Eruptive Phase Research Articles

Brief and intensive volcanic emissions from Ontong Java Nui heralded Oceanic Anoxic Event 1a

The volcanic episode that formed Ontong Java Nui (OJN) in the western Pacific ~ 120 million-year-ago is thought to have triggered Oceanic Anoxic Event (OAE) 1a, yet the cause-effect relationship remains insufficiently understood. Here, we present a Pb-Os-C isotope dataset for tracking OJN volcanism across a sedimentary sequence containing OAE1a record in the central Pacific. Lead isotopic evidence strongly supports the deposition of OJN-sourced volcanic ash layers at this site after a paired seawater δ13Ccarb–187Os/188Os shift and before the onset of OAE1a. The δ13Ccarb–187Os/188Os shift is attributable to the signature of the initial submarine OJN eruption. The subsequent unradiogenic Pb isotope shifts could represent ash fallout from the brief, explosive subaerial/shallow-marine eruption phase accompanied by intensive volcanic degassing and emissions. The apparent time lag between explosive OJN volcanism and OAE1a is intriguing, which can be accounted for by the delayed increase in the productivity after gas emissions.

Challenges in block-and-ash flow hazard assessment: The July 10–11, 2015 eruption of Volcán de Colima, Mexico

On July 10 and 11, 2015, Volcán de Colima, one of the most active Mexican volcanoes, underwent its largest eruption since the 1913 Plinian event. Highly mobile block-and-ash flows (BAF) originated from the dome collapse and subsequent extrusion of bubble gas-rich magma from the conduit. The volume and runout of flows were at least one order of magnitude higher (106 m3) than the events observed previously in the 2004–2005 eruptive episode (105 m3) and only comparable with the pyroclastic density currents emplaced during the Vulcanian eruptive phase that preceded the 1913 Plinian eruption. The TITAN2D code is here used to understand the factors controlling the mobility of the dense BAF undercurrents emplaced during the 2015 eruption. The selection of different input parameters was based on field data, on the seismic signal of the BAFs recorded by a broadband station located a few meters away from the channel, and by considering the different eruptive mechanisms of the July 10 eruptive phase (collapsing dome) with respect to the July 11 event (rapid extrusion of degassed magma directly from the conduit). A collapsing pile best fits the July 10 BAF, with an initial spread on the proximal reach and subsequent emplacement along the Montegrande ravine. Instead, for the July 11 BAF, an influx source best replicates the observed distribution, including the overspilling down the San Antonio ravine at the middle reach and the aggradation at the final depositional fan. Both events were better reproduced with the Voellmy-Salm rheology with respect to the Mohr-Coulomb model. Still, the mobility of the July 11 BAF was controlled mainly by the channel reduced capacity due to the 10 July BAF infilling. This was assessed by modeling the 11 July BAF on the real terrain and on a DEM whose altitude was modified based on the maximum flow depth obtained from the simulation of the former flow. Deep knowledge of the eruptive mechanism and flow behavior during the 2015 eruption allowed us to understand the main factors controlling concentrated pyroclastic density current mobility during sustained, multi-phase eruptions, especially for valley-confined BAF. The results presented here set the basis to improve the hazard zonation for pyroclastic density currents at Volcán de Colima, which should be based on a multifactor, probabilistic analysis.

Simultaneous normal and reverse faulting in reactivating caldera faults: A detailed field structural analysis from Campi Flegrei (southern Italy)

Models of volcanic collapses proposed in the literature rely on combining field examples with analogue and numerical modelling to connect superficial observables to sub-surface volcano-tectonic processes. However, the behaviour of such collapses in an already faulted and fractured medium needs to be better explored.We studied a complex array of normal and reverse faults within the central sector of the active Campi Flegrei caldera, where faults with centimeters-to-meters displacements are hosted in the La Pietra tuff (∼13.5 ka) and the overlying pyroclastic succession of the last ∼5.5 kyr. We analyzed the attitude, kinematics and throw of these structures, employing a UAV-based digital outcrop model. The analysis shows that antithetic normal and reverse faults form in the hanging wall of a pre-existing WNW striking, NNE-dipping master normal fault. Moving northward, the strike of the antithetic faults rotates from WNW to NNW directions, with the latter showing a right-lateral oblique component. The simultaneity and coherence of both kinematics and attitudes are verified by the throw analysis. We associated the formation of this array with the caldera-collapse phase of the Agnano-Monte Spina eruption (∼4.55 ka), which caused off-caldera faulting beyond the main collapsed area.Based on field data, we suggest that during peak caldera-forming phases, wider areas beyond the main caldera scarps can be involved in volcano-tectonic collapses in the presence of a pre-existing fault network and complex tapped reservoirs. This highlights the role of inherited structures in weakening the crust above the magma reservoir that can potentially increase the magnitude and duration of caldera-forming eruptions, as they may induce a broader roof rock subsidence, pressurizing wider regions of the sub-caldera magma system.

