Journal of Volcanology and Geothermal Research最新文献

{"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}

{"title":"Petrogenesis of Miocene volcanism in the Central Anatolia: Geochemical, isotopic and geochronological evidence","authors":"Şenel Özdamar ,&nbsp;Mehmet Z. Billor ,&nbsp;Oral Sarıkaya ,&nbsp;Bala Ekinci Şans ,&nbsp;Taşkın Deniz Yıldız ,&nbsp;Fahri Esenli ,&nbsp;Haibo Zou ,&nbsp;Sarah Sherlock ,&nbsp;Ali Haydar Gültekin","doi":"10.1016/j.jvolgeores.2024.108086","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108086","url":null,"abstract":"<div><p>This paper presents the first ⁴⁰Ar/³⁹Ar age data, new bulk-rock major-trace element compositions and Nd<img>Sr isotope geochemistry, combined with detailed geological mapping of Galatia Volcanic Province (GVP) in the northwest Central Anatolia (Turkey). Here, there are voluminous extrusive rocks in a wide compositional range: a basalt, andesite and trachyte suite, and their pyroclastic equivalents. ⁴⁰Ar/³⁹Ar dating of two whole-rock samples from the GVP yielded plateau ages of 21.76 ± 0.8 Ma and 20.97 ± 0.5 Ma, constrain the volcanic activity at ca. 21 Ma (Aquitanian). The samples show by sub-parallel light rare earth element (LREE)-enrichment and relatively flat heavy rare earth element (HREE) patterns and moderate fractionation [average (La/Yb)_<em>N</em> = 13.5]. Their initial ^87/86Sr values vary between 0.704619 and 0.704998, while initial ^143/144Nd values lie between 0.512673 and 0.512755. Integration of the geochemical and geochronological with geological data we propose that the volcanic rocks in the northern area of GVP with calc-alkaline affinity were produced by a lithospheric mantle magma in an extensional setting.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108086"},"PeriodicalIF":2.9,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140816113","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":"Brittle fragmentation of Fissure 17 enclave magma revealed by fractal analysis","authors":"V. Haag ,&nbsp;B.F. Houghton ,&nbsp;D. Perugini ,&nbsp;A. Soldati","doi":"10.1016/j.jvolgeores.2024.108087","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108087","url":null,"abstract":"<div><p>The 2018 LERZ eruption of Kilauea featured a wide range of eruptive styles. In particular, Fissure 17 (F17) displayed activity ranging from Hawaiian fountaining in the eastern part of the fissure to Strombolian explosions in the western part. Lava erupted from F17-West was highly viscous and contained magmatic enclaves. Magmatic enclaves have previously been observed in many other volcanic systems (e.g. Vulcano Island, IT and Sete Cidades Volcano, PT), where they have been attributed to injection of mafic magma into an evolved magma chamber, resulting in viscous fingering, quenching, and break-off into fragments. The F17 enclaves differ from previous studies in that the chemical compositions of the enclave and host magmas are very similar, and that the enclaves have a limited spatial distribution and lack signs of viscous behavior and quenching, pointing to a different formation mechanism than inferred for other volcanic systems.</p><p>In order to test a different formation hypothesis, we conducted fractal analysis of the size distribution of 84 individual enclaves from F17-West lavas. Our results, including a fractal dimension of fragmentation <span><math><msub><mi>D</mi><mi>f</mi></msub></math></span> of 2.59, indicate that the F17 enclaves likely formed by brittle fragmentation. Since the enclave and host magmas were at temperatures far above the glass transition during the magma hybridization, high strain rates have to be invoked to explain the brittle fragmentation. This may have caused the enclave magma to transition into solid-state behavior, allowing it to break off into fragments that were subsequently picked up by the host magma and carried to the free surface.</p><p>The enclaves from F17-West therefore offer a unique insight into the diversity of processes that characterizes the shallow parts of volcanic systems, as well as the importance of strain rates in modulating the rheological behavior of magmas.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108087"},"PeriodicalIF":2.9,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140816522","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":"Lava squeeze-ups and volcanic resurfacing: a review","authors":"Hetu Sheth ,&nbsp;Anmol Naik ,&nbsp;Arunodaya Shekhar ,&nbsp;B. Astha ,&nbsp;Hrishikesh Samant","doi":"10.1016/j.jvolgeores.2024.108085","DOIUrl":"10.1016/j.jvolgeores.2024.108085","url":null,"abstract":"<div><p>Squeeze-ups are common features of basaltic lava flow-fields on Earth. Squeeze-ups, rootless autointrusions of lava, drive intraflow resurfacing of active flow-fields, and the term is also used for linear or bulbous extrusions (syn. “breakouts”, “outflows”) from