Community Emergency Management During the 2005 Ambae Eruption, Vanuatu, SW Pacific.

No abstract availabl

Impact of ashes from the 2022 Tonga volcanic eruption on satellite ocean color signatures

A powerful eruption within the Hunga Tonga-Hunga Ha’apai (HTHH) volcano (20.64°S, 175.19°W) in the Kingdom of Tonga, occurred on 15 January 2022. The volcanic blast was enormous, leading many scientists to investigate the full impact and magnitude of this event via satellite observations. In this study, we describe a new ocean color signature from a discolored water patch created by the HTHH eruption using NASA and CMEMS products of satellite-derived biological and optical properties. Elevated surface chlorophyll-a concentration (Chl-a) between 0.15 to 2.7 mg.m-3 was not associated with phytoplankton growth, but to basalt-andesitic ash material expelled by the volcano and into the ocean, which resulted in erroneous Chl-a estimates. Distribution of the patch over time was aligned with CMEMS ocean currents for 19 days. The gradual decrease of light attenuation or diffuse attenuation coefficient for downward irradiance at 490 nm, Kd(490), was interpreted as due to the sinking of ash particles with time. It is suggested that due to high porosity of 30-40%, a density close to that of seawater, ash particles stay suspended in the water column for more than 10 days with sustained high values of satellite-derived Chl-a, Kd(490), and particulate backscattering coefficient at 443 nm. The high attenuation of light due to ash, reducing the penetration depth to less than 10 meters during the first period after the eruption may have had implications on ecological processes and biogeochemical cycles in Tongan waters

Isotopically (δ13C and δ18O) heavy volcanic plumes from Central Andean volcanoes: a field study

Stable isotopes of carbon and oxygen in volcanic gases are key tracers of volatile transfer between Earth’s interior and atmosphere. Although important, these data are available for few volcanoes because they have traditionally been difficult to obtain and are usually measured on gas samples collected from fumaroles. We present new field measurements of bulk plume composition and stable isotopes (δ13CCO2 and δ18OH2O+ CO2) carried out at three northern Chilean volcanoes using MultiGAS and isotope ratio infrared spectroscopy. Carbon and oxygen in magmatic gas plumes of Lastarria and Isluga volcanoes have δ13C in CO2 of +0.76‰ to +0.77‰ (VPDB), similar to slab carbonate; and δ18O in the H2O + CO2 system ranging from +12.2‰ to +20.7‰ (VSMOW), suggesting significant contributions from altered slab pore water and carbonate. The hydrothermal plume at Tacora has lower δ13CCO2 of −3.2‰ and δ18OH2O+CO2 of +7.0‰, reflecting various scrubbing, kinetic fractionation, and contamination processes. We show the isotopic characterization of volcanic gases in the field to be a practical complement to traditional sampling methods, with the potential to remove sampling bias that is a risk when only a few samples from accessible fumaroles are used to characterize a given volcano’s volatile output. Our results indicate that there is a previously unrecognized, relatively heavy isotopic signature to bulk volcanic gas plumes in the Central Andes, which can be attributed to a strong influence from components of the subducting slab, but may also reflect some local crustal contamination. The techniques we describe open new avenues for quantifying the roles that subduction zones and arc volcanoes play in the global carbon cycle.Published653V. Proprietà dei magmi e dei prodotti vulcaniciJCR Journa

Unrest at the Nevados de Chillán volcanic complex: a failed or yet to unfold magmatic eruption?

Resuming erupting activity at volcanoes that have been long quiescent poses a significant challenge to hazard assessment, as it require assessment of whether the change in activity is an isolated event or the beginning of a new eruptive sequence. Such inception is often poorly characterised as quiescent volcanoes tend to be poorly equipped and not extensively monitored, especially with respect to gas geochemistry. Here, we report gas composition and flux measurements from a newly opened vent at the very onset of eruptive activity at the Nevados de Chillán volcanic complex (Chile) in January-February 2016. The molar proportions of H2O, CO2, SO2, H2S and H2 gases are found to be 98.4, 0.97, 0.11, 0.01 and 0.5 mol% respectively. The mean SO2 flux recorded in early February 2016 during periods of eruptive discharge amounts to 0.4-0.6 kg s-1. Our results indicate that the new vent opening was propelled by magmatic gases, triggering repeated eruptions. Ash particles ejected by the first blast of 8 January are dominated by lithic fragments of dacitic composition. By contrast the ash ejected in a subsequent eruption contains both lithic fragments of dense dacite, and a fresher, sparsely vesicular material of basaltic andesite composition. By October 2017 the ejected ash is back to being dominated by the dense dacitic lithic material. Together with the seismic and deformation record, these observations point to the explosive activity resulting from a small intrusion of basaltic to andesitic magma at shallow level. The fate of this magma, whether stalling or eventually triggering a magmatic eruption, remains to be seen, but current observations suggest the former is most likely

Caractérisation et suivi du dégazage des principaux édifices volcaniques actifs de l'arc insulaire du Vanuatu par télédétection