Evaluating legal age of 18 years through observation of third molars using Gambier et al. method in an orthopantomographic sample of subadults from South India

In forensic practice, medicolegal physicians are often tasked with estimating age using dental evidence. This calls for an uncomplicated, reliable, and reproducible method for dental age estimation, enabling physicians to proceed without specific odontological expertise. Among various dental methods, third molar eruption analyses are less complicated and easier to perform. In our study, we explored the effectiveness of Gambier et al.'s scoring system, which examines the eruption of all third molars. We retrospectively analysed 1032 orthopantomograms (528 males and 504 females) of individuals aged between 15 and 24 years. The mean chronological age increased with the progression of stages (1 to 3) and phases (A to D) of the third molar eruption for both sexes. In terms of stages, none showed significant discrimination between minors (<18 years) and adults (>18 years), especially for males. However, Gambier’s phase D displayed a relatively high likelihood of being 18 years or older, with an overall 85.9 % of males and 95.7 % of females having all third molars in stage 3 being 18 years or older. While the tested method could be helpful in indicating the completion of the 18th year of life, caution is advised (due to a high percentage of false positives), and it should be used alongside other age assessment methods by experts.

Bartonellosis (Oroya Fever, Peruvian Wart): A Case Report

Bartonellosis (also called Carrión's Disease, Oroya Fever or Peruvian Wart) is caused by the bite of mosquitoes of the Lutzomyia genus belonging to the Psychoid family. They are nocturnal blood-sucking insects, with complete metamorphosis. About 450 species are known, distributed throughout the American continent, mostly in tropical and subtropical areas. In Ecuador, sporadic cases have been reported, with certain characteristics such as, for example, not presenting the blood phase and, in the eruptive phase, not being aggressive. Here, we present a unique case of a 13-year-old boy with a history of congenital heart disease, who presented a clinical picture of one year of evolution suggestive of dermatosis, characterized by papules and nodules that occasionally bleed. The mother reports living in an area of lush vegetation and being in contact with bites. The results of blood count, peripheral blood smear, liver function and coagulation: normal. Blood sample: Negative Bartonella spp. PCR biopsy ribC gene: Positive B. bacilliformis. This case demonstrates the importance of maintaining an entomo-epidemiological surveillance system in patients exposed to arthropod bites that allows for timely detection of cases in order to make a diagnosis and provide timely treatment.

Dynamics of the COVID-19 pandemic in Lebanon between 2020 and 2022

We carry out an evolutionary study of the COVID-19 pandemic, focusing on the case of Lebanon. The disease spread exhibits four eruption phases or waves. Chaos theory tools point toward a correlation of events, essentially obeying a quasi-deterministic chaotic regime. The analysis of the time series yields a largest Lyapunov exponent of 0.263, indicative of a chaotic trend. The review of past and recent analyses and modeling of pandemics could assist in the predictabilty of their course of evolution, effective management and decision making for health authorities.

