Bulletin of Volcanology最新文献

Basaltic fissure eruptions are chiefly characterized by sizable emissions of lava flows and volcanic gases, posing significant hazards. However, such eruptions may be punctuated by explosive episodes, which are comparatively poorly understood but may have important volcanic hazard and environmental implications. The 1730–1736 CE Timanfaya eruption on Lanzarote, Canary Islands, is a large basaltic fissure eruption characterized by a marked temporal–compositional trend from early basanite to late tholeiite lavas, but little is known on its associated pyroclastic deposits and potential environmental repercussions. Here we report field and geochemical data from tephra deposits to reconstruct the temporal evolution of eruptive style and provide constraints on the impact of the Timanfaya eruption. Stratigraphic sections demonstrate the pulsatory nature of explosive activity during the eruption and the wide dispersal of the tephra blanket, for which a minimum bulk volume of ~0.44 km³ is derived. Isopleth data from a basal tephra layer tied to an early, particularly powerful eruption pulse suggest that eruption columns lofted to ≥8 km altitude. We find that nearly all distal tephras are characterized by low SiO₂ content and high incompatible trace element concentrations that only match the compositions of tephras sourced from vents active in the eruption’s initial phase. This implies that the most violent explosive activity, responsible for the emplacement of the tephra blanket, was restricted to the first few months of the eruption, after which eruptive style was dominated by lava effusion and mild cone-building Strombolian activity. We argue that explosive activity at Timanfaya was similar to that of the 1783–1784 CE Laki and 2021 Cumbre Vieja eruptions and highlight the explosive potential of mafic volcanism in the Canary Islands. Trace element proxies for volatile elements suggest that early basanitic magmas were particularly rich in CO₂, sulfur, and chlorine. We infer that the Timanfaya eruption released 65–388 Tg CO₂, 9–23 Tg S, and 2–9 Tg Cl to the atmosphere; however, ice core evidence indicates that little to no sulfur reached Greenland, consistent with tropospheric transport of gas emissions. Some climate proxy records show anomalies that may be related to Timanfaya, but the environmental impact of the eruption beyond Lanzarote remains unclear.

At the end of the summer 2021, an increase in CO₂ emissions at Vulcano brought an increase in the alert level and, consequently, to the upgrade of the monitoring activities by increasing the number of instruments deployed and the rate of the surveys. One of the new devices installed was a geodetic GNSS mobile network for a real-time and high-frequency monitoring of ground deformation, to increase the detail with respect to the existing permanent network. The mobile stations were initially installed at the northern base of the La Fossa crater, where the highest values of soil degassing were recorded. Two stations were co-located with gravimeters, in order to compare and integrate the data. After this very first period of testing, the mobile GNSS array has been reconfigured, to investigate the mud pool area. Thus, four stations were installed around the degassing area, one of them being in the same site of the gravimeter. Data has been acquired at 1 Hz rate and is used for the weekly reporting to Civil Protection. It was the first experience of a light and quick-to-install geodetic real-time and high-rate GNSS mobile network in this area, and it was the occasion for testing its performance, as well as different approaches for the real-time kinematic (RTK) differential positioning in order to find the most suitable for the ongoing phenomena. Furthermore, direct data communication and archiving in the institutional database have been implemented for immediate querying from the control room tools. We report the experiences collected during the installation phase, site selection, RTK approaches, and ground motion and provide the daily raw data in RINEX format for any future precise postprocessing for the mid- to long-term analyses.

For a better assessment of hazards related to tsunamis triggered by pyroclastic flows entering water, it is crucial to know and quantify the contribution of the physical parameters involved in the generation of waves. For this purpose, we investigate experimentally the effect of pyroclastic flow density on tsunami generation by considering variably fluidized granular flows denser or less dense than water, referred to as heavy and light granular flows, respectively, by varying the particle density. Qualitative observations show that differences in bulk flow density mainly affect the propagation of granular flows underwater. In contrast, the bulk flow density has little effect on the amplitude of the leading and largest wave. In fact, the wave amplitude is initially similar to the local water depth along the inclined plane, and then reaches a maximum value that depends mainly on the other flow parameters (i.e., velocity, thickness, volume of flows). Far from the shoreline, we provide evidence of the bulk flow density effect on the wave amplitude, while other characteristics of the leading wave remain broadly unaffected in the range of parameters considered. Finally, a main difference on the tsunami generation between light and heavy granular flows is related to the energy distribution between the leading largest wave and the wave train, which is attributed to different modes of interaction of the two flow types with the water. For tsunami hazard assessment, our study suggests that the contribution of the bulk flow density on tsunami generation has a second-order effect compared to other flow parameters.

