Dataset Information

Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Reunion.

ABSTRACT: The eruptive activity of basaltic hotspot volcanoes displays major fluctuations on times scales of years to decades. Theses fluctuations are thought to reflect changes in the rate of mantle melt supply. However, the crustal filter generally masks the mantle processes involved. Here, we show that the cyclic and generally increasing activity of the Piton de la Fournaise volcano (La Réunion) since the mid 20th century is tightly linked to the fertility of its source, as recorded by 87Sr/86Sr and incompatible trace elements ratios of lavas. We identify a twofold control of source fertility on eruptive activity: melt extraction from fertile, incompatible element-enriched veins initiates decadal-scale eruptive sequences, so that vein distribution in the plume source directly controls the cyclic activity. Indirectly, reactive flow of enriched melts increases mantle porosity and promotes melts extraction from the peridotite matrix. This process is thought to have caused a fourfold increase in magma supply between 1998 and 2014 at Piton de la Fournaise, and could also explain magma surges at other frequently active hotspot volcanoes, such as Kilauea, Hawaii. The short-term eruptive activity of hotspot volcanoes appears to be ultimately linked to the distribution and size of lithological heterogeneities in mantle plumes.

SUBMITTER: Vlastelic I

PROVIDER: S-EPMC6160422 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Réunion.

Vlastélic I I Di Muro A A Bachèlery P P Gurioli L L Auclair D D Gannoun A A

Scientific reports 20180927 1

The eruptive activity of basaltic hotspot volcanoes displays major fluctuations on times scales of years to decades. Theses fluctuations are thought to reflect changes in the rate of mantle melt supply. However, the crustal filter generally masks the mantle processes involved. Here, we show that the cyclic and generally increasing activity of the Piton de la Fournaise volcano (La Réunion) since the mid 20th century is tightly linked to the fertility of its source, as recorded by <sup>87</sup>Sr/ ...[more]

PMID: 30262860

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Project description:Effective and rapid effusive crisis response is necessary to mitigate the risks associated with lava flows that could threaten or inundate inhabited or visited areas. At Piton de la Fournaise (La Réunion, France), well-established protocols between Observatoire Volcanologique du Piton de la Fournaise - Institut de Physique du Globe de Paris (OVPF-IPGP) and civil protection, and between scientists of a multinational array of institutes, allow effective tracking of eruptive crises and hazard management embracing all stakeholders. To assess the outstanding needs for such responses Tsang and Lindsay (J Appl Volcanol 9:9, 2020) applied a gap analysis to assess research gaps in terms of preparedness, response and recovery at 11 effusive centers, including Piton de la Fournaise. For Piton de la Fournaise, their gap analysis implied widespread gaps in the state of knowledge. However, their work relied on incomplete and erroneous data and methods, resulting in a gap analysis that significantly underrepresented this state of knowledge. We thus here re-build a correct database for Piton de la Fournaise, properly define the scope of an appropriate gap analysis, and provide a robust gap analysis, finding that there are, actually, very few gaps for Piton de la Fournaise. This is a result of the existence of a great quantity of published work in the peer-reviewed literature, as well as frequent reports documenting event impact in the local press and observatory reports. At Piton de la Fournaise, this latter (observatory-based) resource is largely due to the efforts of OVPF-IPGP who have a wealth of experience having responded to 81 eruptions since its creation in 1979 through the end of September 2021. Although welcome and necessary, especially if it is made by a group of scientists outside the local management of the volcanic risk (i.e., a neutral group), such gap analysis need to be sure to fully consider all available peer-reviewed literature, as well as newspaper reports, observatory releases and non-peer-reviewed eruption reports, so as to be complete and correct. Fundamentally, such an analysis needs to consider the information collected and produced by the volcano observatory charged with handling surveillance operations and reporting duties to civil protection for the volcano under analysis. As a very minimum, to ensure that a necessarily comprehensive and complete treatment of the scientific literature has been completed, we recommend that a third party expert, who is a recognized specialist in terms of research at the site considered, reviews and checks the material used for the gap analysis before final release of recommendations.Supplementary informationThe online version contains supplementary material available at 10.1186/s13617-021-00111-w.

