Articles de revues sur le sujet « Persisten degassing »
Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Persisten degassing.
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 25 meilleurs articles de revues pour votre recherche sur le sujet « Persisten degassing ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les articles de revues sur diverses disciplines et organisez correctement votre bibliographie.
1
Bonini, Marco. « Can coseismic static stress changes sustain postseismic degassing ? » Geology 50, no 3 (15 décembre 2021) : 371–76. http://dx.doi.org/10.1130/g49465.1.
Texte intégralRésumé :
Abstract Earthquakes can trigger increased degassing in hydrogeological systems. Many of these systems return to preseismic conditions after months, but sometimes postseismic degassing lasts for years. The factors controlling such long-lasting degassing are poorly known. I explored the potential role of diverse triggering mechanisms (i.e., dynamic and static stress changes, volumetric strain) for three large earthquakes that induced postseismic degassing (the Wenchuan [China], Maule [Chile], and Gorkha [Nepal] earthquakes). The lessons from this study suggest that hydrogeological systems can respond to earthquakes in various ways, and different causal mechanisms can play a role. Persistent increased CO2 flux from hot springs has been documented after the Gorkha earthquake. These hot springs had their feeder systems dominantly unclamped, suggesting that sufficiently large normal stress changes may sustain late postseismic degassing. The results of this study are twofold: (1) they show a spatial correlation between unclamping stress and increased gas flow, and (2) they provide an explanation for protracted increased degassing.
2
Beckett, F. M., M. Burton, H. M. Mader, J. C. Phillips, M. Polacci, A. C. Rust et F. Witham. « Conduit convection driving persistent degassing at basaltic volcanoes ». Journal of Volcanology and Geothermal Research 283 (août 2014) : 19–35. http://dx.doi.org/10.1016/j.jvolgeores.2014.06.006.
Texte intégral
3
Pering, Ilanko et Liu. « Periodicity in Volcanic Gas Plumes : A Review and Analysis ». Geosciences 9, no 9 (10 septembre 2019) : 394. http://dx.doi.org/10.3390/geosciences9090394.
Texte intégralRésumé :
Persistent non-explosive passive degassing is a common characteristic of active volcanoes. Distinct periodic components in measurable parameters of gas release have been widely identified over timescales ranging from seconds to months. The development and implementation of high temporal resolution gas measurement techniques now enables the robust quantification of high frequency processes operating on timescales comparable to those detectable in geophysical datasets. This review presents an overview of the current state of understanding regarding periodic volcanic degassing, and evaluates the methods available for detecting periodicity, e.g., autocorrelation, variations of the Fast Fourier Transform (FFT), and the continuous wavelet transform (CWT). Periodicities in volcanic degassing from published studies were summarised and statistically analysed together with analyses of literature-derived datasets where periodicity had not previously been investigated. Finally, an overview of current knowledge on drivers of periodicity was presented and discussed in the framework of four main generating categories, including: (1) non-volcanic (e.g., atmospheric or tidally generated); (2) gas-driven, shallow conduit processes; (3) magma movement, intermediate to shallow storage zone; and (4) deep magmatic processes.
4
D’Arcy, Fiona, Étienne Boucher, J. Maarten De Moor, Jean-François Hélie, Robert Piggott et John Stix. « Carbon and sulfur isotopes in tree rings as a proxy for volcanic degassing ». Geology 47, no 9 (5 juillet 2019) : 825–28. http://dx.doi.org/10.1130/g46323.1.
Texte intégralRésumé :
Abstract Trees are useful archives of past atmospheric conditions. They have most commonly been used to infer large-scale changes in climate, industrial pollution, and the magnitude and frequency of geological hazards. While geochemical changes in tree rings have been linked to localized anthropogenic smelter pollution, their potential to track geochemical changes in volcanic degassing has not yet been fully realized. Here, we applied a new proxy using sulfur and carbon isotopes in tree rings to examine fluctuations in gas emission at Turrialba volcano, Costa Rica. Since 2009, Turrialba has emitted a persistent gas plume and increasingly frequent explosions and ash eruptions as activity has accelerated. We collected cores from a species of alder tree, Alnus acuminata, at several locations surrounding the volcano. Biannual isotopic analysis of rings demonstrated a notable δ34S shift of –5.2‰ and a similarly sharp δ13C shift of +1.3‰ in trees downwind of the plume following the onset of strong degassing in 2009. We propose that these shifts in the isotopic values of the tree correspond to those of the volcanic SO2 and CO2, and in the case of the δ13C, an additional fractionation caused by leaf impairment from exposure to volcanic SO2. This new proxy can be applied to other volcanoes as a novel method of obtaining a temporal record of degassing, a crucial tool for volcano monitoring.
5
Ripepe, M., E. Marchetti, C. Bonadonna, A. J. L. Harris, L. Pioli et G. Ulivieri. « Monochromatic infrasonic tremor driven by persistent degassing and convection at Villarrica Volcano, Chile ». Geophysical Research Letters 37, no 15 (août 2010) : n/a. http://dx.doi.org/10.1029/2010gl043516.