cracks in the solid crust, or from tensional clefts on tumuli. Despite the abundance of squeeze-ups in the active or Recent flow-fields of Hawaii, Etna or Iceland, and in the prehistoric continental flood basalt (CFB) provinces, there has been no dedicated study of them for about a century. Here we present a well-illustrated study of squeeze-ups in subaerial basaltic lavas, with a focus on the Deccan Traps CFB province of India, and show that squeeze-ups have a great range of sizes, shapes, orientations, and host flow-field morphologies including pāhoehoe, slabby pāhoehoe, rubbly pāhoehoe, slab-crusted lavas, and ‘a'ā. Squeeze-ups, as the name suggests, originate from overpressurisation of lava flow interiors, caused by mechanisms such as an increased lava flux, progressive downward solidification of the upper crust, crystallisation leading to volatile exsolution (second boiling), viscous fingering, and constricted or blocked lava tubes. The overpressurised lava may create a hydrofracture in the crustal roof in the manner of a dyke, or open an incompletely sealed contact between adjacent flow-units in a compound flow. Similar-looking features formed by passive tapping of interior lava by fractures forming in the cooling, contracting and deforming crust can be termed “lava crack-seals”. We offer a formal discussion of the theoretical and outcrop similarities and differences between dykes and squeeze-ups, features usually easy to distinguish but not always so. We also discuss the distinctions between feeder dykes and pseudodykes, and between squeeze-ups and lava fingers, features often liable to mutual confusion in outcrop. Finally, we review the existing definitions of squeeze-ups, and provide a new formal definition that includes their surface and subsurface realms, the product, and the process: “Squeeze-ups are rootless autointrusions that cause endogenic growth and intraflow resurfacing in lava flow-fields, or rootless extrusions produced by such resurfacing, involving brittle deformation of their host rock.” It is certain that, with future high-resolution remote sensing imagery, squeeze-ups will be recognised on the surfaces of the terrestrial planets other than Earth, given their ubiquity and essential role in the physical development of basaltic lava flow-fields on Earth.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108085"},"PeriodicalIF":2.9,"publicationDate":"2024-04-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140758816","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":"Magma intrusion process during pre-magmatic period (2010−2013) of Sinabung volcano as revealed by seismicity of volcano-tectonic and hybrid earthquakes","authors":"Vico Luthfi Ipmawan ,&nbsp;Masato Iguchi ,&nbsp;Takahiro Ohkura ,&nbsp;Takeshi Tameguri ,&nbsp;Hetty Triastuty","doi":"10.1016/j.jvolgeores.2024.108078","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108078","url":null,"abstract":"<div><p>Sinabung volcano in Indonesia reactivated, with a series of phreatic eruptions, in August and September 2010. These eruptions were followed by various types of magmatic eruption at the summit, including lava dome growth, pyroclastic density currents, lava flow, and vulcanian eruptions, starting in December 2013. Prior to the magmatic eruptions, Sinabung exhibited two sequences of phreatic eruption and an increase in the seismicity of volcanic earthquakes. This study clarifies the progress of magma intrusion during the pre-magmatic period based on the hypocenter distribution, waveform similarity, seismic moment, rupture length, and stress drop for volcano-tectonic (VT) and hybrid earthquakes. It was found that the hypocenters of VT earthquakes are distributed north and northwest of the summit at a depth range of 1–10 km below sea level. Deep seismicity (4–10 km) alternated with shallow seismicity (2–4 km). The last shallow seismicity, from July to mid-December 2013, was different from previous seismicity in terms of higher intensity, as determined from the seismic moment, a temporary increase in the rupture length, and the migration of hypocenters towards the summit. The seismicity of VT earthquakes was altered by a swarm of hybrid earthquakes in mid-December. The hybrid earthquakes were smaller, in terms of seismic moment (mostly &lt;3 × 10¹⁰ Nm), than the VT earthquakes. Their hypocenters were concentrated in the shallowest depth range (−0.5 to 1.5 km below sea level) directly below the summit, their source process was repeatable (they could be grouped into six earthquake families), their dominant peak was in a low-frequency range (2.5–4.5 Hz), and they had a relatively low stress drop (&lt;0.15 MPa). This suggests that the swarm of hybrid earthquakes was induced by a frequent repeated fracture of fluid-filled cracks due to the intrusion of magma up to directly below the summit. The transition of the earthquake family and the change in its source parameters, namely an increase in the stress drop prior to the appearance of a lava dome and then a slight decrease, may reflect a gradual change in internal pressure in the hypocentral zone through the magma intrusion process.