Eruption Column Research Articles

Pumice cone eruptions at Aluto volcano, Ethiopia

Pumice cones are volcanic landforms that exist worldwide, but whose eruption has never been observed. Interpretations of these eruptions vary significantly in style, intensity, and magnitude, pertinent for volcanic hazard assessment. Aluto volcano (Ethiopia) provides an unprecedented insight into the hazardous nature of these enigmatic eruptions. We investigate nine such pumice cones, and find that they are the product of moderate-intensity explosive eruptions that develop a sustained but unsteady eruption column, deposit lapilli- to block-sized tephra close to the vent forming pumice cones, can deposit distal tephra from an umbrella cloud, produce pyroclastic density currents by repeated partial column-collapse, and end with the emplacement of silicic lava. Like basaltic pyroclastic cones, pumice cones can also undergo collapse by lava flow emplacement. Alongside recent evaluation of distal tephras, we suggest that these eruptions, at least at Aluto, vary in intensity and magnitude from violent-Strombolian to sub-Plinian, and each follow a remarkably similar sequence of eruptive processes.

Numerical and Constitutive Analysis of Granular Column Collapse Experiments Under Reduced-Gravity Conditions

Numerical and Constitutive Analysis of Granular Column Collapse Experiments Under Reduced-Gravity Conditions

The ad 79 Vesuvius eruption revisited: the pyroclastic density currents

Seventeen pyroclastic density currents (PDCs) were produced before, during and after the Plinian phase of the ad 79 eruption of Vesuvius. Their deposits were correlated using the proportions of components, together with the recognition of distinctive intercalated regionally traceable fall marker layers, revealing sectoral and distance-dependent variations. During an extensive field analysis, 27 lithostratigraphic units were detected and mapped and the lateral and vertical variations of 15 lithofacies were documented, described and interpreted. The total volume of PDC units is 1.25 km 3 . We consider that the early PDCs were generated by partial collapses from the sustained Plinian eruption column, whereas the subsequent post-Plinian PDCs were generated by more sustained pyroclastic fountaining. New facies mapping revealed lateral migration and extended travel distances for some of the currents. Most of the lobed PDCs remained relatively uniform, whereas the radial PDCs exhibited fluctuating waxing and waning pulses and changed gradationally down-current. Re-evaluation of the timing of caldera collapse and the transition from a magmatic to a phreatomagmatic eruption style suggests that substrate fracturing during incremental caldera subsidence may have allowed the gradual ingress of groundwater into the erupting magma. These results provide a new chronology of the eruption, revealing that the post-Plinian collapse phase lasted c. 12 h.

Unravelling eruption dynamics at El Reventador, Ecuador: linking the physiochemical properties of volcanic ash with geophysical, geochemical and satellite remote sensing data

The physiochemical properties of volcanic ash are determined by magma ascent and eruption dynamics and provide important insights into controls on the timing and style of volcanic eruptions. However, linking petrological observations to monitoring parameters remains challenging. Here we investigate the relationships between geophysical, geochemical and satellite remote sensing data with the physiochemical properties of volcanic ash to better understand eruptive dynamics at El Reventador volcano, Ecuador. Between 2016 and 2019, eruptive activity at El Reventador was characterised by frequent explosions interspersed with effusive activity from two summit vents. We found that: (1) periods of predominantly effusive behaviour were defined by ash samples with the lowest proportions of juvenile grains, frequent, more intense thermal anomalies and frequent (ca. every 25 min) but low-energy explosions that produced lower average ash column heights (< 1200 m above the summit) and; (2) periods of predominantly explosive behaviour were defined by ash samples with the highest proportions of juvenile grains and also vesicular juvenile grains, low thermal anomalies and less frequent (ca. every 70 min), higher-energy explosions that produced higher average eruption column heights (> 1500 m above the summit). Our study shows that there are strong correlations between the physiochemical properties of erupted material and the multiparametric monitoring data which in turn link to the type of surface activity observed. As a result, the development of physical conduit models and interpretations of eruptive dynamics are made more robust combining both monitoring data and the physical properties of eruptive products.

