#### Bulletin of Volcanology

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ISSN / EISSN : 0258-8900 / 1432-0819
Total articles ≅ 4,232
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Correction
, A. Mark Jellinek
Published: 12 October 2021
Bulletin of Volcanology, Volume 83, pp 1-1; https://doi.org/10.1007/s00445-021-01498-5

, Ana Lillian Martin-Del Pozzo
Published: 7 October 2021
Bulletin of Volcanology, Volume 83, pp 1-17; https://doi.org/10.1007/s00445-021-01490-z

Abstract:
Popocatépetl volcano produced 625 ash emissions to heights greater than1 km between 1994 and 2008. During this time, ash fall affected mostly populations within a 60 km radius around the volcano, a zone which includes 4.5 million people. We assess the effects of prolonged ash fall on human health in these areas between 1994 and 2008. To do this, we considered 94,000 non-infectious respiratory disease (NIRD) records from five health databases. This included the 98 municipalities where ash fall was frequent, plus two municipalities outside of the ash fall area which served as a control group. NIRD rates (cases/1 k inhabitants) from 1992, 2 years before the beginning of the eruptive period, tol 2008 were compared with mapped ash distributions during the same period. Wind dispersed 29% of these ash emissions to the northeast, 20% to the east, 17% to the southwest, 13% to the northwest, 9% to the southeast, and12% in other directions, producing more ash fall in the northeast and east sectors and higher NIRD rates. Results, tested with an analysis of variance (ANOVA) and covariance statistical analyses, show that changes in NIRD rates correlate with ash dispersion direction and the amount of fine ash deposited. During eruptive crises in 1994–2003 and 2005, NIRD rates increased from < 1 to > 2.6, reaching levels up to > 3 in municipalities where ash was sampled. In 2004 and 2006–2008 when ash plume frequency and ash concentration decreased (e.g., only two minor ash emissions in 2004), the NIRD rates remained unchanged. This was a result of the chronic effect on health of the preceding ash fall. We found that health impacts are principally related to the amount of ash, as well as the percentage of fine particles which in turn is also a function of the prolonged nature of the eruption. The fine ash from Popocatépetl is composed of up to 19.2% of particles smaller than 10 μm and up to 5.7% smaller than 2.5 μm and contains plagioclase crystals, lithic particles, glass, pyroxene crystals, cristobalite, and minor amounts of titanomagnetite and sublimates.
Aristle Monteiro, , Tushar Mittal, Shrishail Pujari, Upananda Low, Ahsan Absar
Published: 7 October 2021
Bulletin of Volcanology, Volume 83, pp 1-23; https://doi.org/10.1007/s00445-021-01485-w

Abstract:
We analyse two representative rubbly pāhoehoe lavas (F3 and F5) from drill cores at Tural-Rajwadi, southwest of Koyna, in the southern Deccan Traps. Low vesicle deformation (0.1 to 0.4) indicates that both lavas ultimately cooled under a low-stress regime. The crystal size distributions (CSDs) of most samples from F5 (especially those from within the core) are not linear but instead show kinks. These kinks are attributed to a rise in plagioclase nucleation due to degassing following the brecciation of the crust. Since it is difficult to constrain cooling time for ancient lava flows, we used the products of nucleation rates (Jt, 1.64 × 10–8 to 1.45 × 10–5 μm−3) and growth rates (Gt, 2.1 to 156 μm) with time. When compared with natural analogues as well as experimental results for basalt crystallisation, these values suggest a much faster lava cooling rate (~ 1 to 7℃/hr) than a conductive cooling model (≤ 0.1 ℃/hr). The CSDs for F3 fan with depth suggesting that the lava flow might represent local accumulation (ponding?) in a transitional lava flow field. CSDs for F5 show little variation with depth, with the exception of kinks for samples from the lower crust and core. The relatively higher number density of plagioclase microcrysts in our rubbly pāhoehoe (F5) and their CSD patterns are similar to those measured for transitional lavas from Hawaii. The vesicle data and CSDs indicate that brittle deformation was the primary mode of transition within these lavas. Identifying occurrence of thick ponded lavas within vertical stacks of rubbly pāhoehoe flows in the upper stratigraphic levels of the Deccan Traps are critically important as they demonstrate complex cooling styles, crystallisation histories, and emplacement dynamics. Transitional lavas such as rubbly pāhoehoe are important components of large CFB provinces such as the Deccan Traps and constitute nearly 46 to 85% of all lava types. Modelling of continental flood basalt provinces should therefore account for these diversities within lavas, and any oversimplified version using end-member morphotypes is unrealistic and untenable.
, Hannah R. Dietterich, Matthew P. Patrick, David Fee
Published: 5 October 2021
Bulletin of Volcanology, Volume 83, pp 1-12; https://doi.org/10.1007/s00445-021-01488-7