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108078"},"PeriodicalIF":2.9,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000702/pdfft?md5=b8144ec96a7c0aef145bc0d8fa19791d&pid=1-s2.0-S0377027324000702-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140646584","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 15 January 2022 Hunga (Tonga) eruption: A gas-driven climactic explosion","authors":"Richard W. Henley ,&nbsp;Cornel E.J. de Ronde ,&nbsp;Richard J. Arculus ,&nbsp;Graham Hughes ,&nbsp;Thanh-Son Pham ,&nbsp;Ana S. Casas ,&nbsp;Vasily Titov ,&nbsp;Sharon L. Walker","doi":"10.1016/j.jvolgeores.2024.108077","DOIUrl":"10.1016/j.jvolgeores.2024.108077","url":null,"abstract":"&lt;div&gt;&lt;p&gt;An extraordinarily powerful, explosive eruption occurred from Hunga volcano in the Tonga island arc on 15 January 2022 and generated an eruption column 58 km high. The explosive eruption also generated atmospheric gravity waves, extreme runup tsunamis and quite unusual and destructive meteotsunamis. Together these place this VEI 6 eruption as, globally, one of the largest of the past 300 years.&lt;/p&gt;&lt;p&gt;Based on the oceanic context of Hunga volcano, it has previously been assumed that the eruption was phreatomagmatic through a fuel-coolant Surtseyan-type interaction, but this is not supported by satellite imagery. Similarly, it has been suggested that a caldera-collapse was the eruption trigger, but this is not supported by bathymetric data or the seismicity recorded during the eruption. Here we develop a new model based on the observed energetics and time sequence of the eruption integrated with understanding of the internal structure of active volcanoes and their characteristic high flux discharges of volcanic gas.&lt;/p&gt;&lt;p&gt;It has been shown elsewhere that magma-derived reactive gases (H&lt;sub&gt;2&lt;/sub&gt;O, CO&lt;sub&gt;2&lt;/sub&gt;, SO&lt;sub&gt;2&lt;/sub&gt;, HCl, etc) aggressively alter the volcanic rocks in the core of a volcano leading to self-sealing of gas flow to the surface and consequent changes to deviatoric stress in the structure. Common minerals developed by these reactions include anhydrite (CaSO&lt;sub&gt;4&lt;/sub&gt;), sulphides and silica (quartz), all of which have been recorded in volcanic ejecta including at Hunga.&lt;/p&gt;&lt;p&gt;We here develop a first order numerical model that quantifies how the free discharge of such gas to the surface may progressively become choked by these sealing reactions leading to increased internal gas pressure. Hydraulic fracture of the seal occurs when the transmitted pressure of the compressed magmatic gas beneath the seal increases to a value greater than the lithostatic pressure plus the tensile strength of the sealed rock. This initiates the explosive release of compressed gas whose high-power discharge progressively develops and enlarges a crater. At the same time, the explosion feeds upon itself by generating larger pressure gradients in the pressurized gas within the fractured porous rock mass of the core of the volcano. Excavation of the crater may intersect high level intrusions and produce the pumice rafts that were observed after the eruption. The eruption itself diminished in intensity as the gas pressure in the reservoir declined.&lt;/p&gt;&lt;p&gt;At Hunga, the eruption excavated an 850 m deep, 2-3 km diameter steep-walled crater. This volume may be assumed to approximate the volume of fractured porous rock (the control volume of the eruption) whose trapped gas was mined by the eruption until surrounding gas pressure was depleted. Our numerical model shows that the calculated potential energy of the trapped compressed gas matches the independent observations of the scale of the eruption. Sensor data have since shown that gas bubble flare","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"451 ","pages":"Article 108077"},"PeriodicalIF":2.9,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000696/pdfft?md5=f35894257444b47659252cf03cfcd33c&pid=1-s2.0-S0377027324000696-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140779439","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":"Total CO2 budget estimate and degassing dynamics for an active stratovolcano: Turrialba Volcano, Costa Rica","authors":"Kate M. Nelson ,&nbsp;Christofer Jiménez ,&nbsp;Chad D. Deering ,&nbsp;Maarten J. de Moor ,&nbsp;Joshua M. Blackstock ,&nbsp;Stephen P. Broccardo ,&nbsp;Florian M. Schwandner ,&nbsp;Joshua B. Fisher ,&nbsp;Snehamoy Chatterjee ,&nbsp;Guillermo Alvarado Induni ,&nbsp;Alejandro Rodriguez ,&nbsp;Doménicca Guillén Pachacama ,&nbsp;Alexander