Journal of Volcanology and Geothermal Research最新文献

{"title":"Volcanic history of Gölcük caldera (Isparta, Türkiye) with evidence for a Holocene explosive eruption","authors":"Gökhan Atıcı ,&nbsp;Bjarne Friedrichs ,&nbsp;Mehmet Çobankaya ,&nbsp;Martin Danišík ,&nbsp;Evren Atakay ,&nbsp;Esra Yurteri ,&nbsp;Axel K. Schmitt","doi":"10.1016/j.jvolgeores.2025.108403","DOIUrl":"10.1016/j.jvolgeores.2025.108403","url":null,"abstract":"<div><div>Modern Lake Gölcük near the city of Isparta partially fills a caldera that is the focal point of protracted alkaline, potassic–ultrapotassic volcanism in southwestern Anatolia. Because of Gölcük's proximity to a major regional urban center, and field indications for far-reaching pyroclastic density currents (PDC) erupted from this caldera, improved constraints on eruptive recurrence and timing are required. Through field work and combined U<img>Th and (U<img>Th)/He zircon geochronology, the duration of known volcanism at Gölcük has been extended, both to older and, importantly, to younger ages than previously reported. Early activity in the Late Miocene–Pliocene (Stage 1, 6.0–4.2 Ma) was mostly effusive, whereas explosive activity started in the Early Pleistocene (Stage 2, 2.2–1.8 Ma) forming nine PDCs of the Serençay valley ignimbrite sequence. Following a hiatus, PDC and fallout emplacement resumed during Stage 3 (520–480 ka) and Stage 4 (150 ka), with the modern caldera likely being the result of the Stage 4 Çay ignimbrite eruption. U<img>Th zircon crystallization ages of antecrysts, especially in Stage 4 and 5 pumice, clearly implicate Gölcük as the source of the Stage 2 and 3 explosive eruptions. Stage 5 includes effusive activity and dome formation, but also at least four explosive eruptions starting at c. 24 ka. The discovery of the here termed Isparta ignimbrite, which erupted from Gölcük caldera at 10.7 ± 0.7 ka (2 σ uncertainty), identifies it as an active volcano. Frequent eruptions at recurrence intervals of 4–5 ka during the Late Pleistocene–Holocene transition warrant future research regarding its hazard potential. This also implies that Gölcük may have erupted distal tephra markers for this climatically important interval.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108403"},"PeriodicalIF":2.4,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557622","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":"A Quaternary marine tephrostratigraphic record of New Zealand's explosive volcanism – Integration of medial and distal to ultra-distal marine tephra inventories","authors":"K. Pank ,&nbsp;S. Kutterolf ,&nbsp;J.C. Schindlbeck-Belo ,&nbsp;J.L. Hopkins ,&nbsp;K.-L. Wang ,&nbsp;H.-Y. Lee ,&nbsp;A.K. Schmitt","doi":"10.1016/j.jvolgeores.2025.108404","DOIUrl":"10.1016/j.jvolgeores.2025.108404","url":null,"abstract":"<div><div>Explosive volcanism is characteristic for New Zealand's Taupō Volcanic Zone (TVZ) and precursory arcs. Yet, complex field relationships hinder the establishment of continuous explosive eruption records. Marine environments preserve deposits of explosive volcanic eruptions, leading to comprehensive, continuous and stratigraphically reliable archives of past eruptions. Here, we present an extended and comprehensive marine tephrostratigraphy of New Zealand's explosive Quaternary volcanism and show how it can be used as a framework for global tephra studies.</div><div>We analysed major and trace element glass shard compositions (EMP and LA-ICP-MS) of 546 Quaternary marine tephra samples from IODP Exp. 375/372, ODP Leg 181, IODP Leg 329 and DSDP Leg 90 (south-) east of New Zealand. A combined approach of geochemical fingerprinting and stratigraphic context revealed 331 primary marine tephra layers, further correlated across the study area resulting in 165 individual Quaternary volcanic events being identified. Thirty-three of these volcanic events were further assigned to known onshore deposits (e.g. Taupō tephra, Rotoehu ash, Hikuroa Pumice member, and Welcome Bay Ignimbrite). The continuous marine volcanic time series of New Zealand's explosive volcanism provides new evidence for the temporal transition from Coromandel Volcanic Zone to TVZ volcanism, and yields the most accurate repose times of Quaternary volcanism to date (1:12 kyr between &lt;1.6 Ma, and 1:38 kyr between 2.6 and 1.6 Ma). Furthermore, the marine volcanic record shows examples, like the 53 kyr-lasting pulsed volcanic activity associated with the Kidnappers-B/Potaka tephra eruptions, for very large eruptions occurring as eruptive sequences rather than as one continuous event.