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February 18, 2021, a flank eruption started on the north-western slope of the Klyuchevskoy Volcano (Kamchatka, Russia). Cinder cone was formed at the altitude of 2 850 m above sea level, from which a lava flow was spreading north-west. Having moved 1.2 km downslope, the lava flow entered the Ehrmann Glacier, which resulted in the formation of huge mud-stone flows. The latter made their way further north-east along the Kruten’kaya River bed and reached the length of about 30 km. The eruption brought onto the surface high-aluminous basaltic andesites typical of the Klyuchevskoy Volcano. By March 21, the flank eruption ended. It has been named after G.S. Gorshkov, associate member of USSR Academy of Science, famous Russian volcanologist.

The 2018 summit and flank eruption of Kīlauea Volcano was one of the largest volcanic events in Hawaiʻi in 200 years. Data suggest that a backup in the magma plumbing system at the long-lived Puʻu ʻŌʻō eruption site caused widespread pressurization in the volcano, driving magma into the lower flank. The eruption evolved, and its impact expanded, as a sequence of cascading events, allowing relatively minor changes at Puʻu ʻŌʻō to cause major destruction and historic changes across the volcano. Eruption forecasting is inherently challenging in cascading scenarios where magmatic systems may prime gradually and trigger on small events.

In recent military warfare, lower extremities (LE) accounted for 70% of the total combat fractures [1, 2]. Despite orthopedic blast injuries on the lower extremities being the most prevalent, there is a dearth of human cadaver studies investigating the relevant injury mechanism. To the best of the authors’ knowledge, no experimental investigation has been performed on human cadaver LE to evaluate a lateral blast's effect. In this research work, numerical studies have been performed to evaluate the injury mechanism of a human lower extremity subjected to a lateral blast. Finite element model predictions are observed to be in good agreement with Hull and Cooper’s pioneer experimental study on a goat limb and clinical human injury patterns [3]. Direct blast wave coupling with proximal tibiae has been observed to cause very high strain rates, resulting in bones’ splintering and a characteristic oblique fracture. Based on simulation results, it has been proposed that extremely high strain rates associated with a lateral blast are localized and concentrated at the proximal end of the tibiae. The minimum safe distance to avoid lower extremity injuries has been presented. There is a paucity of experimental data available for close field blast studies due to difficulty in accurately capturing the response parameters involved. Numerical results corroborated by experimental and clinical findings, bring a paradigm shift in our understanding of lateral blast injuries.

Knowledge of Etna's eruptions has been profoundly influenced by the illustrations, though these can only provide limited information on the lava flows and their effects on the territory. Indeed, the absence of iconographic sources or again the disparity between the physical reality and the illustrations has led to many gaps and uncertainties that have lasted for centuries. This paper traces the progress of the representations of the historical eruptions of Etna volcano, from the earliest attempts in the 17th century, be they iconographic documents or pictorial illustrations, to the modern geological cartography of 21st century. It seeks to reconstruct the evolution of the history and methods of representing Etnean eruptions, highlighting the crucial steps in the progress of knowledge on the historical flank eruptions. The turning point in the long process of drawing and rendering the eruptions of Etna came with the work of Sartorius von Waltershausen, with the realization of the first geological map of the volcano at a 1:50,000 scale between 1836 and 1843. In this long history of the representations of eruptions, begun in the 17th century, Sartorius' cartography finally overcame the problem of rendering these events in space by inserting the notion of history in the map. What now remained for those engaged in mapping the volcano was to solve the issue of defining the “time” of Etna's historical lava flows. This would be tackled only at the end of the 20th century with a multidisciplinary approach comprising stratigraphy, historiographical studies and the dating of the lavas. In this frame, the present state of the knowledge of the flank eruptions occurring on Etna in the past 2500 year has evidenced that during the Greek-Roman and Medieval epochs up to the 17th century flank eruptions commonly involved the middle-lower slopes, impacting mainly the south sector of the volcano with the location of the eruptive fissure sometimes below 1000 m of altitude. This eruptive behavior of the volcano has been radically modified following the occurrence of the large 1669 eruptions since the opening of the fissures was mainly concentrated in the upper-middle slopes between 1600 m and 2500 m a.s.l.

A plinian-style eruption with a radially spreading umbrella cloud occurred on February 13, 2014, at Kelud volcano, Indonesia. We present the sequence of this plinian event based on a geological survey of the eruption products and analysis of satellite images. The eruptive deposits were divided into four major depositional units (Units A, B, C, and D) and used to determine the sequence of events. The plinian phase was preceded by partial destruction of the existing lava dome and generation of high-energy pyroclastic density currents (PDCs) mainly toward the NE that produced a series of depositional subunits (Units A0–2) and blown-down trees (stage 1). In the main phase of the plinian eruption, tephra fallout (Unit B) was widely distributed over East Java (stage 2). The winds above the volcano significantly affected the tephra dispersal process. In stage 3, the plinian column collapsed, generating dense PDCs that flowed down the volcano valleys, producing pumiceous lobate deposits (Unit C). The declining phase of the eruption produced fine-rich fallout tephra layers (Unit D1–2) from low-level eruption plumes and/or ash lofted from PDCs. The eruption sequence constructed from field observations is supported by geophysical observations. The deposit features and componentry suggest that newly ascended magma triggered the destruction of the lava dome and the generation of high-energy PDCs, and during the subsequent climactic phase the dome was completely destroyed. We estimate a total erupted volume of 0.25–0.50 km3 (bulk deposit volume, 0.14–0.28 km3 in dense rock equivalent) and a mass eruption rate of 6.5 ± 2.8 × 107 kg/s, with a volcanic explosivity index of 4. The eruption sequence and physical parameters of the 2014 eruption will help assess future volcanic activity and hazards at Kelud volcano.

The dynamics of magmatic processes at large mafic ocean island volcanoes control the likely locations (central caldera versus flanks) and timing of their eruptions. Crystals and their melt inclusions are key witnesses of these processes but are rarely studied in detail and in the same samples. Here we report the crystal and melt inclusion compositions of the April 2007 caldera-forming eruption of Piton de la Fournaise volcano and discuss how they relate to geophysical unrest monitoring data. Olivine crystals show mainly normal zoning (decrease in Mg/Fe) towards the rims, and also around some melt inclusions. Many crystals also show fine-scale skeletal structures defined by high phosphorus concentrations. Melt inclusions contain 53–205 ppm CO2 and 0.25–1.1 wt% H2O, and δD (δD values expressed as δDVSMOW) ranges from −135 to 62‰. Monitoring data show that inflation of the edifice started about a month before the first 2007 eruption: magma intrusion occurred at ≈3 km below sea level, and quickly migrated towards shallower depths (about 1 km above sea level). Such a time frame of magma movement is recorded in the chemical zoning of the olivine crystals that massively and quickly crystallized when reaching shallow depth, without significant interactions between resident and intruding magmas. The intrusion was followed by lateral flank eruption and caldera collapse. The chemical zoning of the olivine crystal rims and around the melt inclusions indicates that the newly created crystal-mush moved laterally towards the surface in matter of days to 3 months. Post-caldera samples show significant H+ loss, likely due to the depressurization of the magmatic system stored at shallow level. Our findings are different from other mafic ocean island volcanoes or stratovolcanoes (e.g. Kilauea, Canary Islands, and Etna), where crystals commonly record magma mixing between evolved and shallow melts and intruding mafic melts. We speculate that the difference between our findings and those of similar mafic ocean island volcanoes is due to the variety of magma supply rates from depth. NRF (Natl Research Foundation, S’pore) Published version

