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Explosive submarine arc volcanoes can cause tsunamis, affect climate, and pose hazards to airplanes and ships. Although 70 % of the Earth is submarine, only 15 % of Holocene arc volcanoes in the Smithsonian Global Volcanism database are submarine. Merging locations of active submarine hydrothermal vents in arcs and the above database, we found 71 unlisted submarine arc volcanoes. Using Baker [2017, doi: 10.1016/j.oregeorev.2017.02.006], only 44 % of hydrothermal vents in arcs are known. Only 77 of the vent fields are on volcanoes in the Smithsonian database. Assuming that unknown submarine arc volcanoes are present in the same proportions as unknown vents, there are ~160 as-yet undiscovered Holocene age submarine arc volcanoes. Using geophysical data, we located 291 unsurveyed seamounts 32 % of Holocene arc volcanoes are submarine.

This study utilizes 3D numerical models to simulate seismic resonances in a volcanic edifice, arising from the interaction between an externally excited wavefield and a magma chamber-conduit system. The magma chamber and conduit efficiently capture the incident wavefield of both P- and S-waves, excited by a high-frequency (~10 Hz) earthquake located within the edifice. Due to multiple internal reflections off the boundaries of the chamber and conduit, prolonged reverberations occur, which are guided along the conduit. Temporal and spectral analyses of synthetic seismograms illustrate that models with larger chambers and wider conduits consistently yield larger resonance amplitudes at distinct frequencies. Our models indicate that a larger magma chamber can produce an intensified scattered wavefield with a broad frequency range, observable up to several hundred meters away from the central conduit. Generally, these externally initiated ‘calabash resonances’ may appear as tremor-like signals at seismometers on the edifice, accompanying more conventional seismic events in its proximity.

This article provides a brief description of the expedition work conducted by the staff of the Institute of Volcanology and Seismology, FEB RAS, in the central part of the Eastern Volcanic belt of Kamchatka, and in the Kamchatka River valley in the Summer-Autumn of 2023. In order to study the conditions for the formation and discharge of thermal waters of large volcanic centers, to estimate the hydrothermal discharge of magmatic volatiles (primarily CO2), hydrochemical and gas testing was carried out on the thermal fields of the Kikhpinych and Bolshoi Semyachik volcanic massifs, and in the Uzon caldera. In parallel with geochemical sampling, aerial and infrared photography of thermal sites was carried out. To determine the degree of influence of volcanic and hydrothermal activity on the ion runoff into the Pacific Ocean, hydrochemical and hydrological works were carried out in the Kamchatka Riverv alley. A comprehensive study of unique alkaline cold springs was carried out in the Belaya River valley (Kamchatsky Peninsula). A large number of water and gas samples, sediments and mineral salts were collected for further analytical studies during the expedition works.

It is now generally accepted that large earthquakes can promote eruptions at nearby volcanoes. However, the prevalence of “triggered” eruptions, as well as the distance and timescale over which triggering occurs, remain unclear. Here, we use modern global earthquake and eruption records to compare volcanic eruption rates before and after large earthquakes with the time- averaged background eruption rate. We quantify the significance of observed deviations from the average eruption rate using Monte Carlo simulations. To integrate our findings with previous eruption triggering studies, we systematically vary the earthquake magnitudes we consider, as well as the distances and timescales used to calculate eruption rates. We also investigate the effects of earthquake depth and slip orientation. Overall, we find that post-earthquake eruption rates are around 1.25 times the average eruption rate within 750 km and one year following Mw ≥ 7 earthquakes, with above-average post-earthquake eruption rates possibly lasting for two to four years. By contrast, pre-earthquake eruption rates are around 0.9 times the average eruption rate within 750 km and182 days before Mw ≥7 earthquakes. Furthermore, deep earthquakes (≥7 0km) appear to more strongly affect eruption rates than shallow earthquakes, while earthquake slip orientation is also important. Further study of the relationships reported here represents a good opportunity to improve our understanding of tectono-magmatic relationships.

Enrolment in geology-related courses has declined over the last few decades, in part due to a lack of understanding of the subject and its relevance to contemporary society. Although a popular medium for entertainment, video games also hold significant pedagogical potential to overcome this problem by immersing players in geology-related topics through the portrayal of a broad range of geological disciplines in the medium’s dynamic environments. This paper focuses on volcanology as portrayed in Nintendo’s The Legend of Zelda series’ (1986-present) Death Mountain, a recurring volcanic peak in the franchise. Volcanic features in each game are documented and compared to real-world examples to determine the accuracy of how the volcanism evolves over time across instalments in the series. I argue that the volcanic history of Death Mountain provides a reasonably realistic evolution, beginning with volcanic hazards like rockfalls and lava from an active stratovolcano, and progressing over time to introduce hydrothermal systems. Then, during divergent timelines, Death Mountain’s volcanism shifts to either explosive, shallow-water eruptions or to showing evidence of massive explosive activity. Through this, I argue that the popularity of The Legend of Zelda series and the gradual introduction of volcanic features can be used together to change the perception of geology as “boring” and encourage people to study the subject by offering a fun and immersive means to engage with its content.

In 2002 and 2003 a collaborative effort was undertaken between Lawrence Berkeley National Laboratory, Sandia National Laboratories, the U.S. Geological Survey (USGS) Menlo Park, the USGS Hawaiian Volcano Observatory, and Electromagnetic Instruments Inc. to study the Kīlauea volcano in Hawaii using the magnetotelluric (MT) technique. The work was motivated by a desire to improve understanding of the magma reservoirs and conduits within Kīlauea and the East and Southwest Rift zones, which has implications for understanding Kīlauea's plumbing system. An improved understanding of the rift zones has implications in understanding large-scale landslides that are generated in the Hilina Slump, which produce significant impacts on coastal communities. Up to eight stations operated simultaneously, with multiple remote reference sites, and data were processed using multi-station robust processing techniques. In total, data were acquired at 70 sites over the Southwest and East rift zones. Good to excellent quality data were obtained even in the harshest conditions, such as those encountered on the fresh lava flows of the East Rift Zone, where electrical contact resistances are on the order of 100 kΩ. A three-dimensional (3D) MT model study was done to guide interpretation of the observed MT measurements. Synthetic modeling demonstrates that conductive bodies in the upper 3 km can be spatially resolved where MT station sampling is good. Resistivity anomalies in the 3D inversions have a high degree of spatial correlation with previously published seismic velocity anomalies beneath Kīlauea. Melt fractions between 0.096 and 0.117 are calculated for the Kīlauea and Puʻuʻōʻō low resistivity anomalies, respectively.