Texte intégral
6
Rybalkin, L. A., et S. V. Serdyukov. « Study of the influence of vibration treatment of coal cores as a way to increase gas permeability ». Interexpo GEO-Siberia 2, no 3 (18 mai 2022) : 307–12. http://dx.doi.org/10.33764/2618-981x-2022-2-3-307-312.
Texte intégralRésumé :
This paper provides the results of a series of experimental studies on seismic action’s effect on the permeability of coal and hydraulic fractures. The experiments have been carried out using solid coal cores, cores with single through longitudinal cracks simulating drainage hydraulic fractures and cores with the single fractures propped with a low-density proppant designed to intensify the degassing of coal seams. The patterns of the seismic impact on the gas permeability of coal under the conditions of all-round compression have been established in accordance with the results of experiments. Also, the experimental results reveal certain patterns of increase of the drainage cracks’ gas permeability observed when the cracks are propped with proppant and are under the low intensity seismic effect under the conditions of all-round compression. The studies show that the effectiveness of seismic action increases with an increase in the accumulated exposure time, followed by stabilization and persistence of the positive effect for at least 3 - 7 days after the cessation of exposure. The obtained results provide the opportunity to assess the possibility of using seismic action to intensify the degassing of non-propped hydraulic fractures in coal mines.
7
Tortini, R., S. M. van Manen, B. R. B. Parkes et S. A. Carn. « The impact of persistent volcanic degassing on vegetation : A case study at Turrialba volcano, Costa Rica ». International Journal of Applied Earth Observation and Geoinformation 59 (juillet 2017) : 92–103. http://dx.doi.org/10.1016/j.jag.2017.03.002.
Texte intégral
8
BALASCO, MARIANNA, JENS HEINICKE, ULRICH KOCH, GIOVANNI MARTINELLI et LUCIANO TELESCA. « FRACTAL ANALYSIS OF THE HOURLY TIME VARIABILITY IN SELF-POTENTIAL AND FLOW VARIATIONS CONCOMITANTLY MEASURED IN THE SOOS NATURE PARK (CZECH REPUBLIC) ». Fractals 10, no 04 (décembre 2002) : 463–72. http://dx.doi.org/10.1142/s0218348x02001294.
Texte intégralRésumé :
Scaling properties of self-potential and carbon dioxide flow rate data, concomitantly recorded in a CO 2 degassing area at Soos, Bohemia (Czech Republic), have been investigated by means of several fractal tools. The power spectra, behaving as power law function of the frequency, show the presence of colored noise-type dynamics. The Higuchi analysis reveals the self-potential and flow signals to have the property of fractal curves. The variograms, analyzing time-scales stretching from one hour to almost 50 hours, reveal the presence of approximately three time-scaling ranges, characterized by different features in terms of persistence of the processes underlying the signals.
9
Lages, Joao, Yves Moussallam, Philipson Bani, Nial Peters, Alessandro Aiuppa, Marcello Bitetto et Gaetano Giudice. « First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu) ». Applied Sciences 10, no 20 (19 octobre 2020) : 7293. http://dx.doi.org/10.3390/app10207293.
Texte intégralRésumé :
Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005–2015) averaged SO2 flux of ~434 t d−1 for Mt. Garet, we estimate a total volatile output of about 6482 t d−1 (CO2 ~259 t d−1; H2O ~5758 t d−1; H2S ~30 t d−1; H2 ~0.5 t d−1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009–2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes.
10
Arellano, Santiago, Bo Galle, Fredy Apaza, Geoffroy Avard, Charlotte Barrington, Nicole Bobrowski, Claudia Bucarey et al. « Synoptic analysis of a decade of daily measurements of SO<sub>2</sub> ; emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change ». Earth System Science Data 13, no 3 (22 mars 2021) : 1167–88. http://dx.doi.org/10.5194/essd-13-1167-2021.
Texte intégralRésumé :
Abstract. Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Datasets for each volcano are made available at https://novac.chalmers.se (last access: 1 October 2020) under the CC-BY 4 license or through the DOI (digital object identifier) links provided in Table 1.
11
Üregen, B., C. Gierl-Mayer et H. Danninger. « Phosphorus in Sintered Steels : Effect of Phosphorus Content and P Carrier in Sintered Steel Fe-C-P ». Powder Metallurgy Progress 16, no 1 (1 octobre 2016) : 1–13. http://dx.doi.org/10.1515/pmp-2016-0001.
Texte intégralRésumé :
Abstract Phosphorus as an alloy element is quite common in powder metallurgy, the contents industrially used being markedly higher than those present in wrought steels. In this study, the influence of phosphorus addition through different P carriers was investigated. PM steels of the type Fe-0.7%C-x%P (x = 0.0 … 0.8%) were manufactured by pressing and sintering in H2. It showed that Fe3P is the best phosphorus carrier, resulting in fine and regular microstructure and in high impact energy data at 0.3 … 0.45%P while red P and also Fe2P showed a tendency to agglomeration, with resulting secondary porosity. At high P levels the mechanical properties tend to drop, for the tensile strength at P > 0.60%P while for the impact energy the threshold is 0.45%P. The dimensional behaviour of Fe-C-P can be related to PM aluminium alloys, expansion by transient liquid phase being followed by shrinkage by persistent liquid phase, at least at higher temperatures. In contrast to the dimensional behaviour, degassing and reduction is hardly affected by the phosphorus content.