Abstract:
The 2018 eruption of Kīlauea Volcano produced large and destructive lava flows from the fissure 8 (Ahu ‘aila ‘au) vent with flow velocities up to 17 m s−1, highly variable effusion rates over both short (minutes) and long (hours) time scales, and a proximal channel or spillway that displayed flow features similar to open channel flow in river systems. Monitoring such dynamic vent and lava flow systems is a challenge. Our results demonstrate that infrasound, combined with ground-based observations and imagery from unoccupied aircraft systems (UAS), can be used to distinguish vent degassing activity from high-speed lava flow activity. We use spectral characteristics and the infrasound frequency index (FI) to distinguish spillway infrasound from vent infrasound. Comparing FI with flow speeds derived from UAS videos reveals that spillway infrasound only occurs when flow speeds were sufficiently high to cause a supercritical flow state and breaking waves (Froude values > 1.7), and we propose that the spillway signals are produced primarily through the interaction of the turbulent lava-free surface with the atmosphere. We show that FI can also provide a means to track bulk effusion rate. Our results indicate that infrasound offers a new way to characterize lava flow channel hydraulics and is a powerful tool for monitoring effusive eruptions when high-speed flows are possible.
, J. Hammer, H. Dietterich, R. Perroy, M. Patrick, T. Shea
Published: 5 October 2021
Bulletin of Volcanology, Volume 83, pp 1-19; https://doi.org/10.1007/s00445-021-01492-x

Abstract:
The 2018 lower East Rift Zone (LERZ) eruption of Kīlauea, Hawai’i, provides an excellent natural laboratory with which to test models of lava flow propagation. During early stages of eruption crises, the most useful lava flow propagation equations utilize readily determined parameters and require fewer a priori assumptions about future behavior of the flow. Here, we leverage the numerous observations of lava flows collected over the duration of the eruption crisis at Kīlauea in 2018 to test simple lava flow propagation models. These models track the one-dimensional propagation of the flows according to three main rheological restraining forces: bulk viscosity, yield strength, and growth of a surface crust. We calculate the predicted changes in length through time of three flows that vary in bulk composition, crystal content, and total flow length. Cooler flows that are more crystal-rich tend to be more dominated by crust growth, though early stages of propagation can be controlled by bulk viscosity. We find that variations in effusion rate significantly impact flows that are short-lived; flows that are produced during steady-state effusion are readily approximated by average values for the entire flow. Thus, accurate knowledge of variations in effusion rate are critical to accurate lava flow propagation forecasting.
, A. Mark Jellinek
Published: 21 September 2021
Bulletin of Volcanology, Volume 83, pp 1-59; https://doi.org/10.1007/s00445-021-01472-1

