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This paper presents the chemical composition (including H2O and CO2) of matrix glass, melt inclusions in phenocrysts, and their host minerals in eruptive products from Aso caldera. We found a group of melt inclusions with clearly lower potassium (0.6–2 wt % K2O at 50–70 wt % SiO2) than previously reported high-K2O whole-rock compositions (3–5 wt % K2O at 55–70 wt % SiO2). While most of the high-K2O intermediate to felsic melt inclusions are vapor undersaturated and show the features of H2O, CO2, and K2O accumulation, the low-K2O basaltic melt already has higher H2O and CO2. We reconcile this discrepancy with a model in which (1) the volatile-rich basalt magmas degas near the surface, (2) migrate back to depths of |$\ge$| 12 km in the crust, and (3) crystallize feldspar and quartz to produce high-K2O felsic melt, (4) magma mixing among the undegassed, degassed, and evolved magmas. By crystallization, about five times as much low-K2O basaltic magma is required to produce high-K2O felsic magma. The quantity of felsic magma ejected from 270 ka (Aso-1) to 90 ka (Aso-4) requires a basalt magma supply rate of 18 to 31 km3/ka. This magma supply rate is comparable to or less than the present-day production rate of degassed magma (73 km3/ka) at an active center of Aso, Nakadake. These findings suggest volcanic gas flux monitoring has the potential to be a 'basalt usage meter' during the dormant period of caldera volcanoes. [ABSTRACT FROM AUTHOR]

Defining the variations in petrological characteristics of erupted magmas within a high-resolution chronostratigraphy provides a necessary framework for monitoring the long-term activity and eruption potential of an active volcano. Here, we investigate the evolution of the magmatic system of Miyakejima volcano, Japan, between the last two caldera-forming eruptions, at ~ 2.3 ka and AD 2000, based on new stratigraphic constraints, radiocarbon ages, and whole-rock geochemical data. The activity of Miyakejima during this interval can be divided into three magmatic periods based on cyclic whole-rock compositional trends. Period 1 spans the interval between ~ 2.3 ka and the 7th century, from the Hatchodaira eruption with caldera collapse to immediately before the Suoana–Kazahaya eruption. Period 2 spans the time period between the seventh century and the fourteenth century, from the Suoana–Kazahaya to the Sonei–bokujyo eruptions. Period 3 covers the period from the two major flank eruptions that occurred in the sixteenth century to the end of the twentieth century until the last caldera-collapse event in AD 2000. The eruption rate decreased from 0.5 km3 per 1000 years in Period 1 to ~ 0.2 km3 per 1000 years in Period 2 and 3. Recharge of primitive basaltic magmas into shallower crustal systems triggered extensive basaltic fissure eruptions at the beginning of each period. Progressively increasing whole-rock SiO2 contents of the hybrid magmas in subsequent eruptions indicates continuous fractional crystallization in small shallow magma chambers which formed at the start of each magmatic period. Intermittent injections of basaltic magma into shallow magma chambers induced magma mixing that caused eruption of hybrid basaltic andesite in each period. We suggest that some basaltic magmas formed isolated magma reservoirs at shallow depth, in which rapid fractionation was able to occur. Rupturing of these isolated magma storage regions filled with gas-rich evolved magma can lead to violent ejection of andesitic magmas, such as for the Suoana–Kazahaya eruption in the seventh century. Our results suggest two main scenarios of eruption for the basaltic magma system at Miyakejima and similar mafic volcanoes in the northern Izu–Bonin arc; (1) eruption of voluminous basaltic lavas after the recharge of primitive basaltic magmas into the shallow magmatic system, and (2) explosive fissure eruption by rupturing of isolated magma bodies filled with gas-rich evolved magmas. [ABSTRACT FROM AUTHOR]