12
Paonita, A. « Long-range correlation and nonlinearity in geochemical time series of gas discharges from Mt. Etna, and changes with 2001 and 2002–2003 eruptions ». Nonlinear Processes in Geophysics 17, no 6 (10 décembre 2010) : 733–51. http://dx.doi.org/10.5194/npg-17-733-2010.
Texte intégralRésumé :
Abstract. In this paper, spectral and detrended fluctuation analyses, as well as time reversibility and magnitude-sign decomposition, have been applied to the 10-year time-series data resulting from geochemical monitoring of gas emissions on the flanks of Mt. Etna, and gases from a CO2 exploitation well located tens of kilometers from the volcano. The analysis of the time series which showed main effects of fractionation between gases due to selective dissolution in aquifers (e.g., the CO2 concentration series), revealed the occurrence of random fluctuations in time, typical of systems where several processes combine linearly. In contrast, the series of He isotopic composition exhibited power-law behavior of the second-order fluctuation statistics, with values of the scaling exponent close to 0.9. When related to the spectral exponent, this value indicates that the isotopic series closely resemble fractal flicker-noise signals having persistent long-range correlations. The isotopic signals also displayed asymmetry under time reversal and long-range correlation of the associated magnitude series, therefore it was statistically proved the presence of nonlinearity. Both long-range correlation and nonlinearity in time series have been generally considered as distinctive features of dynamic systems where numerous processes interact by feedback mechanisms, in accordance with the paradigm of self-organized criticality (SOC). Thus, it is here proposed that the system that generated the isotope series worked under conditions of SOC. Since the fluctuations of the isotope series have been related to magma degassing, the previous results place constraints on the dynamics of such process, and suggest that nonequilibrium conditions must be dominant. It remains unclear whether the signature of SOC is directly due to volatile degassing from magma, or if it derives from the interaction between melt and the stress field, which certainly influences magma decompression. The strength of scaling appears to increase after 2002 (α values from 0.8 up to 1.2), focusing on transition of the Etnean system from typical SOC toward conditions of lower criticality. By comparing this transition with those of geophysical observables, it can be suggested that the drop in the rate of magma supply, subsequent to the paroxysms of 2001 and 2002–2003, was the main cause of the scaling change.
13
Utami, Sri Budhi, Vincent J. van Hinsberg, Bassam Ghaleb et Arnold E. van Dijk. « Oxygen isotope fractionation between gypsum and its formation waters : Implications for past chemistry of the Kawah Ijen volcanic lake, Indonesia ». American Mineralogist 105, no 5 (1 mai 2020) : 756–63. http://dx.doi.org/10.2138/am-2020-7298.
Texte intégralRésumé :
Abstract Gypsum (CaSO4·2H2O) provides an opportunity to obtain information from both the oxygen isotopic composition of the water and sulfate of its formation waters, where these components are commonly sourced from different reservoirs (e.g., meteoric vs. magmatic). Here, we present δ18O values for gypsum and parent spring waters fed by the Kawah Ijen crater lake in East Java, Indonesia, and from these natural samples derive gypsum-fluid oxygen isotope fractionation factors for water and sulfate group ions of 1.0027 ± 0.0003‰ and 0.999 ± 0.001‰, respectively. Applying these fractionation factors to a growth-zoned gypsum stalactite that records formation waters from 1980 to 2008 during a period of passive degassing, and gypsum cement extracted from the 1817 eruption tephra fall deposit, shows that these fluids were in water-sulfate oxygen isotopic equilibrium. However, the 1817 fluid was >5‰ lighter. This indicates that the 1817 pre-eruption lake was markedly different, and had either persisted for a much shorter duration or was more directly connected to the underlying magmatic-hydrothermal system. This exploratory study highlights the potential of gypsum to provide a historical record of both the δ18Owater and δ18Osulfate of its parental waters, and provides insights into the processes acting on volcanic crater lakes or any other environment that precipitates gypsum.
14
Métrich, Nicole, Patrick Allard, Antonella Bertagnini et Andrea Di Muro. « Comment on ‘Conduit convection, magma mixing, and melt inclusion trends at persistent degassing volcanoes’ by Fred Witham, published in Earth Planetary Science Letters (2011) 301, 345–352 ». Earth and Planetary Science Letters 306, no 3-4 (juin 2011) : 306–8. http://dx.doi.org/10.1016/j.epsl.2011.04.012.
Texte intégral
15
Ilanko, Tehnuka, Tom D. Pering, Thomas Charles Wilkes, Julia Woitischek, Roberto D’Aleo, Alessandro Aiuppa, Andrew J. S. McGonigle, Marie Edmonds et Esline Garaebiti. « Ultraviolet Camera Measurements of Passive and Explosive (Strombolian) Sulphur Dioxide Emissions at Yasur Volcano, Vanuatu ». Remote Sensing 12, no 17 (20 août 2020) : 2703. http://dx.doi.org/10.3390/rs12172703.
