic volcanic fields (Debre Zeyt, Wonji and Kone) in the northern Main Ethiopian Rift. Vent clustering initiated when about 60% of the vents formed within each of the above mentioned fields. The Kone volcanic field show vent clustering since the beginning suggesting that, within a specific tectonic setting, vent clustering is favoured by crustal strain partitioning and associated volcanic activity.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108093"},"PeriodicalIF":2.9,"publicationDate":"2024-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000854/pdfft?md5=e8724612c2f9d248c841945b8d01a4fd&pid=1-s2.0-S0377027324000854-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140950943","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Near-real-time multiparametric seismic and visual monitoring of explosive activity at Sabancaya volcano, Peru","authors":"Riky Centeno ,&nbsp;Valeria Gómez-Salcedo ,&nbsp;Ivonne Lazarte ,&nbsp;Javier Vilca-Nina ,&nbsp;Soledad Osores ,&nbsp;Efraín Mayhua-Lopez","doi":"10.1016/j.jvolgeores.2024.108097","DOIUrl":"10.1016/j.jvolgeores.2024.108097","url":null,"abstract":"<div><p>This study presents the development of a multiparametric system that utilizes artificial intelligence techniques to identify and analyze volcanic explosions in near real-time. The study analyzed 1343 explosions recorded between 2019 and 2021, along with seismic, meteorological, and visible image data from the Sabancaya volcano. Deep learning algorithms like the U-Net convolutional neural network were used to segment and measure volcanic plumes in images, while boosting-based machine learning ensembles were used to classify seismic events related to ash plumes. The findings demonstrate that these approaches effectively handle large amounts of data generated during seismic and eruptive crises. The U-Net network achieved precise segmentation of volcanic plumes with over 98% accuracy and the ability to generalize to new data. The CatBoost classifier achieved an average accuracy of 94.5% in classifying seismic events. These approaches enable the real-time estimation of eruptive parameters without human intervention, contributing to the development of early warning systems for volcanic hazards. In conclusion, this study highlights the feasibility of using seismic signals and images to detect and characterize volcanic explosions in near real-time, making a significant contribution to the field of volcanic monitoring.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108097"},"PeriodicalIF":2.9,"publicationDate":"2024-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141032540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Estimating emission flux of H2S from fumarolic fields using vertical sensor array system","authors":"Yutaka Miyagi ,&nbsp;Urumu Tsunogai ,&nbsp;Kohei Watanabe ,&nbsp;Masanori Ito ,&nbsp;Fumiko Nakagawa ,&nbsp;Ryunosuke Kazahaya","doi":"10.1016/j.jvolgeores.2024.108090","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108090","url":null,"abstract":"&lt;div&gt;&lt;p&gt;The emission flux of volatiles from each fumarolic field in volcanic and geothermal areas can be used to evaluate the current state of magmatic activity and predict its future trends. The emission flux of &lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; has been quantified in many fumarolic fields using remote sensing techniques, such as differential optical absorption spectroscopy (DOAS). However, most of these remote sensing techniques are inapplicable to fumarolic fields emitting volatiles depleted in &lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; to which most of the geothermal fields are classified. In this study, we developed a vertical sensor array system to quantify the emission flux of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; from each fumarolic field by integrating the cross-sectional distributions of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; concentrations in the volcanic plume using the vertical sensor array system. In Iwo-yama of the Kirishima volcanic complex, the cross-sectional distribution of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; concentrations was determined using the walking traverse method by moving the vertical sensor array system in the plume perpendicular to the direction of plume transport. The emission flux of &lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt; (2.2 ± 0.4 ton &lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/day) was estimated from that of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; using the walking traverse method (2.6 ± 0.5 ton &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;/day) and the molar ratio of the plume (&lt;span&gt;&lt;math&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;msub&gt;&lt;mi&gt;O&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;/math&gt;&lt;/span&gt;/&lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;45&lt;/mn&gt;&lt;/math&gt;&lt;/span&gt;) corresponds well with that estimated optically by JMA. We concluded that the emission flux quantified using the vertical sensor array system was reliable. In the Oyunuma pond in the Kuttara volcano, the emission flux of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; was quantified as 2.0 ton &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;/day through the fixed point method, wherein the vertical sensor array system was fixed in one point, whereas the cross sectional distribution of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; in the plume was estimated using the natural variation in wind direction. The topography is often irregular and wind direction is variable in most fumarolic fields; thus, in general, the fixed point method should be more suitable to determine the emission flux of &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/msub&gt;&lt;mi&gt;S&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; from fumarolic fields, wherein &lt;span&gt;&lt;math&gt;&lt;msub&gt;&lt;mi&gt;H&lt;/mi&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;/m","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108090"},"PeriodicalIF":2.