The activity of the 2018–2019 eruption of Kuchinoerabujima Volcano in Japan changed from continuous ejection of ash-laden plumes between October 21 and the middle of December, to intermittent explosive activity accompanied by several pyroclastic density currents until January 2019. To understand the behaviors of magma and hydrothermal fluid that controlled the eruptive sequence, we carried out component analysis, X-ray diffractometry, and leachate analysis for ash samples. The proportion of non-altered volcanic ash particles is ~ 15% in the earlier phase, then it decreased to less than 10% in the later explosive phase. Accordingly, the mineral assemblage of the volcanic ash samples changed from plagioclase-dominant to sulfate minerals-dominant. Concentration of SO42− and Cl/SO4 values of the ash-leachates decreased toward the later activity. These results indicate that the proportion of fresh volcanic rocks decreased and sulfuric acid fluid-derived sulfate minerals increased toward the later activities. Consequently, the 2018–2019 eruption at Kuchinoerabujima Volcano changed from magmatic activity to phreatomagmatic activity. Weak glowing of the crater was observed during the magmatic activity, indicating the volcanic conduit was hot enough to dry up the sub-volcanic hydrothermal system. The following phreatomagmatic activity indicates that the hydrothermal fluid recharged after the magmatic eruption phase. Recharge of the hydrothermal fluid likely caused the variation of the eruption style, and is a process that may control the evolution of hazards during future eruption scenarios at similar active volcanoes in Japan and worldwide. [ABSTRACT FROM AUTHOR]

Large calderas are among the Earth's major volcanic features. They are associated with large magma reservoirs and elevated geothermal gradients. Caldera-forming eruptions result from the withdrawal and collapse of the magma chambers and produce large-volume pyroclastic deposits and later-stage deformation related to post-caldera resurgence and volcanism. Unrest episodes are not always followed by an eruption; however, every eruption is preceded by unrest. The Campi Flegrei caldera (CFc), located along the eastern Tyrrhenian coastline in southern Italy, is close to the densely populated area of Naples. It is one of the most dangerous volcanoes on Earth and represents a key example of an active, resurgent caldera. It has been traditionally interpreted as a nested caldera formed by collapses during the 100–200 km 3 Campanian Ignimbrite (CI) eruption at ∼39 ka and the 40 km 3 eruption of the Neapolitan Yellow Tuff (NYT) at ∼15 ka. Recent studies have suggested that the CI may instead have been fed by a fissure eruption from the Campanian Plain, north of Campi Flegrei. A MagellanPlus workshop was held in Naples, Italy, on 25–28 February 2017 to explore the potential of the CFc as target for an amphibious drilling project within the International Ocean Discovery Program (IODP) and the International Continental Drilling Program (ICDP). It was agreed that Campi Flegrei is an ideal site to investigate the mechanisms of caldera formation and associated post-caldera dynamics and to analyze the still poorly understood interplay between hydrothermal and magmatic processes. A coordinated onshore–offshore drilling strategy has been developed to reconstruct the structure and evolution of Campi Flegrei and to investigate volcanic precursors by examining (a) the succession of volcanic and hydrothermal products and related processes, (b) the inner structure of the caldera resurgence, (c) the physical, chemical, and biological characteristics of the hydrothermal system and offshore sediments, and (d) the geological expression of the phreatic and hydromagmatic eruptions, hydrothermal degassing, sedimentary structures, and other records of these phenomena. The deployment of a multiparametric in situ monitoring system at depth will enable near-real-time tracking of changes in the magma reservoir and hydrothermal system. [ABSTRACT FROM AUTHOR]

The composition of volcanic gases discharged from Miyakejima volcano has been monitored during the intensive degassing activity that began after the eruption in 2000. During the 15 years from 2000 to 2015, Miyakejima volcano discharged 25.5 Mt of SO, which required degassing of 3 km of basaltic magma. The SO emission rate peaked at 50 kt/day at the end of 2000 and quickly decreased to 5 kt/day by 2003. During the early degassing period, the volcanic gas composition was constant with the CO/SO = 0.8 (mol ratio), HO/SO = 35, HCl/SO = 0.08, and SO/HS = 15. The SO emission rate decreased gradually to 0.5 kt/day by 2012, and the gas composition also changed gradually to CO/SO = 1.5, HO/SO = 150, HCl/SO = 0.15, and SO/HS = 6. The compositional changes are not likely caused by changes in degassing pressure or volatile heterogeneity of a magma chamber but are likely attributed to an increase of hydrothermal scrubbing caused by large decrease of the volcanic gas emission rate, suggesting a supply of gases with constant composition during the 15 years. The intensive degassing was modeled based on degassing of a convecting magma conduit. The gradual SO emission rate that decrease without changes in volcanic gas composition is attributed to a reduction of diameter of the convecting magma conduit. [ABSTRACT FROM AUTHOR]

An introduction is presented on the special issue on "The phreatic eruption of Mt. Ontake volcano in 2014."