Recent developments on UV spectrometer applications to volcanic degassing offer possibilities for regular measurement of the emission rates of isolated volcanoes whose SO2 output has never or rarely been measured: the only volcanic degassing measurements obtained in Vanuatu were taken in 1999 on just one of Vanuatu's 6 active aerial volcanoes. This thesis describes volcanic degassing studies carried out on 4 active volcanoes of Vanuatu. It brings to light permanent sources of SO2 and halogens on Ambrym and Yasur volcanoes. Degassing measurements were also performed during eruptive events on Aoba/Ambae and Lopevi. Overall results indicate that Vanuatu volcanoes are considerable sources of SO2 and halogens. These sources are related to cyclic and permanent manifestations; they were so far poorly documented, and not taken into account in the overall global assessments. A conservative estimate of the emission rate from these four active volcanoes (Aoba, Ambrym, Lopevi and Yasur) is of the order of 61 kg/s, which represents some 11 to 20 % of the global SO2 release into the atmosphere from volcanoes. Such quantities affect the local ecosystems and result in serious loss of plants and crops critical to the survival of Ni-Vanuatu populations; they occasionally endanger their health and safety. A better understanding of these volcanic gas emissions is an important factor in hazard mitigation for the Vanuatu island group.Les développements récents sur les applications des spectromètres UV miniaturisés pour la mesure des flux de gaz volcaniques ont ouvert la possibilité de mesurer régulièrement le dégazage de volcans isolés, dont les flux de SO2 n'avaient jamais, ou rarement, été mesurés. Au Vanuatu, le dégazage d'un seul volcan sur six aériens actifs a été mesuré (1999). Cette thèse décrit les travaux réalisés sur l'étude du dégazage de quatre des édifices actifs de cet arc insulaire. Ils ont permis de mettre en évidence d'importantes sources permanentes de SO2 et d'halogènes sur les édifices volcaniques des îles d'Ambrym et de Tanna; des mesures de dégazages ont également été effectuées lors des manifestations éruptives sur les îles d'Aoba/Ambae et de Lopevi. Il ressort que les volcans du Vanuatu sont de très importantes sources de SO2 et d'halogènes. Ces sources naturelles d'émissions, liées à des manifestations volcaniques permanentes et cycliques, étaient peu connues et non prises en compte dans des bilans globaux. L'estimation minimum du flux de SO2 libéré par quatre édifices (Aoba, Ambrym, Lopevi, Yasur) du Vanuatu se situe autour de 61 kg/s, ce qui représente entre 11 et 20 % du flux global moyen de SO2 rejetés dans l'atmosphère par les volcans de la planète. Le dégazage perturbe l'écosystème, génère des pertes importantes sur les plantes et cultures dont dépendent les ni-vanuatais pour subsister. Il menace épisodiquement leur sécurité. Son étude est un apport significatif à la quantification du risque volcanique sur l'Archipel

Sulphur dioxide emission rates from Yasur volcano, Vanuatu archipelago

International audienc

Sulphur dioxide emission rates from Yasur volcano, Vanuatu archipelago - art. no. L20309

Yasur volcano has long been suspected as one of the volcanic emission sources responsible for a significant contribution of sulphur dioxide to the atmosphere. But due to its isolation in the south Pacific region, very little is known about its emission rates. We report here sulphur dioxide flux measurements, obtained on Yasur, using ultraviolet spectroscopy, from April 2004 to November 2005. We found an average flux of 7.9 kg.s(-1) of SO2, which constitutes some 1-2% and 1.5-2.5% of estimated global time- integrated volcanic emissions to the atmosphere and troposphere, respectively

Geothermal system as the cause of the 1979 landslide tsunami in Lembata Island, Indonesia

A tsunami landslide which caused hundreds casualties and lots of damage took place on Lembata Island in 1979. In order to understand the characteristics of the landslide mechanism, a field survey was conducted in 2013 which sampled both the origin soil and landslide material, and the water from hotspring around the landslide site. The physical properties of the soil obtained show that the original soil has dominantly coarser grain than the landslide material (80.5% coarser grain compared to 11.8% coarse grain respectively) which indicates that the soil has become finer and softer. Hot spring analysis indicated that the mineral content of the water was 99.48% SO4. This shows that magmatism processes are involved which caused the soil to become acidic and may have fragilised the system. Results of X-ray Diffraction Mineralogy Analysis (XRD) show that the original soil is composed of minerals of cristobalite, quartz, and albite, while the landslide material consists of clay minerals such as quartz, saponite, chabazite, silicon oxide, and coesite which are typical minerals in a hydrothermal environment. Based on these results, it can be concluded that the area was influenced by an active geothermal system that could be the main source mechanism behind this disastrous event

The effusive-explosive transitions at Rokatenda 2012-2013: unloading by extrusion of degassed magma with lateral gas flow

International audienceBetween October 2012 and August 2013, Rokatenda, one of the most poorly understood volcanoes in Indonesia, entered a phase of intense eruptive activity which involved extrusion of viscous lava, gas discharge and explosive activity. During the 10-month-long eruption, a lava volume of 2-5 × 106 m3 was extruded at mean output rate of 0.3 m3 s-1, with 2 to 3-month-long high extrusion rate phases being terminated by explosive events. Extrusion built a lava dome attaining a maximum height of ∼80 m above the crater rim, with a basal width of about 250 m. The composition of the 2012-2013 lava dome is comparable to that of the 1980 lava dome, both being andesite-trachydacite. Mineralogically, the 2012-2013 lava dome is mainly composed of plagioclase, pyroxene and an undetermined opaque mineral. Halogens released during eruption are consistent with the extrusion being fed, at least in the first eruption phase, by a degassed magma. This resulted in the formation of a dense, viscous plug in the conduit that led to a lateral gas flow, with gasses escaping around the plug to form multiple craters surrounding the dome. During the course of the eruptive activity, degassed magma was progressively forced out of the vent to unload deeper magma and force the system into an explosive phase. Such a scenario has occurred in the past at Rokatenda and is likely to be repeated in the future and creates an activity pattern that may be used to characterize such systems