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000829/pdfft?md5=912fda4ba00404380669d349488a7cd2&pid=1-s2.0-S0377027324000829-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140843415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Nieve volcanic cluster: A Pliocene - Pleistocene lava dome cluster in the Michoacán-Guanajuato volcanic field (México)","authors":"Denis-Ramón Avellán ,&nbsp;Silvestre Cardona-Melchor ,&nbsp;Martha Gabriela Gómez-Vasconcelos ,&nbsp;José Luis Macías ,&nbsp;Paul William Layer ,&nbsp;Giovanni Sosa-Ceballos ,&nbsp;María-Camila Ruíz ,&nbsp;Jeff Benowitz ,&nbsp;Guillermo Cisneros-Máximo ,&nbsp;Hugo Murcia ,&nbsp;Mathieu Perton ,&nbsp;Gabriela Reyes-Agustín ,&nbsp;Felipe García-Tenorio","doi":"10.1016/j.jvolgeores.2024.108091","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108091","url":null,"abstract":"<div><p>The Nieve monogenetic volcanic cluster is located in the central–eastern region of the Michoacán–Guanajuato volcanic field, along the Huiramba fault zone, a relay ramp in the Morelia–Acambay fault system produced by oblique north-northwest transtension. This volcanic cluster includes at least 17 middle Pliocene to late Pleistocene lava domes, two small shield volcanoes, and two scoria cones. Between 4 and 3.8 Ma, two effusive eruptions built two small shield volcanoes overlying one another, with a magma volume of 3.93 km³. Between 2.9 Ma and 21.4 ka, 17 lava domes and two scoria cones were emplaced on the flanks of these volcanoes. The entire cluster resulted in a total erupted volume of 17 km³, covering an area of <!--> <!-->326 km² and reaching a thickness of emplaced volcanic material of 1200 m, resulting in a magma eruption rate equivalent to 0.004 km³/ka. All the rocks associated with this cluster are within a relatively restricted range in composition, between 53.9 and 64.2 wt% SiO₂, from andesite enriched in silica to basaltic andesite. The presence of intrusive-rock xenoliths and xenocrysts with dissolution textures reveals that assimilation processes modified the magmas. Based on the regional geological record, we suggest that the establishment of the Nieve volcanic cluster has been controlled by tectonic structures and the basement of the region, which has allowed the chemical evolution of these magma batches that probably had sources in at least two deep reservoirs as reflected by the Nb/Th versus Ta/U ratio.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108091"},"PeriodicalIF":2.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140880175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Short-period flow oscillation during eruptions of Onikobe geyser, NE Japan: Insights from thermal infrared observation and acoustic measurements","authors":"Noriko Teshima ,&nbsp;Takeshi Nishimura","doi":"10.1016/j.jvolgeores.2024.108092","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108092","url":null,"abstract":"<div><p>Geysers are episodic features with variable eruption intervals that range from minutes to years. Although many previous studies on geysers have focused on subsurface properties and processes such as plumbing geometry and recharge process, it is known that erupting fluid column exhibits short-term behaviors such as individual water jets from the vent. In the present study, we conducted observations at Onikobe geyser, NE Japan, a relatively small geyser (geysering well) erupting water up to ∼6–8 m every ∼10 min and observed the erupting fluid column using a thermal infrared camera and an acoustic sensor. We succeed in tracking the water jets by analyzing spatio-temporal temperature map obtained from the thermal infrared observation, which clearly shows the eruptions at Onikobe geyser are not completely stationary but rather a series of intermittent jets with a short period interval of &lt;1 s. We estimate the exit velocity by fitting a ballistic model under the air drag condition of inertial resistance to the jet trajectory. The exit velocity and the averaged gas volume fraction of the erupting fluid are estimated to be ∼4–79 m/s and ∼0.93–0.96, respectively. The exit velocity is ∼30 m/s during the first bursts, then it rapidly increases to ∼50–80 m/s for ∼15 s, and then decreases to ∼20–30 m/s until ∼10 s before the eruption ends. Time series analyses of the thermal infrared and acoustic signals during an eruption indicate harmonic spectra with integer multiple peaks. The fundamental frequency showing ∼4 Hz at the beginning gradually decreases to ∼2 Hz for ∼15 s, keeps almost constant in the following 30 s, and then slightly increases near the end of the eruption. These harmonic spectra may be caused by a resonance mechanism, non-linear fluid motion, and/or subsurface two-phase flow. We discuss the case of a closed organ-pipe resonance in a subsurface crack and attribute the frequency decrease to a decrease in the water level in the crack (an increase in the length of the resonating liquid-vapor column) and/or a decrease in the gas volume fraction of the liquid-vapor mixture in the crack. Since such harmonic characteristics are observed at other geysers, further simultaneous observation of the short-period oscillations on the erupting column proposed in this study with seismic observations of harmonic tremor may provide an improved understanding of geyser subsurface phenomena.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108092"},"PeriodicalIF":2.