Mt. Etna, in Sicily (Italy), produces effusive and explosive eruptions from summit craters and flanks. Petrology of erupted products has proved fundamental to explore the relationship between magma dynamics within the plumbing system and eruptive styles. Data of Sr Nd isotopes are quite scarce if compared with the great number of chemical analyses carried out in products of last decades. We measure Sr Nd isotopes, major and trace elements in products emitted from 2001 to 2012, and consider also published analyses of the 1995–2001 eruptions, because carried out in the same laboratories of 2001–2012 ones. Furthermore, we take into account other published analyses extending back to the 14th century, even if performed by different facilities. Based on this dataset, magma dynamics operating at different timescales inside the volcano's plumbing system have been explored. Our analyses evidence that, from 2001–2012, three magma types are present in the volcano's plumbing system: (i) a deep and poorly evolved basaltic and K-trachybasaltic magma, enriched in radiogenic Sr and LILE, erupted during the 2001 and 2002–03 flank activity; (ii) a shallower more evolved K-trachybasaltic magma, less enriched in radiogenic Sr, feeding both summit and flank eruptions and (iii) an uncommon, and scarcely radiogenic hawaiitic magma, LILE poor, emitted exclusively from a small sector of the 2002–03 eruptive fissures. By considering a broader time scale, from 14th to 21st century, we conclude that: (i) different magmatic components are present in the deep volcano's plumbing system, at about 10–12 km b.s.l; (ii) a decoupling of geochemical and isotopic features in magmas stored at different depths is observed after the 1974 flank eruption up to date; (iii) mixing between different magmas is an efficient magmatic process to produce magma differentiation at Mt. Etna, regardless of the investigated temporal scale.

A main challenge in open conduit volcanoes is to detect and interpret the ultra-small strain ( after the flank eruption of December 2018, Etna generated a violent and spectacular eruptive sequence of lava fountains. There were 23 episodes from December 13, 2020 to March 31, 2021, 17 of which in the brief period 16 February to 31 March with an intensified occurrence rate. The high-precision borehole dilatometer network recorded significant strain changes in the forerunning phase of December 2020 accompanying the final magma migration at the shallower levels, and also during the single lava fountains and during the entire sequence. The source modeling provided further information on the shallow plumbing system. Moreover, the strain signals also gave useful information both on the explosive efficiency of the lava fountains sequence and the estimate of erupted volume. The high precision borehole dilatometers confirm to be strategic and very useful tool, also to detect and interpret ultra-small strain changes associated with explosive eruptions, such as lava fountains, in open conduit volcanoes.

The Etna flank eruption started on 24 December 2018 lasted a few days and involved the opening of an eruptive fissure, accompanied by a seismic swarm and shallow earthquakes, and by large and widespread ground deformation especially on the eastern flank of the volcano. Lava fountains and ash plume from the uppermost eruptive fissure have accompanied the opening stage causing disruption of Catania international airport, and have been followed by a quiet lava effusion within the barren Valle del Bove depression until 27 December. This is the first flank eruption occurring at Etna in the last decade, during which eruptive activity was confined to the summit craters and resulted in lava fountains and lava flow output from the crater rims. In this paper we use ground and satellite remote sensing techniques to describe the sequence of events, quantify the erupted volumes of lava, gas and tephra, and assess volcanic hazard.

During emplacement, lavas modify the pre-existing topography and release a large amount of heat. In spite of the relevance of both heat and mass release, combined morphological and thermal analyses have been seldom carried out at a flow-field scale. Here, we consider a channelised lava flow unit formed at Mt Etna during the 2001 flank eruption, and we show that, by combining a morphological analysis of the pre- and post-emplacement topography with the analysis of the syn-eruptive thermal signature, critical insights about the processes driving mass and heat dissipation can be derived. Our results suggest that, in the considered lava flow, the pre-emplacement slope controls heat dissipation and can influence the thickness of the final lava deposit, with possible implications for hazard assessment. The width of the lava channel, instead, appears less sensitive to the pre-emplacement slope, and tends to regularly increase with increasing distance from the vent.

This compilation re-visits the May 18, 1980 Plinian eruption sequence of Mount St. Helens and correlates new and existing observations and measurements for a revised narrative of when and how eruption behavior changes occurred. It presents new observations of vesicle textures in white pumice and analyses of lithic materials that are correlated with observed eruption behavior. These and the compositional and seismic research by others provide constraints to a proposed process of how the conduit system was modified during the Plinian sequence. The eruption sequence is sub-divided into 3 periods interpreted to represent changes in magma supply and transport as a result of conduit changes. Based on observed pumice textures and composition, the microlite-free, white pumice in the earliest Plinian tephra is interpreted to have been emplaced in a poorly-interconnected, conduit system on or about May 16. The Morning period began with the landslide and lateral blast and initial conduit decompression. The early Plinian column then discharged conduit-resident, white pumice through an effective conduit of ≥20 m radius that produced small, irregular tephra clasts with abundant, small tubular vesicles. Small pyroclastic flows observed about 1010 h started the Transition period and the discharge of small batches of magma from the magma reservoir. Increasingly larger pumice clasts and large, coalesced vesicle textures are attributed to the increased ascent path from the magma reservoir and increased, average ascent rates that increased the rates and extent of bubble growth and coalescence. The eruption intensity that occurred at 1215 h is attributed to an increased magma supply through a modestly, improved conduit. The Afternoon period started at 1300 h as the vertical, eruption column dissipated. Episodic pyroclastic flows from collapsed fountains increased in volume until climax, as a preferred path in the complex, lower conduit was established. Lithic fragments comprise about 40% of deposits of the Pumice Plain and about 70% of the glass was lost as very-fine ash during emplacement. It is proposed that syn-eruptive conduit modification incrementally consolidated adjacent dikes and fractures, improved local interconnections among conduit segments, and removed the lithic debris, so that the conduit configuration was simplified and the effective conduit radius enlarged to ≥43 m during the Climactic phase. The Climactic phase after 1500 h resulted from full conduit interconnection, and magma supply and transport from deeper parts of the reservoir.

Stromboli (Aeolian Archipelago, Italy) is an active volcano that is frequently affected by moderate to large mass wasting, which has occasionally triggered tsunamis. With the aim of understanding the relationship between the geomorphologic evolution and slope instability of Stromboli, remote sensing information from space-born Synthetic Aperture Radar (SAR) change detection and interferometry (InSAR) () and Ground Based InSAR (GBInSAR) was compared with field observations and morphological analyses. Ground reflectivity and SqueeSAR™ (an InSAR algorithm for surface deformation monitoring) displacement measurements from X-band COSMO-SkyMed satellites (CSK) were analysed together with displacement measurements from a permanent-sited, Ku-band GBInSAR system. Remote sensing results were compared with a preliminary morphological analysis of the Sciara del Fuoco (SdF) steep volcanic flank, which was carried out using a high-resolution Digital Elevation Model (DEM). Finally, field observations, supported by infrared thermographic surveys (IRT), allowed the interpretation and validation of remote sensing data. The analysis of the entire dataset (collected between January 2010 and December 2014) covers a period characterized by a low intensity of Strombolian activity. This period was punctuated by the occurrence of lava overflows, occurring from the crater terrace evolving downslope toward SdF, and flank eruptions, such as the 2014 event. The amplitude of the CSK images collected between February 22nd, 2010, and December 18th, 2014, highlights that during periods characterized by low-intensity Strombolian activity, the production of materials ejected from the crater terrace towards the SdF is generally low, and erosion is the prevailing process mainly affecting the central sector of the SdF. CSK-SqueeSAR™ and GBInSAR data allowed the identification of low displacements in the SdF, except for high displacement rates (up to 1.5 mm/h) that were measured following both lava delta formation after the 2007 eruption and the lava overflows of 2010 and 2011. After the emplacement of the 2014 lava field, high displacements in the central and northern portions of the SdF were recorded by the GBInSAR device, whereas the spaceborne data were unable to detect these rapid movements. A comparison between IRT images and GBInSAR-derived displacement maps acquired during the same time interval revealed that the observed displacements along the SdF were related to the crumbling of newly emplaced 2014 lava and of its external breccia. Detected slope instability after the 2014 flank eruption was related to lava accumulation on the SdF and to the difference in the material underlying the 2014 lava flow: i) lava flows and breccia layers related to the 2002–03 and 2007 lava flow fields in the northern SdF sector and ii) loose volcaniclastic deposits in the central part of the SdF. This work emphasizes the importance of smart integration of spaceborne, SAR-derived hazard information with permanent-sited, operational monitoring by GBInSAR devices to detect areas impacted by mass wasting and volcanic activity.

