Crust-mantle interactions and connections with the geodynamic system in the origin and circulation of fluids in the Comoros Archipelago - Indian Ocean

The role of fluids in crust-mantle interactions is of crucial importance in providing information regarding the definition of the origin of magmas, the identification of their depths of origin, and the nature of the interaction processes that determine their characteristics. Complex geodynamic systems may therefore have an articulated history of processes that can be reconstructed by studying the fluids emitted in such areas, and by analysing the fluids included in the rocks that characterise these geological regions. In short, we can cite the thoughtful metaphor of Sadao Matsuo, the first leader of the Commission on the Chemistry of Volcanic Gases (CCVG), who referred to volcanic gas emissions as a “telegram from the Earth’s interior”. This research represents an attempt to read and interpret as much as possible from such complex messages with regard to an area of extreme geological pertinence and interest to contemporary volcanic geochemistry. The chosen area of study for the present work focuses on two islands of the Comoros archipelago: Grande Comore and Mayotte, located within the Mozambique Channel within a complicated geodynamic system of great interest due to the currently existing volcanic and seismic activity, of which a complete descriptive picture is currently lacking. In particular, especially with regard to fluid geochemistry, very little knowledge of gas and fluid emissions yet exists. In this sense, it is now even more compelling to understand these characteristics, not only in consideration of the high level of activity of the Karthala volcano in Grande Comore, but also with regard to the volcanic and seismic activity recently recorded at Mayotte Island, which is very close to the recent submarine volcano formed only 50 km South-East off-shore of Mayotte, and by far the largest known submarine eruption until now (Feuillet et al., 2021; Berthod et al., 2021). The specific aim of this study is to investigate the existing outgassing conditions on both islands in order to include this knowledge within a broader and multidisciplinary framework that will facilitate the understanding of the volcanic dynamics of this particular area of the Indian Ocean. Karthala volcano, located on Grande Comore Island, is the most active volcano in the western Indian Ocean after Piton de la Fournaise at La Reunion. Karthala is a basaltic shield volcano which has erupted regularly in the last century; fourteen eruptions are listed from 1904 to today, where the last eruptive activity occurred in 2007 (Bachèlery et al., 2016). Owing to its remote location, it is still under-studied and, in particular, little is known about its diffuse outgassing. The study of the diffuse outgassing of the Karthala volcano, with particular attention to the emission of CO2 from the flanks of the volcano, is therefore crucial for the assessment of the state of activity of the volcano. In addition, as two significant persistent fumarolic fields are present in its summit crater area, both soil and fumarolic gas emission are investigated in terms of gas-geochemistry in this work. Geochronological data recognize Mayotte as the earliest starting point of magmatic activity among the islands of the archipelago, which dates back to at least 10.58 Ma ago. The islands of Mohéli and Anjouan then follow at around 3.9 and 5 Ma ago, respectively, and finally Grande Comore at around 0.13 Ma (Michon, 2016). No recent eruptions have been recorded at Mayotte since the last occurred around 2050 BCE ± 500 (Smithsonian Institution - https://volcano.si.edu). ; however, stable volcanic activity at Mayotte is still present in the form of a large area of subaerial and underwater outgassing near its south-eastern coast at the Dziani Lake, which is situated in the north part of the island on the small island of Petite Terre. Significantly, Petite Terre was recently affected by a seismic crisis that lasted for several months, and was accompanied by the formation of the largest underwater volcano in recent centuries, about 50 km from its coast (see Ship spies largest underwater eruption ever - https://www.sciencemag.org/news/2019/05/; Berthod et al., 2021a, 2021b; Cesca et al., 2020; Feuillet et al., 2021; Lemoine et al., 2020; REVOSIMA, 2019). The thesis is divided into two sections: the first will focus on the Karthala and Petite Terre gas emissions, considering fumarolic fields, soil emissions and bubbling areas, with the purpose of identifying the main characteristics, similarities and differences, of gas chemistry and isotopic variability in