Texte intégralRésumé :
Here, we present the first ultraviolet (UV) camera measurements of sulphur dioxide (SO2) flux from Yasur volcano, Vanuatu, for the period 6–9 July 2018. These data yield the first direct gas-measurement-derived calculations of explosion gas masses at Yasur. Yasur typically exhibits persistent passive gas release interspersed with frequent Strombolian explosions. We used compact forms of the “PiCam” Raspberry Pi UV camera system powered through solar panels to collect images. Our daily median SO2 fluxes ranged from 4 to 5.1 kg s−1, with a measurement uncertainty of −12.2% to +14.7%, including errors from the gas cell calibration drift, uncertainties in plume direction and distance, and errors from the plume velocity. This work highlights the use of particle image velocimetry (PIV) for plume velocity determination, which was preferred over the typically used cross-correlation and optical flow methods because of the ability to function over a variety of plume conditions. We calculated SO2 masses for Strombolian explosions ranging 8–81 kg (mean of 32 kg), which to our knowledge is the first budget of explosive gas masses from this target. Through the use of a simple statistical measure using the moving minimum, we estimated that passive degassing is the dominant mode of gas emission at Yasur, supplying an average of ~69% of the total gas released. Our work further highlights the utility of UV camera measurements in volcanology, and particularly the benefit of the multiple camera approach in error characterisation. This work also adds to our inventory of gas-based data, which can be used to characterise the spectrum of Strombolian activity across the globe.
16
Tornos, Fernando, Francisco Velasco et John M. Hanchar. « The Magmatic to Magmatic-Hydrothermal Evolution of the El Laco Deposit (Chile) and Its Implications for the Genesis of Magnetite-Apatite Deposits ». Economic Geology 112, no 7 (1 novembre 2017) : 1595–628. http://dx.doi.org/10.5382/econgeo.2017.4523.
Texte intégralRésumé :
Abstract The geology and geochemistry of the El Laco iron oxide deposit (Central Andes, Chile) support a genesis related to the ascent, degassing, and subvolcanic emplacement of an unusual oxidized silica-poor but water-and iron-rich melt that took place during the growth of the host Pliocene-Holocene andesitic volcano. The model proposed in this paper for the evolution of the deposit involves the formation of a shallow telescoped magmatichydrothermal system with complex melt-fluid unmixing in a vertical column of less than 1 km. The dominant mineralization occurs as large stratabound apatite-poor magnetite bodies interfingered with an andesite host and rooted in vertical dikes of magnetite with minor apatite. The stratabound mineralization is crosscut by abundant coeval diatreme-like structures indicative of vigorous degassing. The andesite underlying the mineralization is pervasively replaced by a high-temperature alkali-calcic alteration assemblage (K feldspar-diopside-magnetite-scapolite) that includes coarse-grained diopside-magnetite-anhydrite veins and large subvertical bodies of magmatic-hydrothermal breccias. The host andesite also shows a large strata-bound steam-heated acid alteration that is devoid of any magnetite but has produced the replacement of a significant proportion of the early magnetite by hematite. The El Laco system is rich in anhydrite but poor in sulfides, suggesting that there were persistent oxidizing conditions that inhibited the formation of a sulfide-bearing mineralization. Field evidence, oxygen isotope geothermometry, and thermodynamic constraints suggest that the magnetite mineralization formed close to the surface at temperatures above 800°C. The magnetite textures, similar to those of subaerial low-viscosity basalts, and the presence of melt inclusions in the host andesite recording the presence of immiscible Fe-Mg-Ca-(Si-Ti-P-S) and Si-K-Na-Al melts, suggest that the magnetite ore formed by direct crystallization from an iron-rich melt; its chemistry inhibited the formation of most other magmatic phases except minor apatite, anhydrite, and diopside. The crystallization of the iron-rich melt at shallow depths promoted the separation of large amounts of two immiscible aqueous fluids: a dominant low-density vapor phase and a small volume of hypersaline fluid. Diopside-magnetite-anhydrite veins are interpreted as the product of the crystallization of the residual melts, whereas the interaction of the brine with the host andesite formed the deep alkali-calcic hydrothermal assemblage. The condensation and mixing of the low-density magmatic vapor with meteoric water produced the steam-heated alteration. Isotope data from the host andesite (87Sr/86Sr: 0.7066–0.7074; εNd: −5.5 to −4.1; δ18Owhole rock: 7.2–9.6‰; δ18Omagnetite: 5.1–6.2‰) and an underlying andesite porphyry (87Sr/86Sr: 0.7075–0.7082; εNd: −5.9 to −4.6) reflect the interaction of a primitive mantle melt with Andean crustal rocks. The isotope geochemistry of the magnetite ore (87Sr/86Sr: 0.7083; εNd: −5.4 to −5.1; δ18O 3.5–5.5‰) and the alkali-calcic alteration and related diopside-magnetite-anhydrite veins (87Sr/86Sr: 0.7080–0.7083; εNd: −5.1 to −4.6; δ18Odiopside: 7.2–8.2%c; δ18Omagnetite 4.4–6.3‰) show that the mineralization has a more crustal signature than the host andesite and all the volcanic rocks of the Central Andes. Therefore, ore-forming fluids/melts were not equilibrated with the host volcanic rocks and are interpreted as related to a deep yet undiscovered batch of highly contaminated igneous rocks. Crustal contamination is interpreted as due to major interaction of a juvenile melt with the underlying Late Mesozoic-Tertiary Salta Group, located 1 to 6 km beneath the volcano and which has high 87Sr/86Sr values (0.7140–0.7141).