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108404"},"PeriodicalIF":2.4,"publicationDate":"2025-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144611672","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":"Characterization and evolution of the basaltic magma reservoir beneath the Asal-Ghoubbet rift, Republic of Djibouti","authors":"Araksan Ahmed Aden ,&nbsp;Enikő Bali ,&nbsp;Guðmundur H. Guðfinnsson ,&nbsp;Gylfi Páll Hersir ,&nbsp;Iwona Monika Galeczka ,&nbsp;Kayad Moussa Ahmed","doi":"10.1016/j.jvolgeores.2025.108401","DOIUrl":"10.1016/j.jvolgeores.2025.108401","url":null,"abstract":"<div><div>The Asal-Ghoubbet rift is one of the emergent segments of the Aden Gulf oceanic ridge, which spreads westward on land into the triple junction zone of the Afar depression. The studied rift has been characterized by repeated magmatic and tectonic activity over its ∼1 Ma evolution, and during the latest volcano-tectonic episode in November 1978, a one-week-long basaltic fissure eruption led to the formation of the Ardoukôba volcano. This study investigates the evolution of the basaltic magma reservoir beneath the rift over an eruptive time span from ∼300 ka to the present. In total, eleven basaltic samples were collected and analyzed. We carried out petrography and major and minor element analyses for whole rock, microcrystalline groundmass, glass, and mineral phases. The lava compositions range from transitional to tholeiitic basalts and their chemical variability can largely be explained by fractional crystallization, along with concurrent mixing. The most common macrocryst phase is bytownite plagioclase, whereas olivine and clinopyroxene macrocrysts are found in lesser proportions. Mineral-melt equilibria suggest that olivine and clinopyroxene are dominantly phenocrystic in all formations, crystallizing from their respective carrier liquid. Most plagioclase macrocrysts are antecrysts and too primitive to have crystallized from their carrier liquid. Clinopyroxene-melt and melt-only barometric results indicate that magmas of the last ∼300 ka were extracted from a constant mid- to deep crustal zone at a depth between 7 and 18 km. In contrast, crystallization temperatures indicate progressive cooling and thus evolution of the degree of differentiation, which are interrupted by periodic replenishment of fresh primitive melts. Overall, similar magma storage conditions appear to have been maintained over time, which implies continuous renewal of the geothermal heat source in the Asal-Ghoubbet rift. These results are consistent with previous geophysical studies and thus can be used to update and strengthen our knowledge of the studied magma plumbing system.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108401"},"PeriodicalIF":2.4,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144564070","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":"Evaluating bulk carbon and nitrogen isotope compositions of acidic hot spring and mudpot sediments as biosignatures","authors":"Chance Sturrup,&nbsp;Anna Szynkiewicz","doi":"10.1016/j.jvolgeores.2025.108402","DOIUrl":"10.1016/j.jvolgeores.2025.108402","url":null,"abstract":"<div><div>Carbon (C) and nitrogen (N) isotopes have been widely used as biosignatures to study the origin of organic materials. However, bulk δ¹³C and δ¹⁵N analyses have been underutilized in hydrothermal settings, making relevant comparisons to early Earth environments and other planetary materials difficult. Therefore, in this study we examined if bulk isotope analysis can be successfully used to detect a microbial signature in hydrothermal environments similar to where life might have begun on Earth. We analyzed concentrations and isotope compositions of C and N within acidic hydrothermal sediments in Iceland and the United States. The measured bulk δ¹³C of the hot spring and mudpot sediments was higher in barren Icelandic sites (−25.6 to −14.5 ‰) compared to lower values in more forested sites of the United States (−26.5 to −21.0 ‰). These corresponded to lower C concentration in