Berne ,&nbsp;Cecilia Prada Cordero ,&nbsp;Paola Rivera Gonzalez ,&nbsp;Espree Essig ,&nbsp;Manuel E. Anderson ,&nbsp;Carlos Hernandez","doi":"10.1016/j.jvolgeores.2024.108075","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108075","url":null,"abstract":"<div><p>Distributions and concentrations of carbon dioxide being emitted from active volcanoes elucidate the subsurface controls on gas ascent from the source and provide important information regarding the extent and state of the magmatic system. The main goal of this study was to determine if degassing followed open- or closed-system dynamics, and to define a baseline for eruption monitoring of degassing across the volcanic edifice through the CO₂ budget estimate from the combined results of two CO₂ gas emission surveys from 2021 and 2022 on Turrialba volcano, Costa Rica. This was accomplished by utilizing a new method for estimating total carbon flux on and around this persistently degassing and intermittently erupting volcano by integrating fine and coarse spatial scales of measurements; including an analysis of carbon isotopes to determine the source contributions to the gas emissions. Approximately 99% (2287 ± 1719 t CO₂ day⁻¹) of magma-derived degassing activity is advective and concentrated at the summit crater, with a smaller, continuous component of ∼1% (23.73 ± 6.65 tonnes CO₂ day⁻¹) flank diffuse soil degassing. As the majority of the gas emissions from Turrialba are concentrated in the summit plume, the system is likely experiencing open-system degassing dynamics through one dominant degassing pathway. Though at relatively low levels, the locations and distributions of diffuse degassing on the volcanic flanks allow us to delineate subsurface features that likely reveal the extent of the magmatic system of the volcano. Volcanic CO₂ outputs at Turrialba primarily concentrate along faults and fractures near the summit and across the flanks where permeable zones allow gas ascent, and with limited emissions elsewhere. The results of this study provide a baseline for monitoring future changes in the Turrialba magmatic system and demonstrate the potential for applying this method to other volcanic complexes, particularly those that are poorly monitored or where there is a greater prevalence of diffuse and distal degassing.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108075"},"PeriodicalIF":2.9,"publicationDate":"2024-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140641544","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":"Monitoring hydrothermal fumaroles in the Azores archipelago - Applications and sources of analytical uncertainties","authors":"D. Matias ,&nbsp;M. Antlauf ,&nbsp;F. Viveiros ,&nbsp;L. Moreno ,&nbsp;C. Silva ,&nbsp;S. Oliveira","doi":"10.1016/j.jvolgeores.2024.108076","DOIUrl":"https://doi.org/10.1016/j.jvolgeores.2024.108076","url":null,"abstract":"<div><p>The Azores archipelago is located in the North Atlantic Ocean and is formed by nine volcanic islands. Present-day volcanic activity in the archipelago comprises not only seismic swarms and episodes of ground deformation in some volcanoes, but also hydrothermal gas manifestations. The main fumaroles are associated with central quiescent volcanoes and have been sampled in the past decade through the Giggenbach methodology. Analysis of the fumarolic fluids from four volcanic systems in São Miguel, Terceira, and Graciosa islands are displayed for the period between July 2015 and February 2023. No significant changes have been observed both on the selected gas ratios (CO₂/CH₄, H₂/CH₄, He/CH₄, He/CO₂, and H₂/Ar), and on the equilibrium temperatures estimated for the reservoirs feeding the fumaroles using the H₂/Ar gas geothermometer, what is in agreement with the dormant state of activity of the studied volcanic systems. Equilibrium temperatures ranging between 223 °C and 262 °C are estimated for Fogo and Furnas fumarolic fields (São Miguel Island), and an average equilibrium temperature of 254 °C is inferred for Terceira fumaroles. This study also suggests a procedure based on established guidelines to evaluate the analytical uncertainties of the methodologies associated with the Giggenbach sampling strategy. Comparison of the analytical uncertainties with the overall data variation (including additional natural variations and sampling uncertainty), shows that the analytical uncertainties are not the limiting factor for the interpretation of the survey results.</p></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"450 ","pages":"Article 108076"},"PeriodicalIF":2.9,"publicationDate":"2024-04-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0377027324000684/pdfft?md5=8e3139fdbb5682512b5ed3f12e0725be&pid=1-s2.0-S0377027324000684-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140638528","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}