17
Marchese, Francesco, Diego Coppola, Alfredo Falconieri, Nicola Genzano et Nicola Pergola. « Investigating Phases of Thermal Unrest at Ambrym (Vanuatu) Volcano through the Normalized Hot Spot Indices Tool and the Integration with the MIROVA System ». Remote Sensing 14, no 13 (29 juin 2022) : 3136. http://dx.doi.org/10.3390/rs14133136.
Texte intégralRésumé :
Ambrym is an active volcanic island, located in the Vanuatu archipelago, consisting of a 12 km-wide summit caldera. This open vent volcano is characterized by an almost persistent degassing activity which occurs in the Benbow and Marum craters, which were also the site of recent lava lakes. On 15 December 2018, about three years after an intense lava effusion, the first recorded since 1989, a small-scale intra-caldera fissure eruption occurred. On 16 December, the eruption stopped, and the lava lakes at the Benbow and Marum craters were drained. In this work, we investigated the thermal activity of the Ambrym volcano, before, during, and after the 15 December 2018 eruption, using daytime Sentinel-2 (S2) Multispectral Instruments (MSI) and Landsat-8 (L8) Operational Land Imager (OLI) data, at a mid-high spatial resolution. The results were integrated with Moderate Resolution Imaging Spectroradiometer (MODIS) observations. Outputs of the Normalized Hotspot Indices (NHI) tool, retrieved from S2-MSI and L8-OLI data, show that the thermal activity at the Ambrym craters increased about three weeks before the 15 December 2018 lava effusion. This information is consistent with the estimates of volcanic radiative power (VRP), which were performed by the Middle Infrared Observation of Volcanic Activity (MIROVA) system, by analyzing the nighttime MODIS data. The latter revealed a significant increase of VRP, with values above 700 MW at the end of the October–November 2018 period. Moreover, the drastic reduction of thermal emissions at the craters, marked by the NHI tool since the day of the fissure eruption, is consistent with the drop in the lava lake level that was independently suggested in a previous study. These results demonstrate that the S2-MSI and L8-OLI time series, combined with infrared MODIS observations, may contribute to detecting increasing trends in lava lake activity, which may precede effusive eruptions at the open vent volcanoes. This study addresses some challenging scenarios regarding the definition of possible threshold levels (e.g., in terms of VRP and total Short Wave Infrared radiance) from the NHI and MIROVA datasets, which could require special attention from local authorities in terms of the occurrence of possible future eruptions.
18
Laiolo, Marco, Maurizio Ripepe, Corrado Cigolini, Diego Coppola, Massimo Della Schiava, Riccardo Genco, Lorenzo Innocenti et al. « Space- and Ground-Based Geophysical Data Tracking of Magma Migration in Shallow Feeding System of Mount Etna Volcano ». Remote Sensing 11, no 10 (18 mai 2019) : 1182. http://dx.doi.org/10.3390/rs11101182.
Texte intégralRésumé :
After a month-long increase in activity at the summit craters, on 24 December 2018, the Etna volcano experienced a short-lived lateral effusive event followed by a rapid resumption of low-level explosive and degassing activity at the summit vents. By combining space (Moderate Resolution Imaging Spectroradiometer; MODIS and SENTINEL-2 images) and ground-based geophysical data, we track, in near real-time, the thermal, seismic and infrasonic changes associated with Etna’s activity during the September–December 2018 period. Satellite thermal data reveal that the fissural eruption was preceded by a persistent increase of summit activity, as reflected by overflow episodes in New SouthEast Crater (NSE) sector. This behavior is supported by infrasonic data, which recorded a constant increase both in the occurrence and in the energy of the strombolian activity at the same crater sectors mapped by satellite. The explosive activity trend is poorly constrained by the seismic tremor, which shows instead a sudden increase only since the 08:24 GMT on the 24 December 2018, almost concurrently with the end of the infrasonic detections occurred at 06:00 GMT. The arrays detected the resumption of infrasonic activity at 11:13 GMT of 24 December, when tremors almost reached the maximum amplitude. Infrasound indicates that the explosive activity was shifting from the summit crater along the flank of the Etna volcano, reflecting, with the seismic tremor, the intrusion of a gas-rich magma batch along a ~2.0 km long dyke, which reached the surface generating an intense explosive phase. The dyke propagation lasted for almost 3 h, during which magma migrated from the central conduit system to the lateral vent, at a mean speed of 0.15–0.20 m s−1. Based on MODIS and SENTINEL 2 images, we estimated that the summit outflows erupted a volume of lava of 1.4 Mm3 (±0.5 Mm3), and that the lateral effusive episode erupted a minimum volume of 0.85 Mm3 (±0.3 Mm3). The results presented here outline the support of satellite data on tracking the evolution of volcanic activity and the importance to integrate satellite with ground-based geophysical data in improving assessments of volcanic hazard during eruptive crises.