Iceland (0.13 to 0.55 wt%) and higher C concentrations in the United States (0.04 to 4.78 wt%). The distinctive negative ranges of bulk δ¹³C were indicative of life processes occurring in-situ (microbial activity) and in the surrounding area (production of plant biomass). The higher δ¹³C of the Icelandic sediments were consistent with smaller C isotope fractionations associated with thermophile (microbial) activity, wherein more negative bulk δ¹³C values corresponded to increasing input of allochthonous plant matter in the United States. Conversely, the bulk δ¹⁵N results (−18.4 to +3.7 ‰) were less useful in differentiating biosignatures because of overlapping δ¹⁵N values between various N sources such as allochthonous plant matter, volcanic/hydrothermal gases, and microbial processes.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108402"},"PeriodicalIF":2.4,"publicationDate":"2025-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557308","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":"Petrophysical properties of hydrothermally-altered pyroclastic deposits from Deception Island (Bransfield Strait, Antarctica)","authors":"Michael J. Heap ,&nbsp;Adelina Geyer ,&nbsp;Jasmine Dibben ,&nbsp;James Hickey ,&nbsp;Guillem Gisbert ,&nbsp;Oriol Vilanova-Pagès ,&nbsp;Jordi Ibañez-Insa ,&nbsp;Antonio Polo-Sánchez ,&nbsp;Santiago Giralt ,&nbsp;Maëlys Moulin ,&nbsp;Antonio M. Álvarez-Valero","doi":"10.1016/j.jvolgeores.2025.108399","DOIUrl":"10.1016/j.jvolgeores.2025.108399","url":null,"abstract":"<div><div>Deception Island is a composite volcano located in the Bransfield Strait, between the South Shetland Islands and the Antarctic Peninsula. The volcano is defined by a caldera-forming event, and the rocks forming the island—which range in composition from basalts to trachydacites-rhyolites—are typically classified as either pre-, <em>syn</em>-, or post-caldera. Here, we provide petrophysical properties (bulk density, porosity, P-wave velocity, permeability, thermal properties, Young's modulus, and uniaxial compressive strength) for representative lapilli tuffs (pyroclastic density current and fall deposits) from the pre-, <em>syn</em>-, and post-caldera volcanic activity. We find that dry bulk density varies from ∼982 to ∼1813 kg·m⁻³, connected porosity varies from 0.30 to 0.62, P-wave velocity varies from ∼0.3 to ∼1 km·s⁻¹, permeability varies from ∼10⁻¹⁵ to ∼10⁻¹¹ m², thermal conductivity varies from ∼0.3 to ∼0.65 W·m⁻¹·K⁻¹, thermal diffusivity varies from ∼0.35 to ∼0.25 mm²·s⁻¹, specific heat capacity varies from ∼0.8 to ∼1.3 J·kg⁻¹·K⁻¹, Young's modulus varies from ∼1 to ∼9 GPa, and that uniaxial compressive strength varies from ∼1 to ∼25 MPa. Our data show that P-wave velocity, Young's modulus, uniaxial compressive strength, thermal conductivity, and thermal diffusivity decrease, permeability increases, and specific heat capacity does not change systematically as a function of increasing porosity. We also find that the fall tuffs are more porous than the pyroclastic density current tuffs, and therefore have a lower P-wave velocity, Young's modulus, uniaxial compressive strength, thermal conductivity, and thermal diffusivity, but a higher permeability. Our data expose the heterogeneity of the petrophysical properties of the lapilli tuffs at Deception Island, and are in good agreement with those for similar lapilli tuffs from Surtsey volcano (Iceland) and Cracked Mountain (Canada). Microscale models for permeability, thermal conductivity, and uniaxial compressive strength provide insight into the microscale factors controlling the petrophysical properties of the lapilli tuffs, and can be used to help predict their petrophysical properties when data are absent or laboratory experiments are not possible. Large-scale hydromechanical models that use our laboratory data provide the range of expected surface displacement at Deception Island following fluid injection at depth, and highlight the importance of choosing appropriate rock property input parameters for volcano modelling.