The results of field work at the active volcanoes Alaid and Ebeko, located in the northern part of the Kuril Island Arc, carried out in June−July 2023 are described. At Alaid volcano, the first survey of lava flows and fumarolic mineralization products of the 2022 eruption was carried out at various heights, including the summit, and geological sampling of the Taketomi cone and eruptive rocks of the eastern coast of Atlas Island was also conducted. An aerial photo and area temperature survey of the area occupied by the products of the 2022 eruption was undertaken at the summit of Alaid volcano using a high-precision quadrocopter equipped with a thermal imaging camera. At Ebeko volcano, mineral samples were taken from fumarole sites located on its eastern slope, and an aerial photo and area temperature survey were done.

Enrolment in geology-related courses has declined over the last few decades, in part due to a lack of understanding of the subject and its relevance to contemporary society. Although a popular medium for entertainment, video games also hold significant pedagogical potential to overcome this problem by immersing players in geology-related topics through the portrayal of a broad range of geological disciplines in the medium's dynamic environments. This paper focuses on volcanology as portrayed in Nintendo's The Legend of Zelda series' (1986-present) Death Mountain, a recurring volcanic peak in the franchise. Volcanic features in each game are documented and compared to real-world examples to determine the accuracy of how the volcanism evolves over time across instalments in the series. I argue that the volcanic history of Death Mountain provides a reasonably realistic evolution, beginning with volcanic hazards like rockfalls and lava from an active stratovolcano, and progressing over time to introduce hydrothermal systems. Then, during divergent timelines, Death Mountain's volcanism shifts to either explosive, shallow-water eruptions or to showing evidence of massive explosive activity. Through this, I argue that the popularity of The Legend of Zelda series and the gradual introduction of volcanic features can be used together to change the perception of geology as "boring" and encourage people to study the subject by offering a fun and immersive means to engage with its content. [ABSTRACT FROM AUTHOR]

Understanding the processes that initiate volcanic eruptions after periods of quiescence are of paramount importance to interpreting volcano monitoring signals and mitigating volcanic hazards. However, studies of eruption initiation mechanisms are rarely systematically applied to high-risk volcanoes. Studies of erupted materials provide important insight into eruption initiation, as they provide direct insight into the physical and chemical changes that occur in magma reservoirs prior to eruptions, but are also often underutilized. Petrologic and geochemical studies can also constrain the timing of processes involved in eruption initiation, and the time that might be expected to elapse between remote detection of increased activity and eventual eruption. A compilation and analysis of literature data suggests that there are statistical differences in the composition, volume, style and timescales between eruptions initiated by different mechanisms. Knowledge of the processes that initiate eruptions at a given volcano may thus have significant predictive power.

Infrasound data are routinely used to detect and locate volcanic and other explosions, using both arrays and single sensor networks. However, at local distances (

Abstract In the infrasonic observation of a fumarolic field, distinguishing multiple fumarolic sources is challenging. The array technique effectively estimates the source locations and identifies the target signal from other signals and noise. We conducted an experiment at Kirishima Iwo-Yama, Japan, where two active fumarolic areas were separated by ~ 450 m. A three-element array with an aperture of ~ 20 m was installed between the two fumarolic areas. In addition, a single microphone was installed near one of the fumaroles. The array combined with the waveform correlation analysis estimated the most prominent source but failed to estimate the other weak source. A joint analysis of the array and the single microphone effectively resolved the two sources. It was also confirmed that newly developed power-saving MEMS microphones were useful for observing the fumaroles. This paper presents the instrumentation and analytical method that would be beneficial for monitoring volcanoes that have multiple hydrothermally active vents. Graphical Abstract

The hydraulic parameters of porous media, such as porosity (φ) and hydraulic conductivity (K), are the most important factors for planning and managing water exploitation from aquifers. This study aims to estimate the hydraulic conductivity parameters using the geoelectric method on volcanic deposits on the northern slope of Mount Ciremai. For this purpose, four data types were used to estimate K and φ, including lithological profiles, water table, groundwater quality, pumping test data, and vertical electrical sounding (VES). Based on Archie's law and Kozeny's equation, we get the alpha (α) values and cementation factor (m) from which the median values of α = 1.01 and m = 1.36 represent the studied aquifer. The porosity (φ) of the aquifer varies from 0.097 to 0.187 with an average of 0.141 and is spatially related to the hydraulic conductivity (kgm), which varies from 4.97 × 10-6 to 6.75 × 10-5 m/s after the application of Kozeny's equation. The hydraulic conductivity (Kp) calculated from the pumping tests varies from 9.07 × 10-6 to 1.06 × 10-4 m/s and is strongly correlated (r = 0.87). Furthermore, a relation between resistivity and hydraulic conductivity was established for the studied aquifer to estimate these parameters in sites lacking data.

This report presents a brief description of the expeditionary work performed by the staff of the Institute of Volcanology and Seismology, Far Eastern Branch of the Russian Academy of Sciences as part of the research topic and the Russian Science Foundation project on the Kuril Islands in the summer of 2022. In order to study the chemical erosion of volcanic islands and to assess the hydrothermal removal of magmatic volatiles, in addition to the works carried out in 2020 and 2021, hydrological and hydrochemical studies were comducted on the rivers draining the slopes of the volcanic ridges of the Paramushir, Onekotan and Shiashkotan islands. For the first time, with the help of a quadrocopter, sampling of the endorheic Lake Koltsevoe, which occupies the caldera of the Tao-Rusyr volcano (Onekotan Island), was carried out. A detailed hydrochemical testing on the thermal fields of the active volcanoes Sinarka and Kuntomintar (Shiashkotan Island) was performed, a number of regime observations of the Upper Yuryevsk springs (Paramushir Island) were replenished. In order to construct orthophotomaps and determine the boundaries of thermal anomalies, aerial and infrared surveys were carried out at the main study sites in parallel with geochemical sampling. A large number of water and gas samples were taken for further analytical studies during the expedition and the collection of sediments was replenished.