The total mass discharged by the phreatic eruption of Ontake Volcano, central Japan, on September 27, 2014, was estimated using several methods. The estimated discharged mass was 1.2 × 10 t (segment integration method), 8.9 × 10 t (Pyle's exponential method), and varied from 8.6 × 10 to 2.5 × 10 t (Hayakawa's single isopach method). The segment integration and Pyle's exponential methods gave similar values. The single isopach method, however, gave a wide range of results depending on which contour was used. Therefore, the total discharged mass of the 2014 eruption is estimated at between 8.9 × 10 and 1.2 × 10 t. More than 90 % of the total mass accumulated within the proximal area. This shows how important it is to include a proximal area field survey for the total mass estimation of phreatic eruptions. A detailed isopleth mass distribution map was prepared covering as far as 85 km from the source. The main ash-fall dispersal was ENE in the proximal and medial areas and E in the distal area. The secondary distribution lobes also extended to the S and NW proximally, reflecting the effects of elutriation ash and surge deposits from pyroclastic density currents during the phreatic eruption. The total discharged mass of the 1979 phreatic eruption was also calculated for comparison. The resulting volume of 1.9 × 10 t (using the segment integration method) indicates that it was about 1.6-2.1 times larger than the 2014 eruption. The estimated average discharged mass flux rate of the 2014 eruption was 1.7 × 10 kg/h and for the 1979 eruption was 1.0 × 10 kg/h. One of the possible reasons for the higher flux rate of the 2014 eruption is the occurrence of pyroclastic density currents at the summit area. [ABSTRACT FROM AUTHOR]

Abstract: We develop an analytical model to infer the total volume of a magma chamber associated with caldera collapse and the critical volume of magma that must be withdrawn to induce caldera collapse. The diameter of caldera border fault, depth to the magma chamber, and volumes of magma erupted before the onset of collapse and of entire eruption are compiled for 14 representative calderas. The volume of erupted magma at the onset of collapse aligns between the total erupted volume of the other representative caldera-forming eruptions and the volume of eruptions without collapse during the post-caldera stage, correlating with the structural diameter of the calderas. The total volume of magma chamber is evaluated using a piston-cylinder collapse model, in which the competition between the decompression inside magma chamber and friction along the caldera fault controls the collapse. Estimated volumes of the magma chambers associated with caldera collapse are 3–10 km3 for Vesuvius 79 A.D. to 3000–10 500 km3 for Long Valley, correlating with the cube of caldera diameters. The estimated volumes of magma chamber are always larger than the total volume of erupted magma for caldera formation, suggesting that the magma chambers are never completely emptied by the caldera-forming eruptions. The minimum volumes of erupted magma to trigger collapse are calculated from the correlation between the caldera diameters and the evaluated volume of magma chambers. The minimum eruptive volume for the collapse correlates with the square of the caldera radius r and the square of the depth to the magma chamber h, and inversely correlates with the bulk modulus of magma, which is mainly controlled by the bubble fraction in the magma. A bubble fraction between 5 and 10% at the onset of collapse may explain the distribution of the erupted volumes at the onset of collapse of the calderas in nature. [Copyright &y& Elsevier]

Basaltic feeder systems exposed in the caldera wall of Miyakejima volcano are classified into three groups: (1) effusive feeders, (2) moderately explosive feeders, and (3) highly explosive feeders. The surface deposits and feeder systems reveal a wide variation in the explosivity of the eruptions that produced them, ranging from non-explosive lava effusions to violent explosive eruptions, despite the apparent lack of influence of external water. Effusive feeders are filled with coherent (non-fragmented) intrusive rock, indicating no significant fragmentation in the feeder system. The other two types of feeder systems consist of a coherent dike in their deeper part and a pyroclastic fill in their uppermost part. Their uppermost parts show an upward-flaring shape. The transition from coherent intrusion to pyroclastic fill in the feeder systems suggests underground fragmentation of the rising magma. The depth of the coherent-pyroclastic transition is deeper (20-150 m) in highly explosive feeders than in the moderately explosive feeders (<20 m), and coincides with the depth at which the system flares upwards. Presence of lithic fragments derived from the host rock in the products of the highly explosive feeder systems indicates the removal of the wall rock by explosive activity. This observation suggests that the fragmentation of rising magma promoted the enlargement of the feeder systems to form their upward-flaring shapes, by mechanical erosion and wall collapse. [ABSTRACT FROM AUTHOR]