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140893327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Fluid geochemistry of the Cerro Galán geothermal system (Southern Puna, Argentina): Implications for the geothermal potential of one of the youngest giant calderas in the Andes","authors":"A. Chiodi ,&nbsp;W. Báez ,&nbsp;F. Tassi ,&nbsp;E. Bustos ,&nbsp;R. Filipovich ,&nbsp;J. Murray ,&nbsp;A.L. Rizzo ,&nbsp;O. Vaselli ,&nbsp;G. Giordano ,&nbsp;J.G. Viramonte","doi":"10.1016/j.jvolgeores.2024.108089","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108089","url":null,"abstract":"&lt;div&gt;&lt;p&gt;The exploration of novel geothermal systems, particularly those promising for electrical power generation, plays a fundamental role in incorporating new renewable sources into the energy matrix. Geothermal systems associated with volcanic calderas are considered ideal targets for exploration. This study focuses on the geochemical features of fluids from the Cerro Galán hydrothermal system, which is hosted within a major resurgent caldera with &gt;3.5 Myr of magmatic evolution situated on the Southern Puna (Central Volcanic Zone of the Andes, NW Argentina). The main aim is constructing the first geochemical conceptual model and provide information on the geothermal potential of this interesting resource. The main hydrothermal reservoir consists of a Na&lt;img&gt;Cl aquifer with estimated temperatures up to 187 °C at depth. This reservoir is likely hosted within the fractured pre-caldera basement rocks, mainly including Miocene-Pliocene volcanic rocks and Proterozoic-Cambrian igneous and metamorphic rocks. The confinement of the deep reservoir is attributed to the deposits of the Toconquis Group and Cueva Negra Ignimbrite, along with the basal section of the Cerro Galán Ignimbrite, which exhibit low permeability due to hydrothermal alteration. The presence of a phreatic explosion crater near one of the hot spring-rich areas is likely indicating past over-pressurization of the hydrothermal aquifer, resulting from efficient sealing. Furthermore, the absence of anomalous soil CO&lt;sub&gt;2&lt;/sub&gt; flux values on the top of the reservoir, except where the thermal spring discharges are located, can be explained by an effective cap-rock layer. Deep circulation of meteoric water, enriched with atmospheric gases, receives inputs of magmatic fluids (∼11% of primordial helium), leading to the development of the hydrothermal Na&lt;img&gt;Cl aquifer. However, this deep fluid contribution might be underestimated due to significant crustal assimilation (up to 50%) involved in the magma genesis of the Cerro Galán Volcanic Complex, a process which modifies the He isotopic signature of the magmatic endmember. The hot springs, characterized by high flow rate (up to 459 m&lt;sup&gt;3&lt;/sup&gt;/h) are positioned at the intersection between the caldera margins and the NNE-SSW oriented tectonic structures, suggesting favorable permeability conditions. The preliminary geothermal gradient for the Cerro Galán area is estimated at around 98–101 °C/km. Such a high gradient can be attributed to the considerable heat flux generated by the transcrustal plumbing system of the Cerro Galán caldera, which includes the shallow crystal mush reservoir (&lt;4 km depth). The preliminary geothermal potential of this giant caldera was performed using the volumetric method along with Monte Carlo simulations. The results indicate a probable power production capacity of 2.09 MWe and 10.85 MWe at 90 and 50% confidence level, respectively. The results presented in this work constitute a foundational knowledge base","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108089"},"PeriodicalIF":2.9,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140823623","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Very-long-period signal reveals lava lake sloshing and its interaction with a deep reservoir in Nyiragongo volcano","authors":"Jieming Niu","doi":"10.1016/j.jvolgeores.2024.108088","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108088","url":null,"abstract":"<div><p>The longevity of lava lakes in open-vent volcanoes reflects a hydraulic connection between the lake and the deep part of the magma plumbing system. Constraining the size of the shallow magmatic system and resolving the rheology of magma filling in the system is essential to evaluate potential hazards like lava flow and other activities. As the lava lake is often perturbed by degassing bursts, rockfall, and even convection, seismic waves radiated from the oscillation of fluid and its mechanical coupling with the surrounding solid walls provide invaluable information on probing system geometry and magma rheology. In this report, I show the first observation of very long-period signals in Nyiragongo volcano, to uncover the sloshing of the world's largest known lava lake and its dynamic interaction with a deep reservoir during the relatively quiet period. The signal is manifested as the ground oscillations with two isolated spectral peaks at ∼15 s and ∼16 s sustaining up to half an hour and a spectral peak at a longer period of ∼76 s. The radiated seismic energy can be well recognized by the stations with distances of &lt;50 km to the lava lake. The traveling time, particle-motion polarization, and deformation inversion suggest that the 15 s' and 16 s' modes are related to two orthogonal horizontal forces at a very shallow depth, likely pointing to the sloshing dynamics of the lava lake. The 76 s' mode is considered as the dynamic coupling between the lake bottom to a deep reservoir at a depth of 8–16 km through a conduit driven by the sloshing. The dynamic modeling of the 76 s' mode points to a deep reservoir storativity of ∼8 m³/Pa and a spherical reservoir with a radius of ∼7.5 km. High-frequency seismic waves before the onset of the 15 s' and 16 s' modes suggest that the signals may be excited by rigorous degassing or rockfall. Variations in the period and quality factor of the modes reflect the changes in the lake/reservoir geometry and magma rheology. This finding may improve our ability to understand the magmatic plumbing system, track magma evolution in Nyiragongo, and further probe the formation of lava lakes in active volcanoes.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108088"},"PeriodicalIF":2.9,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140823329","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}