19
Boichu, Marie, Olivier Favez, Véronique Riffault, Jean-Eudes Petit, Yunjiang Zhang, Colette Brogniez, Jean Sciare et al. « Large-scale particulate air pollution and chemical fingerprint of volcanic sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Bárðarbunga volcano (Iceland) ». Atmospheric Chemistry and Physics 19, no 22 (27 novembre 2019) : 14253–87. http://dx.doi.org/10.5194/acp-19-14253-2019.
Texte intégralRésumé :
Abstract. Volcanic sulfate aerosols play a key role in air quality and climate. However, the rate of oxidation of sulfur dioxide (SO2) precursor gas to sulfate aerosols (SO42-) in volcanic plumes is poorly known, especially in the troposphere. Here we determine the chemical speciation as well as the intensity and temporal persistence of the impact on air quality of sulfate aerosols from the 2014–2015 Holuhraun flood lava eruption of Icelandic volcano Bárðarbunga. To do so, we jointly analyse a set of SO2 observations from satellite (OMPS and IASI) and ground-level measurements from air quality monitoring stations together with high temporal resolution mass spectrometry measurements of an Aerosol Chemical Speciation Monitor (ACSM) performed far from the volcanic source. We explore month/year long ACSM data in France from stations in contrasting environments, close and far from industrial sulfur-rich activities. We demonstrate that volcanic sulfate aerosols exhibit a distinct chemical signature in urban/rural conditions, with NO3:SO4 mass concentration ratios lower than for non-volcanic background aerosols. These results are supported by thermodynamic simulations of aerosol composition, using the ISORROPIA II model, which show that ammonium sulfate aerosols are preferentially formed at a high concentration of sulfate, leading to a decrease in the production of particulate ammonium nitrate. Such a chemical signature is however more difficult to identify at heavily polluted industrial sites due to a high level of background noise in sulfur. Nevertheless, aged volcanic sulfates can be distinguished from freshly emitted industrial sulfates according to their contrasting degree of anion neutralization. Combining AERONET (AErosol RObotic NETwork) sunphotometric data with ACSM observations, we also show a long persistence over weeks of pollution in volcanic sulfate aerosols, while SO2 pollution disappears in a few days at most. Finally, gathering 6-month long datasets from 27 sulfur monitoring stations of the EMEP (European Monitoring and Evaluation Programme) network allows us to demonstrate a much broader large-scale European pollution, in both SO2 and SO4, associated with the Holuhraun eruption, from Scandinavia to France. While widespread SO2 anomalies, with ground-level mass concentrations far exceeding background values, almost entirely result from the volcanic source, the origin of sulfate aerosols is more complex. Using a multi-site concentration-weighted trajectory analysis, emissions from the Holuhraun eruption are shown to be one of the main sources of SO4 at all EMEP sites across Europe and can be distinguished from anthropogenic emissions from eastern Europe but also from Great Britain. A wide variability in SO2:SO4 mass concentration ratios, ranging from 0.8 to 8.0, is shown at several stations geographically dispersed at thousands of kilometres from the eruption site. Despite this apparent spatial complexity, we demonstrate that these mass oxidation ratios can be explained by a simple linear dependency on the age of the plume, with a SO2-to-SO4 oxidation rate of 0.23 h−1. Most current studies generally focus on SO2, an unambiguous and more readily measured marker of the volcanic plume. However, the long persistence of the chemical fingerprint of volcanic sulfate aerosols at continental scale, as shown for the Holuhraun eruption here, casts light on the impact of tropospheric eruptions and passive degassing activities on air quality, health, atmospheric chemistry and climate.
20
Thivet, Simon, Andrew J. L. Harris, Lucia Gurioli, Philipson Bani, Talfan Barnie, Maxime Bombrun et Emanuele Marchetti. « Multi-Parametric Field Experiment Links Explosive Activity and Persistent Degassing at Stromboli ». Frontiers in Earth Science 9 (28 mai 2021). http://dx.doi.org/10.3389/feart.2021.669661.