Prior to the 2018 lower East Rift Zone (ERZ) eruption and summit collapse of Kīlauea Volcano, Hawai‘i, continuous gravimeters operated on the vent rims of ongoing eruptions at both the summit and Pu‘u ‘Ō‘ō. These instruments captured the onset of the 2018 lower ERZ eruption and the effects of lava withdrawal from both locales, providing constraints on the timing and style of activity and the physical properties of the lava lakes at both locations. At the summit, combining gravity, lava level, and a three-dimensional model of the vent indicates that the upper ∼200 m of the lava lake had a density of about 1700 kg m−3, slightly greater than estimates from 2011–2015 and possibly indicating a gradual densification over time. At Pu‘u ‘Ō‘ō, gravity and vent geometry were used to model both the density and the rate of crater collapse, which was unknown owing to a lack of visual observations. Results suggest the withdrawal of at least 11 × 10 6 m3 of lava over the course of two hours, and a material density of 1800–1900 kg m−3. In addition, gravity data at Pu‘u ‘Ō‘ō captured a transient decrease and increase about an hour prior to crater collapse and that was probably related to a small, short-lived fissure eruption on the west flank of the cone and possibly to dike intrusion beneath Pu‘u ‘Ō‘ō. The fissure was the first event in the subsequent cascade that ultimately led to the extrusion of over 1 km3 of lava from lower ERZ vents, collapse of the summit caldera floor by more than 500 m, and the destruction of over 700 homes and other structures. These results emphasize the importance of continuous gravity in operational monitoring of active volcanoes.

The 6-month long eruption at Holuhraun (August 2014–February 2015) in the Bárðarbunga-Veiðivötn volcanic system was the largest effusive eruption in Iceland since the 1783–1784 CE Laki eruption. The lava flow field covered ~84 km2 and has an estimated bulk (i.e., including vesicles) volume of ~1.44 km3. The eruption had an average discharge rate of ~90 m3/s making it the longest effusive eruption in modern times to sustain such high average flux. The first phase of the eruption (August 31, 2014 to mid-October 2014) had a discharge rate of ~350 to 100 m3/s and was typified by lava transport via open channels and the formation of four lava flows, no. 1–4,which were emplaced side by side. The eruption began on a 1.8 km long fissure, feeding partly incandescent sheets of slabby pāhoehoe up to 500 m wide. By the following day the lava transport got confined to open channels and the dominant lava morphology changed to rubbly pāhoehoe and ‘a’ā. The latter became the dominating morphology of lava flows no. 1–8. The second phase of the eruption (Mid-October to end November) had a discharge of ~100–50 m3/s. During this time the lava transport system changed, via the formation of a b1 km2 lava pond ~1 km east of the vent. The pond most likely formed in a topographical low created by a the pre-existing Holuhraun and the newHoluhraun lava flow fields. This pond became themain point of lava distribution, controlling the emplacement of subsequent flows (i.e. no. 5–8). Towards the end of this phase inflation plateaus developed in lava flowno. 1. These inflation plateaus were the surface manifestation of a growing lava tube system, which formed as lava ponded in the open lava channels creating sufficient lavastatic pressure in the fluid lava to lift the roof of the lava channels. This allowed new lava into the previously active lava channel lifting the channel roof via inflation. The final (third) phase, lasting from December to end-February 2015 had a mean discharge rate of ~50 m3/s. In this phase the lava transport was mainly confined to lava tubes within lava flows no. 1–2, which fed breakouts that resurfaced N19 km2 of the flow field. The primary lava morphology from this phase was spiny pāhoehoe, which superimposed on the ‘a’ā lava flows no. 1–3 and extended the entire length of the flow field (i.e. 17 km). Thismade the 2014–2015 Holuhraun a paired flow field,where both lava morphologies had similar length. We suggest that the similar length is a consequence of the pāhoehoe is fed from the tube systemutilizing the existing ‘a’ā lava channels, and thereby are controlled by the initial length of the ‘a’ā flows., The work was financed with crisis response funding from the Icelandic Government along with European Community's Seventh Framework Programme Grant No. 308377 (Project FUTUREVOLC) and along with the Icelandic Research fund, Rannis, Grant of Excellence No. 152266-052 (Project EMMIRS). Furthermore, Vinur Vatnajökuls are thanked for support.

Mount Cleveland volcano (1730 m) is one of the most active volcanoes in the Aleutian arc, Alaska, but heightened activity is rarely accompanied by geophysical signals, which makes interpretation of the activity difficult. In this study, we combine volcanic gas emissions measured for the first time in August 2015 with longer-term measurements of thermal output and lava extrusion rates between 2011 and 2015 calculated from MODIS satellite data with the aim to develop a better understanding of the nature of volcanic activity at Mount Cleveland. Degassing measurements were made in the month following two explosive events (21 July and 7 August 2015) and during a period of new dome growth in the summit crater. SO2 emission rates ranged from 400 to 860 t d− 1 and CO2/SO2 ratios were

Mount Etna in Sicily (Italy) shows more than 2,500 years of interactions between volcanic eruptions and human activity, and these are well documented in historical sources. During the last 400 years, flank eruptions have had major impacts on the urban fabric of the Etna region, especially in 1651, 1669, 1923 and 1928, and it is the last of these which is the focus of this paper. In this paper a detailed field and historical reconstruction of the 1928 eruption is presented which allows three themes to be discussed: the evolution of the flow field, lava volume and average magma discharge rate trend; the eruption's human impact, particularly the destruction of the town of Mascali; and the recovery of the region with re-construction of Mascali in a new location. Detailed mapping of lava flows allowed the following dimensions to be calculated: total area, 4.38 x 106 m2; maximum length, 9.4 km; volume, 52.91 ± 5.21 × 106m3 and an average effusion rate of 38.5 m3 s-1. Time-averaged discharged rates are calculated allowing the reconstruction of their temporal variations during the course of the eruption evidencing a high maximum effusion rate of 374 m3 s-1. These trends, in particular with regard to the Lower Fissure main phase of the eruption, are in accordance with the ‘idealized discharge model’ of Wadge (1981), proposed for basaltic eruptions driven by de-pressurization of magma sources, mainly through reservoir relaxation (i.e. elastic contraction of a magma body). The eruption took place when Italy was governed by Mussolini and the fascist party. The State response both, during and in the immediate aftermath of the eruption and in the years that followed during which Mascali was reconstructed, was impressive. This masked a less benign legacy, however, that can be traced for several subsequent decades of using responses to natural catastrophes to manufacture State prestige by reacting to, rather than planning for, disasters.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. Despite their generally low volume fraction, Fesingle bondTi oxides have the potential to greatly influence the eruptive style because they lower the supersaturation pressure for heterogeneous bubble nucleation. Once nucleated, bubbles respond fast to pressure changes, fostering rapid expansion and explosive behavior. Yet, oxide microlite quantifications are often absent from data of explosive products. We used new, re-analyzed, and published data to build a compilation of oxide number densities (ONDs) and vesicle number densities (VNDs) of trachytic and calc-alkaline products. Four eruptive styles were selected: 1) Vulcanian explosions from Soufrière Hills volcano, Montserrat, Lascar volcano, Chile, and Kilian volcano, France, 2) blasts from Mt. Pelée volcano, Lesser Antilles, Mount St. Helens, USA, and Merapi volcano, Indonesia, 3) a sub-Plinian explosion from Merapi volcano, and 4) lava dome effusions with intermittent collapse from Soufrière Hills and Mt. Pelée volcanoes. Natural samples were separated into two groups according to the dominant texture of the products of each event: 1) vesicular pumice clasts from explosions with a strong vertical component and 2) dense clasts with diktytaxitic textures from dome collapse event and lateral blast. Group 1 samples are either distributed alongside the 1:1 trend between VND and OND that spans from 1015 to 1017 m−3, or have a constant VND of 1016–16.5 m−3 regardless of OND. A large proportion of oxides (55–100%) touch vesicles. A more variable proportion of vesicles (16–72%) are in contact with oxides because of syn-explosive growth and coalescence. Group 2 samples have ONDs in the same broad range as group 1 samples. We also used new and published data to build a compilation of ONDs and VNDs of five series of experimental decompression of rhyolitic and phonolitic melts. In samples with OND ≈ VND, most bubbles are in contact with more than one oxide and 64–88% of the oxides are in contact with bubbles. Such high levels of connectivity suggest that the role of oxides in controlling bubble nucleation has been underestimated. When VND ≥ OND, nucleation densities of experimental vesicles can be reproduced by heterogeneous nucleation models, which we used to calculate syn-explosive decompression rates from VNDs at Merapi, Soufrière Hills, and Kilian. These rates and textural evidence suggest that the decompression front accompanying these Vulcanian and sub-Plinian explosions is responsible for syn-explosive bubble nucleation. We calculated the average pre-explosive ascent rates necessary to yield the observed ONDs at Soufrière Hills and Merapi volcanoes. The resulting rates, 0.005–20 m/s, overlap considerably with the range of critical ascent rate inferred for the effusive–explosive transition, supporting the hypothesis that this transition is primarily controlled by oxide microlites in the conduit because oxides are a primer for explosive behavior when present in sufficiently high number densities. Focusing on the older eruption of Kilian, for which no observation is available, we infer that pre-explosive ascent rates of >7 × 10−3 m/s were necessary for explosive behavior to occur.