The earliest stages of volcanic vent degradation are rarely measured, leaving a gap in the knowledge that informs landform degradation models of cinder cones and other monogenetic vent structures. We documented the initial degradation of a 500-m-long spatter rampart at the primary vent of the 2014–2015 Holuhraun eruption in northern Iceland with high-resolution topographic change maps derived from terrestrial laser scanning (TLS) and photogrammetric surveys using an unoccupied aircraft system (UAS). Topographic differencing shows a total negative volume change of 42,637 m³, and a total positive volume change (basal deposition) of 10,304 m³ (primarily as deposition at the base of steeply sloping surfaces). Two distinct styles of volume changes were observed on the interior and exterior of the spatter rampart. Material on the interior of the vent was removed from oversteepened slopes by discrete rockfalls, while diffusive processes were qualitatively evident on the exterior slopes. We propose a novel conceptual landform evolution model for spatter ramparts that combines rockfall processes on the interior walls, diffusive gravitational sliding on the exterior slopes, and incorporates cooling contraction and compaction over the entire edifice to describe the observed modes of topographic change during the onset of degradation. Potential hazards at fresh spatter ramparts are rockfalls at high slope areas of the vent interior walls where contacts between spatter clasts are prone to weakening by fumarolic activity, weathering, and settling. To capture such hazards, our data suggest a cadence for monitoring changes yearly for the first few years post-eruption, and at longer intervals thereafter.

The Cracked Mountain edifice is a basaltic subglacial volcano (i.e. tuya) situated in southwest British Columbia, Canada. The edifice is dominated by subaqueously deposited, massive to poorly stratified, variably palagonitized lapilli tuffs intruded by syn-eruptive dikes and lobes of peperitic pillow-lavas (15–20 vol.%); minor stacks of pillow-lava are found on the margins of the edifice. Here, we present mineralogical, textural, and physical property data for 134 sample cores from the palagonitized volcaniclastic deposits. Our sample suite includes three specific field environments defined by proximity to intrusive heat sources: (i) proximal (< 1 m) deposits (ENV1), (ii) deposits within 1–5 m of intrusions (ENV2), and (iii) deposits far removed (> 5 m) from discernible heat sources (ENV3). The dataset comprises mineralogy and measurements of density, porosity, permeability, P-wave velocity, uniaxial compressive strength, and paleomagnetism. Increased palagonitization is marked by increases in authigenic mineral abundance (smectite and analcime), density, strength, and P-wave velocity and concomitant decreases in porosity and permeability. Paleomagnetic data show a common pole direction recorded by all volcanic deposits indicating volcanism occurred within a single paleomagnetic moment (< 200 years). Palagonitization of the volcaniclastic deposits is driven by heat supplied by syn-eruptive intrusions and is most intense in ENV1, where dikes raised temperatures (> 150 °C) for a prolonged duration (< 1 year), and weakest in ENV3 deposits reheated to lower temperatures (< 150 °C). The timescale of palagonitization was short and coincident with the emplacement and cooling of syn-eruptive intrusions. The mapped intensity of palagonitization and thermal modelling are used to define a ‘palagonite window’ as a function of time and distance from heat sources (i.e. dikes).

We present a new stratigraphy of a 50 × 20 km area of the Ethiopian Plateau near Seladingay in northern Shewa province, some 160 km northeast of Addis Ababa. Situated near the rim of the plateau where the Afar depression funnels southwest into the Ethiopian rift, the area consists of > 1200 m of basalt lavas and interbedded rhyolitic volcanics. We describe three detailed stratigraphic sections and establish stratigraphic units on the basis of lithology and thin-section petrography, placed in the context of the regional stratigraphic framework and existing geochronology. We identify and name five new formations, each a package of either basaltic or rhyolitic units. Interlayered sedimentary strata and paleosols attest to intervals of volcanic quiescence. Likely initiating in the Paleogene, volcanism in our study area differs from the coeval Ethiopian Traps both in terms of lava composition and mechanism of magma genesis and extends into the Miocene (~ 15 Ma). From this, we determine that the first four of the volcanic formations in the central Ethiopian Plateau record a unique episode of volcanism in East Africa.

Small-to-moderate explosive eruptions involve VEIs ≤ 3, tephra volumes ≤ 0.1 km³ and often eject a significant amount of ash-sized pyroclastic material. This reduces the preservation potential of associated deposits and leads to an underrepresentation of these low- to mid-intensity explosive eruptions in long-term, frequency-magnitude datasets. Mt. Ruapehu is one of New Zealand’s most active volcanoes, having produced at least 32 small-to-moderate eruptions over the past 1800 years. The largest of these eruptions deposited the widespread T13-sequence and lasted several months to years. The cumulative deposit volume is estimated at 0.15 km³, thus being an order of magnitude larger than the average deposit volumes of the last 1800 years at Ruapehu. The sequence of pyroclastic fall deposits can be subdivided into six depositional sub-units representing at least five eruption phases of variable intensity and magnitude. The ash-lapilli sequence displays variable dispersal, deposit textures and pyroclast characteristics. While the initial phase is characterised by dispersal limited to the proximal 11 km and a tephra volume of 8.5 × 10⁵ m³ (± 3%), the following high-intensity “peak” phase is estimated at 8.8 × 10⁷ m³ (± 37.8%), representing about ⁓60% of the cumulative tephra volume. The combination of deposit characteristics with textural analysis of different types of juvenile clasts suggests that changes in eruption style and intensity were mainly controlled by shallow processes in the conduit, such as degassing and crystallisation and changes in conduit geometry. Multilobate, irregular dispersal patterns and laterally variable pyroclast assemblage indicate unsteady eruption conditions characterised by weak eruption plumes controlled by prevailing winds. This study testifies the complexity of tephra sequences associated with long-lasting, small-to-moderate eruptions, and describes the key eruption parameters that can be obtained through a detailed characterisation and identifies the main limitations related to the classification of these eruptive styles.