The seismic crisis that began in May, 2018 off the coast of Mayotte announced the onset of a volcanic eruption that started two months later 50 km southeast of the island. This seismicity has since been taken as an indicator of the volcanic and tectonic activity in the area. In response to this activity, a network of stations was deployed on Mayotte over the past three years. We used the machine learning-based method PhaseNet to re-analyze the seismicity recorded on land since March 2019. We detect 50,512 events compared to around 6508 manually picked events between March 2019 and March 2021. We locate them with NonLinLoc and a locally developed 1-D velocity model. While eruptions are often monitored through the analysis of Volcano-Tectonic (VT) seismicity (2–40 Hz), we focus on the lower frequency, Long Period (LP) earthquakes (0.5–5 Hz), which are thought to be more directly related to fluid movement at depth. In Mayotte, the VT events are spread between two clusters, whereas the LP events are all located in a single cluster in the bigger proximal VT cluster, at depths ranging from 25 to 40 km. Moreover, while the VT earthquakes of the proximal cluster occur continuously with no apparent pattern, LP events occur in swarms that last for tens of minutes. We show that during the swarms, LP events generally migrate downward at a speed of 5 m/s. While these events do not appear directly linked to upward fluid migration, their waveform signature could result from propagation through a fluid-rich medium. They occur at a different location than VT earthquakes, also suggesting a different origin which could be linked to the Very Long Period events (VLP) observed above the LP earthquakes in Mayotte.

The volcanoes of Galápagos, Ecuador, are among the most active in the world, with an average of five eruptions per decade. Monitoring and communication of their activity are essential for timely management of events. In this context, the Instituto Geofísico de la Escuela Politécnica Nacional carries out constant surveillance of Galápagos volcanoes using geophysical monitoring, remote sensing, and field campaigns with the support of the Dirección del Parque Nacional Galápagos. Collaborations with national emergency agencies and international scientists have been key to ensuring the protection of the population, economic activities, and endemic fauna of Galápagos. Since 2010, there have been numerous changes in the way volcanic unrest and eruptions are detected and communicated to decision-makers and the general public. This paper summarizes six eruptions and one period of unrest from different Galápagos volcanoes that occurred in the last decade to illustrate and discuss the evolution of surveillance and hazard communication.

The paper reports the appearance of a new crater lake on the Ebeko volcano. There has been no thermal lake within the Northern Crater since mid-2006. The last eruption began on October 19, 2016 and ended on November 19, 2021. The pyroclastic cone of the new crater, which was named Korbut Crater, rose within the Northern Crater. There was strong fumarolic activity in the Korbut crater, which persists today. The lake in the still erupting Korbut crater was first recorded by the authors on a satellite image from September 17, 2021; already on a satellite image from September 25, the crater was dry again. After the end of the Ebeko eruption, due to the intensive flow of fluid with bottom fumaroles and due to a large amount of meteoric precipitation, a lake was formed in the Korbut crater (Sentinel 2 satellite data of December 11, 2021). In January 2022, the authors examined the Korbut crater: the diameters of the lake were 61 and 80 m (latitude and meridian, respectively), the mirror area was 4.5 thousand m2, and water temperature was 43°C. A brief literature review of the existence of thermal lakes on the northern flank of the Ebeko volcano is given.

Gas and particulate matter (PM) emissions from Masaya volcano, Nicaragua, cause substantial regional volcanic air pollution (VAP). We evaluate the suitability of low-cost SO2 and PM sensors for a continuous air-quality network. The network was deployed for six months in five populated areas (4-16 km from crater). The SO2 sensors failed and recorded erroneous values on multiple occasions, likely due to corrosion, requiring significant maintenance commitment. The PM sensors were found to be robust but data required correction for humidity. SO2 measurements could not be used as stand-alone tools to detect occurrence of VAP episodes (VAPE), but SO2/PM correlation reliably achieved this at near-field stations, as confirmed by meteorological forecasts and satellite imagery. Above-background PM concentrations reliably identified VAPE at both near-field and far-field stations. We suggest that a continuous network can be built from a combination of low-cost PM and SO2 sensors with a greater number of PM-only sensors.

Ignimbrites within calderas host intrusions with hazardous and/or economically significant hydrothermal systems. The Hvítserkur ignimbrite at Breiðuvík caldera, north-eastern Iceland, is intruded by basaltic dykes. Our data show that the ignimbrite immediately adjacent to the dyke is hard, dark-coloured, recrystallised quartz, plagioclase, and alkali feldspar with a low permeability and porosity and frequent macrofractures. At 1-2 m from the dyke, the ignimbrite is hard, dominantly glassy with pervasive perlitic microfractures, has high permeability, but low porosity and frequent macrofractures. A narrow zone of pervasive unlithified clay exists 2 m from the dyke. Beyond this, the ignimbrite is soft and zeolite-rich, has low permeability, high porosity and fewer macrofractures. The dyke intrusion promoted a narrow zone of welding, fracturing and perlitisation in the ignimbrite resulting in high permeability and focussed alteration. Our study shows how intrusions and their thermal aureoles create vertical pathways for, and horizontal barriers to, geothermal fluid flow.

Summary: The eruption of the Tonga volcano created globally propagating spherical shockwaves in the atmosphere. Analyses are done to data from two southern U.S. stations of the author sampling at 3–21 s intervals and 189 weather stations at 1–5 min intervals. The shockwaves arrived from two routes in the atmosphere: the shortest spherical arc and the longer spherical arc through the antipole. In most stations, signals up to the 6th path of shockwaves were recorded as the waves traveled around the globe multiple times. The speed of shockwaves is estimated to be 309.5 ± 2.9 m/s, consistent with the speed of sound at the top of the troposphere where a waveguide exists. Discussion is made on the post-shockwave ringing of 4–8 min as higher amplitude oscillations above the level of pre-shockwaves background noise. A theoretical wave dispersion is derived which verifies that the spherical shockwave’s phase speed is the same as the speed of sound.