An understanding of destructive historic eruptions has important implications for the assessment of active plumbing systems and the processes that might precede future hazardous eruptions. At Mount Etna (Sicily, Italy), magma production and eruption frequency have increased dramatically since 1970, however, the recent eruptions are considerably less voluminous than those of the 17th century, which occurred at greater intervals. Seventeenth century activity culminated in the 1669 flank eruption, the most voluminous and destructive in Etna’s recorded history, marking the beginning of a new eruptive period. In this study, we examine trace element zoning patterns recorded in clinopyroxene (lava hosted microcrysts: 0·5–1 mm, lava hosted macrocrysts: 1–5 mm and scoria hosted megacrysts: >5 mm) to reconstruct magma dynamics leading up to the 1669 eruption. The clinopyroxene data are considered alongside previous studies of olivine and plagioclase to present an updated conceptual model for the plumbing system, providing a better understanding of magmatic processes in the lead up to hazardous volcanism. Petrological observations in combination with laser ablation ICP-MS mapping reveal sharp compositional zoning of clinopyroxene, not seen in major element transects. Trace element data, including Cr, Zr, Ni and rare earth elements, show that core, mantle and rim regions originated in distinct magmatic environments. Chromium-rich cores (up to 1080 ppm Cr) are in disequilibrium with the glassy-microcrystalline host groundmass and indicate crystal inheritance from a primitive magma source. Oscillatory zoning in the mantle of the crystals suggests a sustained period of magma replenishment and crystallization. Finally, ubiquitous Cr-rich (170–220 ppm) rims host many large melt inclusions, suggesting a final recharge event inducing relatively rapid crystal growth and eruption. Temperatures of 1120–1160 ± 27°C and pressures of 300–600 ± 200 MPa calculated for the three magmatic environments based on clinopyroxene composition at 2 wt % H2O place most of the clinopyroxene crystallization at more than 10 km depth. Measuring the consistent thickness of crystal rims (219 ± 33 µm) and assuming growth at a low degree of undercooling (10−8 cm/s), we calculate that the eruption triggering magma recharge invaded the plumbing system less than a month before eruption onset, in agreement with historical accounts of pre-eruptive seismicity. Notably, Cr enrichment in the recharge magma was not coupled with increases in MgO content. We therefore propose that a cryptic recharge with similar composition to the resident melt may have tipped the system to erupt, and that the volume of recharge rather than composition or temperature acted as the primary trigger. Finally, LA-ICP-MS maps of clinopyroxene from the previous eruption of Mount Etna (1651–53) revealed strikingly similar compositional zonation to that of 1669, supporting the notion that magmatic storage environments, associated with voluminous 17th century activity, were long-lived.

INTRODUCTION The 2018 flank eruption and summit collapse of Kīlauea Volcano was one of the largest and most destructive volcanic events in Hawai‘i in the past 200 years. The eruption occurred on the volcano’s lower East Rift Zone (ERZ), draining magma at a high rate from the summit reservoir and triggering incremental collapse of the overlying caldera floor. Lava flows erupted for 3 months, destroying several residential subdivisions and burying miles of roads. The eruption rate exhibited cyclic behavior on multiple time scales, resulting in repeated lava breakouts and overflows. Multidisciplinary observations provide insight into the nature of these variations, driving forces in the magmatic system, and implications for hazard. RATIONALE Volumetric eruption rate is a primary control on the vigor and hazard of lava flows, but the processes that control its temporal variations are not well understood because of limited observational data. We integrated field observations, photos and video from time-lapse cameras and unmanned aircraft systems, seismic tremor, and infrasound to track the time scales and magnitude of fluctuations in eruption rate at the primary vent for the 2018 eruption on Kīlauea’s LERZ. We combined these data with documentation of summit caldera collapses to investigate the origins and impacts of these fluctuations. RESULTS Cyclic variations in eruption rate occurred on two disparate time scales. First, short-term fluctuations (“pulses”) in eruption vigor had periods of 5 to 10 min, but had no major implications for lava flow hazard. Flow rate in the lava channel was inversely related to fountaining and outgassing intensity at the vent. Second, long-term fluctuations (“surges”) had periods of 1 to 2 days and began within minutes of episodic caldera collapse events at the summit, 40 km upslope. These surges triggered overflows from the channel that produced hazardous enlargement of the lava flow field, which could be forecast several hours in advance. We also show that seismic tremor and infrasound were correlated with lava flow eruption rates. CONCLUSION We conclude that the two types of eruption rate cycles were controlled by two distinct processes. Short-term pulses were driven by changes in outgassing efficiency of the lava at shallow depths. Long-term surges in eruption rate were driven by pressure transients induced by the summit collapses and transmitted through the magma conduit over a distance of 40 km. The pressure-driven surges in eruption rate demonstrate that the episodic rhythm of summit caldera collapse sequences may be imparted on the accompanying flank eruption. The surges also help to constrain the efficient hydraulic connection between Kīlauea’s summit magma system and rift zones and demonstrate that pressure communication over distances of 40 km can occur on a time scale of minutes. Seismic tremor and infrasound may be effective proxies for lava flow eruption rates, allowing for improved tracking of lava flow hazards. Our multidisciplinary data provide a clear link between eruption rate fluctuations and their driving processes in the magmatic system.

We investigated the relationship between the temporal monitoring series routinely recorded at Mt. Etna and the flank eruptions that occurred between January 2001 and April 2005 by the K-contractive map (K-CM) method pattern classifier with supervised learning. The reference dataset includes 28 variables and 1580 records collected over 52 months for a total of 301 eruptive days. A two-step analysis was performed. In the first step analysis, we used the 28 parameters of each day to recognize anomalies heralding a flank eruption. K-CM estimated a sensitivity higher than 95% and a specificity close to 100%. In the second step analysis, we considered each record comprising the 28 variables for 6 days as an input (for a total of 180 inputs) and the outcomes of the seventh day as an output to predict eruption or rest. In this case, K-CM showed sensitivity and specificity close to 98% and 100%, respectively. Results highlight the reliability of the K-CM method to build up a prediction algorithm able to alert the volcano experts a day before the occurrence of a potential flank eruption. The robustness of the two analyses was investigated by the behavior of the receiver operating characteristic curve. The relative area under the curve showed values close to 1, thus providing a valid measure of the performance of the classifier. Finally, a complete overview of the performance levels of the method used was explored analyzing the retrieved Molchan error diagram, in both cases, trajectories very close to the theoretical minimum.