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108399"},"PeriodicalIF":2.4,"publicationDate":"2025-06-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144580250","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":"Rapid emplacement of the Keaīwa Lava Flow of 1823 from the Great Crack in the Southwest Rift Zone of Kīlauea volcano","authors":"Andrea Tonato ,&nbsp;Thomas Shea ,&nbsp;Drew T. Downs ,&nbsp;Karim Kelfoun","doi":"10.1016/j.jvolgeores.2025.108391","DOIUrl":"10.1016/j.jvolgeores.2025.108391","url":null,"abstract":"<div><div>The Keaīwa Lava Flow of 1823 in the Southwest Rift Zone of Kīlauea volcano is unusual for its expansive pāhoehoe sheet flow morphology and lack of constructive vent topography, despite having a similar tholeiitic basalt composition to other lavas erupted from Kīlauea. This lava flow issued from a ∼10-km-long continuous fissure now known as the Great Crack, and has an unusually thin sheet flow morphology with margin thicknesses of ∼15–110 cm (average of 42 cm). Based on field observations of the lava flow at its fissure vent (e.g., drain-back features), we propose that the Great Crack formed, or at least significantly widened, just prior to and syn-eruptively with this 1823 eruption. The absence of pyroclastic cones or spatter ramparts indicates that the eruption consisted of a rapid outpouring of relatively degassed lava as the fissure unzipped. The rapidly moving lava flow overtopped pre-existing tumuli and scoria cones (e.g., Lava Plastered Cones) up to ∼10 m tall. Glass and whole-rock chemistry yield homogeneous compositions for the lavas erupted from the Great Crack, with glass compositions of 6.40 ± 0.10 wt% MgO and whole-rock compositions of 7.39 ± 0.07 wt% MgO. Lava pads erupted from a short western fissure system are richer in mafic minerals (e.g., olivine and clinopyroxene), and show slightly more MgO-rich whole-rock compositions (7.79 ± 0.05 wt%). MgO-in-glass thermometry on juvenile spatter yield eruption temperatures of 1153 ± 13°C that are typical of Kīlauea lavas. Thus, the extensive sheet-like lava flow morphology is not a direct consequence of unusual magmatic or rheological conditions (i.e., low viscosity). Instead, the flow morphology is associated with high effusion rates caused by sudden drainage of uprift magma as it erupted from the Great Crack. Lava flow modeling on a 2-m-resolution digital elevation model indicates that a minimum bulk effusion rate of ∼5800 m³/s (∼3500 m³/s dense rock equivalent) and a minimum flow velocity of ∼11 m/s are required for the lava flow to overcome the topography of the Lava Plastered Cones. This effusion rate is among the highest inferred for eruptions in Hawaiʻi and around the world. This study highlights a less frequent eruption style at Hawaiian volcanoes characterized by a sudden outpouring of lava from an unusual fissure system. Local eyewitness accounts indicate that the 1823 eruption was preceded by seismicity. Given the complex magmatic-volcanic-tectonic relations across Kīlauea, we speculate that the south flank could have slipped over one or more events that ultimately triggered unzipping of the Great Crack and passive release of briefly stored uprift magma. An eruption similar to 1823 at Kīlauea or Mauna Loa, with an eruptive timeframe that could be as short as an hour, with high effusion rates and rapid flow front velocities, would not easily allow for a timely response.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108391"},"PeriodicalIF":2.4,"publicationDate":"2025-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144313513","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":"CO2 flux and water geochemistry in Ribeira Quente river: A case study from a river draining an active central volcano (Furnas Volcano – São Miguel, Azores)","authors":"J. Virgílio Cruz ,&nbsp;César Andrade ,&nbsp;Letícia Ferreira ,&nbsp;Fátima Viveiros ,&nbsp;António Cordeiro ,&nbsp;Diogo Braga","doi":"10.1016/j.jvolgeores.2025.108398","DOIUrl":"10.1016/j.jvolgeores.2025.108398","url":null,"abstract":"<div><div>Building on previous studies that suggest that river water chemistry in Ribeira Quente watershed (Furnas Volcano) is influenced by hydrothermal discharges, measurements of the CO₂ fluxes along the major river and tributaries were made. The annual runoff in the river is estimated as 9.75 × 10⁶ m³ yr⁻¹, presenting a well-marked seasonal variation.