the two islands; the second section of the thesis focuses on the difference between the two known bubbling areas at Petite Terre, where I include the further study of the Lake Dziani gas emissions that have been investigated only in the most recent surveys. In this study, I attempt to address the existing gap in knowledge regarding gas geochemistry on the islands focusing specifically on gas emissions, using an approach that combines different research objectives, and fieldwork and laboratory techniques, in order to: 1) define the chemical and isotopic characteristics of magmatic fluids in terms of the major gas components (CO2, CH4, H2S, H2 and H2O) in free gases, noble gases (He-Ne-Ar) and C isotope ratios; 2) measure soil CO2 concentration and identifying their 13C isotope signatures; 3) identify the similarities and differences regarding the volatiles emitted from the main volcanic and geothermal areas in both Grande Comore and Mayotte Islands; 4) conceptualise a geochemical model of the complex geodynamic framework of the archipelago, integrating the gas geochemistry results obtained through the processes entailed in points 1-3; 5) evaluate the impact of volcanic emissions in the local area for monitoring purposes. The success of such an approach has been previously demonstrated with regard to other magmatic systems worldwide, such as Mount Etna (Paonita et al. 2012, 2021), but particularly in relation to La Reunion, which is located in the Indian Ocean in a comparable geodynamic system of intraplate volcanism (Liuzzo et al., 2015; Boudoire et al. 2016, 2018, 2020). In terms of gas geochemistry, the various findings of this thesis converge towards the recognition of some notable peculiarities with regard to the two target islands, which can be summarised according to the following four points: First, the soil CO2 emissions are spatially distributed along the main structural features of both Grande Comore and Petite Terre; however, the carbon isotopic signature of soil CO2 emissions highlights a low magmatic contribution at distal areas of Karthala volcano, and a significantly higher magmatic contribution in CO2 emissions at Petite Terre. This difference may be ascribed to the different states of volcanic activity on the two islands at the time of the surveys. Second, with regard to the helium isotopic signature, the 3He/4He data are within the range of measurements in fluid inclusions of Grande Comore (Class et al., 2005), indicating for the gas emissions a low level of 3He/4He values ( ~6 ≤ Rc/Ra ≤ ~7.5 Petite Terrre; ~4.6 ≤ Rc/Ra ≤ ~5.8 Karthala), if compared with La Reunion signature (~12≤ Rc/Ra ≤~15 Boudoire et al. 2020). Third, the bubbling area on the sea (BAS) and Lake Dziani are likely fed by a common source (about 17 km below Petite Terre); however, Dziani lake is significantly affected by secondary processes that are mainly related to biotic activities in the lake, which result in the higher variability of gas chemistry, 13C in methane and CO2 than BAS. Fourth, the increased value of Rc/Ra between 2008 and 2018-19, and a not-reached isotopic equilibrium of 13CCH4 from the hydrothermal fluid, may be ascribed to the volcanic activity that generated the new submarine volcano 50 km offshore from Petite Terre. This consideration is also consistent with the final interpretation of this work, where the input of heated CO2-rich fluid into the Petite Terre hydrothermal system is a consequence of the perturbation of the shallow plumbing system by the offshore submarine eruption, resulting in higher equilibrium temperatures in 2018 and subsequent cooling down during and after the seismo-volcanic activity. This work is expected to make a significant step forward in the current knowledge of the gas geochemistry of the Comores archipelago, and, in particular, results in a better knowledge of the main characteristics of the emitted volcanic fluids. More importantly, it will assist in the recognition of which geochemical markers may be of potential relevance for volcanic monitoring purposes, thereby improving the understanding of the present state of its volcano activity. This latter aspect is especially important for the Karthala volcano and with regard to the ongoing sub-marine volcanic activity close to Mayotte. This would be of great support for local observation infrastructures and contribute to the improvement of applications in volcanic and environmental monitoring of this populated area. Finally, this work would also provide a valuable case study that may be applicable to other similar contexts worldwide, allowing the definition of a comprehensive model considering volcanological effect and social impacts within the same framework