Первое историческое извержение вулкана Камбальный началось 24 марта 2017 г. с мощной эмиссии пепла из вершинного кратера до 6 км над уровнем моря. По данным тефрохронологии предполагается, что сильные извержения вулкана происходили 200 (?) и 600 лет назад. 25–26 марта отмечалась максимальная интенсивность выноса пепла – непрерывный шлейф, нагруженный пепловыми частицами, распространился на несколько тысяч километров, изменяя направление распространения от вулкана с юго-западного на южный и юго-восточный. 27–29 марта пепловый шлейф протягивался на запад, 30 марта – на юго-восток, 2 апреля – на восток от вулкана. 31 марта и 1 апреля вулкан был относительно спокоен. Возобновление активности вулкана после двух суток покоя выразилось в мощных выбросах пепла до 7 км над уровнем моря. Небольшой пепловый шлейф был отмечен 4 апреля, 9 апреля вновь произошел выброс пепла до 7 км над уровнем моря. Площадь отложений пепла на суше составила 1300 км2, общая площадь территории, охваченной пеплопадами, например, 25 марта – 650 тыс. км2. Для наблюдений за извержением вулкана были использованы преимущественно спутниковые данные среднего разрешения информационной системы «Мониторинг активности вулканов Камчатки и Курил» (VolSatView).

The mechanical conditions for a volcanic eruption to occur are conceptually simple: a magma-driven fracture (normally a dyke) must be able to propagate from the source to the surface. The mechanics of small to moderate eruptions (eruptive volumes less than 10 km3) is reasonably well understood, whereas that of large eruptions (eruptive volumes of 10–1000 km3) is poorly understood. Here I propose that, while both large and small eruptions are primarily driven by elastic energy and may come from the same magma chambers and reservoirs, the mechanisms by which the elastic energy is transformed or relaxed in these eruptions are different. More specifically, during small to moderate eruptions, the excess pressure in the source (the primary pressure driving the eruption) falls exponentially until it approaches zero, whereby the feeder-dyke closes at its contact with the source and the eruption comes to an end. Under normal conditions, the ratio of the eruptive and intrusive material of the eruption to the volume of a totally molten shallow basaltic crustal magma chamber (at the common depth below the surface of 1-5 km) is about 1400, and that of a partially molten deep-seated basaltic magma reservoir (in the lower crust or upper mantle) is about 5000. Many magma chambers are partially molten, in which case the ratio could be close to that of reservoirs. Most magma chambers are estimated to be less than about 500 km3, for which the maximum eruptive volume would normally be about 0.4 km3. An eruptive volume of 1 km3 would require a totally molten chamber of about 1400 km3. While chambers of this size certainly exist, witness the volumes of the largest eruptions, large eruptions of 10–1000 km3 clearly require a different mechanism, namely one whereby the excess pressure is maintained during much of the eruption. I suggest that the primary excess-pressure maintenance mechanism is through caldera subsidence for shallow magma chambers and graben subsidence for deep-seated magma reservoirs. In this mechanism, it is the subsidence, of tectonic origin, and associated volume reduction (shrinkage) of the magma source that drives out an exceptionally large fraction of the magma in the source, thereby generating the large eruption. Most explosive eruptions that exceed volumes of about 25 km3, and many smaller, are associated with caldera collapses. The data presented suggest that many large effusive basaltic eruptions, in Iceland, in the United States, and elsewhere, are associated with large graben subsidences In terms of the present mechanism, successful forecasting of large eruptions requires understanding and monitoring of the volcanotectonic conditions that trigger large caldera and graben subsidences.

Preceded by 14 days of intense seismic activity, a new eruption started on the south flank of Mt. Etna, Sicily (Italy) early in the morning of 11 March 1669 opening up a series of NS eruptive fissures. The eruption is one of the most destructive flank eruptions of Etna in historical times; it lasted until 11 July, and was characterized by simultaneous explosive and effusive activity during the first three months, while only lava flow output in the last month. The activity built up the large composite cone of the “Monti Rossi” at the lower end of the eruptive fissures, and caused severe damage to the nearby inhabited areas. The prolonged effusive activity generated lava flows for > 15 km, which destroyed several villages and the western part of the town of Catania before reaching the coastline and entering the sea. In this paper, we examine the tephro-stratigraphy of the products of the explosive activity. An in-depth analysis of historical accounts was used to define the chronology of the main eruptive phases (precursors, explosive activity and initial effusive phenomena). The geology of the cone and of the fallout deposits were defined through a field survey over a distance of 5 km from the Monti Rossi. Textural (grain-size, morphological, componentry), density and petrological analyses of tephra samples provided a sedimentological, physical and geochemical characterization of erupted products. Integrating ground and historical data enabled defining the evolution of the cone, identifying and correlating four main cone-forming units. By tracing the dispersal map of the main distal tephra beds (the finer ash being dispersed mainly to the NE as far as Calabria and to the south of Sicily and the 10-cm isopach of the total deposit covering an area up to 53 km2), we estimated a total tephra fallout volume, including the Monti Rossi cone, of about 6.6 × 107 m3 (about 3.2 × 107 m3 DRE). The 1669 event can be considered an archetype of the most hazardous expected eruption on the densely populated flanks of Etna. Reconstructing the eruptive chronology and styles of the 1669 eruption therefore, represents the basic data to assess volcanic hazard from eventual similar flank events in the future.

Eruption rates at the mid-ocean ridges (MORs) are believed to strongly control the morphology and length of lava flows emplaced along the ridge axis, and thus the structure and porosity of the upper oceanic crust. Eruption rate also represents one of the few tools to gain insight into the driving pressures within sub-ridge magmatic systems. As eruption rate is inferred to vary systematically along the global mid-ocean ridge system, understanding of how to assess eruption rate in submarine systems and how it maps to observable features of the ridge axis would provide a powerful tool to understand Earth's largest magmatic system. Eruption rates at MORs are poorly constrained, however, because of a lack of direct observations, preventing the duration of an eruption to be quantified. This study uses decompression experiments of MORB samples and numerical modeling of CO 2 degassing to reconstruct the timescales for magma ascent and lava emplacement during the 2005–06 eruption of the East Pacific Rise at ca. 9°51′N. Samples collected from the lava flow are all supersaturated in dissolved CO 2 contents, but CO 2 decreases with distance from the vent, presumably as a consequence of progressive CO 2 diffusion into growing bubbles. Samples collected at the vent contain ∼10 5 vesicles per cm 3 . Pieces of these samples were experimentally heated to 1225 °C at high pressure and then decompressed at controlled rates. Results, plus those from numerical modeling of diffusive bubble growth, indicate that magma rose from the axial magma chamber to the seafloor in ≤1 h and at a rate of ≥2–3 km h −1 . Our modeling, as validated by experimental decompression of MORB samples with ∼10 6 vesicles cm −3 , also suggests that CO 2 degassed from the melt within ∼10–100 min as the vesicular lava traveled ∼1.7 km along the seafloor, implying a volumetric flow rate on order of 10 3–4 m 3 s −1 . Given an ascent rate of ≥0.2 m s −1 , the width of a rectangular dike feeding the lava would have been ∼1–2 m wide. MORB samples from the Pacific ridge are generally more supersaturated in dissolved CO 2 than those from slower spreading Atlantic and Indian ridges. Our results suggest that Pacific MORBs ascend to the seafloor faster than Atlantic or Indian MORBs.

An energetic eruption started on 25 May 2015 from a circumferential fissure at the summit of Wolf volcano on Isabela Island, western Galapagos. Further eruptive activity within the Wolf caldera followed in mid-June 2015. As no geodetic observations of earlier eruptions at Wolf exist, this eruption provides an opportunity to study the volcano's magmatic plumbing system for the first time. Here, we use interferometric synthetic aperture radar (InSAR) data from both the Sentinel-1A and ALOS-2 satellites to map and analyze the surface deformation at four time periods during the activity. These data allow us to identify the two eruption phases and reveal strong co-eruptive subsidence within the Wolf caldera that is superimposed on a larger volcano-wide subsidence signal. Modeling of the surface displacements shows that two shallow magma reservoirs located under Wolf at ~1 km and ~5 km below sea level explain the subsidence and that these reservoirs appear to be hydraulically connected. We also suggest that the transition from the circumferential to the intra-caldera eruption may have involved ring fault activity.