The Whakamaru magmatic system (Taupō Volcanic Zone, New Zealand), part 2: Evidence from ignimbrite deposits for the pre-eruptive distribution of melt-dominated magma and magma mush

The complex volcanology and petrology of the Whakamaru volcanic deposits in Aotearoa New Zealand have thus far obscured the number of eruptive phases and the relative timing of these eruption(s). We investigate pumice clasts from multiple localities to elucidate the relative timing of the eruptions, with a focus on the pre-eruptive conditions of the melt-dominated magma bodies that fed the Whakamaru eruptions and on the mushes from which these magmas were extracted. Paired whole-rock and glass compositions confirm four magma types erupted during the Whakamaru eruptions (types A, B, C, D; originally identified by Brown et al., 1998). Using the glass compositions of the pumice clasts, we calculate pre-eruptive storage temperatures (using zircon saturation geothermometry) and pressures (using rhyolite-MELTS geobarometry). Using matching whole-rock compositions from a subset of pumice clasts, we calculate extraction pressures from magma mush (also using rhyolite-MELTS geobarometry). Pre-eruptive storage pressures estimate the depths where melt-dominated magma bodies were located prior to eruption; extraction pressures, in contrast, estimate the depths at which melt was extracted from magma mush to form melt-dominated magma bodies at shallower levels of the crust. Magmas were stored at shallow depths (∼50-150 MPa) prior to eruption. Extraction pressures for types B and C are well constrained to 155-355 MPa (with an assemblage including plagioclase and quartz). Extraction pressures for types A and D depend on oxygen fugacity (fO2), as the extraction assemblage includes plagioclase and orthopyroxene (170-290 MPa for ΔNNO = 0 to +0.5 and 290-360 MPa for ΔNNO = +1 to +1.5). The four magma types likely represent independent magma bodies, with these melt-dominated magma bodies stored shallower than and separate from the mush. At least two different magma subsystems fed the Whakamaru eruptions – one subsystem sourced the type A and type D magmas, while the other sourced the type B and type C magmas. The distribution of magma types recorded in the ignimbrite deposits and in the correlated tephras (Harmon et al., 2024) reveal the sequence of eruption for the four different mappable ignimbrites. The ignimbrites to the east of the caldera (Rangitaiki ± Te Whaiti) erupted before the Whakamaru ignimbrite (sensu stricto) to the west of the caldera. The youngest Whakamaru ignimbrite eruptions likely deposited to the northwest of the caldera contemporaneously with the Manunui ignimbrite to the west of the caldera. The combination of petrological data from the ignimbrites and associated tephras suggest a complex system that included laterally juxtaposed melt-dominated magmas as well as laterally juxtaposed magma mushes that spanned much of the shallow crust, but with regions in which magma appeared in low concentration or was entirely absent. This complex pre-eruptive architecture probably contributed to the complex eruptive patterns observed for the Whakamaru eruptions.

Eruption plumes extended more than 30 km in altitude in both phases of the Millennium eruption of Paektu (Changbaishan) volcano

AbstractThe Millennium Eruption of Paektu volcano, on the border of China and North Korea, generated tephra deposits that extend &gt;1000 km from the vent, making it one of the largest eruptions in historical times. Based on observed thicknesses and compositions of the deposits, the widespread tephra dispersal is attributed to two eruption phases fuelled by chemically distinct magmas that produced both pyroclastic flows and fallout deposits. We used an ensemble-based method with a dual step inversion, in combination with the FALL3D atmospheric tephra transport model, to constrain these two different phases. The volume of the two distinct phases has been calculated. The results indicate that about 3-16 km3 (with a best estimate of 7.2 km3) and 4-20 km3 (with a best estimate of 9.3 km3) of magma were erupted during the comendite and trachyte phases of the eruption, respectively. Eruption rates of up to 4 × 108 kg/s generated plumes that extended 30-40 km up into the stratosphere during each phase.

SO2 emissions from the Timanfaya eruption (1730–36 CE), Lanzarote, Canary Islands