Volcano Young Sheveluch is one of the most active volcanoes in Kamchatka. Since August 1980 to the present time, an extrusive dome has been growing in the crater of the volcano. Plastic lavas in the form of large ribbons were noted on the dome already in 1980–1981, the first lava flow was observed after a paroxysmal eruption on May 9, 2004. The next large block of lava started to extrude in the end of April – beginning of May 2020. By June, 11th, it rose above the dome on 50–80 m, and up to 120 m by the end of October. On September 28, it was noted that the lava block acquired smooth surfaces. Portions of lava squeezed out from inside of the volcano in August – September were plastic. By December 8, the block had collapsed. In February 2021, a new block of plastic lava began to rise from the destroyed block. In March its height above the dome exceeded 50–60 m, and 200 m in June.

This report gives a brief description of field work on the Kuril Islands in summer 2021 carried out by staff of the Institute of Volcanology and Seismology of FEB RAS within the framework of the Institute research theme and projects of the Russian Science Foundation (RSF) and Russian Fund for Basic Research (RFBR). To study chemical erosion of volcanic islands and to estimate hydrothermal export of magmatic volatiles, hydrological and hydrochemical works were carried out on the rivers draining the slopes and thermal fields of the Baransky volcano and the Bogdan Khmelnitsky volcanic massif (Iturup Island). Detailed hydrochemical studies with water sampling at different depths and a bathymetric survey of Lake Kipyashchey located in the caldera of Golovnin volcano (Kunashir Island) were performed. We also proceeded with studying the CO2 diffusion flux through thermal fields and volcanic lakes. In the course of ongoing regime observations on Ebeko volcano (Paramushir Island), aerial and infrared imaging of its near-crater part was carried out. For the first time since the eruption began in 2016, a quadcopter survey of the lake located in the Srednii (middle) crater of the volcano was conducted. For further analytical studies a large number of water and gas samples were taken, and the collection of sediments was replenished.

Abstract A volcanic eruption transmits both seismic and infrasound signals. The seismo-acoustic power ratio is widely used to investigate the eruption behaviors and the source dynamics. It is often the case that seismic data during an eruption are significantly contaminated or even dominated by ground shaking due to infrasound (air-to-ground signals). To evaluate the contribution of infrasound-originated power in the seismic data, we need a response function of the seismic station to infrasound. It is rare to obtain a seismo-acoustic data set containing only infrasound signals, though it is ideal for calculating the response function. This study proposes a simple way to calculate the response function using seismo-acoustic data containing infrasound and independent seismic waves. The method requires data recorded at a single station and mainly uses the cross-correlation function between the infrasound data and the Hilbert transform of the seismic data. It is tested with data recorded by a station at Kirishima volcano, Japan, of which response function has been constrained. It is shown that the method calculates a proper response function even when the seismic data contain more significant seismic power (or noise) than the air-to-ground signals. The proposed method will be useful in monitoring and understanding eruption behaviors using seismo-acoustic observations.

Abstract Many andesites erupted at arc volcanoes are the products of magma mixing, and this process could be important in triggering their eruption. Throughout the life of Ngauruhoe volcano (∼2.5 ka), erupted andesites lack macroscopic enclaves or lithological features of mingled magma. However, intricate microscopic features of magma mixing and mingling occur. Plagioclase phenocrysts have a wide range of textures. Their diverse 87Sr/86Sr values (0.7039–0.7060) are mostly discordant with the groundmass (∼80%), and many phenocrysts (>40%) are isotopically zoned. Resorbed calcic cores overgrown by sodic rims are common, and record a gradient of increasing 87Sr/86Sr, the result of progressive mixing with a radiogenic melt. Clinopyroxenes and orthopyroxenes have relict cores that nucleated in silicic melts (∼Mg# 30–40), and their rims record cycles of growth in mafic melts (∼Mg# 50–60). Olivine‐bearing, mafic glassy blebs (mostly

This study aims to identify the potential groundwater in Jedong, Malang, East Java. The hydrogeomorphological approach is a suitable approach to describe the relationship between hydrological and geomorphological processes on and below the earth's surface. The survey of geoelectricity complements the hydrogeomorphological approach. It will give a better description of the groundwater conditions below the earth's surface. Based on the research, there are 2 hydrogeomorphological units in the study area, which are: Volcanic Foot Valley Unit and Volcanic Foot Ridge Unit. The best groundwater potential is in Volcanic Foot Valley Hydrogeomorphological unit, namely Awar-awar Valley and Cokro Valley. The valleys are dominated by gully erosion and landslides. They have surface deposits up to a depth of 7 meters, and lots of outcrops of breccia, pumice, and andesite boulders. The valley’s springs discharge between 56 - 198 m3/day. The average infiltration rate in the valley is 1776 mm / hour, with sandy soil material. The best aquifer consisting of sandy material is more than 10 meters in depth, based on the geoelectrical survey. Water in the aquiclude layer, cannot be exploited because it is breccia and tuff material. The Sawah valley cannot be exploited further because the groundwater potential is very low. This can be identified by the thick water outflow seepage. In the Volcanic Foot Ridge Hydrogeomorphological unit, the groundwater potential is also very small. Hydrogeomorphically, water will flow down the slope to the valley. It will reduce the infiltration rate. In general, the ridge area is only used for settlement, while the slopes are used for dryland agriculture. The geoelectric analysis results show that the groundwater potential is at a depth of more than 45 meters. This research’s results show that the combination of the hydrogeomorphological approach and the geoelectric use will provide a better description of the potential groundwater.