Determinazione in continuo di CO2, CH4 e H2Ov in ambiente atmosferico attraverso tecnica ad assorbimento laser (UGGA)

Molti dei composti chimici presenti nell’atmosfera terrestre prendono il nome di “gas serra”. Queste specie gassose consentono alla radiazione solare di entrare liberamente nell’atmosfera e di trattenere parte della radiazione solare riflessa dalla superficie terrestre come energia termica. Nel corso del tempo si instaura un complesso equilibrio termico tra la quantità di energia inviata dal sole e quella irradiata dalla superficie. L’alterazione di questo equilibrio, con l’aumento di uno o più gas serra in atmosfera, porta a degli squilibri termici e un conseguente innalzamento delle temperature. Questo fenomeno è definito come “effetto serra”. I principali gas serra in natura che prendono parte a questo fenomeno sono: vapor d’acqua (H2Ov), anidride carbonica (CO2), metano (CH4), e ossido nitroso (N2O). Il vapore acqueo è il più potente gas serra ed è responsabile per circa due terzi dell’effetto serra naturale. Il secondo gas serra più importante è l’anidride carbonica. Il suo contributo è responsabile per il 5 - 20% dell’effetto serra naturale ed è la causa principale dell’effetto sera accelerato essendo il più emesso attraverso attività umane, difatti la sua concentrazione in atmosfera è aumentata del 142% dal livello pre– industriale al 2013 [WMO Greenhouse Gas Bulletin, n° 10: 06 November 2014]. Il terzo gas serra più importante è il metano. Anche se possiede un tempo di residenza in atmosfera breve e una concentrazione atmosferica bassa, è una molecola estremamente efficiente nell’assorbire il calore ed è responsabile per circa 8% dell’effetto serra, con picchi del 20% [G. Etiope et. al.,2008]. La concentrazione di metano in atmosfera è aumentata di 772ppb (parti per miliardo) dal periodo pre-industriale fino al 2013 [WMO Greenhouse Gas Bulletin, n° 10: 06 November 2014]. L’ossido nitroso ha una concentrazione atmosferica molto limitata ma un efficienza nel trattenere il calore molto elevata, circa 300 volte quella dell’anidride carbonica. Come abbiamo accennato, i gas serra possono essere di origine sia naturale che antropica. Elevate quantità di vapor d’acqua e anidride carbonica vengono rilasciate ogni anno in atmosfera dai sistemi vulcanici attivi, non solo durante i periodi eruttivi ma anche nei periodi di quiescenza. Emissioni naturali di metano in atmosfera sono legati al degassamento di vulcani di fango, largamente diffusi sull’intero pianeta. Recentemente l’organizzazione mondiale Intergovernmental Panel on ClimateChangedelle Nazioni Unite ha pubblicato una relazione internazionale (ICCP 2013) in cui, attraverso informazioni tecnicoscientifiche e socioeconomiche, ha valutato come il rischio del cambiamento climatico sia legato all’emissione di gas serra (principalmente CO2, H2O(v) e CH4), stimando che la temperatura media globale del suolo è aumentata di 0,6 ± 0.2K dalla fine del 19° secolo. L’IPCC rivela che: “c’è una nuova e più forte evidenza che gran parte del riscaldamento e dell’emissione di questi gas negli ultimi 50 anni siano attribuibili alle attività antropiche più che alle attività naturali” [Crosson, 2008]. Essendo l’effetto serra diventato un problema globale per la salute del pianeta è di fondamentale importanza disporre di strumentazioni analitiche per il monitoraggio di queste specie chimiche in atmosfera. Nel corso degli anni si sono utilizzate diverse tecniche analitiche per lo studio di questi gas in atmosfera al fine di capirne l’evoluzione. La tecnica più consolidata utilizzata per le misurazioni di specie gassose in atmosfera per oltre un decennio è stata la spettroscopia a raggi infrarossi non dispersiva (NDIRS). Nonostante la tecnica NDIRS abbia una buona precisione di misurazione per la maggior parte dei gas serra, questa tecnica risulta essere molto macchinosa e complessa in quanto necessita di frequenti azzeramenti e calibrazioni allungando notevolmente i tempi di analisi. Ultimamente in commercio sono stati introdotti dei nuovi strumenti molto più sensibili e precisi dei classici NDIRS. Questi strumenti, assimilabili ai vecchi spettrofotometri a doppio raggio, utilizzano una particolare cavità ottica Cavity Ringdown Spectroscopy (CRDS) che oltre ad offrire una maggiore sensibilità analitica, per un ampio numero di specie gassose, riducono i tempi analitici e non richiedono particolari operazioni di calibrazione. Alcuni di questi strumenti hanno come caratteristica principale, oltre la determinazione e quantificazione della specie gassosa, anche la determinazione della composizione isotopica, come ad esempio il Thermo Fischer Delta Ray per analisi del δ13C dell’anidride carbonica e il Picarro CRDS per l’analisi del δ13C del metano. Negli ultimi tempi questi strumenti al laser hanno esteso il loro campo di applicazione, difatti in aggiunta agli studi sulla qualità dell’aria, vengono anche impiegati per il monitoraggio di gas naturali, rilevamento di perdite nei giacimenti di carbone e studi sui flussi di gas dal suolo [Carapezza et. al., 2003]. In questo lavoro sono state testate le potenzialità in laboratorio ed in campagna del nuovo analizzatore Ultra-Portable Greenhouse Gas Analyzer (UGGA) prodotto da Los Gatos Research (LGR). Lo strumento è basato sull’implementazione della tecnica CRDS denominata “Off-Axis ICOS” che permette di determinare simultaneamente ed in continuo le concentrazioni di CO2, H2O(v) e CH4 in atmosfera all’interno di intervalli di concentrazioni dell’ordine dei ppm. Il lavoro ha avuto l’obiettivo di studiare gli errori e i tempi analitici per la determinazione delle concentrazioni di CO2, H2O e CH4 in atmosfera. Lo strumento è stato da prima testato in laboratorio e poi in campagna. Le analisi in laboratorio sono state svolte presso i laboratori analitici dell’Istituto Nazionale di Geofisica e Vulcanologia di Palermo. Le prospezioni sono state eseguite lungo percorsi urbani e periferici di Palermo e lungo la faglia della Pernicana, nella zona etnea, a cui sono state associate tramite un GPS (Global Position System) informazioni sulle coordinate geografiche