The 1730–36 CE eruption of Lanzarote (Canary Islands) is the third largest basaltic fissure eruption known to have occurred in the last 1000 years, after the Icelandic events of Laki (1783–84 CE) and Eldgja (939 CE). Approximately 5.2 km3 (1.1 × 1012 kg) of alkalic basalt (sensu lato) lava and pyroclastic rocks were emplaced on land, with a further unknown amount entering the sea, The activity occurred in five eruptive phases from vents situated along a 15-km long, E-W trending fissure. Each phase began with Strombolian fire fountain activity, building large spatter and scoria cones, accompanied and followed by effusive ‘a'ā and pāhoehoe lava flow emplacement. Phases I and II were the most explosive and occurred between 1st September 1730 and June 1731. Samples of scoria and lava surfaces were collected from all phases and the major elements, S, Cl and F contents of matrix glasses and glass inclusions in olivine (the dominant phenocryst phase) were analysed by electron microprobe. Water contents of selected glasses were measured on polished wafers by Fourier Transform Infrared spectroscopy. Glass compositions mimic the range of published whole rock compositions, with Phase I being predominantly basanitic and later phases alkali basalt. Whole rock variations in incompatible trace element ratios are mimicked by ratios involving TiO2, K2O and P2O5 in glass. Matrix and glass inclusion analyses in a given sample are similar, indicating that the inclusions formed synchronously with eruption and that most phenocryst crystallization occurred during earlier evolution of the magmas. Matrix glasses in scoria and surface lava samples have 80–300 ppm S and 260–750 ppm H2O, whereas glass inclusions in olivine have 420–2650 ppm S and 0.1 to 0.5 wt% H2O. Glass inclusions with low sulfur contents were trapped during degassing-induced crystallization as the magma approached the surface. The inclusions with the highest sulfur contents, at given P2O5/TiO2 ratio, are inferred to represent un-degassed melt, and their S content and S/K2O ratios correlate very strongly with incompatible element concentrations and P2O5/TiO2 ratios. The original S contents of 131 matrix glasses were calculated from their P2O5/TiO2 ratios and compared to their measured degassed S contents. The mass of S released per unit mass of magma ranged from about 0.25% in Phase I Episode 1to 0.17% in later phases, with propagated uncertainties of about 2 to 5%. About 40 Mt. of SO2 was released overall, with ca. 25 Mt. being released during the first 5 months of the eruption (Phase I). Estimates of average magma discharge rates imply that plumes remained in the troposphere, with the possible exception of those associated with extreme peak discharge rates during Phase I Episode 1 which may have just reached the upper troposphere – lower stratosphere. Lower eruption rates during the later phases would have confined SO2 emissions to the troposphere. Although acid and sulfate peaks dated to 1730 and 1731 have been reported from some Greenland ice cores, the evidence for stratospheric impact, such as cooling at the Earth's surface and increased stratospheric turbidity, is minimal.

Study of Eruption Mechanism Pyroclastic Deposit of Banten Tuff (Qpvb) in Pancanegara and its surrounding Using Grainsize Distribution and Componentry Analysis

Banten Tuff (Qpvb) is pyroclastic deposit that is very significant in western Java Island. The importance of this deposit is caused by spreading and covering most of Banten region. In the middle of Banten Tuff, there is a caldera that has rectangular shape and the large area 13.7 km x 6.5 km. The research in this area has not studied yet that explain the characteristics of pyroclastics deposit in detail, therefore it’s hard to tell how the eruption process and mechanism that happened based on the deposit. This study become solution of a puzzle about process, mechanism, history, and episode of eruption. The research methods are using qualitative and quantitative analysis such as grain-size distribution and componentry. The study has succeed obtaining more than ten outcrops that described in detail. Description of outcrops resulted tephra-stratigraphy correlation in four facies unit. These four facies categorized into three eruption phases. Eruption phases are arranged into a story which is useful for determining historical and episode eruption in Pancanegara and its surrounding.

The magmatic system under Hunga volcano before and after the 15 January 2022 eruption

One of the largest explosive eruptions instrumentally recorded occurred at Hunga volcano on 15 January 2022. The magma plumbing system under this volcano is unexplored because of inherent difficulties caused by its submarine setting. We use marine gravity data derived from satellite altimetry combined with multibeam bathymetry to model the architecture and dynamics of the magmatic system before and after the January 2022 eruption. We provide geophysical evidence for substantial high–melt content magma accumulation in three reservoirs at shallow depths (2 to 10 kilometers) under the volcano. We estimate that less than ~30% of the existing magma was evacuated by the main eruptive phases, enough to trigger caldera collapse. The eruption and caldera collapse reorganized magma storage, resulting in an increased connectivity between the two spatially distinct reservoirs. Modeling global satellite altimetry–derived gravity data at undersea volcanoes offer a promising reconnaissance tool to probe the subsurface for eruptible magma.