Abstract Eastern Indonesia is one of the world’s most complex regions in terms of tsunami hazards, as it accommodates numerous seismic and non-seismic tsunami sources with a history of deadly tsunamis. This study is an effort to enhance tsunami hazard knowledge in eastern Indonesia where limited data and analyses exist. We provide a brief understanding of eastern Indonesia’s tsunami hazards by modelling selected deterministic tsunami scenarios from tectonic, submarine mass failure (SMF), and volcanic sources. To our knowledge, this is the first time that tsunami hazards modelling from such diverse sources in Indonesia has been performed. Our methodology is a deterministic tsunami hazard analysis considering credible tsunami sources from historical and contemporary data, modelling them using state-of-the-art simulation tools. We modelled two Mw7.8 tsunamigenic earthquake scenarios on the Flores back-arc thrust, one rupturing the basal fault (FBT-BF) and the other rupturing the splay fault (FBT-SF), showing that the two scenarios produce maximum tsunami amplitudes of $$\sim$$ ∼ 5.3 m and $$\sim$$ ∼ 4.2 m, respectively, which are comparable to the deadly 1992 Flores tsunami. We modelled potential SMF-generated tsunamis in the Makassar Strait with SMF volumes of 5 $$\hbox {km}^3$$ km 3 and 225 $$\hbox {km}^3$$ km 3 which yielded maximum tsunami heights of $$\sim$$ ∼ 1.1 m and $$\sim$$ ∼ 4.3 m along the eastern coast of Kalimantan Island and $$\sim$$ ∼ 2.9 m and $$\sim$$ ∼ 11.1 m along the west shore of Sulawesi Island, respectively. The 1871 Ruang volcanic tsunami is studied through existing historical documents and a source model is proposed comprising a flank collapse with volume of $$0.10\ \mathrm{km}^3$$ 0.10 km 3 . Such a source model successfully reproduced the 25 m runup reported in a historical account.

Summary: The network of lava tubes is one of the most unexploited natural wonders of the Galapagos Islands. Here, we provide the first morphological, mineralogical, and biogeochemical assessment of speleothems from volcanic caves of the Galapagos to understand their structure, composition, and origin, as well as to identify organic molecules preserved in speleothems. Mineralogical analyses revealed that moonmilk and coralloid speleothems from Bellavista and Royal Palm Caves were composed of calcite, opal-A, and minor amounts of clay minerals. Extracellular polymeric substances, fossilized bacteria, silica microspheres, and cell imprints on siliceous minerals evidenced microbe-mineral interactions and biologically-mediated silica precipitation. Alternating depositional layers between siliceous and carbonate minerals and the detection of biomarkers of surface vegetation and anthropogenic stressors indicated environmental and anthropogenic changes (agriculture, human waste, and cave visits) on these unique underground resources. Stable isotope analysis and Py-GC/MS were key to robustly identify biomarkers, allowing for implementation of future protection policies.

Nisyros Geopark, an island geopark in the Southeastern Aegean Sea, Greece, is here presented as an official candidate for the UNESCO Global Geoparks designation, featuring outstanding geological, natural and cultural characteristics tightly connected to its volcanic origin. It covers a total area of 481 km2 and includes Nisyros, an active volcano and the main island, the surrounding islets of Pachia, Strongyli, Pergousa, Kandeliousa and the marine region among them. It features 24 geosites and a network of well-established walking trails. Furthermore, there are two internationally designated Natura 2000 areas covering its entire surface and also exceptional archaeological and cultural sites, including fortresses, remnants of ancient habituations and numerous churches and monasteries. It is the only area in the broader region of the Eastern Mediterranean that hosts all these features within such a restricted area. The initial efforts of the management body of Nisyros Geopark and its scientific team to promote its unique geodiversity included the complete design, construction and launch of the official website, the mobile application “Nisyros Volcano App’’, a modern informative leaflet regarding the region of the hydrothermal craters (Lakki), a Geopark guidebook and a series of panels and signs for the geosites.

This report provides a brief description of the field work on the Kuril Islands. It was performed within the framework of the R&D theme, projects of the RSF and the RFFR, which are realized in the laboratory of postmagmatic processes of the Institute of Volcanology and Seismology FEB RAS. Hydrological and hydrochemical works were performed on the rivers draining the slopes and thermal fields of the Sinarka, Kuntomintar volcanic massifs (Shiashkotan Island), and the Vernadsky and Karpinsky Ridges (Paramushir Island). The study of the chemical erosion of volcanic islands and the assessment of the hydrothermal export of magmatic volatiles are the goals of this work. Infrared photography was taken and the total flux of volcanic SO2 and diffusion flux of CO2 were measured on thermal fields in the caldera of Golovnin volcano. A detailed hydrogeochemical survey was made on the thermal fields of the Ebeko volcano to study the relationship of volcanic and hydrothermal activity of the volcano. For further analytical work, a large number of water and gas samples were taken and a representative collection of rocks and sediments was collected during the expedition.

The present contribution is based on the methodological approach and on the typical objectives of cultural geography that sees the cultural work as an important source to read the territorial and landscape contexts. Through this paper we then want to critically report about the 1954 short documentary Isole di Fuoco (Islands of Fire), awarded in Cannes, that the director Vittorio De Seta mainly shot on the volcanic island of Stromboli, in Sicily, during an eruption occurred in 1954.

Abstract The GCOM-C (SHIKISAI) satellite was developed to understand the mechanisms of global climate change. The second-generation global imager (SGLI) onboard GCOM-C is an optical sensor observing wavelengths from 380 nm to 12.0 μm in 19 bands. One of the notable features is that the resolution of the 1.63, 10.8, and 12.0 µm bands is 250 m, with an observation frequency of 2–3 days. To investigate the effective use and potential of the 250 m resolution of these SGLI bands in the study of eruptive activities, we analyzed four practical cases. As an example of large-scale effusive activity, we studied the 2018 Kilauea eruption. By analyzing the series of 10.8 μm band images using cumulative thermal anomaly maps, we could observe that the lava effused on the lower East Rift Zone, initially flowed down the southern slope to the sea, and then moved eastward. As an example of lava dome growth and generation of associated pyroclastic flows, the activity at Sheveluch between December 2018 and December 2019 was analyzed. The 1.63 and 10.8 µm bands were shown to be suitable for observing growth of the lava dome and occurrence of pyroclastic flows, respectively. We found that the pyroclastic flows occurred during periods of rapid lava dome expansion. For the study of an active crater lake, the activity of Ijen during 2019 was analyzed. The lake temperature was found to rise rapidly in mid-May and reach 38 °C in mid-June. We also analyzed the intermittent activities of small-scale vulcanian eruptions at Sakurajima in 2019. The 1.63 µm band was useful for detecting activities that are associated with vulcanian eruptions. Analytical results for these case studies demonstrated that the GCOM-C SGLI images are beneficial for observing various aspects of volcanic activity, and their real-time use may contribute to reducing eruption-related disasters.