Implementation of electrochemical, optical and denuder-based sensors and sampling techniques on UAV for volcanic gas measurements : examples from Masaya, Turrialba and Stromboli volcanoes

Volcanoes are a natural source of several reactive gases (e.g., sulfur and halogen containing species) and nonreactive gases (e.g., carbon dioxide) to the atmosphere. The relative abundance of carbon and sulfur in volcanic gas as well as the total sulfur dioxide emission rate from a volcanic vent are established parameters in current volcanomonitoring strategies, and they oftentimes allow insights into subsurface processes. However, chemical reactions involving halogens are thought to have local to regional impact on the atmospheric chemistry around passively degassing volcanoes. In this study we demonstrate the successful deployment of a multirotor UAV (quadcopter) system with custom-made lightweight payloads for the compositional analysis and gas flux estimation of volcanic plumes. The various applications and their potential are presented and discussed in example studies at three volcanoes encompassing flight heights of 450 to 3300m and various states of volcanic activity. Field applications were performed at Stromboli volcano (Italy), Turrialba volcano (Costa Rica) and Masaya volcano (Nicaragua). Two in situ gas-measuring systems adapted for autonomous airborne measurements, based on electrochemical and optical detection principles, as well as an airborne sampling unit, are introduced. We show volcanic gas composition results including abundances of CO2, SO2 and halogen species. The new instrumental setups were compared with established instruments during ground-based measurements at Masaya volcano, which resulted in CO2 = SO2 ratios of 3.6 0.4. For total SO2 flux estimations a small differential optical absorption spectroscopy (DOAS) system measured SO2 column amounts on transversal flights below the plume at Turrialba volcano, giving 1776 1108 T d1 and 1616 1007 T d1 of SO2 during two traverses. At Stromboli volcano, elevated CO2 = SO2 ratios were observed at spatial and temporal proximity to explosions by airborne in situ measurements. Reactive bromine to sulfur ratios of 0.19 104 to 9.8 104 were measured in situ in the plume of Stromboli volcano, down wind of the vent.Published2441-24574V. Processi pre-eruttiviJCR Journa