Texte intégralRésumé :
Visually unattainable magmatic processes in volcanic conduits, such as degassing, are closely linked to eruptive styles at the surface, but their roles are not completely identified and understood. To gain insights, a multi-parametric experiment at Stromboli volcano (Aeolian Islands, Italy) was installed in July 2016 focusing on the normal explosive activity and persistent degassing. During this experiment, gas-dominated (type 0) and particle-loaded (type 1) explosions, already defined by other studies, were clearly identified. A FLIR thermal camera, an Ultra-Violet SO₂ camera and a scanning Differential Optical Absorption Spectroscopy were deployed to record pyroclast and SO2 masses emitted during individual explosions, as well as persistent SO₂ fluxes, respectively. An ASHER instrument was also deployed in order to collect ash fallouts and to measure the grain size distribution of the samples. SO2 measurements confirm that persistent degassing was far greater than that emitted during the explosions. Further, we found that the data could be characterized by two periods. In the first period (25–27 July), activity was mainly characterized by type 0 explosions, characterized by high velocity jets. Pyroclast mass fluxes were relatively low (280 kg/event on average), while persistent SO2 fluxes were high (274 t/d on average). In the second period (29–30 July), activity was mainly characterized by type 1 explosions, characterized by low velocity jets. Pyroclast mass fluxes were almost ten times higher (2,400 kg/event on average), while persistent gas fluxes were significantly lower (82 t/d on average). Ash characterization also indicates that type 0 explosions fragments were characterized by a larger proportion of non-juvenile material compared to type 1 explosions fragments. This week-long field experiment suggests that, at least within short time periods, Stromboli’s type 1 explosions can be associated with low levels of degassing and the mass of particles accompanying such explosive events depends on the volume of a degassed magma cap sitting at the head of the magma column. This could make the classic particle-loaded explosions of Stromboli an aside from the true eruptive state of the volcano. Instead, gas-dominated explosions can be associated with high levels of degassing and are indicative of a highly charged (with gas) system. We thus suggest that relatively deep magmatic processes, such as persistent degassing and slug formation can rapidly influence the superficial behavior of the eruptive conduit, modulating the presence or absence of degassed magma at the explosion/fragmentation level.
21
La Rocca, Mario, Danilo Galluzzo, Lucia Nardone, Guido Gaudiosi et Francesca Di Luccio. « Hydrothermal Seismic Tremor in a Wide Frequency Band : The Nonvolcanic CO2 Degassing Site of Mefite d’Ansanto, Italy ». Bulletin of the Seismological Society of America, 28 février 2023. http://dx.doi.org/10.1785/0120220243.
Texte intégralRésumé :
ABSTRACT Mefite d’Ansanto (Italy) is a nonvolcanic field characterized by persistent strong degassing activity. A seismic field monitoring carried out during the Summer 2021 reveals a persistent, extended, and complex source of seismic tremor characterized by a spectrum with a frequency content from about 1 Hz to more than 35 Hz. While at frequency smaller than 3 Hz the signal amplitude is stationary, in the intermediate frequency band (3–20 Hz) sudden changes of amplitude are often observed, suggesting the existence of an intermittent source (every few minutes to tens of minutes). Furthermore, very short bursts of high-frequency energy are recognized in the tremor signal. Results of array analysis and seismological observation indicate that the sources of the analyzed tremor are located in a small area centered on the main vent of the degassing area. The persistent low-frequency tremor and the intermediate frequency signals propagate as surface waves to the seismic stations installed around the source and indicate a very shallow source. On the contrary, impulsive signals at frequencies greater than 20 Hz propagate as body waves, revealing a deeper source likely located between 50 and 100 m depth.
22
van Manen, Saskia M. « Perception of a chronic volcanic hazard : persistent degassing at Masaya volcano, Nicaragua ». Journal of Applied Volcanology 3, no 1 (10 juin 2014). http://dx.doi.org/10.1186/s13617-014-0009-3.
Texte intégral
23
Sergio Calabrese, Sarah Scaglione, Silvia Milazzo, Walter D'Alessandro, Nicole Bobrowski, Giovanni Bruno Giuffrida, Dario Tedesco, Francesco Parello et Mathiew Yalire. « Passive degassing at Nyiragongo (D.R. Congo) and Etna (Italy) volcanoes ». Annals of Geophysics 57 (27 février 2015). http://dx.doi.org/10.4401/ag-6637.
Texte intégralRésumé :
<p>Volcanoes are well known as an impressive large natural source of trace elements into the troposphere. Etna (Italy) and Nyiragongo (D.R. Congo) are two stratovolcanoes located in different geological settings, both characterized by persistent passive degassing from their summit craters. Here, we present some results on trace element composition in volcanic plume emissions, atmospheric bulk deposition (rainwater) and their uptake by the surrounding vegetation, with the aim to compare and identify differences and similarities between these two volcanoes. Volcanic emissions were sampled by using active filter-pack for acid gases (sulfur and halogens) and specific teflon filters for particulates (major and trace elements). The impact of the volcanogenic deposition in the surrounding of the crater rims was investigated by using different sampling techniques: bulk rain collectors gauges were used to collect atmospheric bulk deposition, and biomonitoring technique was carried out to collect gases and particulates by using endemic plant species. The estimates of the trace element fluxes confirm that Etna and Nyiragongo are large sources of metals into the atmosphere, especially considering their persistent state of passive degassing. The large amount of emitted trace elements has a strong impact on the close surrounding of both volcanoes. This is clearly reflected by in the chemical composition of rainwater collected at the summit areas both for Etna and Nyiragongo. Moreover, the biomonitoring results highlight that bioaccumulation of trace elements is extremely high in the proximity of the crater rim and decreases with the distance from the active craters.</p>
24
Ruth, D. C. S., et F. Costa. « A petrological and conceptual model of Mayon volcano (Philippines) as an example of an open-vent volcano ». Bulletin of Volcanology 83, no 10 (10 septembre 2021). http://dx.doi.org/10.1007/s00445-021-01486-9.