We produced new multi-temporal Digital Elevation Models (DEMs) of the April 2007 summit collapse at Piton de la Fournaise from previously unused aerial photographs. This dataset revealed the precise temporal evolution of collapsed volume and caldera morphological changes. Four days after the onset of an eruption at an unusually low elevation, the summit started to collapse (20:48 UTC April 5th). During the first 30 hours, collapsing was relatively fast (840 m3 s-1 average), and continued for at least the following 12 days, at a slower rate (46 m3 s-1 average). On April 19th, the collapse reached 96% of its final volume, while the remaining 4% were probably attained by May 1st (end of lava emission at the vent). The post-collapse hydrothermal activity in the caldera is closely associated with the main ring faults evidenced as active during the collapse, which are now preferential paths for fluids to reach the surface.

The paper presents the results of integrated geophysical observations of the Ebeko Volcano’s activity in late 2018 and early 2019. The instrument complex for observation was located at the Severo-Kurilsk seismic station at a distance of 7.2 km far from the volcanic crater. Three types of response in the vertical component of the electric field of the atmosphere have been distinguished during the drift of eruptive clouds from the Ebeko Volcano’s explosions, which gives evidence for various mechanisms of their occurrence. The registration of infrasonic acoustic signals in the near zone made it possible to estimate the trinitrotoluene equivalent for the strongest explosions, which was calculated to be about 100 kg of trinitrotoluene. The authors have revealed certain regularities in the dynamics of the volumetric activity of radon, associated with variations in meteorological values and hydrological features of the registration point. A long period of its activity and the proximity of the observation point to the crater give reason to suggest Ebeko Volcano to be a natural laboratory for studying the mechanisms of eruptions.

Abstract Nishinoshima volcano suddenly resumed eruptive activity in April 2017 after about 1.5 years of dormancy since its previous activity in 2013–2015. Nishinoshima is an uninhabited isolated island. We analyzed the eruption sequence and the eruptive process of the 2017 eruption (17 April–10 August: 116 days) by combining high-temporal-resolution images from Himawari-8 and high-spatial-resolution images from the ALOS-2, Landsat-8, and Pleiades satellites. We used these data to discuss how temporal variations in the lava effusion rate affected the flow formations and topographical features of the effused lava. The total effused volume was estimated to be 1.6 × 107 m3, and the average effusion rate was 1.5 × 105 m3/day (1.7 m3/s). Based on variations in the thermal anomalies in the 1.6-μm band of Himawari-8, which roughly coincided with that of the lava effusion rate estimated by ALOS-2, the activity was segmented into five stages. In Stage 1 (17–30 April: 14 days), the lava effusion rate was the highest, and lava flowed to the west and southwest. Stage 2 (1 May–5 June: 36 days) showed a uniform decrease in flow, and lava flowed to the southwest and formed the southwestern lava delta. During Stage 3 (6–15 June: 10 days), the lava effusion rate increased in a pulsed manner, the flow direction changed from southwestward to westward, and a narrow lava flow effused from the southern slope of the cone. In Stage 4 (16 June–31 July: 46 days), the lava effusion rate decreased and lava flowed westward through lava tubes, enlarging the western lava delta. Around the end of July, lava effusion mostly stopped. Finally, in Stage 5 (1–10 August: 10 days), explosive eruptions occurred sporadically. The variation in lava effusion rate seemed to play an important role in forming different flow patterns of lava on Nishinoshima. In Stages 1 and 3, lava flowed in multiple directions, while in Stages 2 and 4, it flowed in single direction, probably because the effusion rate was lower. A pulsed increase in the lava effusion rate during Stage 3 caused new breaks and disturbances of the lava passages near the vents, which resulted in changes in flow directions. Differences in the size of lava lobes between the southwestern and western deltas are also considered to result from differences in the lava effusion rate.

Abstract Infrasound (low‐frequency acoustic waves) has proven useful to detect and characterize subaerial volcanic activity, but understanding the infrasonic source during sustained eruptions is still an area of active research. Preliminary comparison between acoustic eruption spectra and the jet noise similarity spectra suggests that volcanoes can produce an infrasonic form of jet noise from turbulence. The jet noise similarity spectra, empirically derived from audible laboratory jets, consist of two noise sources: large‐scale turbulence (LST) and fine‐scale turbulence (FST). We fit the similarity spectra quantitatively to eruptions of Mount St. Helens in 2005, Tungurahua in 2006, and Kīlauea in 2018 using nonlinear least squares fitting. By fitting over a wide infrasonic frequency band (0.05–10 Hz) and restricting the peak frequency above 0.15 Hz, we observe a better fit during times of eruption versus non‐eruptive background noise. Fitting smaller overlapping frequency bands highlights changes in the fit of LST and FST spectra, which aligns with observed changes in eruption dynamics. Our results indicate that future quantitative spectral fitting of eruption data will help identify changes in eruption source parameters such as velocity, jet diameter, and ash content which are critical for effective hazard monitoring and response.

Abstract Taupō volcano, New Zealand, is a large caldera volcano that has been highly active through the Holocene. It most recently erupted ∼1,800 years ago but there have been multiple periods of historic volcanic unrest. We use seismological and geodetic analysis to show that in 2019 Taupō underwent a period of unrest characterized by increased seismic activity through multiple swarms and was accompanied by ground deformation within the caldera. The earthquakes, which include non‐double‐couple events, serve to outline an aseismic zone beneath the most recent eruptive vents. This aseismic zone is coincident with an inflating source, based on forward modeling of ground deformation data. We infer that this aseismic and deforming region delineates the location of the present day magma reservoir that is ≥250 km3 in volume and has a melt fraction of >20%–30%, inhibiting seismic activity. Our analysis shows that the 2019 unrest at Taupō was volcanic in nature and origin, demonstrating that this is an active and potentially hazardous volcano, and that improving our monitoring and understanding of its behavior is important.