Abstract: The 2000 AD eruption of Miyakejima was characterized by a series of phreatomagmatic eruptions from the subsiding caldera. Six major eruptive events occurred, and they can be divided into the first and second periods separated by a 25-day hiatus. The phreatomagmatic eruptions produced a total of ~2×1010 kg of tephra, which mainly comprised fine-grained volcanic ash. The tephra layers could be divided into six fall units corresponding to the six major eruptive events. The grains of the 2000 tephra consisted mainly of accessory fragments derived from the previous edifice. Juvenile fragments were identified in four major units. The angular and blocky shape of the juvenile fragments showed rapid cooling of magma by external water, indicating the mechanical mixing of ground water and magma. The removal of the load on the aquifer by caldera subsidence and the intrusion of magma into the decompressed aquifer caused a series of phreatomagmatic eruptions from the subsiding caldera. The absence of surface water in the subsiding caldera during the eruption showed that groundwater participated in the phreatomagmatic eruptions. Rising magma along the ring faults intruded into the decompressed aquifer surrounding the caldera and caused phreatomagmatic explosions. The 2000 eruption of Miyakejima indicated that the fine-grained tephra abundant in hydrothermally altered rock fragments is a possible indicator of the phreatomagmatic eruptions in the hydrothermal system during the caldera formation in basaltic volcanoes. [Copyright &y& Elsevier]

Abstract: Dikes with lateral and outward intrusion directions (named L-type dike) and dikes with vertical and upward intrusion directions (V-type dike) are recognized in a radial dike swarm of Komochi Volcano, Japan, by the combined analysis of the preferred orientations of deformed vesicles and anisotropy of magnetic susceptibility (AMS). Intrusion directions of magmas were examined for 41 dike outcrops. Among them, 19 dikes were classified as L-type dike and 15 dikes were as V-type. The L-type dikes distribute over the area of the dike swarm radiating from the central conduit, which is named Daikokuiwa stock, and the V-type dikes occur mainly in the peripheral portion of the volcano. The L-type dikes are characterized with evolved whole-rock compositions similar to those of rocks consisting of the central conduit, whereas the V-type dikes have less-fractionated composition and are enrich in mafic phenocryst as compared to the L-type dikes. The outward intrusion directions of the L-type dikes and their petrological similarity to the rock of the central conduit indicate that these dikes intruded from the shallow part of the central conduit where the magmas underwent fractional crystallization and degassing. The petrological characteristics of the V-type dikes suggest that the less-fractionated magma intruded directly from a magma chamber, in which mafic phenocryst crystals accumulated. The larger dike thickness and higher magnetic foliation of the V-type dike as compared to the L-type dike indicate higher magmatic overpressure, which was possibly result of the direct connection to the pressurized magma chamber and vertical-growth of the dikes with buoyant magma. Solidification of the central conduit is favorable for the accumulation of internal excess pressure in the magma chamber to break the wall rock. Fissure eruptions independent of the central conduit have occurred in many volcanoes and these fissure eruptions might be fed by the dikes directly propagated from the deeper magma chamber. [Copyright &y& Elsevier]

Detecting transitions between different eruption styles through real-time monitoring can mitigate the risk posed by volcanic hazards. During periods of eruptive activity, changes in ash characteristics can reflect changes in magma behavior in the conduit. However, conventional methods for characterizing ash involve manual field processes followed by laboratory observations, which leads to a potential lag between a change in eruption style and the time at which the change is detected. We have developed the Visual Observation Laboratory Capturing Ash Transition (VOLCAT), a new field-based instrument for automatic onsite microphotograph imaging of ash particles with minimum interval of one hour during periods of ongoing volcanic activity. The VOLCAT successfully captured microphotographs of ash particles during eruptions at Shinmoedake and Sakurajima, and helped rapid characterization of the ash particles. The rapid characterization of ash particles using the VOLCAT will allow quasi-real-time evaluation of eruption style during periods of ongoing activity. • We developed VOLCAT which is a new field-based instrument for volcano monitoring. • The VOLCAT performs automatic onsite imaging of ash microphotographs from ongoing activity. • The VOLCAT successfully captured the characters of ash particles from two volcanoes in Japan. • Ash characterization by the VOLCAT will contribute to quasi-realtime eruption style monitoring. [ABSTRACT FROM AUTHOR]

