Bulletin of Volcanology最新文献

Quantifying subsurface fluid flows and related heat and gas fluxes can provide essential clues for interpreting the evolution of volcanic unrest in volcanoes with active hydrothermal systems. To better constrain the distribution of current hydrothermal activity, we mapped diffuse soil CO(_2) degassing, ground temperature and self-potential covering the summit of La Soufrière de Guadeloupe during 2022–2023. We identify areas of fluid recharge and the zones and extent of major ascending hydrothermal flows. This paper provides a first estimate for summit ground CO(_2) flux of 4.20±0.86 t(text {d}^{-1}), representing about half the CO(_2) emissions from the summit fumaroles. We find an extensive area of ground heating of at least 22250±6900 m(^{2}) in size and calculate a total ground heat flux of 2.93±0.78 MW, dominated by a convective flux of 2.25±0.46 MW. The prominent summit fractures exert significant control over hydrothermal fluid circulation and delimit a main active zone in the NE sector. The observed shift in subsurface fluid circulation towards this sector may be attributed to a changing ground permeability and may also be related to observed fault widening and the gravitational sliding of the dome’s SW flank. Our results indicate that the state of sealing of the dome may be inferred from the mapping of hydrothermal fluid fluxes, which may help evaluate potential hazards associated with fluid pressurisation.

We investigated the magma conduit system beneath three active craters that have repeatedly generated Vulcanian eruptions at Sakurajima Volcano, Japan, by analysing seismic, infrasound, and tilt data. The hypocentres of the earthquakes associated with the Vulcanian eruptions are distributed separately at shallow depths of approximately 0.5 km beneath the craters. Infrasound indicated that the swelling of the crater floor starts approximately 0.2 s after the occurrence of earthquakes and that the eruption starts about 0.3 to 0.5 s later. During an eruption, tilt vectors at a station approximately 2.7 km far from the active craters indicated a deflationary trend directed toward one of the three active craters. A 1-D conduit flow simulation indicated pressure build-up at a depth of 0.4–1.0 km beneath the crater, consistent with previously reported pressure sources during eruptions detected by geodesy. Volcanic lapilli emitted from the three craters have the same chemical composition; hence, Vulcanian eruptions of all three studied craters originate from a common magma source.

Crops are regularly impacted by tephra from explosive volcanic eruptions, causing significant economic losses and jeopardising farmers’ livelihood at the local to regional scales. Crop vulnerability to tephra remains poorly understood, impeding the construction of robust risk models for agriculture. Previous studies of crop vulnerability to tephra are semi-quantitative and consider tephra accumulation as the only hazard intensity metric. Here, we provide a robust evaluation of crop vulnerability based on the analysis of 700 sets of quantitative data, allowing for the assessment of the influence of various volcanic and non-volcanic factors. We collected farmers’ perceptions of damage to fodders, root and tuber crops, leafy crops, legumes, cereals, tree fruits, non-tree fruits, and estimations of their yield loss due to the August 16–17, 2006, October–November, 2015, and February–March, 2016, eruptions of Tungurahua volcano, Ecuador. Crop yield loss increased with tephra loads (48 ± 35, 69 ± 33, and 76 ± 34% for < 0.5, 0.5–5, and 5–50 kg m⁻², respectively), and we found that exposure to tephra led to a greater decline in yield compared to existing predictions. The results further highlight the plant phenological stage as a key factor of vulnerability. Exposure to tephra during the flowering period of legumes, cereals, and tree fruits caused a median yield loss ≥ 80%. Legumes, tree fruits, and non-tree fruits are more vulnerable to tephra than onions. Quantitative knowledge on crop vulnerability to tephra can be obtained from post-eruption impact assessments provided that a large population sample is collected and careful uncertainty analysis is conducted.