During extrusive eruptions of andesitic and dacitic volcanoes, in some cases, squeezing of viscous lava was accompanied by the occurrence of «drumbeats» earthquakes. The peculiarities of this earthquake regime are: their close energies, similarity of wave forms, and quasi-periodicity over a long period of time (from several hours to months). The article provides an overview of the micro-earthquakes of the regime «drumbeats» recorded on several volcanoes of our planet during the extrusion of extrusive domes: Redout (the Aleutian Islands), St. Helens (the Cascade Mountains, North America), Soufriere Hills (Montserrat Island, the Lesser Antilles), Pichincha (the Andes, South America). During the eruption of Kizimen Volcano (Kamchatka Peninsula) in 2010–2013 the «drumbeats» mode was observed during the movement of a viscous lava flow. According to the record form, earthquakes of the «drumbeats» regime refer to hybrid or long-period earthquakes, with prevailing frequencies within the range of 0.3–7 Hz.

Temperature can be an important characteristic used to distinguish primary pyroclastic density currents or block-and-ash flows from other collapses not primarily related to an eruption, and also governs the type and level of hazard presented by these mass flows. We examined several mass-flow deposits within the AD1000-1800 Maero Formation at Mt. Taranaki, New Zealand, for field characteristics of hot emplacement - such as the presence of charcoal, baking of soils, or gas-elutriation piping - and conducted a paleomagnetic study of their thermoremanent magnetization (TRM) to determine emplacement temperatures. Results show that the majority of the deposits result from block-and-ash flows emplaced over ~500°C. Some of these deposits were indistinguishable in the field from a re-worked or low-temperature emplaced lahar or landslide deposit, indicating that sedimentary features are not a clear determinant of high emplacement temperature. The high emplacement temperatures suggest that the time between dome emplacement and collapse during this period was usually brief (

Abstract In order to investigate the role of dikes in the volcanic evolution and the triggering mechanisms of catastrophic mass wasting volcanoes, we have sampled for a pilot study, seven dikes within the Wai’anae volcano, Oahu, Hawaii. The width of the dikes ranged between 0.4 and 2.5 m. This work focuses on the characterization of the magma flow directions using anisotropy of magnetic susceptibility (AMS) data in dikes of the inner part of the Wai’anae volcano. This part is now exposed, because this volcano experienced destabilization and flank collapse. Rock magnetism data show composite magnetic mineralogy, corresponding when plotted on the Day diagram to be dominated by single domain (SD) and pseudo-single domain particles of pure titanomagnetite, suggesting possible inverse magnetic fabric associated with the SD grains. The obtained magnetic fabric does not reflect such grain sizes and is probably partly related to the presence of different magnetic phases, resulting in part of our samples as having “abnormal” fabrics. We therefore used a simple criterion to eliminate most of the abnormal fabrics in order to analyze the magnetic fabric data in a clearer way. After rejection of most of the abnormal data, the determination of the magnetic zone axis, which underlines the effect of imbrication in dike margins, yielded reliable magma flow directions in most of the studied dikes, with a predominance of vertical to subvertical AMS directions. The inferred dominantly vertical to subvertical magma flow of dikes (feeding from below) within the most internal parts of the volcano, suggests a process of accumulation of new magma at different levels within the inner part of the edifice. This process was enhanced by subhorizontal magma flow toward the volcano center in two other dikes. Such accumulation helps to explain the inflation, subsequent destabilization, and flank collapse of the Wai’anae volcano.

Abstract Volcanic eruptions bring high-temperature gas or magma to the surface. Therefore, thermal observations of volcanic eruptions can be used to investigate the timeline of eruptive sequences. Eruptive activity includes processes that can change over short periods of time, which is sometimes related to the eruptive mode or the timing of its transitions. If we could observe short-term eruptive processes by detecting thermal changes, this would be beneficial for analyzing the eruptive sequence of volcanoes. Himawari-8 is a meteorological geostationary satellite operating above the equator at a longitude of 140.7°E and carrying a newly developed sensor, the Advanced Himawari Imager (AHI). With its improved performance, the Himawari-8 AHI enables the collection of high-frequency thermal observations that had never been obtained before. However, while observing volcanoes with the AHI, we noticed a frequent thermal anomaly in the nighttime 1.6-µm and 2.3-µm images. Because this anomaly occurred regardless of volcanic activity, it was considered to be a pseudo-thermal anomaly. In-depth examination of the AHI observation data for several inactive volcanoes showed that the pseudo-thermal anomaly was often seen around the vernal and autumn eclipse periods, and its influence persisted for about 6 months of each year. Further, daily variation of the anomaly peaked when it was midnight in the areas around 140°E. At this time and position, the AHI was facing the sun, suggesting that the anomaly was caused by stray light. We devised a correction method by assuming that the observed thermal radiance in a pixel consists of components from the radiating volcanic ground surface and stray light contamination. The latter can be estimated using values from nearby inactive pixels. Thus, the component from the radiating volcanic ground surface can be obtained by subtracting the estimated stray light from the observed thermal radiance. We evaluated the validity of this method using data from the 2017 Nishinoshima eruption and found that it satisfactorily removed the stray light component. An adoption of this correction allowed us to use all nighttime 1.6-µm and 2.3-µm images obtained by the AHI, half of which were formerly unusable due to the degradation caused by stray light.