A pyroclastic density current (PDC) was observed with the phreatomagmatic eruption of the Kuchinoerabujima volcano, southern Japan, on May 29, 2015. The PDC flowed down in all direction from the source crater, forming three major branches. The PDC reached the western coast of the island and the edge of the habitation area, which is ~ 2.4 km away from the source crater. The average speed of PDC along the Mukaehama River was estimated as 42 m/s. The PDC involved both surge and block-and-ash flow. Pyroclastic surge left thin layer of volcanic ash, though no remarkable signature of the lateral transportation was found in the surge deposit. The surge deposit occupies ~ 85% of the area covered with the PDC. Block-and-ash flow deposits were also recognized, but their distribution was limited mainly at the foot of the steep slope of the edifice of Shindake. The erupted materials from the May 29, 2015 eruption were estimated to be ~ 1.3 × 109 kg, including 2.4 × 108 kg of the PDC deposit and ~ 1.1 × 109 kg of the fallout deposit in proximal and distal area. The PDC deposit consisted of rock fragments with various degrees of hydrothermal alteration. The least-altered glassy blocks of andesite, which was the candidate for the juvenile materials, occupied less than 10% of the deposit. The area covered by the PDC was damaged by both mechanical and thermal effects. The dynamic pressure of the PDC damaged the forest in the inner portion of the area covered with the PDC. The thermal influence of the PDC caused dieback of the vegetation and deformation of some plastic materials. The absence of carbonization of wood in PDC indicates that the temperature was below the ignition temperature of wood. These observations suggest that the temperature of the PDC was between 100 and 240-270 °C. [ABSTRACT FROM AUTHOR]

We estimate the total mass of ash fall deposits for individual eruptions of Sakurajima Volcano, southwest Japan based on distribution maps of the tephra fallout. Five ash-sampling campaigns were performed between 2011 and 2015, during which time Sakurajima continued to emit ash from frequent Vulcanian explosions. During each survey, between 29 and 53 ash samplers were installed in a zone 2.2-43 km downwind of the source crater. Total masses of erupted tephra were estimated using several empirical methods based on the relationship between the area surrounded by a given isopleth and the thickness of ash fall within each isopleth. We obtained 70-40,520 t (4.7 × 10−8-2.7 × 10−5-km3 DRE) as the minimum estimated mass of erupted materials for each eruption period. The minimum erupted mass of tephra produced during the recorded events was calculated as being 890-5140 t (5.9 × 10−7-3.6 × 10−6-km3 DRE). This calculation was based on the total mass of tephra collected during any one eruptive period and the number of eruptions during that period. These values may thus also include the contribution of continuous weak ash emissions before and after prominent eruptions. We analyzed the meteorological effects on ash fall distribution patterns and concluded that the width of distribution area of an ash fall is strongly controlled by the near-ground wind speed. The direction of the isopleth axis for larger masses is affected by the local wind direction at ground level. Furthermore, the wind direction influences the direction of the isopleth axes more at higher altitude. While a second maximum of ash fall can appear, the influence of rain might only affect the finer particles in distal areas. [ABSTRACT FROM AUTHOR]

A hot and acid crater lake is located in the Nakadake crater, Aso volcano, Japan. The volume of water in the lake decreases with increasing activity, drying out prior to the magmatic eruptions. Salt-rich materials of various shapes were observed, falling from the volcanic plume during the active periods. In May 2011, salt flakes fell from the gas plume emitted from an intense fumarole when the acid crater lake was almost dry. The chemical composition of these salt flakes was similar to those of the salts formed by the drying of the crater lake waters, suggesting that they originated from the crater lake water. The salt flakes are likely formed by the drying up of the crater lake water droplets sprayed into the plume by the fumarolic gas jet. In late 2014, the crater lake dried completely, followed by the magmatic eruptions with continuous ash eruptions and intermittent Strombolian explosions. Spherical hollow salt shells were observed on several occasions during and shortly after the weak ash eruptions. The chemical composition of the salt shells was similar to the salts formed by the drying of the crater lake water. The hollow structure of the shells suggests that they were formed by the heating of hydrothermal solution droplets suspended by a mixed stream of gas and ash in the plume. The salt shells suggest the existence of a hydrothermal system beneath the crater floor, even during the course of magmatic eruptions. Instability of the magmatic-hydrothermal interface can cause phreatomagmatic explosions, which often occur at the end of the eruptive phase of this volcano. [ABSTRACT FROM AUTHOR]

