Search

The Sheveluch volcano is the most active volcano in Kamchatka. The paroxysmal explosive eruption of the volcano that destroyed the lava dome in the volcanic crater continued on April 10–13, 2023. According to various satellite data, the height of the separate eruptive clouds probably exceeded 15 km above sea level. A powerful cyclone, which dominated the entire Kamchatka Peninsula, pulled the eruptive cloud to the west, turned it to the south, stretched it to the north, and directed it to the east from the volcano. The dynamics of the development of ash and aerosol clouds of this eruption is reflected in the animations made from a series of Himawari-9 satellite images in the VolSatView IS from 08:00 UTC on April 10 to 07:00 UTC on April 14 (http://d33.infospace.ru/jr%5fd33/materials/2023v20n2/283-291/1683110898.webm) and of the Arctica-M1 satellite from 16:00 to 21:30 UTC on April 10 (http://d33.infospace.ru/jr%5fd33/materials/2023v20n2/283-291/1683821166.webm). It was noted that the eruptive column was not vertical: for example, at the initial moment of the eruption on April 10 at 13:20 UTC, it deviated to the north–northeast; on April 11, at 12:00 UTC to the northwest; and, on April 12, at 7:00 UTC to the southwest. During the paroxysmal eruption, sulfur dioxide continuously entered the atmosphere, the maximum amount of which was released on April 10–11, as a result of the explosive destruction of the lava dome of the Sheveluch volcano. Ash clouds along with aerosol clouds on April 10–13 were stretched into a strip more than 3500 km long from west to northeast. On April 21–22, the Sheveluch aerosol cloud was observed in the region of the Scandinavian Peninsula. The total area of the territory of Kamchatka and the Pacific Ocean where ash and aerosol plumes and clouds were observed during the April 10–13 eruption was about 3 280 000 km2. The paroxysmal eruption of Sheveluch volcano belongs to the sub-Plinian type because it is characterized by a large height of the eruptive cloud and a long event duration. For this eruption, the Volcanic Explosivity Index is estimated to be 3–4. A detailed description of the paroxysmal explosive eruption of the Sheveluch volcano and the spread of the eruptive cloud was performed based on data from various satellite systems (Himawari-9, NOAA-18/19, GOES-18, Terra, Aqua, JPSS-1, Suomi NPP, Arctica-M1, etc.) in the information system "Remote Monitoring of Kamchatka and Kuril Islands Volcanic Activity" (VolSatView, http://kamchatka.volcanoes.smislab.ru). [ABSTRACT FROM AUTHOR]

Interactions between volcanoes and glaciers provide insight to the evolution of a volcanic edifice and may be an indicator for renewed volcanic activity. At Mount St. Helens, Crater Glacier, which has formed in the volcanic crater after the eruption in 1980, is one of the world's last expanding glaciers and provides a unique opportunity to characterize the evolution of a glacier expanding onto an area of significant thermal flux. We combine photographic documentation and glaciovolcanic cave surveys with remote sensing data from Google Earth, UAS, and LiDAR to analyze the present state of Crater Glacier and reconstruct its development since the emplacement of the 2004–2008 lava dome. Our results show that snow accumulation has caused Crater Glacier to grow from 2009 to 2019 by approximately 13.8 × 106 m3, during which time the glacier toe advanced by several hundred meters. The glacier-dome interface shift toward higher elevations against the 2004–2008 lava dome and subsequent encroachment onto thermally active areas led to glacier modification via extensive subglacial cave system formation. Analysis of subglacial tephra layers revealed the existence of juvenile material from the 2004–2008 eruption cycle, providing insights about glacier subsidence of ~ 40 m since 2004/2005 in spite of net growth. Although the lava dome is cooling, the glacier-dome interface seems to have become increasingly stable in the past few years. Our results suggest that glacier development in the accumulation area adjacent to the dome is now being affected by the thermal characteristics of the lava dome itself, making monitoring internal glacier development via tracking glaciovolcanic cave expansion a potentially important volcano monitoring tool. [ABSTRACT FROM AUTHOR]