Project description:Piton de la Fournaise volcano, La Réunion, France, erupted between the 2 and 6 April 2020, one of a series of eruptive phases which occur typically two or three times per year. Here, we use back trajectory analysis of satellite data from the TROPOMI instrument to determine that gas emissions during the June 2020 eruption were of unusually high intensity and altitude, producing 34.9 ± 17.4 kt of SO2 and plume heights up to 5 km a.s.l. The early stages of the eruption (2-4 April 2020) were characterised by relatively low SO2 emission rates despite strong low frequency tremor (LFT); the latter phase followed an increase in intensity and explosivity in the early hours of 5 April 2020. This period included lava fountaining, significantly increased SO2 emission rates, increased high frequency tremor (HFT) and decreased LFT. Using the PlumeTraj back trajectory analysis toolkit, we found the peak SO2 emission rate was 284 ± 130 kg/s on the 6 April. The plume altitude peaked at ~ 5 km a.s.l. on 5 April, in the hours following a sudden increase in explosivity, producing one of the tallest eruption columns recorded at Piton de la Fournaise. PlumeTraj allowed us to discriminate each day's SO2, which otherwise would have led to a mass overestimate due to the plumes remaining visible for more than 24 h. The eruption exhibited a remarkable decoupling and anti-correlation between the intensity of the LFT signal and that of the magma and gas emission rates. LFT intensity peaked during the first phase with low magma and SO2 emissions, but quickly decreased during the second phase, replaced by unusually strong HFT. We conclude that the observation of strong HFT is associated with higher intensity of eruption, degassing, and greater height of neutral buoyancy of the plume, which may provide an alert to the presence of greater hazards produced by higher intensity eruptive activity. This might be particularly useful when direct visual observation is prevented by meteorological conditions. This eruption shows the importance of combining multiple data sets when monitoring volcanoes. Combining gas and seismic data sets allowed for a much more accurate assessment of the eruption than either could have done alone.Supplementary informationThe online version contains supplementary material available at 10.1007/s00445-023-01628-1.

Project description:Objectif Analyse de l’impact du premier mois de confinement lié à l’épidémie SARS-CoV-2 sur l’activité de consultation des otorhinolaryngologistes libéraux de l‘île de La Réunion. Méthode Étude observationnelle, multicentrique, prospective analysant l’activité de consultation de douze praticiens. Objectif principal Évaluer le nombre, les caractéristiques et les modalités des consultations réalisées. Objectifs secondaires : préciser les symptômes amenant les patients à consulter, les diagnostics évoqués, les prescriptions instaurées, les éventuelles conséquences néfastes et l’impact sur le chiffre d‘affaire. Résultats 693 consultations étaient réalisées, dont 50 % étaient demandées en urgence. 57,9 % des consultations étaient réalisées en présence du patient, 28,4 % étaient effectuées au téléphone et 13,7 % et en téléconsultation. Lors des consultations présentielles, les otorhinolaryngologistes portaient des gants et un masque respectivement dans 53,8 % et 92,2 % des cas. Le masque porté était de type chirurgical et de type FFP2 dans 71,6 % et 28,4 % de cas, respectivement. Les trois symptômes les plus fréquents (48,5 % des cas) étaient l’otalgie, les troubles de l’audition et les vertiges. Les trois diagnostics les plus fréquents (60,6 % des cas) étaient, les otites, les corps étrangers d’oreille (cérumen inclus) et les infections pharyngées. Les trois examens complémentaires les plus prescrits (74,3 % des cas) étaient l’imagerie, l’audiométrie, et l’avis d’un spécialiste médical. Les trois familles thérapeutiques les plus prescrites (52,7 % des cas) étaient les gouttes auriculaires, les antibiotiques, et les lavages de nez et/ou sprays nasaux. L’incidence des conséquences néfastes était de 0,001 % et aucun des otorhinolaryngologistes ou des patients ne semblait avoir été infecté par la Covid 19. Une baisse de 47,3 % à 91 % (médiane : 75,6 %) du chiffre d’affaire de consultation était notée. Conclusion Cette étude souligne la disponibilité et l’adaptabilité des ORL réunionnais libéraux en contexte épidémique malgré un impact économique très négatif.

Project description:Space-based, operational instruments are in unique positions to monitor volcanic activity globally, especially in remote locations or where suborbital observing conditions are hazardous. The Multi-angle Imaging SpectroRadiometer (MISR) provides hyper-stereo imagery, from which the altitude and microphysical properties of suspended atmospheric aerosols can be derived. These capabilities are applied to plumes emitted at Karymsky volcano from 2000 to 2017. Observed plumes from Karymsky were emitted predominantly to an altitude of 2-4 km, with occasional events exceeding 6 km. MISR plume observations were most common when volcanic surface manifestations, such as lava flows, were identified by satellite-based thermal anomaly detection. The analyzed plumes predominantly contained large (1.28 µm effective radius), strongly absorbing particles indicative of ash-rich eruptions. Differences between the retrievals for Karymsky volcano's ash-rich plumes and the sulfur-rich plumes emitted during the 2014-2015 eruption of Holuhraun (Iceland) highlight the ability of MISR to distinguish particle types from such events. Observed plumes ranged from 30 to 220 km in length, and were imaged at a spatial resolution of 1.1 km. Retrieved particle properties display evidence of downwind particle fallout, particle aggregation and chemical evolution. In addition, changes in plume properties retrieved from the remote-sensing observations over time are interpreted in terms of shifts in eruption dynamics within the volcano itself, corroborated to the extent possible with suborbital data. Plumes emitted at Karymsky prior to 2010 display mixed emissions of ash and sulfate particles. After 2010, all plumes contain consistent particle components, indicative of entering an ash-dominated regime. Post-2010 event timing, relative to eruption phase, was found to influence the optical properties of observed plume particles, with light-absorption varying in a consistent sequence as each respective eruption phase progressed.

