Bulletin of Volcanology最新文献

The Ecuadorian arc is composed of an unusually high number of volcanoes, organized as along-arc alignments and across-arc clusters, in a relatively small area. Although several geochronological studies have been carried out in the last three decades, the eruptive history of the central zone of the arc remains poorly documented, preventing analysis of the initiation of volcanism of the whole arc. In this study, we present new K–Ar ages obtained from this central area, referred to as the Quito segment. These results were then incorporated into an updated comprehensive geochronological database of about 250 ages, allowing us to describe, at the arc scale, the spatial and temporal evolution of Quaternary volcanism in Ecuador. About eighty Quaternary volcanoes have been identified in the Ecuadorian Andes, 45 of which have been radioisotopically dated and/or identified as active or potentially active. The volcanic arc developed in three stages, characterized by an increase in the total number of active volcanoes. During the oldest Plio-Early Pleistocene stage, documented volcanic activity was mostly concentrated in the Eastern Cordillera of the Quito segment, with minor effusive eruptions in the southern Back-Arc. Since ~ 1.4 Ma, activity has spread to the surroundings of the Quito segment, and new edifices also appeared in the Western Cordillera and the Inter-Andean Valley. Towards the end of this intermediate stage (i.e., ~ 800 ka), volcanism occurred in isolated areas north and south of the Inter-Andean Valley. Finally, the late and current has been characterized by a remarkable increase in volcanic activity since ~ 600 ka. About 50 volcanoes were active during this stage. The spatial distribution of the Ecuadorian arc volcanism seems to be guided by deep mechanisms (i.e., slab geometry and age, amount and composition (fluids and melts) of slab input, mantle heterogeneities) and old crustal tectonic structures of the Western Cordillera, while neotectonics seems to influence the development of stratovolcanoes. In addition, we note that the spatial and temporal evolution of volcanism highlights the influence of the Carnegie Ridge and the young Nazca crust on the thermal regime of the subduction system, which in turn increases of volcanic activity in Ecuador.

The Alaska Volcano Observatory (AVO) uses multidisciplinary data to monitor and study dozens of active and potentially active volcanoes. Here, we provide an overview of internally and externally generated data types, tools and resources used in their management, and challenges faced. Data sources include the following: (1) a multiparameter (seismic, infrasound, GNSS, web cameras) ground-based monitoring network that spans 3000 km and transmits data in real time; (2) a variety of satellite-borne sensors that provide information about surface change and volcanic emissions; (3) geologic and gas field campaigns; and (4) other external data products that provide situation awareness. Each data type requires distinct acquisition, processing, storage, visualization, and archiving approaches. AVO uses a variety of externally and internally developed tools to handle individual data types as well as multidisciplinary volcanological data. A primary tool is the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA), which stores detailed, searchable information on more than 140 volcanoes and over 1000 eruptions and unrest events, including images, eruption descriptions, and geologic station and sample data, metadata, and analyses. It interacts with other internal tools that store monitoring reports and other operational records. Additional data management resources used by AVO assist with alarms and alerts, state-of-health monitoring, and multiparameter visualization. Requirements for 24/7 accessibility, the ever-expanding portfolio of data, and transitioning new tools from development to operations are all challenges faced by AVO and other volcano observatories. AVO strives to meet FAIR data practices and ensure that data are available to national and international community efforts using external repositories as well as those hosted by AVO and its parent institutions.

The International Network for Volcanology Collaboration (INVOLC) is a network formalised by the International Association of Volcanology and Chemistry of the Earth’s Interior (IAVCEI) with the specific ambition to enhance volcanology globally through improved international collaboration. IAVCEI-INVOLC was created with a focus on volcano scientists working in resource-constrained contexts, including those based in low- or middle-income countries. After a community-wide online survey and inaugural workshop during which INVOLC’s ambitions were discussed, a series of challenges, as commonly experienced by those working in resource-constrained settings, were identified. These challenges may present barriers to participation in volcano science in an international context and are related to both organisational resources (financial, human, technical) and inclusion in research collaborations. In this perspectives paper, we present a series of 15 guidelines for best-engagement protocols in international collaboration in volcanology that may be adopted during times of quiescence, volcanic unrest and/or an eruption and its aftermath. Our aspiration is that these guidelines will help build more respectful, equitable and sustainable partnerships that will ultimately advance the science of volcanology.