Reconciling complex stratigraphic frameworks reveals temporally and geographically variable depositional patterns of the Campanian Ignimbrite

Abstract The 39.8-ka Campanian Ignimbrite was emplaced during a large caldera-forming eruption of Campi Flegrei near Naples, Italy. The ignimbrite is found up to 80 km from the caldera, and co-ignimbrite ash-fall deposits occur 3200 km away. The proximal and distal stratigraphy of the Campanian Ignimbrite has not been definitively correlated due to the dissimilar appearance of the proximal and distal deposits, a lack of medial exposures, and the inconsistency and heterogeneity of the proximal stratigraphy. Here, we document the major-element glass-shard chemistry, matrix componentry, and lithic componentry of the proximal and distal stratigraphic sequences of the ignimbrite to attempt to correlate the units. The results of these disparate observations taken together suggest that the established stratigraphic units cannot be directly and uniquely correlated between the proximal and distal regions and that neither the proximal nor distal stratigraphy provides a record of the entire eruptive sequence. However, the characteristics studied can be used to demarcate eruptive phases that are connected to some of the defined units in the proximal and distal stratigraphy.

Cryptotephra preserved in Lake Suigetsu (SG14 core) reveals the eruption timing and distribution of ash fall from Japanese volcanoes during the Late-glacial to early Holocene

Long sedimentary successions extracted for palaeoclimate research regularly preserve volcanic ash (tephra) fall from explosive eruptions and are increasingly used to elucidate the timing and scale of past events. This study investigates the non-visible tephra (cryptotephra) layers preserved in the annually laminated and intensively 14C dated sediments of Lake Suigetsu (SG14 core), Japan. The cryptotephra investigations reported here focus on the Late-glacial to early Holocene sediments that were deposited between two visible tephra layers, the Ulleungdo (U)-Oki (10.2 ka) and the Sambe ‘Sakate’ (19.6 ka), and consequently span an interval of abrupt climate change making any newly identified cryptotephra layers invaluable chrono-stratigraphic markers. Using major and trace element volcanic glass compositions the cryptotephra are used to assign provenance to chrono-stratigraphically relevant eruption units. Five new cryptotephra layers are identified within this time interval. Three cryptotephra layers are from Kyushu volcanoes (SG14-1337 and SG14-1554 [Sakurajima]; and SG14-1806 [Kirishima]), all of which offer important chronological constraints on archaeological (Jomon) cultural transitions in southern Japan during the last termination. Another cryptotephra (SG14-1579), is assigned to activity on Niijima Island providing the first known distal occurrence and age of the eruption. Finally, the SG14-1798 cryptotephra precisely dated at 16,619 ± 74 IntCal20 yrs BP (2σ) is linked to Asama (As) volcano and more precisely the later phases of the As-YKU eruption. This discovery greatly expands the distribution of ash fall from this multi-phased eruption at Asama volcano, which affected an area in the region of 120,000 km2. Refining the timing of the eruption and the distribution of As-YKU ash fall is important as it offers an excellent chrono- and climato-stratigraphic marker suitable for assessing spatial variability in environmental response to past climate change during the termination of the last glacial.

Framing analysis of the print media coverage of the 2020 Taal volcano eruption

The media became a primary source of information for the public during the 2020 Taal Volcano Eruption in the Philippines. However, before this study, the quality of media communication about Taal remained unknown. Understanding the content and manner of media coverage during the eruption is important in understanding and enhancing volcanic risk communication. Hence, this study analysed 384 stories about the 2020 Taal Volcano Eruption using the Framing Theory and Social Amplification of Risk Framework as analytical lenses. Specifically, it aimed to identify the salient frames used by the news media and describe the potential implications of framing to risk amplification or attenuation. It was determined that the frames used by the media largely functioned as a problem identifier, with a particular focus on human interest and governance. Potentials for risk amplification were also noted in the use of dramatization and projection of future risks. However, amplification was balanced by attenuating signals such as the downplaying of economic impacts and clarifications on governance conflict. On the other hand, due to the limited use of cause diagnosis frames, the volcanic risk was not well-discussed. Numerical uncertainty statements were also missing in the coverage but some stories used verbal, albeit vague, uncertainty statements. Furthermore, moral evaluation and solution recommendations were noted, although media coverage was dominated by disaster response actions. In conclusion, while the media was able to provide useful information during the eruptive phase of Taal Volcano in 2020, it fell short of conveying comprehensive risk information towards better-informed decision-making and responses.