The ad 79 Vesuvius eruption revisited: Plinian and post-Plinian falls

The well-exposed Plinian fall deposit of the ad 79 Vesuvius eruption is herein divided into 12 lithostratigraphic units: seven units in the white pumice deposit and five units in the grey pumice deposit. These distinct units are distinguished by significant variations in grain size and the ratio of lithic to juvenile clasts, enabling us to reconstruct the highly fluctuating dynamics of the eruptive column during the Plinian phase of the ad 79 eruption with previously undetected detail. These characteristics allow their distributions around the vent to be mapped, showing that the plume fluctuated between 14 and 34 km in height, depositing 6.4 km 3 of tephra in 17 h. To broaden the scope of our investigation, we extended our research to encompass five lithic-rich fall layers that occurred after the Plinian phase, providing information on the dispersion and eruptive parameters of these late fallout phases. Post-Plinian sustained column pulses persisted for several tens of minutes, with the first pulse being the longest, lasting for 44 min. This initial pulse possibly facilitated the attempts made by numerous Pompeians to flee the city following the arrival of the first two weak pyroclastic density currents.

Geology, Archaeology, and Historical Studies of the Late 16th Century Plinian Eruption of Raung Volcano: A Potential Case for Disaster Geotourism in Ijen UNESCO Global Geopark, East Java, Indonesia

The enigmatic major eruption in the late 16th century, believed to have originated from Raung, the most active stratovolcano in the Ijen UNESCO Global Geopark in East Java, Indonesia, has ignited significant debate among researchers and historians due to its profound impact on the region. This research aims to substantiate Raung as the likely source of the major eruption by integrating geological, archaeological, and historical data. This study synthesizes current findings and explores ongoing debates surrounding historical volcanic activities. Eruption parameters suggest that the late 16th century eruption exhibited a Plinian type, characterized by an explosive eruption column reaching the stratosphere, widespread pumiceous tephra fallout, and pyroclastic density current (PDC). Stratigraphic succession reveals that the eruption occurred in five phases, with deposits from 10 eruptive units. These deposits are mainly concentrated on the northwestern flank of Raung. Archaeological findings, historical records, and local legends converge to pinpoint the occurrence of this catastrophic event in the late 16th century. These diverse sources estimate that the eruption resulted in approximately 10,000 casualties, marking it as one of the most significant volcanic disasters in the past 500 years. The implications of this eruption extend beyond historical documentation, providing a critical case study for advancing disaster mitigation strategies through geotourism in the geopark area. Moreover, the eruption record outcrops identified in this study can be proposed as potential new geosites within the Ijen UNESCO Global Geopark, enhancing its educational and touristic value. We propose the Jebung Kidul, Alas Sumur, and Batu Sappar sites as potential disaster-based geosites, considering that these sites record the eruption process and preserve archaeological structures. This addition would not only commemorate the historical event but also promote awareness and preparedness for future volcanic activities in the region.

The effect of particle size distribution on the collapse of wet polydisperse granular materials

Low-saturation liquid-containing granular materials are commonly encountered in both natural and industrial settings, where interstitial liquids significantly affect the motion of particles, while particle size polydispersity plays a crucial role in determining the level of system cohesion. In this study, the collapse of wet polydisperse granular columns is numerically investigated based on the developed discrete element model, with corresponding dam-break experiments performed to validate our numerical model and methodology. The dependence of the dynamics and flow mobility on particle size distribution is primarily examined, and the underlying mechanisms are also explored by analyzing particle path lengths and average fidelity. Building upon the effective Bond number proposed using the mixing theory, a macroscopic cohesion parameter at the material scale is defined by considering the dependence of the collapse on the system size effect. The relevance of this cohesion parameter in describing different wet polydisperse granular collapses is further validated based on our designed experimental tests and DEM simulations. The approach of constructing the cohesion parameters at different scales can be extended to characterize cohesion effects in more complex wet polydisperse granular flows and describe their associated rheological behaviors.

Do Seasonality and Latitude Dictate the Formation of Strong or Weak Volcanic Eruption Plumes?

AbstractIn this study, we propose a method to predict the classification of the eruption plume types: “strong plumes” and “weak plumes”. Our method reproduces the general features that the eruption plume types depend on, both the meteorological conditions and eruption conditions, and successfully reproduces the classification of the plume types for historical eruption events. Application of the method to Monte Carlo simulations revealed that eruption plumes at a low latitude tend to form strong plumes due to weak ambient winds, whereas eruption plumes at a mid latitude tend to form weak plumes due to the strong ambient winds associated with the jet stream. The simulation also revealed that mid‐latitude eruption plumes tend to be strong plumes in the summer when ambient winds are lowered by a weakening and poleward movement of the jet stream.