</div><div>Waters are mainly of the Na-HCO₃ type, presenting a mean temperature of 19.53 ± 5.16 °C (median = 18.5 °C), reaching values as high as 38.5 °C, a mean EC equal to 325.24 ± 177.77 μS cm⁻¹ (median = 304.5 μS cm⁻¹), and are slightly acid to basic (mean pH = 7.07 ± 0.57; median = 7.1). Physico-chemical parameters and major-ion composition depict noticeable variations whenever hydrothermal discharges occur in the river channel. Besides mixing with hydrothermal discharges, water chemistry is also influenced by silicate weathering, processes also shown by the ¹³C/¹²C and ⁸⁷Sr/⁸⁶Sr isotopic ratios.</div><div>The total amount of CO₂ emitted along selected paths range between 20.5 t d⁻¹ and 23.8 t d⁻¹, values higher than the ones calculated dividing the river channel in separate sections (13 t d⁻¹–15.5 t d⁻¹), as the former values overestimates the area, thus leading to a higher overall flux calculation. CO₂ flux for all the watershed, estimated considering the contribution of all tributaries, is in the range of 14.6 t d⁻¹ to 17.7 t d⁻¹. Even if the CO₂ flux associated to surface water bodies in the study area is much lower than soil diffuse emissions, results point out to the need to characterize C-based GHG emissions from rivers draining active volcanic areas.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108398"},"PeriodicalIF":2.4,"publicationDate":"2025-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144297012","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":"Stochastic ground motion simulation of earthquakes associated with September 19, 2021, Cumbre Vieja (La Palma Island) eruption: Determination of the quality factor Q, spectral decay parameter kappa, and site response","authors":"J. Rueda ,&nbsp;J. Mezcua","doi":"10.1016/j.jvolgeores.2025.108397","DOIUrl":"10.1016/j.jvolgeores.2025.108397","url":null,"abstract":"<div><div>The relatively strong damage caused by the seismicity associated with historical eruptions in La Palma (Canary Islands) makes it necessary to upgrade the seismic hazard of the island to produce seismic scenarios for future eruptions. Moreover, ancient earthquakes related to older eruptions can be studied if the seismic waves they produced are reproduced. To simulate such scenarios, the characteristics of the unknown earthquake must be determined: its focal characteristics including focal mechanism, location, magnitude, and stress drop; path properties, namely the geometrical spreading, quality factor Q, and its frequency dependence, along which the seismic waves propagate; and site effect. For the site effects, we considered the crustal and Vs30 amplification factors and the kappa value for the station, which represent the spectral amplitude diminution in the high-frequency band.</div><div>The simulation process used in this study is known as the stochastic simulation technique, which is based on the stochastic properties of strong ground motion and the utilization of a simple physical model for the source.</div><div>Considering the seismicity registered during the last eruption on the island of La Palma on September 19, 2021, we calculated the parameters required for the simulation to reproduce the strong ground motion of some of the recorded events. The adjustment of the observed to the recorded strong-motion records revealed the goodness of fit and the extent to which future simulations will be close to the real data.</div><div>The use of the calculated parameters in future studies would permit us to increase our knowledge of the seismic hazards on the island by considering different possible scenarios.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108397"},"PeriodicalIF":2.4,"publicationDate":"2025-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144288803","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":"Heat from dyke intrusions released by boiling of warm groundwater and steaming into the atmosphere during the 1975–1984 eruptive and intrusive activity at Krafla, Iceland","authors":"Patricia Fehrentz ,&nbsp;Magnús T. Gudmundsson ,&nbsp;Hannah I. Reynolds ,&nbsp;Anette K. Mortensen ,&nbsp;Sydney R. Gunnarson ,&nbsp;Joaquin M.C. Belart ,&nbsp;Michaela A. Chodora","doi":"10.1016/j.jvolgeores.2025.108396","DOIUrl":"10.1016/j.jvolgeores.2025.108396","url":null,"abstract":"<div><div>The Krafla volcano-tectonic episode in NE-Iceland in 1975–1984 was associated with approximately 10 m widening of the plate boundary within the Krafla caldera, where a high-temperature geothermal system is located. A