Atypical presentation of mpox in Irrua environs: a case report

BackgroundMpox, previously known as monkeypox, -is an orthopoxvirus infection of the skin and previously a public health emergency of international concern. It reemerged in Nigeria over 5 years ago and has since spread to other parts of the world. This is a case report of a confirmed patient who was managed at Irrua Specialist Teaching Hospital, Irrua, Edo State, Nigeria before the global surge. This report shows peculiar differences from previous patients managed at the same center in terms of the relatively prolonged eruptive phase, possible seasonal occurrence of mpox in the community, and some traditional care for mpox and skin rashes. It also corroborates previous reports of possible sexual transmission of mpox in Nigeria before the report from the global outbreak.Case presentationThe patient is a 30-year-old Nigerian male artisan with a 2-month history of raised rashes on the body that started on the genitals then involved other parts of the body. There was history of sore throat and unprotected sex with a female partner with similar rash whose other sexual history could not be ascertained. There was also history of “seasonal” rash in his village for about 7 years prior to his symptoms. Examination showed multiple vesicles and some nodules (ulcerating, healing, and healed) on the face, trunk, limbs, gluteal region, scrotum, palms, and sole, an almost circumferential penile ulcer, and lymphadenopathy. Polymerase chain reaction skin samples sent for mpox returned positive, while retroviral and coronavirus disease 2019 screenings were negative. He was managed in isolation while contact tracing in the affected community was initiated.ConclusionAtypical presentations of mpox, as managed in Irrua before the global surge, emphasize the varied spectrum of presentations (typical and atypical) in Nigeria. Therefore, there is a need for a higher index of suspicion for the uncommon presentations which will strengthen case recognition, case management, and community-based interventions as well as surveillance in the prevention and control of mpox in Irrua, its environs, Nigeria, and the world.

Decoding subcontinental lithosphere processes: The key role of fractional crystallization in Central Andes monogenetic volcanism - Insight from El Negrillar volcanic field, Chile

Subduction zones are complex geodynamic settings in which volcanic arcs form due to the interaction between subducting slabs, water, and continental materials. Investigating this extensive Earth recycling system offers valuable insights into the exchange of materials between the crust and mantle. While previous research has primarily focused on analyzing polygenetic volcanoes to explore this interaction, monogenetic volcanic fields (MVF) present an opportunity to delve into the mechanisms operating within the upper and lower mantle. Monogenetic volcanoes are a class of volcanoes that are typically smaller in size but showcase a range of eruptive styles and compositions. These volcanoes can be found in various locations along the arc, including the main Central Volcanic Zone (CVZ) (arc-front volcanoes), and even far from the tectonic plate boundaries in the back-arc region (intraplate volcanism).We carried out a detailed geochemical study of El Negrillar (EN) MVF, located in the Central Andes main-arc, on the Altiplano-Puna Plateau's southwestern border. The volcanic field has 35 eruptive centers and a total of 86 eruptive phases originating from its three clusters: Northern, Central, and Southern. EN magmas range in composition from basaltic andesite to dacite and have produced over 6.8 km3 (DRE) of lava and pyroclastic material, which makes it the most voluminous volcanic field in the Central Andes, and therefore, an excellent example to study MVF in arc-systems. We have conducted an extensive study encompassing major and trace elements, as well as isotopic analysis using whole rock Sr-Nd-Pb. We also present an analysis of our results with available geochemical data from the back-arc and main-arc volcanoes, including other monogenetic volcanoes near EN (<80 km, EN's neighbors). The results revealed that EN magmas and their neighbors are strongly related and exhibit a clear similarity in major and trace element compositions and isotopic ratios, indicating a common source and origin of their melts. Our comparison across the arc surprisingly reveals similarities between EN and back-arc monogenetic volcanism. Both regions indicate geochemical signatures that do not support melting via slab metasomatism, typical of subduction zones. Instead, they show low Th/Ce (<0.1 ppm) and Ba/La (<30 ppm) and high Ce/Pb (>6 ppm), Ba/Th (>100 ppm), high 143Nd/144Nd > 0.51240, and La/Yb ratios at a given La/Sm compared to the main-arc polygenetic volcanoes. Interestingly, EN also exhibits adakite-like signatures with increasing SiO2 content (high Sr > 600 ppm, Sr/Y > 40, and high La/Yb > 20), a term used for igneous rock suites with chemical characteristics that are identical to those of adakites but produced through petrogenetic processes that do not include a slab component. We explore how fractional crystallization and crustal assimilation participate in the development of monogenetic volcanoes, and our findings underscore the significant influence of fractional crystallization on the monogenetic volcanic processes in the Salar de Atacama region. The geochemical changes observed in this area can be attributed to a combination of varying degrees of fractional crystallization within magmas generated through the partial melting of a garnet-enriched environment, which could be primary lower crust or partial melting of a peridotite mantle that has later equilibrated with garnet-bearing crustal melts.