Project description:Introduction L’âge, facteur principal de la COVID-19 sévère/mortelle, explique que les résidents des EHPAD, âgés et/ou comorbides, soient à risque. L’ivermectine (IVM), anti-parasitaire, a montré une activité antivirale anti-SARS-CoV-2 in vitro (étude australienne). La moxidectine (MOX) pourrait aussi être intéressante (demi-vie longue). Lors d’une épidémie de gale en EHPAD où les résidents ont reçu de l’IVM orale, nous rapportons son impact sur la Covid-19 survenue en parallèle. Observation Le 6/03/20 : patiente de 66 ans = résidente-1, EHPAD-A (Seine-et-Marne, 77), hospitalisée pour gale profuse. Incluse dans l’essai contrôlé randomisé (ECT) « gale CRUSTED ; NCT02841215 », a reçu 3 doses d’IVM (400 ou 200 ?g/kg en insu ; J0-J7-J14). Trois autres résidents avaient une gale ; et résidents et personnels ont reçu IVM 200 ?g/kg J0–J7 (n = 121). Retour de la résidente-1 à l’EHPAD-A le 17/03 (plan blanc). Étude épidémiologique : Les cas probables ou confirmés (PCR) de COVID-19 de l’EHPAD-A entre 5/03 et 15/05 ont été identifiés, facteurs de risque, sévérité et mortalité précisés. Durant cette période, les infections COVID-19 et décès des autres EHPAD du 77 étaient déclarés à l’ARS. Une comparaison EHPAD-A et contrôles (EHPAD du 77 comparables en âge, effectif et tarif) était réalisée. Étude virologique in vitro : Mesure de l’activité anti-SARS-CoV-2 de l’IVM et MOX sur cellules VeroE6 à doses croissantes (0,05–10 ?M) par quantification ARN et immunofluorescence ; viabilité des cellules surveillée. Résultats Soixante-neuf résidents (incluant résidente-1) et 52 personnels EHPAD-A ont reçu l’IVM : âge médian résidents 90 ans (84–94), 78,3 % femmes, 98,6 % au moins une comorbidité à risque de COVID-19 sévère. 11 sujets présentaient une COVID-19 probable ou certaine (7/69 résidents et 4/52 personnels, fréquence 10,1 %). Parmi les résidents, 90,9 % (10/11) ont eu une COVID-19 minime, sans oxygène ou hospitalisation, aucun mort. Parmi les 177 EHPAD du 77, 45 étaient inclus comme contrôles, soit 3062 résidents (âge médian 86,2 ans, 77,3 % femmes). Parmi eux, 22,6 % [95 %IC 16,3-28,9] ont eu la COVID-19 vs. 1,4 % EHPAD-A avec une mortalité attribuable de 4,9 % [95 %IC 3,2-6,5] vs. 0 % EHPAD-A. Une activité antivirale majeure in vitro de l’IVM et MOX (EC50 IVM 0,14 ± 0,02 ?M et MOX 0,48 ?M ± 0,08 ?M) avec viabilité cellulaire préservée était observée. Discussion Tous les cas observés de COVID-19 dans l’EHPAD-A « traité » par IVM étaient mineurs, sans décès durant la période d’étude, alors que les résidents des EHPAD « contrôles » (sans IVM), appariés selon âge, effectif et niveau socio-économique, ont montré une fréquence de COVID-19 et une mortalité plus élevées. L’IVM pourrait avoir un rôle protecteur (suggéré depuis dans étude US), conforté par l’étude virologique. Malgré les limites –caractère observationnel et absence de corrélation démontrée in vitro/in vivo–, la plausibilité est suffisante pour réaliser un ECT en cluster de prévention par IVM et MOX en EHPAD.

Dataset Information

Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Reunion.

Publications

Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Réunion.

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