Geothermal monitoring is an effective tool for predicting volcanic eruptions, as well as for assessing the geothermal energy potential of geothermal areas. Increased magmatic activity, an indicator of which is the penetration of hot volcanic gases through faults, has been observed in recent years on the Elbrus volcano. Since Elbrus is a year-round resort of world importance, in order to control volcanic and seismic activity, forecast and reduce the risks of eruption and earthquakes, it is recommended to drill a observation well on the slope of Elbrus with the installation of an underground fiber-optic system for temperature and pressure monitoring. In combination with microseismic, gravimetric and inclinometric observations, satellite IR imaging and geochemical gas testing, the continuously obtained information on the thermodynamic conditions of the subsoil will provide a reliable complex for the operational forecast of natural geophysical disasters. Utilization of the geothermal energy of the magma chamber in the artificial circulation systems of small GeoPPs, water injection from the surface and obtaining superheated water and steam from producing wells will reduce the risks of eruption and at the same time provide the resort with environmentally friendly thermal and electric power. Technological justification for the construction of a GeoPP will also require exploratory drilling to the area of ​​hot rocks, therefore information on the distribution of temperature and pressure along the wellbore is doubly valuable. In geothermal fields that are under development, to assess the spatial heterogeneity of the filtration characteristics can be a useful method of “thermal interference testing” – as a complement or alternative to hydrodynamic interference testing. It is recommended to conduct such an experiment at the North Mutnovsky geothermal field.

Abstract Abundant seismicity beneath the Island of Hawai‘i from mantle depths to the surface plays a central role in understanding how volcanoes work, grow, and evolve at this intraplate oceanic hotspot. We perform systematic waveform cross‐correlation, cluster analysis, and relative relocation of 347,445 events representing 32 years of seismicity on and around the island from 1986 to 2018. We successfully relocate 275,009 (79%) events using ∼1.7 billion differential times (P and S) from ∼128 million similar‐event pairs. The results reveal a dramatic sharpening of seismicity along faults, streaks, rings, rift zones, magma pathways, and mantle fault zones; seismicity delineating crustal detachments on the flanks of Kīlauea and Mauna Loa is particularly well‐resolved. The resulting high‐precision spatio‐temporal image of seismicity captures almost the entire 1983–2018 Pu‘u ‘Ō‘ō‐Kūpaianaha eruption of Kīlauea with its numerous distinct episodes and wide‐ranging activity, culminating in the 2018 lower East Rift Zone eruption and summit collapse.

The Euganean Hills (NE Italy) magmatic district represents the final volcanic activity of the Veneto Volcanic Province. Alkaline to subalkaline magmatic suite dominated by intermediate to felsic volcanic rocks characterises the latest volcanic activity of the Euganean Hills. Magmatic (intrusive and volcanic) enclaves are common in Euganean Hills trachytes. We used the ability of clinopyroxene to record variations of P, T, and fO2 to reconstruct the geological history of the volcanic enclaves and trachytic host. Despite similar major and trace elements composition, clinopyroxene from host is higher in Ca and Na (and Fe3+) and lower in Mg than enclaves and is slightly enriched in trace elements but with the same pattern distribution. Minor differences in geochemistry and crystal structure of clinopyroxene from enclaves and trachytic host suggest similar parental magmas that differs by small degrees of fractional crystallisation. Clinopyroxene geobarometry performed combining X-ray diffraction with mineral geochemistry for volcanic enclaves–trachytic host combined with amphibole geobarometry for intrusive enclaves and crystal mushes points to a crystallisation pressure range between 4.8–2.0 kbars. Our data support the model of a complex system of magma chambers at intermediate to shallow crustal level where mafic magma accumulated, evolved by fractionation processes and mixed.

Abstract Prolonged volcanic activity can induce surface weathering and hydrothermal alteration that is a primary control on edifice instability, posing a complex hazard with its challenges to accurately forecast and mitigate. This study uses a frequently active composite volcano, Mt Ruapehu, New Zealand, to develop a conceptual model of surface weathering and hydrothermal alteration applicable to long‐lived composite volcanoes. The alteration on Mt Ruapehu was classified using ground samples as non‐altered, supergene argillic, intermediate argillic, and advanced argillic. The first two classes have a paragenesis that is consistent with surficial infiltration and circulation of low‐temperature (

Abstract Changbaishan/Paektu volcano straddles the border between the Democratic People's Republic of Korea and China. It was responsible for one of the largest eruptions in history, the “Millennium Eruption' of 946 CE. An episode of unrest between 2002 and 2005, characterized by inflation and seismicity, refocused attention on this volcano. While satellite remote sensing has provided synoptic observations, ground‐based surveillance has hitherto supported only disparate analyses and geophysical interpretations on either side of the border. Here, we derive receiver functions using seismic records from both Democratic People's Republic of Korea and China. H‐κ stacking indicates thick crust (up to 40 km) and high average crustal VP/VS (up to 1.93) beneath the volcano. Grid search inversions constrain a significant velocity reduction at 4–8 km depth (below sea level), and harmonic analysis suggests this dips away from the volcano, with shallowest depths centered beneath the volcano. Common conversion point migrations show that this anomaly extends ∼30 km from the volcano summit and possibly as far as neighboring volcanoes. The colocation of the velocity reduction with a zone of high‐conductivity, low‐velocity, and low‐density material at the depth of the inflation source implicated in the 2002–2005 unrest indicates that partial melt is present directly beneath Changbaishan/Paektu, likely recharged during the episode of unrest. Our study highlights the importance of continued surveillance of the volcano and the need for further geophysical studies to constrain more fully the triggers for unrest and controls on its evolution.

Abstract Volcanic activity involves processes that can change over short periods of time, which are sometimes closely related to the eruptive mode or the timing of its transitions. Eruptions bring high-temperature magma or gas to the surface; thermal observations of these eruptions can be used to determine the timeline of eruptive sequences or eruptive processes. In 2014, a new-generation meteorological satellite, Himawari-8, which carried a new sensor, the Advanced Himawari Imager (AHI), was launched. The AHI makes high-frequency infrared observations at a spatial resolution of 2 km during 10-min observation cycles. We analyzed an effusive eruption that occurred in 2015 at Mt Raung in Indonesia using these AHI images, which was the first attempt applying them to volcanological study. Based on the detailed analysis of the time-series variations in its thermal anomalies, this eruptive sequence was segmented into a Precursory Stage, Pulse 1, Pulse 2 and a Terminal Stage. Pulses 1 and 2 are effusive stages that exhibited a consecutive two-pulse pattern in their variations, reflecting changes in the lava effusion rate; the other stages are non-effusive. We were also able to determine the exact times of the onset and reactivation of lava flow effusion, as well as the precursory signals that preceded these events.