Chemistry and petrography of early 19th century basaltic andesites and basalts from the Kamakaiʻa Hills in the Southwest Rift Zone of Kīlauea volcano, Hawaiʻi

Kīlauea is a frequently active, open-system volcano on the Island of Hawaiʻi known for erupting olivine-dominated tholeiitic basalt compositions. On rare occasions it erupts more differentiated magmas (<1% of erupted volume), such as basaltic andesites and andesites, from its rift zones. These differentiated magmas offer an opportunity to understand better the petrology, magma storage, magma mixing, and eruptive triggers that occur in Kīlauea's rift zone reservoirs. This study focuses on an eruption from the Southwest Rift Zone of Kīlauea, which is dominantly basaltic andesite with subordinate basalt. This eruption originated at the Kamakaiʻa Hills during the early 19th century and has two eruptive phases: 1) an early ‘a‘ā phase that is primarily exposed in the eastern part of the flow field, with minor western lobes, and 2) a late pāhoehoe phase that makes up most of the western part of the flow field. The early ‘a‘ā phase covers at least 5.8 km2 with an erupted volume of ∼150 × 106 m3 and consists of uniform composition basaltic andesites with 3.72–4.15 wt% MgO over its ∼7 km flow length. The late pāhoehoe phase reached >10 km from its vent, covers an area of ∼7.1 km2, has a volume of ∼100 × 106 m3, and initially erupted basaltic andesite near its vent (4.50–5.64 wt% MgO extending to 3.8 km from vent) with channel and tube-fed basalt (6.21–12.38 wt% MgO sampled at >3.8 km from vent) emplaced during its waning stages. Most Kamakaiʻa Hills lavas are crystal-poor, containing ≤1.5% glomerocrysts and individual phenocrysts of plagioclase + clinopyroxene + FeTi oxides ± orthopyroxene, as well as olivine in lavas with >6 wt% MgO.Major-oxide and trace-element concentrations throughout the Kamakaiʻa Hills lavas demonstrate the involvement of three distinct magmatic processes. First, the basaltic andesites of the early ‘a‘ā phase are the products of fractionation of plagioclase + clinopyroxene + FeTi oxides ± orthopyroxene, indicative of magmas that have been stored in rift zone reservoirs for decades or longer. Second, the near-vent (within ∼400 m of vent) basaltic andesites of the late pāhoehoe phase yield chemical concentrations that indicate magma mixing with a more differentiated magma (of a similar evolved composition to basaltic andesites at ∼55–56 wt% SiO2 and ∼3.4–4.1 wt% MgO that erupted in the lower East Rift Zone in 2018). Third, the progressively more mafic magma (containing olivine + plagioclase + clinopyroxene) that continued to erupt throughout the waning stages of activity suggests an eruptive triggering process whereby an intruding summit or uprift reservoir basalt overpressurized and forced out the stored, differentiated magma of the Kamakaiʻa Hills rift zone reservoir.