Dry granular column collapse: Numerical simulations using the partially regularized [formula omitted]-model via stabilized finite elements and phase field formulation

We revisit the gravitational collapse of a 2D column of dry granular material surrounded by air, using a continuum mechanics approximation. By employing the Cahn-Hilliard phase-field equation as an interface capturing technique and by coupling it with the Cauchy equation, we numerically simulate this multiphase system, eliminating the need for any ad-hoc numerical adjustment to prevent the finger formation of light fluid between the material and the solid boundary due to the no-slip boundary condition. We implement the μ(I)-rheology in our stabilized Finite Element method, highlighting the presence of instabilities when using this constitutive law. Our study is characterized by three main goals. First, we address the instability issue by implementing the partially regularized formulation of the μ(I)-rheology proposed by Barker and Gray (2017). An important outcome is that using shock-capturing terms in the momentum equation can significantly smooth these oscillations by adding dissipation in the direction of the gradients. Second, we systematically study the fluid dynamics under realistic conditions. Our results accurately replicate the material dynamics during collapse, confirming three distinct stages: free-fall, spreading, and cessation. We identify two regions in the material during the spreading phase: a quasi-static zone with negligible velocities and deformations, and a flowing layer exhibiting high shear rates. These observations closely align with experimental data. Additionally, we examine the evolution of the yielded/unyielded regions based on the Drucker-Prager criterion, and we also explore an empirical criterion, based on a critical value of the velocity norm, that satisfactorily separates these regions. Finally, we perform an extensive parametric study covering a wide range of rheological parameters.

Conduit armouring preceding explosive activity at an andesitic stratovolcano, an example from Taranaki Mounga, New Zealand

The strength and permeability of volcanic conduits can directly influence eruption dynamics via moderating the outgassing of ascending magma and the density of eruption plumes. Lithic clasts in pyroclastic ejecta can be used to understand the dynamic evolution of conduit walls because they are incorporated into the ascending melt-gas-particle mixture during volcanic eruptions. We examine the 1655 CE Burrell eruption of Taranaki Mounga, which transitioned from effusive activity to an explosive sub-Plinian phase and ended in unsteady columns. This episode was followed by a series of effusive eruptions of lower explosivity. Using textural analysis and physical properties, we distinguish five dominant lithic clast types within Burrell deposits that represent different regions of the shallow conduit and vent. Lithic types 1–3 represent juvenile (‘intrusive cognate’) and older (‘intrusive accessory’) conduit-filling plug materials. Lithic type 4 represents juvenile (‘extrusive cognate’) vent-filling lava dome extruded at the eruption onset, while Type 5 lithics (‘extrusive cognate’) represent sintered/compacted cognate material from the shallow vent accumulated during transitions in eruptive style. Crystalline andesite lithics (type 1) show a microlite-dominated groundmass. Hydrothermally altered andesite lithics (type 2) show breakdown of phenocrysts and increased seismic velocity relative to type 1 lithics. Brecciated andesite lithics (type 3) comprise fractured and sintered clasts of crystalline andesite. Glassy andesite lithics (type 4) show sub-rounded vesicles and glass-hosted microlites. Banded vitrophyre lithics (type 5) show bands of varying vesicularity, crystallinity and clast load. Physical property data reveals porosity, fracturing, sintering and alteration extent dictate dynamic changes in conduit permeability and potentially strength. Our results show how, during the explosive phase of the Burrell eruption, the conduit was lined with juvenile and remnant shallow plug material that was variably fractured, sintered and altered before being eroded and ejected. Comparison with previous work on Taranaki and dome-plug material from around the world shows how fracturing and sintering of conduit walls, combined with lining with dense juvenile material, cause overall permeability reduction and strengthening of the conduit. This inhibits outgassing and preserves conduit structure, facilitating the transition to explosive activity and the establishment of a stable eruption column.