The 2050 ± 50 ¹⁴C yBP caldera-forming eruption of Okmok volcano, Alaska, had a global atmospheric impact with tephra deposits found in distant Arctic ice cores and a sulfate signal found in both Greenland and Antarctic ice cores. The associated global climate cooling was driven by the amount of sulfur injected into the stratosphere during the climactic phase of the eruption. This phase was dominated by pyroclastic density currents, which have complex emplacement dynamics precluding direct estimates of the sulfur stratospheric load. We simulated the dynamics of the climactic phase with the two-phase flow model MFIX-TFM under axisymmetric conditions with several combinations of mass eruption rate, jet water content, vent size, particle size and density, topography, and emission duration. Results suggest that a steady mass eruption rate of 1.2–3.9 × 10¹¹ kg/s is consistent with field observations. Minimal stratospheric injections occur in pulses issued from the central plume initially rising above the caldera center and from successive phoenix ash-clouds caused by the encounter of the pyroclastic density currents with topography. Most of the volcanic gas is injected into the stratosphere by the buoyant liftoff of dilute parts of the currents at the end of the eruption. Overall, 58–64 wt% of the total amount of gas emitted reaches the stratosphere. A fluctuating emission rate or an efficient final liftoff due to seawater interaction is unlikely to have increased this loading. Combined with petrological estimates of the degassed S, our results suggest that the eruption injected 11–20 Tg S into the stratosphere, consistent with the subsequent climate response and Greenland ice sheet deposition. Our results also show that the combination of the source Richardson number and the mass eruption rate is able to characterize the buoyant–collapse transition at Okmok. We extended this result to 141 runs from 10 published numerical studies of eruptive jets and found that this regime diagram is able to capture the first-order layout of the buoyant–collapse transition in all studies except one. An existing multivariate criterion yields the best predictions of this regime transition.

The morphology of the shield volcanoes on Bioko, a volcanic island in central Africa, is controlled both by tectonic and volcanic processes, but the complex interplay of these regional and local mechanisms is poorly understood. Using a TanDEM-X digital elevation model, we are able to create an inventory of 436 vents and monogenetic cones, and over 1330 structural elements and lineaments, and perform a comprehensive morphological and geospatial analysis. We provide detail on the general geomorphology of Bioko Island, and describe its flat top, apical graben-like structures, and the setting of the structural inventory created. Based on vent density and lineament mapping, we are able to identify volcanic rift zones that are governed by vent clustering and the asymmetry of associated monogenetic cones. Specifically, we find that eruption vents are not only clustered but aligned and follow the principal NE-SW axis, although we also highlight evidence for complex structures such as side-stepping alignments and en échelon patterns indicative of strike-slip contributions to the volcano-tectonic fabrics. We discuss possible volcano-tectonic and regional tectonic contributors, such as the Cameroon Volcanic Line and intersecting fracture zones, as well as gravity-tectonic processes dominant at Bioko Island. In this view, our results are relevant for understanding the past and recent volcanic activity and discuss the influence of regional and local volcano-tectonic architectures.

El Chichón volcano is the most active volcano in the state of Chiapas, México, and experienced its last Plinian eruption (VEI = 5) in 1982. To better assess its volcanic hazard, we studied its readiness to erupt by estimating changes in its internal stress state. These stress changes are difficult to calculate accurately, for example in the absence of focal mechanisms, but their existence can be indirectly revealed by the presence of volcano-tectonic earthquakes, for example following a large tectonic earthquake. We show that the seismic rate recorded at El Chichón volcano increased slightly after the large M_w8.2 Tehuantepec earthquake of 8 September 2017, Chiapas. However, this rate quickly returned to its background level after only 2 months, without any external volcanic manifestations, suggesting that the volcano is not ready to erupt in the near future. Previous observations of slight increases in the volcanic seismicity rate following large earthquakes have been explained by the presence of active hydrothermal systems in the vicinity of the volcano. We propose a similar explanation for El Chichón volcano which is known for its large hydrothermal system. Furthermore, the characteristics of the 2017 seismicity (spatial and magnitude distributions), and the horizontal-to-vertical spectral ratio also confirm the presence of high amounts of water near the volcano. We show that the 2017 volcano-tectonic seismicity is of hydrothermal rather than magmatic origin, in agreement with recent independent geochemical and aeromagnetic studies.

Aircraft encounters with volcanic ash have caused significant damage over the past 40 years, resulting in particular attention being given to the issue. We analyzed the volcanic ash-aircraft encounter database published by the USGS. We added new volcanic eruptions and parameters such as eruption types, and dry–wet. Then, we applied standard and advanced statistical methods.