To discover how magmas move and interact beneath an arc we have examined the temporal and spatial evolution of the largest Izu-Bonin frontal arc volcano Izu-Oshima and the adjacent Izu-Tobu field of backarc volcanoes. Extensive 14 C ages and geochemical analysis of subaerial satellite cones as well as other effusives has enabled us to construct a well-constrained ∼ 14 ka record of Izu-Oshima volcanism. The geochemistry of Izu-Oshima is found to change systematically through the last 14 000 yr. Ba/La, Pb/Ce, 87 Sr/ 86 Sr, 143 Nd/ 144 Nd and 206 Pb/ 204 Pb all decrease between 10 ka and 5 ka before increasing between 5 ka and the present, while La/Yb and Nb/Zr show the reverse. These changes in composition match the addition of Izu-Tobu (backarc) magma to the Izu-Oshima plumbing system with a maximum of a 40% Izu-Tobu at around 5 ka. Progressive but asymptotically declining changes in composition through the 10–5 ka period are found to fit a model where pre-mixed magma is episodically added to, and mixed with, a chamber beneath Izu-Oshima. The 5–0 ka period reverses this trend, but is again progressive and declining, suggesting a switch to a progressive influx of pure Izu-Oshima frontal arc magma. Combining flux and eruption volume estimates with the observed geochemical mixing rates indicates that the accessible melt volume of the Izu-Oshima magma system is ∼ 16 km 3 . Interaction and pre-mixing between the fluid-dominated frontal arc melt and the sediment-bearing backarc magmas must occur at deeper levels within the arc crust. This deep reservoir receives a continuous feed from the frontal arc mantle, but may periodically intercept rising magmas from the backarc source to produce episodes of magma mixing on timescales of ∼ 5000 yr . This study demonstrates that interaction between frontal arc and backarc magma needs to be considered to achieve better understanding of material transfers and elemental budgets at subduction zones. [ABSTRACT FROM AUTHOR]

Quantitative morpho-textural analysis of volcanic ash is one of the most effective tools to characterize the style of ash-dominated volcanic activity, and to investigate the complex interplay between conduit processes and the associated eruptive dynamics. In this framework, many questions still remain unanswered about the role of conduit processes, particularly of the magma fragmentation processes, in controlling the eruptive dynamics of the unsteady and highly-transient Vulcanian explosions. For this reason, we analyzed ash samples collected during a five days-long eruptive sequence at Sakurajima volcano (Japan), to derive information about ash morphometry and textural features over the entire sequence. During the observed sequence, eruptive activity showed high unsteadiness in the modalities of ash emission, which included all the main different eruptive styles typical of the recent period of Sakurajima activity. Three main intra-eruptive phases (Phase1, Phase2 and Phase3) were recognized based on visual observations and thermal data. Quantitative information about external ash morphometry (i.e., shape) and internal textures were measured for the particles associated with the different phases and discussed in terms of the observed eruptive variability. We quantified crystallinity and vesicularity of ash grains, the crystal size distribution (CSD) of microlites and the microlite number density (MND) of the groundmass for a representative set of ash particles. We discussed the links between the eruptive dynamics and the dominant processes of magma fragmentation, as shown by the combination of the morpho-textural features of ash throughout the whole eruptive sequence and the observed variations of the eruptive phases. All the evidence presented in this work confirm the constant presence at Sakurajima of a highly stratified and degassed magma within the conduit, suggesting that the transient dynamics of the eruption were strongly controlled by variations in the process of magma fragmentation driving the eruptions during the different phases. In particular, the morpho-textural characteristics of ash suggest that Vulcanian eruptions at Sakurajima can be controlled by the progressive pressurization of the upper portion of the magma conduit (between 10 and 50 m in depth). Moreover, using crystal textures, we inferred that the time needed for conduit refilling during intra-eruptive stages is comprised between 1 and 10 month. The resulting information on the eruptive dynamics of Sakurajima is of primary importance for a more exhaustive comprehension of the low-to-mid intensity, ash-dominated explosive activities. [ABSTRACT FROM AUTHOR]