composite dyke was formed, with an estimated volume 0.15–0.31 km³ within the geothermal reservoir, releasing thermal energy of 0.5–1.0 × 10¹⁸ J. An empirical relation between the area of steam clouds in air photos and their heat output was used to assess heat loss to the atmosphere by steaming during the Krafla fires. The applicability of this method for Krafla was tested in 2024 at selected locations where steam flow could be measured directly. Analyses of vertical air photos obtained several times in 1976–1985, notably during and after the eruptive events, show that steaming was mainly prevalent in the vicinity of the eruptive fissures. The heat loss to the atmosphere within the geothermal area was ∼0.9 MW/m during eruptions, declining to a more long-term value (∼0.05 MW/m) in 50–100 days. This enhanced steaming after the dyke injection/ eruption is considered to be caused by the interaction of the groundwater/shallow geothermal fluid with the uppermost 110–400 m of the dyke and appears to account for about one-third of the total heat lost in this way to the atmosphere. The remaining two-thirds were lost gradually throughout the rifting episode. The heat lost to the atmosphere (∼5–10 % of the total energy) was an order of magnitude smaller than the 90–95 % of the thermal energy added to the geothermal reservoir by the dyke.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108396"},"PeriodicalIF":2.4,"publicationDate":"2025-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144502372","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":"Influence of cristobalite and diktytaxitic textures on the physical properties of submarine rhyolite lavas from Havre volcano (Kermadec volcanic arc, Pacific Ocean)","authors":"Michael J. Heap ,&nbsp;Samuel J. Mitchell ,&nbsp;Rebecca J. Carey ,&nbsp;Alexandra R.L. Kushnir","doi":"10.1016/j.jvolgeores.2025.108392","DOIUrl":"10.1016/j.jvolgeores.2025.108392","url":null,"abstract":"<div><div>The <em>syn</em>-eruptive alteration of lavas can influence their physical, mechanical, and hydraulic properties, with implications for the outgassing of magmatic volatiles and the stability of volcanic structures. Although glass corrosion, resulting in porous diktytaxitic textures, and cristobalite precipitation is a common alteration type at both submarine and subaerial volcanoes, little is known as to their impact on rock properties. Here, therefore, we provide laboratory measurements of porosity, permeability, P-wave velocity, Young's modulus, and uniaxial compressive strength for a suite of rhyolitic lavas from the 2012 eruption at Havre volcano (Kermadec volcanic arc, Pacific Ocean; sampled in 2015) that have variable textures and contain variable quantities of cristobalite. We find that the cristobalite content of the lavas varies from 0 to ~26 area%, and that the cristobalite-rich (&gt; 10 area%) lavas are all associated with porous diktytaxitic textures. Lavas from the outermost, glassy carapace are cristobalite-poor, and lavas from the interior carapace are cristobalite-rich. Although porosity and permeability do not systematically increase with cristobalite content, the cristobalite-rich lavas from the interior carapace—those also associated with porous diktytaxitic textures—are consistently porous (&gt; ~0.13) and permeable (&gt; ~10⁻¹⁵ m²) and contain essentially no isolated porosity, which can reach up to 0.1 in the cristobalite-poor lavas from the outermost, glassy carapace. The presence of porous diktytaxitic textures in the cristobalite-rich lavas appears to lower P-wave velocity, but does not appear to reduce Young's modulus or uniaxial compressive strength. The presence of commonly-observed macrofractures in lavas from the outermost, glassy carapace increases their permeability and lowers their strength. We discuss the implications of these laboratory data for fluid movement and outgassing in, and the structure—in terms of rock physical, mechanical, and hydraulic properties—and stability of, submarine lava domes.</div></div>","PeriodicalId":54753,"journal":{"name":"Journal of Volcanology and Geothermal Research","volume":"466 ","pages":"Article 108392"},"PeriodicalIF":2.4,"publicationDate":"2025-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144263155","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}