Volcano observatories (VOs) around the world are required to maintain surveillance of their volcanoes and inform civil protection and aviation authorities about impending eruptions. They often work through consolidated procedures to respond to volcanic crises in a timely manner and provide a service to the community aimed at reducing the potential impact of an eruption. Within the International Airways Volcano Watch (IAVW) framework of the International Civil Aviation Organisation (ICAO), designated State Volcano Observatories (SVOs) are asked to operate a colour coded system designed to inform the aviation community about the status of a volcano and the expected threats associated. Despite the IAVW documentation defining the different colour-coded levels, operating the aviation colour code in a standardised way is not easy, as sometimes, different SVOs adopt different strategies on how, when, and why to change it. Following two European VOs and Volcanic Ash Advisory Centres (VAACs) workshops, the European VOs agreed to present an overview on how they operate the aviation colour code. The comparative analysis presented here reveals that not all VOs in Europe use this system as part of their operational response, mainly because of a lack of volcanic eruptions since the aviation colour code was officially established, or the absence of a formal designation as an SVO. We also note that the VOs that do regularly use aviation colour code operate it differently depending on the frequency and styles of eruptions, the historical eruptive activity, the nature of the unrest, the monitoring level, institutional norms, previous experiences, and on the agreement they may have with the local Air Transport Navigation providers. This study shows that even though the aviation colour code system was designed to provide a standard, its usage strongly depends on the institutional subjectivity in responding to volcano emergencies. Some common questions have been identified across the different (S)VOs that will need to be addressed by ICAO to have a more harmonised approach and usage of the aviation colour code.

We propose a vast area in the middle of Lombok, Indonesia, dominated by hummock hills, is a debris avalanche deposit (DAD). We define this > 500 km² area as Kalibabak DAD that may originate from Samalas volcano. No descriptions of the morphology, stratigraphy, mechanism, and age of this DAD have yet been reported; this contribution bridges this research gap. Here we present morphological and internal architecture analysis, radiocarbon dating, paleotopographic modeling, and numerical simulation of the DAD. We also present geospatial data e.g., topographical and geological maps, digital elevation models (DEMs), satellite imagery – in combination with stratigraphic data constructed from field surveys, archived data, and electrical resistivity data. Results show that the DAD was formed by a sector-collapse of Samalas volcano and covers an area of 535 km², with a deposit width of 41 km and a runout distance up to 39 km from the source. The average deposit thickness is 28 m, reaching a measured local maximum of 58 m and a calculated volume of ~ 15 km³. Andesitic breccia boulders and a sandy matrix dominate the deposit. Using ShapeVolc, we reconstructed the pre-DAD paleotopography and then used the reconstructed DEM to model the debris avalanche using VolcFlow. The model provides an estimate of the flow characteristics, but the extent of the modelled deposit does not match the present-day deposit, for at least two reasons: (i) the lack of information on the previous edifice topography that collapsed, and (ii) limited understanding of how DADs translate across the landscape. Fourteen radiocarbon dating samples indicate that the DAD was emplaced between 7,000–2,600 BCE. The DAD's enormous volume, vast extent and poorly weathered facies strongly suggest that it was not triggered by a Bandai-type debris avalanche (solely phreatic eruption), but more likely by a Bezymianny-type (magmatic eruption). This event was potentially triggered by a sub-Plinian or Plinian eruption (high eruption column with umbrella-like cloud) dated ~ 3,500 BCE, which produced the Propok pumice fall deposits.

The Campi Flegrei caldera is characterized by the phenomenon of bradyseism, as evidenced by stratigraphic records of alternate oceanic and continental sediments dating back over a thousand years. Since 2005, the caldera has been in a phase of unrest, which is increasing volcanic deformations and associated seismicity around the region, resulting in a growing concern over the dense population in the inhabitation. Recent studies have highlighted that the caldera dynamics are driven by a combination of endogenous processes and modulation phenomena induced by exogenous processes, e.g., rainfall, atmospheric pressure, and tidal loading. Although the complex feedback mechanisms of both endogenous and exogenous processes are still under debate, the present study is focused on the increased potential of modulation due to exogenous processes with the increase or evolution in the degree of inflation of the magma chamber. Specifically, Campi Flegrei volcanic system shows sensitivity to seasonal hydrological cycles during slower rates of inflation and to short-period tidal modulations during higher rates of inflation. The observed seasonal modulations of seismic activity are explained in terms of water infiltration into the shallow aquifers, basins, and vent depression system of the caldera. The rainfall-induced pore pressure build-up also favours the instability of the brittle cap rock, promoting seismicity. In addition, this study suggests that the tidal loadings provide horizontal NS extensions to the mostly NW–SE, NE–SW, and EW-oriented scattered fractures and further contribute towards fracture propagation. During this process, a cyclic opening and sealing of fractures by volatile outgassing and silicate settling may, respectively, produce the episodic behaviour of the seismicity. The seismicity in relation to exogenous processes imposed by seasonal rainfall and tidal loadings shows that the degree of correlation depends on the different rates of inflation. The long-period seasonal modulations and short-period tidal modulations during the evolution of the degree of inflation are finally interpreted in the framework of the fault resonance destabilization model, under rate-and-state dependant frictional formalism.