Cordon Caulle is a large fissural volcano that has erupted rhyodacitic magma of the same composition in its past three historical eruptions in 1921, 1960 and 2011-2012. There was significant ground deformation observed before and during the 2011-2012 eruption – here we use C and X band InSAR time series results to document post-eruptive uplift up to 0.8 m between March 2012 and May 2015, with LOS rates up to 45 cm/yr that have been largely aseismic, along with subsidence in the 2011-2012 lava flow. The 2012 uplift rate is one of the largest for silicic systems, and was likely produced by the intrusion of ~0.125 km3 of magma in the same tectonically controlled plumbing system that has been active during the historical eruptions. Nevertheless the uplift ended before the reservoir refilled with the erupted volume, maybe due to a change in the pressure gradient produced by the 2011-2012 eruption.

The local seismicity during the 2012–2013 eruption of Tolbachik Volcano and the 2008–2009 steam–gas eruption of Koryakskii Volcano is here considered as resulting from injections of magma that produced dikes, sills, and renewed activity at preexisting faults. We identified plane-oriented earthquake clusters in order to reveal the above zones using earthquake catalogs made at the Kamchatka Branch of the Geophysical Service of the Russian Academy of Sciences (KB GS RAS). Subsequent space–time analysis of these observations lends itself to the following interpretation. The November 27, 2012 Tolbachik lava eruption was preceded by an injection of magma resulting in a series of dikes trending west-northwestward in the range of absolute depths between –4 and +3 km in a zone situated southeast of the Ploskii Tolbachik Volcano edifice. The dikes penetrated into a nearly horizontal permeable zone at an absolute depth of approximately zero, producing sills and emplacing a magma-conducting dike along the top of the zone of cinder cones (the dip angle is 50° toward the azimuth 300°) 5.5 km from the epicenter of the initial magma injection. The summit steam–gas eruption of Koryakskii Volcano in 2008–2009 was preceded by magma filling a crustal chamber (the top of the chamber is at –3 km absolute depth; the chamber is 2.5 km across) close to the southwestern base of Koryakskii. Further, magma injection in a nearly north–south zone (7.5 by 2.5 km), the absolute depth between –2 and –5 km) in the north sector of Koryakskii Volcano was occurring concurrently with the summit steam–gas eruption. The injection of magma into the cone of Avacha Volcano (2010) produced sills (at altitudes between +1600 and +1900 m) and dikes (mostly striking northwest).

The 2014–2015 Holuhraun eruption on Iceland was located within the Askja fissure swarm butwas accompanied by caldera subsidence in the Barðarbunga central volcano 45 km to the southwest. Geophysica ...

International audience; Identifying the onset of volcano unrest and providing an unequivocal identification of volcano reawakening remain challenging problems in volcanology. At Piton de la Fournaise, renewal of eruptive activity in 2014–2015, after 41 months of quiescence and deflation, was associated with long-term continuous edifice inflation measured by GNSS. Inflation started on June 9, 2014, and its rate progressively increased through 2015. Inflation onset was rapidly followed by an eruption on June 20–21, 2014, showing that volcano reactivation can be extremely fast, even after long non-eruptive phases. This short-lived eruption involved a shallow source (1.3–1.9 km depth below the summit). The inflation that followed, and eruptions in 2015, involved a larger depth range of fluid accumulation, constrained by inverse modeling at ca. 3.9 to 1.2–1.7 km depth. This time evolution reveals that volcano reawakening was associated with continuous pressurization of the shallowest parts of its plumbing system, triggered by progressive upwards transfer of magma from greater depth. A deep magma pulse occurred in mid-April 2015 and was associated with deep seismicity (3 to 9.5 km depth) and CO2 enrichment in fluids emitted by summit fumaroles. From this date, ground deformation accelerated and the output rates of eruptions increased, culminating in the long-lasting, large-volume, August–October eruption (~ 36 Mm3). This evolution suggests that deep magma/fluid transfer through an open conduit system first provoked the expulsion of the top of the plumbing system in June 2014, and then induced the progressive vertical transfer of the entire plumbing system down to 9 km (four eruptions in 2015). The new sustained feeding of the volcano was also at the origin of the hydrothermal system perturbation and the acceleration of the eastern flank motion, which favor lateral dike propagation and the occurrence of frequent and increasingly large eruptions. Our results highlight the fast and progressive way in which basaltic magmatic systems can wake up.

The Wudalianchi Volcano Field (WDF) is a typical intraplate volcano in northeast China with generation mechanism not yet well understood. As its last eruption was around 300 years ago, the present risk for volcano eruption is of particular public interest. We have carried out a high-resolution ambient noise tomography to investigate the location of magma chambers beneath the volcanic cones with a dense seismic array of 43 seismometers and ~ 6 km spatial interval. Significant low-velocity anomalies up to 10% are found at 7–13 km depth under the Weishan volcano, consistent with the pronounced high electrical-conductivity anomalies from previous magnetotelluric survey. We propose these extremely low velocity anomalies can be interpreted as partial melting in a shallow magma chamber with volume at least 200 km3 which may be responsible for most of the recent volcanic eruptions in WDF. Therefore, this magma chamber may pose a serious hazard for northeast China.

The quantification of eruptive activity represents one major challenge in volcanology. Digital comparison of lidar-based elevation models of Etna (Italy) was made to quantify the volumes of volcanics emitted in 2007–2010. During this period, Etna produced several summit paroxysms followed by a flank eruption. We integrated the total volume difference resulting from the subtraction of the 2007 and 2010 digital elevation models with volumes of eruptive products based on field and aerial surveys to attribute volumes with hitherto unrealized precision to poorly constrained eruptions. The total erupted volume of 2007–2010 is >86 × 106 m3, most (~74 × 106 m3) of which is made up by the lava flows of the 2008–2009 flank eruption. The survey also reveals the high lava volume (5.73 × 106 m3) and average eruption rate (~400 m3 s−1) of the 10 May 2008 paroxysm, whose flow front stopped 6.2 km from the vent, not far from the town of Zafferana Etnea.

In the case of extrusive eruption, we consider the problem on magma degassing which rises in a volcano conduit crossing porous water-saturated rocks. We show that the intensity of outflow of volcanic gases into the rocks is comparable to the intensity of their transport with the rising magma. The magma degassing in the rocks substantially affects the eruption dynamics, in particular, the duration of the periods of eruptive activity.

Although analytical expressions for deformation due to simple reservoirs and planar dikes have been in use for decades, seldom are there sufficient data to provide well-constrained detailed models of volcanic activity. Deformation due to the eruption of Miharayama, Izu-Oshima, Japan, in November 1986 was captured by a wider array of monitoring than usual at that time. Here we show that the first eruptive stage requires a shallow non-spherical source, extended perpendicular to the axis of maximum tectonic tension, together with a deeper reservoir. The shallow reservoir was partially recharged, from a deeper reservoir, during the eruption, with a magma ascent rate of ~ 10 km/day; this has important implications for estimation of reservoir gas content. Precursory changes starting 2 h before the second phase require dike propagation from at least 10 km depth. Surface elevation changes are indicative of a long sub-surface dike. A model incorporating dikes and a deep (10 km) reservoir, extended in the same direction as the dikes, provides a very good match to the data. Such reservoir geometry may explain why the eruption was unexpected.