Abstract:
It is increasingly recognized that the gravitational stability of explosive eruption columns is governed by complex ash-pumice-gas (multiphase) interactions as well as the mechanics of turbulent entrainment in the lower momentum-driven (fountain) and upper buoyancy-driven (plume) regions of typical Plinian eruption columns (volcanic jets). We use analog experiments on relatively dense mono- and bi-disperse particle-freshwater and particle-saltwater jets injected into a linearly stratified saltwater layer to revisit, characterize and understand how transitions among Buoyant Plume (BP), Total Collapse (TC) and Partial Collapse (PC) multiphase jet regimes in a traditional source strength (−Ri0) - particle concentration (ϕ0) parameter space are modified by particle inertial effects expressed through a Stokes number (St) and particle buoyancy effects expressed through a Sedimentation number (Σ). We show that “coarse particles” (1.4 ≤St ≤ 6.0) enhance entrainment and modify significantly published conditions favoring BP and TC jets. Furthermore, the transition between BP and TC regimes occurs smoothly over a PC regime that extends a large $-\text {R}\text {i}_{0} \leftrightarrow \phi _{0}$ parameter space. Large volume annular sedimentation waves excited periodically at the fountain-plume transition height and the cloud level of neutral buoyancy (LNB) in PC and TC regimes lead to “phoenix clouds” spreading at multiple altitudes and build terraced deposits. Applied to volcanic jets, we develop a new set of conceptual models for jets in the BP, TC and PC regimes that make explicit links among source parameters, column heights, sedimentation wave properties, cloud structures and deposit architectures. These conceptual models make predictions for cloud structures and deposit characteristics that agree with observations made for well-studied historic and pre-historic eruptions and explain the origin of common but enigmatic features of proximal explosive eruption deposits, such as alternating air-fall and pyroclastic flow layering in subaerial deposits and terracing in submarine Catastrophic-Caldera Forming (CCF) eruption deposits. Additionally, our models provide guidance for real-time monitoring of eruption column stability for eruptions undergoing a typical BP→PC→TC regime evolution and predict pyroclastic flows to occur more frequently as columns transition from the PC→TC regime. Our experimental results combined with scaling considerations expressed through a set of new conceptual models provide exciting new pathways for future laboratory-, computer- and field-based studies of explosive eruptions.
, Atsushi Toramaru, Tomoharu Miyamoto, Yasuo Miyabuchi, Takahiro Yamamoto
Published: 14 September 2021
Bulletin Volcanologique, Volume 83, pp 1-20; https://doi.org/10.1007/s00445-021-01484-x

Abstract:
The eruption of the Tambora volcano in 1815 was initiated by two precursory Plinian falls and formed two generations of pyroclastic density current (PDC) deposits. In this study, we found slight changes in phenocrysts (modal mineralogy, content, and size), bulk-rock and feldspar microlite chemical compositions, and bubble and microlite number densities through the stratigraphic position. Plinian fall units are characterized by a lower phenocryst abundance (avg. of 5.1%), smaller phenocryst size (avg. of 0.06 mm2), and higher silica content (bulk-rock, 58–58.5 wt.%). The PDC deposits are characterized by a relatively higher crystal abundance (avg. of 12.1%), larger phenocryst sizes (avg. of 0.13 mm2), and lower silica content (bulk-rock, 56.7–57.9 wt.%). Therefore, the deposit stratigraphy and analyses suggest that phenocryst stratification in the magma chamber was established prior to the 1815 eruption and was thus responsible for yielding a slight contrast in bulk compositions. Feldspar microlite moves toward slightly more albitic compositions from Plinian falls to the PDCs, suggesting a slight decrease in the initial melt temperature from the upper to the lower magma chamber portion. Because the Plinian eruptions extracted the hottest magma, the degree of supercooling became low, and consequently yielded microlite-poor juveniles. By contrast, the PDCs experienced a larger degree of supercooling because the temperature was relatively low, thus yielding microlite-rich juveniles. Moreover, such temperature stratification coupled with the evidence of homogeneous melt composition (58.5–58.9 wt.% SiO2) and the minor evidence of crystal mush (at most 27%) might suggest that the Tambora case is still in the early stage of magmatic evolution under cooling from the surrounding rocks.
Published: 10 September 2021
Bulletin Volcanologique, Volume 83, pp 1-28; https://doi.org/10.1007/s00445-021-01486-9