Abstract

Based on published and new data for explosive events at Stromboli (Italy), we propose an empirical relation that links mass discharge rate (MDR) and at-vent gas jet velocity (G_v). We use 65 simultaneous measurements of MDR and G_v and find two trends in both the cross-correlation and rank order statistics. Cross-correlation gives a power law relation: (MDR= {10}^{(0.015{G}_{v}+2.434)}) kg/s, R² = 0.81, and applies to ash-dominated emissions. Combining this relation with the conservation of mass equation allows at-vent plume density and/or vent area to be derived from MDR = G_v ρ A, ρ being plume density and A being vent cross-sectional area. We find that while a vent radius of 2 m and plume density of 0.35 kg/m³ fits with the “normal” activity at Stromboli, a 290 × 2.5 m vent area likely feeds a 10 kg/m³ jet during paroxysmal activity. Initial tests on available data shows promise in extending the correlation beyond Stromboli and/or to events with higher MDR (> 10⁷ kg/s). However, the exact relation will depend on magma composition, temperature and volatile content, as well as conduit radius and vent overpressure.

A half-day workshop was held following the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) Scientific Assembly in Rotorua, New Zealand, on 5 February 2023. The workshop took advantage of the presence of operationally focused meteorologists, leaders from the World Meteorological Organization (WMO) and volcanologists (mostly from volcano observatories) for an aviation workshop over the previous 2 days. Our workshop focused on non-aviation issues but sought to develop the ‘big-picture’ of multi-hazard arrangements, particularly noting the intertwining of the disciplines for many volcanic hazards, and a global push towards better integrated, impact-based multi-hazard early warning systems, including especially the Sendai Framework and the ‘Early Warnings for All’ initiative. The hazards requiring joint multi-disciplinary arrangements include tsunamis, ashfall and airborne/water-borne ash, rainfall-induced dome collapses, lahars, pumice, glacial floods, and gas. Of these, only airborne ash for aviation users has received much attention. Following an afternoon of presentations, panel discussions, and breakout discussion, two summary visualisations were prepared—a future ‘vision’ and a future ‘roadmap’ for multi-hazard operations. These are presented as input towards follow-up actions, including ensuring that volcanic ash for aviation arrangements are embedded within a holistic multi-hazard and multi-user approach.

The volcanic stratigraphy and petrography of compositionally bimodal volcanic rocks in the Mekane Selam area were characterized by detailed field investigation, spatial and systematic sampling, and petrographic analysis. Three successions of basaltic rocks with rhyolitic and trachytic rock units at the top with a substantial volume of felsic pyroclastic deposits were categorized as the typical lithological formations in the study area. Volcanic rock types present in the study area include plagioclase phyric basalt, plagioclase-pyroxene phyric basalt, pyroxene-plagioclase phyric basalt, pyroxene-olivine phyric basalt, pyroxene phyric basalt, olivine phyric basalt, rhyolite, and trachyte from bottom to top. The basaltic rocks are composed of plagioclase, clinopyroxene, and olivine phenocrysts with minor Fe-Ti oxides (ilmenite and magnetites). The common phenocrysts of trachyte rocks are sanidine, plagioclase, Fe-Ti oxides, and minor hornblende and green pyroxenes (aegirine). Rhyolites contain quartz and sanidine phenocrysts.