Monitoring broad emission-line components in spectra of the two low-metallicity dwarf compact star-forming galaxies SBS 1420+540 and J1444+4840

ABSTRACT We report the discovery of broad components with P-Cygni profiles of the hydrogen and helium emission lines in the two low-redshift low-metallicity dwarf compact star-forming galaxies SBS 1420+540 and J1444+4840. We found small stellar masses of 106.24 and 106.59 M⊙, low oxygen abundances 12 + log O/H of 7.75 and 7.45, high velocity dispersions reaching σ ∼ 700 and ∼1200 km s−1, high terminal velocities of the stellar wind of ∼1000 and ∼1000–1700 km s−1, respectively, and large EW(H β) of ∼300 Å for both. For SBS 1420+540, we succeeded in capturing an eruption phase by monitoring the variations of the broad-to-narrow component flux ratio. We observe a sharp increase of that ratio by a factor of 4 in 2017 and a decrease by about an order of magnitude in 2023. The peak luminosity of ∼1040 erg s−1 of the broad component in L(H α) lasted for about 6 yr out of a three-decades monitoring. This leads us to conclude that there is probably a luminous blue variable candidate (LBVc) in this galaxy. As for J1444+4840, its very high L(H α) of about 1041 ergs s−1, close to values observed in active galactic nuclei (AGNs) and Type IIn supernovae (SNe), and the variability of no more than 20 per cent of the broad-to-narrow flux ratio of the hydrogen and helium emission lines over a 8 yr monitoring do not allow us to definitively conclude that it contains an LBVc. On the other hand, the possibility that the line variations are due to a long-lived stellar transient of type AGN/SN IIn cannot be ruled out.

An Investigation on the Ionospheric Response to the Volcanic Explosion at Hunga Ha'apai in 2021

AbstractThe Hunga Ha'apai volcano eruption (20.536°S, 175.382°W in Tonga), which started intermittently around December 2021 and most violently erupted on 15 January 2022, is considered to be the largest volcanic outbreak in recent decades. In this research, we derived the ionospheric total electron content (TEC) over Sanya (18.400°N, 109.600°E), Wuhan (30.530°N, 114.610°E), and Mohe (53.500°N, 122.370°E), from the Global Navigation Satellite System observations. Then we investigated the coupling between the volcano eruption and ionosphere through the TEC variations. The TEC anomaly decayed from about 10 days before main eruption of the Hunga Ha'apai volcano, and showed obvious fluctuations during the eruption phase. The TEC anomaly propagated periodically, with its autocorrelation‐analyzed period of about 16.5 hr during the intermittent outbreak and about 8 hr during the main outbreak phase. Its independently derived wavelet‐analyzed periods are about 9.4 hr during the intermittent outbreak and about 9.4 and 18.8 hr during the main outbreak phase. The propagation is mainly expressed in low frequencies, with energy concentrated in the range of 0–10−3 Hz. This study highlights that the preeruption activities may play an important role in the coupling between the volcanic eruption and ionosphere disturbances.

Geochemical benchmarks in the Phanerozoic LIPs constrained from well-cores in the Deccan Volcanic Province, India

The ∼66 Ma Deccan flood basalt province is one of the largest in the World. Here, we present mineral chemistry, bulk-rock geochemistry and NdSr isotopes in the ∼1000 m thick basalt lava sequence extracted from the deep bore-hole well-cores KBH-8 and KBH-7 from the main Deccan Plateau in the southwestern Deccan Volcanic Province. On the basis of trace and rare earth element systematics, we have statistically grouped the accumulated lava into fifteen Eruptive Phases (EPs). The basalts show extreme variation in their initial 87Sr/86Sr (0.7038–0.7166) and εNd (+5.9 to −12.1) isotopic compositions consistent with the involvement of depleted and enriched mantle sources in their genesis. The lavas sourced from the enriched subcontinental lithospheric mantle has been categorized as EP4-type, and EP11-type represents the isotopically depleted lavas derived from a plume asthenospheric source. The remaining EPs resulted from mixing of the components from these two endmembers in some proportion. This essentially reflects upon source contamination rather than crustal assimilation enroute to eruption or emplacement. The unique geochemical and isotopic fingerprint of EP4 and EP11 is traceable in the Phanerozoic LIPs, as well. Therefore, they potentially qualify as “geochemical benchmarks”. The systematic “pinch and swell” pattern observed in the trace element and isotopic compositions throughout the depth profile cannot be reconciled with continuous outpouring of lava. Instead, the EPs erupted in discreet batches in a quick span of time from a periodically replenished tapped fractionated magma chamber fed by a mantle plume at the asthenosphere-lithosphere interface. The results of this study enunciate the critical role of subcontinental lithospheric mantle in the evolution of a continental flood basalt province, irrespective of space and time.