Texte intégralRésumé :
AbstractMayon is a basaltic andesitic, open-vent volcano characterized by persistent passive degassing from the summit at 2463 m above sea level. Mid-size (< 0.1 km3) and mildly explosive eruptions and occasional phreatic eruptions have occurred approximately every 10 years for over a hundred years. Mayon’s plumbing system structure, processes, and time scales driving its eruptions are still not well-known, despite being the most active volcano in the Philippines. We investigated the petrology and geochemistry of its crystal-rich lavas (~ 50 vol% phenocrysts) from nine historical eruptions between 1928 and 2009 and propose a conceptual model of the processes and magmatic architecture that led to the eruptions. The whole-rock geochemistry and mineral assemblage (plagioclase + orthopyroxene + clinopyroxene + Fe-Ti oxide ± olivine) of the lavas have remained remarkably homogenous (54 wt% SiO2, ~ 4 wt% MgO) from 1928 to 2009. However, electron microscope images and microprobe analyses of the phenocrysts and the existence of three types of glomerocrysts testify to a range of magmatic processes, including long-term magma residence, magma mixing, crystallization, volatile fluxing, and degassing. Multiple mineral-melt geothermobarometers suggest a relatively thermally buffered system at 1050 ± 25 °C, with several magma residence zones, ranging from close to the surface, through reservoirs at ~ 4–5 km, and as deep as ~ 20 km. Diffusion chronometry on > 200 orthopyroxene crystals reveal magma mixing timescales that range from a few days to about 65 years, but the majority are shorter than the decadal inter-eruptive repose period. This implies that magma intrusion at Mayon has been nearly continuous over the studied time period, with limited crystal recycling from one eruption to the next. The variety of plagioclase textures and zoning patterns reflect fluxing of volatiles from depth to shallower melts through which they eventually reach the atmosphere through an open conduit. The crystal-rich nature of the erupted magmas may have developed during each inter-eruptive period. We propose that Mayon has behaved over almost 100 years as a steady state system, with limited variations in eruption frequency, degassing flux, magma composition, and crystal content that are mainly determined by the amount and composition of deep magma and volatile input in the system. We explore how Mayon volcano’s processes and working model can be related to other open-vent mafic and water-rich systems such as Etna, Stromboli, Villarrica, or Llaima. Finally, our understanding of open-vent, persistently active volcanoes is rooted in historical observations, but volcano behavior can evolve over longer time frames. We speculate that these volcanoes produce specific plagioclase textures that can be used to identify similar volcanic behavior in the geologic record.
25
Liu, Kang, Maosheng Jiang, Liyu Zhang et Daizhao Chen. « A new high-resolution paleotemperature record during the Middle–Late Ordovician transition derived from conodont δ18O paleo-thermometry ». Journal of the Geological Society, 5 avril 2022, jgs2021–148. http://dx.doi.org/10.1144/jgs2021-148.
Texte intégralRésumé :
Climate cooling has been commonly considered as one of the most plausible triggers of the Great Ordovician Biodiversification Event (GOBE). However, the details of coeval sea-surface temperature (SST) variation during and after the biodiversification peak are still unclear due to lack of continuous, high-resolution paleotemperature records. Here, we report the first high-resolution in situ Secondary Ion Mass Spectrometry (SIMS) conodont apatite oxygen isotope (δ18Oapatite) curve from the Kalpin Shuinichang and Dawangou sections (the auxiliary global stratotype section and point (GSSP) for the base of the Upper Ordovician Series) to reconstruct the detailed Ordovician paleotemperature history in the Tarim Basin, northwestern China. The new oxygen isotope data, based on mono-generic specimens, reveal a similar first-order variation trend with published records from other paleocontinents, which is suggestive of a global signal. A -0.7‰ δ18Oapatite shift (∼3.2 °C warming) is identifiable in the Dawangou Formation (early–middle Darriwilian). This is followed by a long-term +2.2‰ positive shift in δ18Oapatite (∼10 °C cooling) in the overlying strata spanning the Saergan and the Kanling formations (late Darriwilian–Sandbian), likely indicating a global climatic signal. Examining the coeval marine 87Sr/86Sr records, the early–middle Darriwilian minor δ18Oapatite decrease is coincident with the onset of long-term negative 87Sr/86Sr excursion, possibly indicating a slight climate warming in response to increasing volcanic degassing in the context of accelerating spreading of mid-oceanic ridges. In contrast, the following long-term positive δ18Oapatite excursion, in parallel with persistent 87Sr/86Sr drop, likely indicates a major climate cooling initially caused by the rapid tropical continental weathering, which in turn may have reduced the continental radiogenic Sr influx.Supplementary material: Three supplementary tables (S1, S2, and S3) indicating the in-situ oxygen isotopic results of conodont apatite from the Kalpin Shuinichang-Dawangou composite section, Qinghu standard, and Durango standard, respectively. https://doi.org/10.6084/m9.figshare.c.5924175