Abstract:
Mayon is a basaltic andesitic, open-vent volcano characterized by persistent passive degassing from the summit at 2463 m above sea level. Mid-size (< 0.1 km3) and mildly explosive eruptions and occasional phreatic eruptions have occurred approximately every 10 years for over a hundred years. Mayon’s plumbing system structure, processes, and time scales driving its eruptions are still not well-known, despite being the most active volcano in the Philippines. We investigated the petrology and geochemistry of its crystal-rich lavas (~ 50 vol% phenocrysts) from nine historical eruptions between 1928 and 2009 and propose a conceptual model of the processes and magmatic architecture that led to the eruptions. The whole-rock geochemistry and mineral assemblage (plagioclase + orthopyroxene + clinopyroxene + Fe-Ti oxide ± olivine) of the lavas have remained remarkably homogenous (54 wt% SiO2, ~ 4 wt% MgO) from 1928 to 2009. However, electron microscope images and microprobe analyses of the phenocrysts and the existence of three types of glomerocrysts testify to a range of magmatic processes, including long-term magma residence, magma mixing, crystallization, volatile fluxing, and degassing. Multiple mineral-melt geothermobarometers suggest a relatively thermally buffered system at 1050 ± 25 °C, with several magma residence zones, ranging from close to the surface, through reservoirs at ~ 4–5 km, and as deep as ~ 20 km. Diffusion chronometry on > 200 orthopyroxene crystals reveal magma mixing timescales that range from a few days to about 65 years, but the majority are shorter than the decadal inter-eruptive repose period. This implies that magma intrusion at Mayon has been nearly continuous over the studied time period, with limited crystal recycling from one eruption to the next. The variety of plagioclase textures and zoning patterns reflect fluxing of volatiles from depth to shallower melts through which they eventually reach the atmosphere through an open conduit. The crystal-rich nature of the erupted magmas may have developed during each inter-eruptive period. We propose that Mayon has behaved over almost 100 years as a steady state system, with limited variations in eruption frequency, degassing flux, magma composition, and crystal content that are mainly determined by the amount and composition of deep magma and volatile input in the system. We explore how Mayon volcano’s processes and working model can be related to other open-vent mafic and water-rich systems such as Etna, Stromboli, Villarrica, or Llaima. Finally, our understanding of open-vent, persistently active volcanoes is rooted in historical observations, but volcano behavior can evolve over longer time frames. We speculate that these volcanoes produce specific plagioclase textures that can be used to identify similar volcanic behavior in the geologic record.
Correction
, K. S. Panter
Published: 20 August 2021
Bulletin of Volcanology, Volume 83, pp 1-1; https://doi.org/10.1007/s00445-021-01483-y

, Arthur Jolly, Robin S. Matoza, Ben Kennedy, Geoff Kilgour, Richard Johnson, Esline Garaebiti, Sandrine Cevuard
Published: 17 August 2021
Bulletin of Volcanology, Volume 83, pp 1-15; https://doi.org/10.1007/s00445-021-01474-z

Abstract:
A new episode of unrest and phreatic/phreatomagmatic/magmatic eruptions occurred at Ambae volcano, Vanuatu, in 2017–2018. We installed a multi-station seismo-acoustic network consisting of seven 3-component broadband seismic stations and four 3-element (26–62 m maximum inter-element separation) infrasound arrays during the last phase of the 2018 eruption episode, capturing at least six reported major explosions towards the end of the eruption episode. The observed volcanic seismic signals are generally in the passband 0.5–10 Hz during the eruptive activity, but the corresponding acoustic signals have relatively low frequencies (< 1 Hz). Apparent very-long-period (< 0.2 Hz) seismic signals are also observed during the eruptive episode, but we show that they are generated as ground-coupled airwaves and propagate with atmospheric acoustic velocity. We observe strongly coherent infrasound waves at all acoustic arrays during the eruptions. Using waveform similarity of the acoustic signals, we detect previously unreported volcanic explosions at the summit vent region based on constant-celerity reverse-time-migration (RTM) analysis. The detected acoustic bursts are temporally related to shallow seismic volcanic tremor (frequency content of 5–10 Hz), which we characterise using a simplified amplitude ratio method at a seismic station pair with different distances from the vent. The amplitude ratio increased at the onset of large explosions and then decreased, which is interpreted as the seismic source ascent and descent. The ratio change is potentially useful to recognise volcanic unrest using only two seismic stations quickly. This study reiterates the value of joint seismo-acoustic data for improving interpretation of volcanic activity and reducing ambiguity in geophysical monitoring.