Controlling rock damage induced by lateral blasting excavation is a source of concern. In underground mines, large-diameter-hole lateral blasting excavation often causes engineering disasters such as large blocks falling and overall collapse of the remaining rock mass. Because of their high cost and cumbersome operation, conventional contour blasting techniques, such as smooth and presplit blasting, are unsuitable for production boreholes. In this paper, based on the large-diameter-hole lateral blasting excavation of the Shaxi underground mine in China, a field lateral blast test with a single row was initially conducted, and the sonic wave speeds and goaf boundaries were measured to evaluate the damage degree to the remaining rock mass. A numerical model with three rows of boreholes was developed and calibrated against the lateral blast test with a single row. The calibrated numerical model was used to simulate the blasting process. The blast-induced damage characteristics with different charge structures in different rows were investigated, and the optimal charge structure for each row was obtained. The results indicate that the rock damage control effect can be achieved by a reasonable combination of charge structures and number of blasted rows, and it is more satisfactory with an increasing number of blasted rows and a reasonable decrease in the charge coefficient row by row. The rock breaking pattern at Cut X2 shows that most of the boulders are caused by the collapse of the remaining rock mass under the impact of blasting excavation. The ratio of broken rock in Part 4 indicates that the blast impact of the last row plays a dominant role in the damage to the remaining rock mass. Two optimized schemes were applied to the field of large-diameter-borehole lateral blasting, and satisfactory effects were achieved in the blast-induced damage control of the remaining rock mass.

In this paper, the finite element software ABAQUS is used to simulate the RC beams under the short distance lateral blast load, consider the constraint effect of the plate, and analyze the influence of proportional distance, strength of concrete, strength of reinforcement, ratio of longitudinal reinforcement and other influencing factors on the dynamic response of RC beam. The results show that the CONWEP loading blast is reliable. The proportional distance is less than 0.200, and the lateral blast load has a great influence on the maximum lateral displacement of reinforced concrete beam with plate constraint. The influence of the strength grade of concrete and steel on the dynamic response of RC beams with slab constraints is limited. There is a negative correlation between the ratio of longitudinal reinforcement and the lateral displacement of RC beams with slab constraints. When longitudinal reinforcement ratio is more than 2.11%, RC beams with slab constraint can well resist lateral explosion load, but the lifting amplitude is not obvious.

In situ and remote-sensing measurements have been used to characterize the run-up phase and the phenomena that occurred during the August⁻November 2014 flank eruption at Stromboli. Data comprise videos recorded by the visible and infrared camera network, ground displacement recorded by the permanent-sited Ku-band, Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) device, seismic signals (band 0.02⁻10 Hz), and high-resolution Digital Elevation Models (DEMs) reconstructed based on Light Detection and Ranging (LiDAR) data and tri-stereo PLEIADES-1 imagery. This work highlights the importance of considering data from in situ sensors and remote-sensing platforms in monitoring active volcanoes. Comparison of data from live-cams, tremor amplitude, localization of Very-Long-Period (VLP) source and amplitude of explosion quakes, and ground displacements recorded by GBInSAR in the crater terrace provide information about the eruptive activity, nowcasting the shift in eruptive style of explosive to effusive. At the same time, the landslide activity during the run-up and onset phases could be forecasted and tracked using the integration of data from the GBInSAR and the seismic landslide index. Finally, the use of airborne and space-borne DEMs permitted the detection of topographic changes induced by the eruptive activity, allowing for the estimation of a total volume of 3.07 ± 0.37 × 106 m3 of the 2014 lava flow field emplaced on the steep Sciara del Fuoco slope.

Due to the frequent eruptive activity of Etna volcano, it is of primary importance to interpret the near-real time geophysical data as best as possible in order to understand the unrest vs. eruptive timescales. After the main flank eruption of 2008-2009 and until 2017, Etna volcano was characterized by a lively eruptive activity of different phases. These comprised 44 lava fountain episodes that formed a new crater named New South East Crater (NSEC) during 2011-2013, two sequences of close episodes of lava fountains from the Voragine crater (VOR) on 3-5 December 2015 (4 events) and May 18-21, 2016 (3 events), as well as some periods of summit effusive activity with a more prolonged supply of lava flows during 2014. Several studies have described and modelled single episodes of lava fountains of both the NSEC and VOR. In particular, during lava fountainings the high precision data from borehole strain-meters revealed short-term changes, which allowedinference into the source of decompression at a shallow level (shallow plumbing system) of at ~ sea level for the events of the NSEC and at deeper level (~2-5 km b.s.l.) for those of VOR, respectively. In this study, we also considered the middle-term volcano recharging/discharging periods preceding/accompanying the different eruptive phases during 2009-2017, and through the deformation recorded by the permanent GPS network, we constrained the position of the sources. Together with the modelling deduced from the strain-meter data we produce a more complete representation of the different sources that characterized the different periods both in the middle-term (i.e. the preparatory phases showing inflation and the eruptive phases showing deflation) and in the short-term (i.e. the fast discharge associated with each eruptive event). Our highly resolved modelling explains the pathway of magma from the intermediate-shallow plumbing system to the surface. Our results are consistent with petrological constraints on the spatio-temporal evolution of magma transfer and storage.

Catastrophic volcanic eruptions triggered by landslide collapses can jet upwards or blast sideways. Magma intrusion is related to both landslide-triggered eruptive scenarios (lateral or vertical), but it is not clear how such different responses are produced, nor if any precursor can be used for forecasting them. We approach this problem with physical analogue modelling enhanced with X-ray Multiple Detector Computed Tomography scanning, used to track evolution of internal intrusion, and its related faulting and surface deformation. We find that intrusions produce three different volcano deformation patterns, one of them involving asymmetric intrusion and deformation, with the early development of a listric slump fault producing pronounced slippage of one sector. This previously undescribed early deep potential slip surface provides a unified explanation for the two different eruptive scenarios (lateral vs. vertical). Lateral blast only occurs in flank collapse when the intrusion has risen into the sliding block. Otherwise, vertical rather than lateral expansion of magma is promoted by summit dilatation and flank buttressing. The distinctive surface deformation evolution detected opens the possibility to forecast the possible eruptive scenarios: laterally directed blast should only be expected when surface deformation begins to develop oblique to the first major fault.

Eruptions of similar explosivity can have divergent effects on the surroundings due to differences in the behavior of the tephra in the eruption column and atmosphere. Okmok volcano, located on Umnak Island in the eastern Aleutian Islands, erupted explosively between 12 July and 19 August 2008. The basaltic andesitic eruption ejected ∼0.24 km3 dense rock equivalent (DRE) of tephra, primarily directed to the northeast of the vent area. The first 4 h of the eruption produced dominantly coarse-grained tephra, but the following 5 wk of the eruption deposited almost exclusively ash, much of it very fine and deposited as ash pellets and ashy rain and mist. Meteorological storms combined with abundant plume water to efficiently scrub ash from the eruption column, with a rapid decrease in deposit thickness with distance from the vent. Grain-size analysis shows that the modes (although not their relative proportions) are very constant throughout the deposit, implying that the fragmentation mechanisms did not vary much. Grain-shape features consistent with molten fuel-coolant interaction are common. Surface and groundwater drainage into the vents provided the water for phreatomagmatic fragmentation. The available water (water that could reach the vent area during the eruption) was ∼2.8 × 1010 kg, and the erupted magma totaled ∼7 × 1011 kg, which yield an overall water:magma mass ratio of ∼0.04, but much of the water was not interactive. Although magma flux dropped from 1 × 107 kg/s during the initial 4 h to 1.8 × 105 kg/s for the remainder of the eruption, most of the erupted material was ejected during the lower-mass-flux period due to its much greater length, and this tephra was dominantly deposited within 10 km downwind of the vent. This highlights the importance of ash scrubbing in the evaluation of hazards from explosive eruptions.