The composition of gas emissions at Petite Terre (Mayotte, Comoros): inference on magmatic fingerprints

The Comoros archipelago is an active geodynamic region located in the Mozambique Channel between East continental Africa and Madagascar. The archipelago results from intra-plate volcanism, the most recent eruptions having occurred on the youngest island of Grande Comore and on the oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite Terre Island, where two main and persistent gas seep areas are present (Airport Beach, namely BAS, and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore; 3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared with older datasets acquired between 2005 and 2016 from different research teams. The relation between \mbox {}^{3}\mathrm{He}/\mbox {}^{4}\mathrm{He} and $\delta ^{13}\mathrm{C}$-$\mathrm{CO}_{2}$ shows a clear magmatic origin for Mayotte bubbling gases, while the variable proportions and isotopic signature of $\mathrm{CH}_{4}$ is related to the occurrence of both biogenic and abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibrium temperature steadily decreases since 2018. The increased knowledge on the gas-geochemistry at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring programs

Small-scale spatial variability of soil CO2 flux: Implication for monitoring strategy

In recent decades, soil CO2 flux measurements have been often used in both volcanic and seismically active areas to investigate the interconnections between temporal and spatial anomalies in degassing and telluric activities. In this study, we focus on a narrow degassing area of the Piton de la Fournaise volcano, that has been chosen for its proximity and link with the frequently active volcanic area. Our aim is to constrain the degassing in this narrow area and identify the potential processes involved in both spatial and temporal soil CO2 variations in order to provide an enhanced monitoring strategy for soil CO2 flux. We performed a geophysical survey (self-potential measurements: SP; electrical resistivity tomography: ERT) to provide a high-resolution description of the subsurface. We identified one main SP negative anomaly dividing the area in two zones. Based on these results, we set ten control points, from the site of the main SP negative anomaly up to 230 m away, where soil CO2 fluxes were weekly measured during one year of intense eruptive activity at Piton de la Fournaise. Our findings show that lateral and vertical soil heterogeneities and structures exert a strong control on the degassing pattern. We find that temporal soil CO2 flux series at control points close to the main SP negative anomaly better record variations linked to the volcanic activity. We also show that the synchronicity between the increase of soil CO2 flux and deep seismicity can be best explained by a pulsed process pushing out the CO2 already stored and fractionated in the system. Importantly, our findings show that low soil CO2 fluxes and low carbon isotopic signature are able to track variations of volcanic activity in the same way as high fluxes and high carbon isotopic signature do. This result gives important insights in terms of monitoring strategy of volcanic and seismotectonic areas in geodynamics contexts characterized by difficult environmental operational conditions as commonly met in tropical areaPublished13-264A. Oceanografia e climaJCR Journa

The composition of gas emissions at Petite Terre (Mayotte, Comoros): inference on magmatic fingerprints