Over 130 encounters have been documented in the mentioned database, with volcanic ash causing severe abrasions to the windshield, airframe, wings, and engine components. In nine cases, aircraft engines failed. We applied the binary regression analysis and some laboratory melting experiments on volcanic ash. Besides phreatomagmatism, we use the term external water in this work to describe meteoric water that enters volcanic plumes through precipitation or melting ice on ice-capped volcanoes. We demonstrated that engine failure occurs when our regression analyses undergo dry-to-wet conditions. In other words, statistically, there is a positive correlation between wet ash encounters with aircraft and engine failure incidents. Moreover, experiments conducted at 900 °C and under 40 bar pressure showed increased sintering in the dry sample, while melting textures were more prevalent in hydrated samples. We concluded that despite the various eruptive dynamics of volcanic ash, the introduction of external water into the volcanic plumes, probably causing instantaneous hydration of volcanic ash, is a common factor in engine failure incidents. Thus, we have identified the reasons behind engine failures during encounters between aircraft and volcanic ash and the specific damage that can occur depending on the type of eruption involved.

This paper presents a framework designed to collect, archive, and share time series data coming from sensor networks at Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (Italy), which we have developed and called Time Series Database management System (TSDSystem). The framework proposes a flexible database model for the standardization of sensor networks data and implements an optimized technology for storage and retrieval of acquired time series data. It is designed for the implementation of multiparametric databases and then suitable for development in volcanological observatories worldwide. The proposed framework provides a web service to perform writing and reading data via a standard web communication protocol, which easily enables interaction with other instruments or automatic systems. All results provided by the TSDSystem web service are represented using common data formats in the context of online services. In particular, the station networks metadata representation follows a schema inspired by the International Federation of Digital Seismograph Networks, widely known in seismology. A web GUI (graphical user interface) is provided to test and document the web service. Additionally, basic built-in web applications are supplied with the web GUI to perform joint and synchronized time series data visualization as well as representation of stations on a geographical map. The web GUI also offers administration tools for data access policy management, creation of monitoring dashboards and data publication through web pages. The framework implements an authorization system that can be used to restrict both writing or reading operations. The TSDSystem can also be a useful tool for engineering surveillance systems. The implementing code of the framework is available with an open source license on a public repository together with a user manual.

The gravitational instability of hot material deposited during eruptive activity can lead to the formation of glowing avalanches, commonly known as deposit-derived pyroclastic density currents (PDCs). These currents can travel hundreds of metres to several kilometres from the source at exceptionally high temperatures, posing a catastrophic hazard to areas surrounding steep-slope volcanoes. The occurrence of deposit-derived PDCs is often associated with crater rim failure, which can be triggered by various factors such as magma thrust from dike injection, magma fingering, bulging or less commonly, powerful explosions. Here, the in-depth study of data from the multi-parametric monitoring network operating on Stromboli (Italy), including video surveillance, seismicity and ground deformation data, complemented by remote topographic sensing data, has facilitated the understanding of the events leading to the crater rim collapse on 9 October and 4 December 2022. The failures resulted in the remobilisation of 6.4 ± 1.0 × 10³ m³ and 88.9 ± 26.7 × 10³ m³ of material for the 9 October and the 4 December 2022, respectively, which propagated as PDCs along the NW side of the volcano and reached the sea in a few tens of seconds. These events were characterised by a preparatory phase marked by an increase in magmatic pressure in the preceding weeks, which correlated with an increase in the displacement rate of the volcano’s summit. There was also an escalation in explosive degassing, evidenced by spattering accompanied by seismic tremors in the hours before the collapse.

These events have been interpreted as an initial increase in magma vesicularity, followed by the release of gas once percolation threshold was reached. The degassing process induced densification of the magma, resulting in increased thrust on the conduit walls due to increased magmastatic pressure. This phase coincided with crater rim collapse, often followed or accompanied by the onset of lava overflow phases. A mechanism similar to the one proposed may shed light on similar phenomena observed at other volcanoes. The analysis performed in this study highlights the need for a multi-parametric and multi-platform approach to fully understand such complex phenomena. By integrating different data sources, including seismic, deformation and remote sensing data, it is possible to identify the phenomena associated with the different phases leading to crater rim collapse and the subsequent development of deposit-derived PDCs.