A Composite Seismic Source Model for the First Major Event During the 2022 Hunga (Tonga) Volcanic Eruption

AbstractThe violent eruption of the Hunga (Tonga) submarine volcano on 15 January 2022 caused a 58 km‐heigh ash plume, catastrophic tsunami, and significant global seismic and infrasound waves. However, the physical mechanism underpinning its multiple‐explosive events remains unclear, and its resolvability relies on the seismic waveform source inversion. The studies of two different point‐source models, the seismic moment tensor (MT) and the single force (SF), have been performed separately for this eruption, which, interestingly, can explain the seismic data adequately. Here, we use a joint inversion of MT and SF to unravel a composite source of an explosion‐like MT and a significant upward force for the first major explosive event. Regarding the direction and magnitude, we propose that the upward force is likely a rebound force in response to the pressure drop on the seafloor because the water body above the volcano was abruptly uplifted by the shallow underwater explosion.

Investigation of anomalous lightning activity during the January 15, 2022 Tonga volcano eruption based on measurements of the VLF and ELF electromagnetic fields

An anomalous increase in the level of Very Low Frequency (VLF, 3–30 kHz) and Extremely Low Frequency (ELF, 3–3000 Hz) radio noise and the rate of VLF atmospherics was registered during the explosive eruption of the Tonga volcano on January 15, 2022 at the Akademik Vernadsky station (65.246°S; 64.257°W) about 8870 km from the volcano. At the peak activity around 5 UT, the number of atmospherics in 2-min intervals increased by almost 15 times compared to the period preceding the eruption. At this point, the estimated rate reached 360 VLF atmospherics per second. At the same time, an increase in the power spectral density of the magnetic field by 5–9 times was observed in both the ELF and VLF ranges. After 40 min, only on ELF an increased peak lasting ∼10 min was observed, comparable in magnitude to the main peak. According to the Worldwide Lightning Location Network (WWLLN), increased thunderstorm activity was concentrated very close to the volcano during this period. This discrepancy between the intensities of ELF and VLF radiation suggests a significant difference in the parameters of currents in lightning discharges occurring in the area of the volcano vent and in the area of the volcanic ash plume.

Numerical and experimental investigation of the effect of interstitial liquid viscosity on the collapse of wet granular columns

The collapse of wet granular columns with high- and low-viscosity interstitial liquid is investigated through experiments and numerical simulations. By incorporating both capillary and viscous force models of interstitial liquid in the Discrete Element Method (DEM), simulations have been conducted and reproduced consistent collapse processes with the experiment. The influence of water content, contact angle, particle diameter, liquid surface tension, and viscosity is explored over a large parameter space using DEM. For wet granular columns with low-viscosity interstitial liquid of water, the final profile of the collapsed column can be predicted by Bond number (Bo), a ratio of particle gravity to capillary force. For wet granular columns where the inertial effect dominates and both capillary and viscous forces are significant, dimensional analysis is employed to characterize the collapse, indicating that the collapsed profile can be predicted by Bo and Galileo number (Ga). Using water and silicone oils with different viscosities as interstitial liquids, simulations show that the collapsed profile depends on Bo with a low capillary number (Ca ∼ 10−3), Bo and Ga when Ca is intermediate (Ca ∼ 10−1). When Ca is high (Ca > 100), the final profile is solely controlled by Bo and a rolling-collapsed regime is observed.

Subsurface structural trends in Central-Western India: Inferences from magnetotelluric data using the complex MT apparent resistivity tensor

The central-western part of the Indian subcontinent exhibits significant geological diversity and possesses a rich record of different tectonothermal events in the earth's evolutionary history, spanning from the Archean to the present. Precambrian geology in the region is mostly obscured by Cretaceous-Tertiary/Paleocene volcanic eruptions and Proterozoic to Quaternary/recent sedimentary cover. Magnetotelluric (MT) impedance and tipper responses from 146 stations, covering central-western India in a grid fashion with a spacing of ∼55 km, were analyzed to evaluate the subsurface structural trends, dimensionalities, and qualitative characteristics of the electric lithosphere in the region. An advanced Complex Apparent Resistivity Tensor (CART) approach, along with the popular Phase Tensor (PT) approach and induction arrows are utilized to achieve the above goals. The analysis revealed a high degree of 3D induction effects in the data at almost every station and period. The directionality information retrieved from the tensor properties showed that the structural trends in the deep crust and upper mantle of the major geologic domains correlate with the known surface tectonic trend of the respective geologic domain. This study provides vital evidence to support the suspected bifurcation of the Precambrian Aravalli-Delhi Mobile Belt (ADMB) tectonic trend and its extensions into neighboring Kutch, Saurashtra, and Central Indian Tectonic Zone (CITZ) domains. The analysis results indicate a lithospheric scale enhanced conductivity beneath the Malwa plateau, which marks the first major phase of the Reunion mantle plume eruption in India. A critical finding of this study is that the Resistivity Phase Tensor better defines the subsurface resistivity structure and provides much clearer structural information than the conventional Phase Tensor.