The Comoros archipelago is an active geodynamic region located in the Mozambique Channel between East continental Africa and Madagascar. The archipelago results from intra-plate volcanism, the most recent eruptions having occurred on the youngest island of Grande Comore and on the oldest one of Mayotte. Since 2018, the eastern submarine flank of Mayotte has been the site of one of the largest recent eruptive events on Earth in terms of erupted lava volume. On land, the most recent volcanic activity occurred in Holocene on the eastern side of Mayotte, corresponding to the small Petite Terre Island, where two main and persistent gas seep areas are present (Airport Beach, namely BAS, and Dziani Dzaha intracrateric lake). The large submarine eruption at the feet of Mayotte (50 km offshore; 3.5 km b.s.l.) is associated with deep (mantle level) seismic activity closer to the coast (5–15 km offshore) possibly corresponding to a single and large magmatic plumbing system. Our study aims at characterizing the chemical and isotopic composition of gas seeps on land and assesses their potential link with the magmatic plumbing system feeding the Mayotte volcanic ridge and the recent submarine activity. Data from bubbling gases collected between 2018 and 2021 are discussed and compared with older datasets acquired between 2005 and 2016 from different research teams. The relation between \mbox {}^{3}\mathrm{He}/\mbox {}^{4}\mathrm{He} and $\delta ^{13}\mathrm{C}$-$\mathrm{CO}_{2}$ shows a clear magmatic origin for Mayotte bubbling gases, while the variable proportions and isotopic signature of $\mathrm{CH}_{4}$ is related to the occurrence of both biogenic and abiogenic sources of methane. Our new dataset points to a time-decreasing influence of the recent seismo-volcanic activity at Mayotte on the composition of hydrothermal fluids on land, whose equilibrium temperature steadily decreases since 2018. The increased knowledge on the gas-geochemistry at Mayotte makes the results of this work of potential support for volcanic and environmental monitoring programs

The deep Chandra survey in the SDSS J1030+0524 field

We present the X-ray source catalog for the ∼479 ks Chandra exposure of the SDSS J1030+0524 field, which is centered on a region that shows the best evidence to date of an overdensity around a z > 6 quasar, and also includes a galaxy overdensity around a Compton-thick Fanaroff-Riley type II (FRII) radio galaxy at z = 1.7. Using wavdetect for initial source detection and ACIS Extract for source photometry and significance assessment, we create preliminary catalogs of sources that are detected in the full (0.5-7.0 keV), soft (0.5-2.0 keV), and hard (2-7 keV) bands, respectively. We produce X-ray simulations that mirror our Chandra observation to filter our preliminary catalogs and achieve a completeness level of > 91% and a reliability level of ∼95% in each band. The catalogs in the three bands are then matched into a final main catalog of 256 unique sources. Among them, 244, 193, and 208 are detected in the full, soft, and hard bands, respectively. The Chandra observation covers a total area of 335 arcmin2 and reaches flux limits over the central few square arcmins of ∼3 × 10-16, 6 × 10-17, and 2 × 10-16 erg cm-2 s-1 in the full, soft, and hard bands, respectively This makes J1030 field the fifth deepest extragalactic X-ray survey to date. The field is part of the Multiwavelength Survey by Yale-Chile (MUSYC), and is also covered by optical imaging data from the Large Binocular Camera (LBC) at the Large Binocular Telescope (LBT), near-infrared imaging data from the Canada France Hawaii Telescope WIRCam (CFHT/WIRCam), and Spitzer IRAC. Thanks to its dense multi-wavelength coverage, J1030 represents a legacy field for the study of large-scale structures around distant accreting supermassive black holes. Using a likelihood ratio analysis, we associate multi-band (r, z, J, and 4.5  μm) counterparts for 252 (98.4%) of the 256 Chandra sources, with an estimated reliability of 95%. Finally, we compute the cumulative number of sources in each X-ray band, finding that they are in general agreement with the results from the Chandra Deep Fields.We acknowledge the referee for a prompt and constructive report. We acknowledge financial contribution from the agreement ASI-INAF n. 2017-14-H.O. We thank P. Broos for providing great support for the analysis of our simulations with AE, and H. M. Günther for the support provided for using MARX. We also thank B. Luo for providing us the log(N)–log(S) of the 7Ms CDF-S. FV acknowledges financial support from CONICYT and CASSACA through the Fourth call for tenders of the CAS-CONICYT Fund, and CONICYT grants Basal-CATA AFB-170002. DM and MA acknowledge support by grant number NNX16AN49G issued through the NASA Astrophysics Data Analysis Program (ADAP). Further support was provided by the Faculty Research Fund (FRF) of Tufts University