A new fissure eruption began on 27 November 2012 on the southern slope of Plosky Tolbachik volcano, which is located in central Kamchatka, Russia, and is part of the Klyuchevskoy volcano group. We analyzed the displacement of the earth surface and the seismicity during several months before the eruption onset. According to seismic and GPS data the eruption was preceded by about 4–5 months (July–November 2012) of synchronous crustal deformation and seismicity. The seismic anomaly comprises low energy level seismicity (mainly M = 1.2–2.3) under Plosky Tolbachik volcano at a depth of less than 5 km. In the 2–3 weeks immediately preceding the eruption the rate of seismicity and the amount of radiated seismic energy exceeded the long-term average values (2000–2011) by more than 40 times. The deformation anomaly was recorded by displacement of the GPS points at distances from 20 to 60 km to the north of Tolbachik. The principal axis of the compressive strain was approximately directed towards the Tolbachik eruption site. The permanent GPS network detected radial compression and tangential stretching. The compressive strain reached about 10 − 7 prior to eruption onset. The comparable duration of seismic and deformation anomalies (~ 4–5 months before the eruption) is consistent with a common origin, connected to magma rising from depth, and is interpreted as indicating that they were medium-term precursors to the eruption. Data recorded during this unrest episode of the Tolbachik volcanic zone will contribute to understanding of the reawakening of volcanic activity in this region and others worldwide with similar characteristics.

We present a broad overview of the 2012–13 flank fissure eruption of Plosky Tolbachik Volcano in the central Kamchatka Peninsula. The eruption lasted more than nine months and produced approximately 0.55 km3 {DRE} (volume recalculated to a density of 2.8 g/cm3) of basaltic trachyandesite magma. The 2012–13 eruption of Tolbachik is one of the most voluminous historical eruptions of mafic magma at subduction related volcanoes globally, and it is the second largest at Kamchatka. The eruption was preceded by five months of elevated seismicity and ground inflation, both of which peaked a day before the eruption commenced on 27 November 2012. The batch of high-Al magma ascended from depths of 5–10 km; its apical part contained 54–55 wt. SiO2, and the main body 52–53 wt. SiO2. The eruption started by the opening of a 6 km-long radial fissure on the southwestern slope of the volcano that fed multi-vent phreatomagmatic and magmatic explosive activity, as well as intensive effusion of lava with an initial discharge of > 440 m3/s. After 10 days the eruption continued only at the lower part of the fissure, where explosive and effusive activity of Hawaiian–Strombolian type occurred from a lava pond in the crater of the main growing scoria cone. The discharge rate for the nine month long, effusion-dominated eruption gradually declined from 140 to 18 m3/s and formed a compound lava field with a total area of ~ 36 km2; the effusive activity evolved from high-discharge channel-fed 'a'a lavas to dominantly low-discharge tube-fed pahoehoe lavas. On 23 August, the effusion of lava ceased and the intra-crater lava pond drained. Weak Strombolian-type explosions continued for several more days on the crater bottom until the end of the eruption around 5 September 2013. Based on a broad array of new data collected during this eruption, we develop a model for the magma storage and transport system of Plosky Tolbachik that links the storage zones of the two main genetically related magma types of the volcano (high-Al and high-Mg basalts) with the clusters of local seismicity. The model explains why precursory seismicity and dynamics of the 2012–13 eruption was drastically different from those of the previous eruption of the volcano in 1975–76.

Following 84 years of repose, Tungurahua volcano, Ecuador initiated its present eruptive episode in October 1999, but its PDC activity only began in July 2006. A period of highly energetic Vulcanian eruptions started in 2012, those of 14 July 2013, 18 October 2013, and 1 February 2014 being the most important. These eruptions were well-monitored by a 5-station broadband seismic and acoustic array. Repeated repose intervals of ~ 3.5 months between Vulcanian events (VEI ~ 2) suggest that gases in the ascending juvenile magma experienced sequential pressurization cycles, as magma of preceding eruptive events solidified to form plugs that sealed the conduit. Every 34 months plug failure occurred, abrupt decompression followed, and the resulting Vulcanian explosions are associated with the highest seismic and acoustic energies ever registered anywhere. Small to moderate-sized PDC flows associated with the explosions and fountain collapses were generated and traveled ≤ 7 km down the steep N, NW, and W flanks of Tungurahua's cone at velocities of 11 to 18 m/s, although a small lateral blast and its PDC were clocked at 33 m/s descending the N flank. The explosive fragmentation of the plugs (a dense microcrystalline andesite) and the juvenile magma (a vesiculated glassy andesite) comprise the principal rock fragments of the PDC deposits. Each deposit typically consisting of two layers; a thin upper layer of large segregated and abraded clasts with few fines and a thicker lower layer that is fines-rich with few large clasts. Many deposits were studied and photographed within a few days of their formation, which are presented.

The Michoacán–Guanajuato Volcanic Field is the largest subduction-related monogenetic volcanic field in the world and includes more than 1000 scoria cones and a few hundred medium-sized volcanoes. Although medium-sized volcanoes (domes and shields) are less abundant, hazards associated with the renewal of this type of activity should not be neglected. Here, we focus on El Metate volcano, the morphologically youngest shield of the field. This volcano has a minimum volume of ~9.2 km3 DRE, and its viscous lava flows were emplaced during a single eruption over a period of ~30 years covering an area of 103 km2. El Metate is thus best labeled as a monogenetic andesite shield. This eruption had a significant impact on the environment (modification of the hydrological network, forest fires, etc.), and hence, nearby human populations probably had to migrate. New C14 dates for the eruption yield a young age (~AD 1250), which briefly precedes the initial rise of the Tarascan Empire (AD 1350–1521) in this region. By volume, this is certainly the largest eruption during the Holocene in the Trans-Mexican Volcanic Belt, and it is the largest andesitic effusive eruption known worldwide for this period. Such a large volume erupted in a relatively short time bears important implications for evaluating future hazards in the Michoacán–Guanajuato Volcanic Field.

A close relationship between earthquake swarms, volcanic eruptions, and ground deformation at Mt. Etna was well documented shortly before the beginning of the July–August 2001 eruption. Past experiences at this volcano suggest how magma/dike intrusion in the shallow crust or in the upper part of the volcanic pile normally occurs after several years/months of internal recharging. Since seismic investigations provide a means to study the scale and origin of stress perturbations at active volcanoes, allowing to better investigating the preparation phase of an eruption, in this paper, we performed a close examination of the seismic activity recorded at Mt. Etna in the months preceding the 2001 eruption and in particular between November 2000 and July 2001. After integrating data recorded by the two networks operating during that time and run by the Istituto Internazionale di Vulcanologia and SISTEMA POSEIDON, we relocated 522 earthquakes by using the tomoDD code in a 3D velocity model, and then we computed their fault plane solutions. The application of different selection criteria enabled obtaining a good-quality revised data set consisting of 111 fault plane solutions. The high-precision locations identified well-defined seismic clusters, in different periods, suggesting a link with the magma migration from a depth of 8–13 km b.s.l. towards shallower zones. Moreover, the computed maximum compressive stress axis, as inferred from earthquake focal mechanisms, indicated a roughly W-E-oriented σ 1 . This findings reflect an overpressure of the mid to shallow crust due to the progressive magma uprising in central portion of the volcano and also highlighted a rotation of the local stress field with respect to the regional one N-S trending. In addition, P-axis distribution pointed out the presence of a center of pressure located to the south of the Central Craters. These results provide particularly compelling evidence for a direct causal link between pressurization of the mid-level volcanic plumbing system by ascending magma and precursory local stress field reorientations, demonstrating that seismological analysis can be used to detect subtle local stress changes that herald eruptive activity.

Monogenetic volcanism produces small-volume volcanoes with a wide range of eruptive styles, lithological features and geomorphic architectures. They are classified as spatter cones, scoria (or cinder) cones, tuff rings, maars (maar–diatremes) and tuff cones based on the magma/water ratio, dominant eruption styles and their typical surface morphotypes. The common interplay between internal, such as the physical–chemical characteristics of magma, and external parameters, such as groundwater flow, substrate characteristics or topography, plays an important role in creating small-volume volcanoes with diverse architectures, which can give the impression of complexity and of similarities to large-volume polygenetic volcanoes. In spite of this volcanic facies complexity, we defend the term “monogenetic volcano” and highlight the term’s value, especially to express volcano morphotypes. This study defines a monogenetic volcano, a volcanic edifice with a small cumulative volume (typically ≤1 km3) that has been built up by one continuous, or many discontinuous, small eruptions fed from one or multiple magma batches. This definition provides a reasonable explanation of the recently recognized chemical diversities of this type of volcanism.