A numerical analysis of wave type and steepness effects on cylindrical buoy dynamic characteristics

In the intricate realm of ocean-atmosphere dynamics, the sustained and stable operation of buoy observation systems under rough seas is crucial for ensuring marine resource security. This study employs a coupled Level-Set and Volume of Fluid (CLSVOF) method alongside the immersed boundary method. It investigates the physical processes of wind-wave interaction, the dynamic characteristics of cylindrical buoys, as well as the underlying mechanisms. The research highlights the significant impact of wave types (wind waves, swells) and wave steepness on the buoy's drift and oscillatory behavior. An increase in wave steepness and a shift from wind waves to swell markedly intensify both the buoy's drift and its oscillatory motions. Additionally, a thorough analysis of the loads on the buoy under varying maritime conditions is performed. By examining the vertical momentum equation on the windward and leeward sides, the secondary load cycle phenomenon is found to originate from collapse of the water column formed by the convergence of water flow behind the buoy. Wind waves are found to be less conducive to secondary load cycles compared to swell waves. Furthermore, the study investigates the relationship between the drag coefficient and the wave crest height on the windward side of the buoy, revealing a robust negative correlation between the two. This research not only illuminates the complex dynamics of wind-wave couplings but also offers theoretical insights for the optimization of buoy design.

A Characteristic Electrostatic Structure of Eruptive Plumes Emitted by Large Explosive Eruptions of Shiveluch and Bezymianny Volcanoes, Kamchatka

A Characteristic Electrostatic Structure of Eruptive Plumes Emitted by Large Explosive Eruptions of Shiveluch and Bezymianny Volcanoes, Kamchatka

Origin of Basaltic Subplinian Eruption at Shishaldin Volcano (Alaska): A Vigorously Degassing Magma Reservoir Hosting Small Bubbles

AbstractThe 1999 basaltic eruption of Shishaldin volcano (Alaska) displayed a transition between Subplinian and Strombolian activity. Strombolian bubbles indicate the presence of a periodically unstable foam at the top of magma reservoir. In contrast, a long foam, whose rupture led to the eruptive column, was also able to collect in the conduit. Laboratory experiments show that long foams can be produced in a conduit by the spreading of a stable foam accumulated at the top of the reservoir. The existence of a Taylor bubble at the onset of the Subplinian phase, also reproduced by my laboratory experiments, suggests that the foam in the reservoir was just at the transition between stable and unstable. This constrains the bubble diameter prior to the Subplinian phase to be 0.034–0.038 mm when using the foam dimensionless analysis and the underlying gas flux (0.52–0.80 m3/s). The increase in bubble diameter and potentially gas flux prior to the Strombolian activity, 0.81–1.4 m3/s, is sufficient to explain the foam in transition to be unstable. The radius of the magma reservoir is small, 200–210 m, as expected. The bubble diameter is the smallest of those estimated for classical basaltic eruptions (Etna, Kı̄lauea, Erta 'Ale), while the gas flux is among the largest. A dilute suspension of small and isolated bubbles cannot explain the large gas flux at Shishaldin. This implies numerous bubbles with a gas volume fraction ≥0.63−2%, a regime for which the bubbles form bubble clusters. The diameter of these bubble clusters, 3.0–5.4 mm, is sufficient to explain large gas fluxes.