Characterization of seismic signals recorded in Tethys Bay, Victoria Land (Antarctica): data from atmosphere-cryosphere-hydrosphere interaction

In this paper, we analysed 3-component seismic signals recorded during 27 November 2016 - 10 January 2017 by two stations installed in Tethys Bay (Victoria Land, Antarctica), close to Mario Zucchelli Station. Due to the low noise levels , it was possible to identify three different kinds of signals: teleseismic earthquakes, microseisms, and icequakes . We focus on the latter two. A statistically significant relationship was found between microseism amplitude and both wind speed and sea swell. Thus, we suggest that the recorded microseism data are caused by waves at the shore close to the seismic stations rather than in the deep ocean during storms. In addition, w e detected three icequakes , with dominant low frequencies (below 2 Hz), located in the David Glacier area with local magnitude of 2.4-2.6. These events were likely to have been generated at the rock–ice interface under the glacier. This work shows how seismic signals recorded in Antarctica provide insights on the interactions between the atmosphere-cryosphere-hydrosphere. Since climate patterns drive these interactions, investigations on Antarctic seismic signals could serve as a proxy indicator for estimating climate changes

PRISM (Polarized Radiation Imaging and Spectroscopy Mission): A White Paper on the Ultimate Polarimetric Spectro-Imaging of the Microwave and Far-Infrared Sky

PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in response to the Call for White Papers for the definition of the L2 and L3 Missions in the ESA Science Programme. PRISM would have two instruments: (1) an imager with a 3.5m mirror (cooled to 4K for high performance in the far-infrared---that is, in the Wien part of the CMB blackbody spectrum), and (2) an Fourier Transform Spectrometer (FTS) somewhat like the COBE FIRAS instrument but over three orders of magnitude more sensitive. Highlights of the new science (beyond the obvious target of B-modes from gravity waves generated during inflation) made possible by these two instruments working in tandem include: (1) the ultimate galaxy cluster survey gathering 10e6 clusters extending to large redshift and measuring their peculiar velocities and temperatures (through the kSZ effect and relativistic corrections to the classic y-distortion spectrum, respectively) (2) a detailed investigation into the nature of the cosmic infrared background (CIB) consisting of at present unresolved dusty high-z galaxies, where most of the star formation in the universe took place, (3) searching for distortions from the perfect CMB blackbody spectrum, which will probe a large number of otherwise inaccessible effects (e.g., energy release through decaying dark matter, the primordial power spectrum on very small scales where measurements today are impossible due to erasure from Silk damping and contamination from non-linear cascading of power from larger length scales). These are but a few of the highlights of the new science that will be made possible with PRISM.Comment: 20 pages Late

A CO2-gas precursor to the March 2015 Villarrica volcano eruption

We present here the first volcanic gas compositional time-series taken prior to a paroxysmal eruption of Villarrica volcano (Chile). Our gas plume observations were obtained using a fully autonomous Multi-component Gas Analyser System (Multi-GAS) in the 3 month-long phase of escalating volcanic activity that culminated into the 3 March 2015 paroxysm, the largest since 1985. Our results demonstrate a temporal evolution of volcanic plume composition, from low CO$_2$/SO$_2$ ratios (0.65-2.7) during November 2014-January 2015 to CO$_2$/SO$_2$ ratios up to ≈ 9 then after. The H$_2$O/CO$_2$ ratio simultaneously declined to <38 in the same temporal interval. We use results of volatile saturation models to demonstrate that this evolution toward CO$_2$-enriched gas was likely caused by unusual supply of deeply sourced gas bubbles. We propose that separate ascent of over-pressured gas bubbles, originating from at least 20-35 MPa pressures, was the driver for activity escalation toward the 3 March climax.This work was funded by the DECADE research initiative of the DCO observatory