The unprecedented 2018 summit collapse at Kīlauea and subsequent 2020–2021 eruption within the newly deepened Halema‘uma‘u Crater provide an unparalleled opportunity to understand how collapse events impact a volcano’s shallow reservoir system and magmatic processes. Glass and olivine from tephra ejected by lava fountains and several explosions on 20–21 December, within a few hours of the 2020 eruption onset, yield information about pre-eruptive magma storage and transport. The olivine population is bimodal with zoned and non-zoned phenocrysts. Normally zoned olivine crystals with core compositions around Fo₈₈ have 30–50 μm wide Fo₈₂ overgrowth rims that have skeletal textures. Two skeletal xenocrysts (cores Fo₇₄ and Fo₈₁) are also reversely zoned up to Fo₈₂ rims. The crystal cores have trace element records of at least two cycles of growth and dissolution prior to the formation of the overgrowth rims. These rims and a separate population of non-zoned Fo₈₂ crystals are in Fe–Mg equilibrium with their host glass (average MgO of 6.9 ± 0.4 wt% (1σ), Mg# [Mg / (Mg + Fe²⁺)] of 0.57), which suggests undercooling after intrusion of magma to shallow levels in the plumbing system. In the years prior to the 2018 collapse, non-zoned Fo₈₁ olivine and slightly lower MgO glasses (6.8 wt%) reflected continuous mixing and compositional buffering of magma recharge into several km³ of stored magma in the Halema‘uma‘u reservoir (1–2 km depth). The 2020 olivine crystals lack evidence of an intrusion mixing with resident shallow magma, indicating that magma transport occurred in a disrupted system, and/or it may not have significantly mixed with stored magma remaining in the Halema‘uma‘u reservoir after the events of 2018. Diffusion modeling of Fe–Mg exchange in the zoned 2020 olivine crystals yield timescales that are mostly 60 days prior to the eruption or less, which aligns well with 22–24 October 2020 and subsequent seismic swarms at Nāmakani Paio ~ 5 km west of Kīlauea’s summit caldera. This correlation indicates that magma intruding beneath the summit (volume accommodation, recorded by the olivine crystals) was expressed by tectonic earthquakes along the Ka‘ōiki fault zone (stress accommodation). The absence of precursory SO₂ within minutes prior to eruption also indicates that the 2020 December magma may have risen from 1 to 2 km depth to the surface in as little as 10 min.

Early detection of volcanic ash clouds is crucial to aviation safety and airspace surveillance. With the increase in air traffic and the frequency of volcanic eruptions, the need for effective warning procedures and improved detection methods has become obvious. The eruption of the Eyjafjallajökull volcano in 2010 showed that air traffic operations were severely disrupted and highlighted the importance of effective communication strategies between stakeholders. To improve monitoring capabilities, satellite techniques have become essential due to their wide coverage and rapid response. This article presents the HOTVOLC 3.0 web-Geographic Information System (GIS) interface, an enhanced version of the French operational monitoring platform developed at the Observatoire de Physique du Globe de Clermont-Ferrand (OPGC) and certified by the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS-INSU). By integrating data from the Meteosat Second Generation (MSG) satellites, HOTVOLC 3.0 enables early detection of volcanic activity and monitoring of ash plumes and clouds. The HOTVOLC service is designed to support volcanic observatories, volcano research institutes, Volcanic Ash Advisory Centers (VAAC), and other operational actors who play a crucial role in decision-making and the implementation of effective risk management strategies for aviation safety. After a description of how the system works, we provide details of the updated web interface, which enhances the user experience by offering an interface with an operational mode and an archive mode, enabling easy access to past eruptions for training purposes. In the second part, we look at the various ash-related observation products (detection algorithms and quantitative products) that are disseminated via the new interface. Finally, we explore future developments of the platform, including the use of machine learning for ash detection, the integration of data from other geostationary satellites to improve product quality, and the forthcoming arrival of data from Meteosat Third Generation (MTG) satellites.