Fast, furious, and gassy: Etna's explosive eruption from the mantle

The 3930 BP Fall Stratified (FS) eruption at Mt. Etna is a rare example of a highly explosive eruption of primitive (picritic) magma directly from the mantle. The eruption produced ash plumes up to an estimated 20 km height, leading to a volcanic explosivity index (VEI) 4 (subplinian). Given its volatile-rich and primitive nature, the FS magma may have ascended rapidly from great depths to avoid fractionation and mixing within the extensive plumbing system beneath Etna. To determine the pressures from which the FS magma derived, we perform rehomogenization experiments on melt inclusions hosted in Fo90–91 olivines to resorb shrinkage bubbles and determine the initial H2O and CO2 in the melt. With measured CO2 concentrations of up to 9600 ppm, volatile solubility models yield magma storage pressures of 630–800 MPa. These correspond to depths of 24–30 km, which are comparable to the seismologically estimated Moho. Therefore, the magma's high CO2 concentration must come from carbon in the mantle (likely from subducted carbonates), as opposed to assimilation of shallow (<10 km) crustal carbonates.Diffusion modeling of H2O and forsterite zonation profiles in clear, euhedral, and crystallographically oriented olivines indicates rapid ascent of magma directly from its source region to the surface. Forsterite profiles exhibit a narrow rim of growth zoning but no detectable diffusional zoning, reflecting maximum ascent times of 1–5 days. Eighteen measured H2O profiles result in remarkably uniform decompression rates of 0.47 MPa/s (95% confidence interval of 0.16–1.28 MPa/s), which is among the fastest measured for basaltic-intermediate magmas. These decompression rates indicate that the final stage of magma ascent over the region in which H2O degasses (between the surface and ∼ 15 km) occurred extremely fast at ∼ 17.5 m/s. This eruption may provide a link between primary magma composition and eruption intensity: we propose that the unusually explosive nature of this picritic eruption was driven by high H2O and CO2 concentrations, which led to continuously rapid ascent without stalling, all the way from the Moho.

Identification of tephra horizons in a glacier on the Ushkovsky volcano (Kamchatka)

Identification of tephra and its allocation (association) with known eruptive events allows obtainng chronostratigraphic markers, on the basis of which an age scale for dating glacial strata can be developed. To determine the sources of ash in the ice core obtained in 2022 during drilling of glacier in the crater of the Ushkovsky volcano in Kamchatka, the chemical composition of volcanic glass in individual ash particles was analyzed. The accuracy of determination of the volcanic glass composition was verified by analyzing of international standard samples of volcanic and synthetic glass. Based on a comparison of the data we obtained with published data on the composition of tephra glasses from the present-day eruptions in Kamchatka, we determined affiliation of each tephra horizon to specific volcano-source. We have found that the main source of tephra in the ice core of the Ushkovsky Glacier is the Kliuchevskoi volcano, which is the closest and the most productive one among the Kamchatka volcanoes. Ash particles from Bezymyannyi volcano were identified in two horizons. A mixed population of particles was found in one of the horizons, including the ash particles from volcanoes Kizimen, Kliuchevskoi and Bezymyannyi. Analysis of published data on the chronology and distribution of ash plumes from known eruptive events made it possible to confidently correlate the tephra horizon at a depth of 762–777 cm with the initial phase of the eruption of the Kizimen volcano in late 2010–early 2011. Ash from the uppermost tephra buried in the glacier at depths of 89–94 cm belongs to the Bezymyannyi volcano eruption, which the most likely occurred in October 2020. Single particles with rhyolitic composition of glass in the sample from the depth of 348–354 cm may belong to the eruption of the Shiveluch volcano in December 2018. The results of our work can be used on further studying of the ice core from the Ushkovsky volcano, in particular for comparison and correlation with the chronostratigraphic data obtained by glacio-chemical and isotope methods.

Explosive eruption style modulates volcanic electrification signals

Volcanic lightning detection has proven useful to volcano monitoring by providing information on eruption onset, source parameters, and ash cloud directions. However, little is known about the influence of changing eruptive styles on the generation of charge and electrical discharges inside the eruption column. The 2021 Tajogaite eruption (La Palma, Canary Islands) provided the rare opportunity to monitor variations in electrical activity continuously over several weeks using an electrostatic lightning detector. Here we show that throughout the eruption, silicate particle charging is the main electrification mechanism. Moreover, we find that the type of electrical activity is closely linked to the explosive eruption style. Fluctuations in the electrical discharge rates are likely controlled by variations in the mass eruption rate and/or changes in the eruption style. These findings hold promise for obtaining near real-time information on the dynamic evolution of explosive volcanic activity through electrostatic monitoring in the future.