Spatial approaches, based on the deformation measurement of volcanic domes and crater rims, is key in evaluating the activity of a volcano, such as Merapi Volcano, where associated disaster risk regularly takes lives. Within this framework, this study aims to detect localized topographic change in the summit area that has occurred concomitantly with the dome growth and explosion reported. The methodology was focused on two sets of data, one LiDAR-based dataset from 2012 and one UAV dataset from 2014. The results show that during the period 2012–2014, the crater walls were 100–120 m above the crater floor at its maximum (from the north to the east–southeast sector), while the west and north sectors present a topographic range of 40–80 m. During the period 2012–2014, the evolution of the crater rim around the dome was generally stable (no large collapse). The opening of a new vent on the surface of the dome has displaced an equivalent volume of 2.04 × 104 m3, corresponding to a maximum −9 m (+/−0.9 m) vertically. The exploded material has partly fallen within the crater, increasing the accumulated loose material while leaving "hollows" where the vents are located, although the potential presence of debris inside these vents made it difficult to determine the exact size of these openings. Despite a measure of the error from the two DEMs, adding a previously published dataset shows further discrepancies, suggesting that there is also a technical need to develop point-cloud technologies for active volcanic craters. [ABSTRACT FROM AUTHOR]

Understanding the stress evolution of extinct volcanoes can improve efforts to forecast flank eruptions on active systems. Field, petrographic, and seismic data are combined with numerical modeling to investigate the paleo‐stress field of New Zealand's Akaroa Volcano, or Akaroa Volcanic Complex. Field mapping identifies 86 radially oriented dikes and seven lava domes found only within a narrow elevation range along Akaroa's erosional crater rim. These observations suggest that crater rim dike emplacement resulted from lateral deflection of vertically ascending intrusions from a centralized magma source, which in turn may have facilitated formation of the lava domes, as well as two scoria cones. We postulate that dike deflection occurred along a stress barrier, as neither a compositional change nor structural boundary are present. We use a finite element model (FEM) simulating Akaroa to test how different factors may have influenced the system's stress state and dike geometry. Elastic, non‐flexural ("roller") model configurations containing a large, oblate, and shallow magma chamber produce stress barriers most conducive to radial dike emplacement along Akaroa's crater rim. These configurations also simulate rapid edifice construction above a preexisting lithospheric "bulge." Conversely, simulating flexural stresses exerted on the lithosphere by Akaroa's large mass hinder rather than promote radial dike emplacement. Temperature‐dependent viscoelastic relaxation promotes gradual increases in stress barrier elevation, though this effect is strongly dependent on magma chamber parameters. These results suggest that Akaroa was constructed rapidly (within ∼100 kyr) prior to crater rim dike emplacement, which occurred throughout the volcano's remaining active lifespan. Plain Language Summary: Fully understanding how magma moves within active volcanoes requires scientists to study solidified remnants of once‐molten magma "plumbing systems" that have been unearthed by the erosion of extinct (i.e., no longer active) volcanoes. Here we present new observations of New Zealand's Akaroa Volcano, an extinct volcanic mountain or "edifice" built from lava eruptions and underground magma movement that occurred in multiple regions rather than one central summit vent. Observations include on‐the‐ground measurements of rock formations, microscope analysis of rock samples, satellite‐derived elevation data, and underground properties inferred from earthquake‐generated seismic waves. We incorporate these observations into a computer model of the once‐active volcano to understand why magma followed the paths it did, erupting on Akaroa's sides, or flanks, rather than its central summit region. Based on the results of our computer model, these eruptions occurred throughout Akaroa's one‐million‐year lifespan, after the volcano itself was constructed in the geologically "brief" period of roughly 100,000 years. Our computer simulations also provide a framework for improving scientists' assessments of future eruption risks on the slopes of active volcanoes with a similar shape and chemical composition to Akaroa, such as Sicily's Mt. Etna or the Galapagos' Fernandina volcano. Key Points: Field, petrographic, and seismic observations constrain the formation of dikes, lava domes and scoria cones on Akaroa Volcano's crater rimTwo‐dimensional axisymmetric finite element model (FEM) indicates a stress barrier may have promoted radial dike emplacement along Akaroa's crater rimOptimal stress barriers occur in elastic, non‐flexural FEMs with large, shallow, oblate chamber and edifice rapidly built on inclined bulge [ABSTRACT FROM AUTHOR]

Mount St. Helens, one of the highest-risk volcanoes in the Cascade Volcanic Arc, hosts a novel system of glaciovolcanic caves that has formed around the 2004-2008 lava dome. From 2014 to 2021 a multidisciplinary research team systematically explored and mapped these new caves to ascertain their characteristics. Air and fumarole temperatures, volume flow rates, and wind regimes were also monitored. More than 3.0 km of cave passages have formed in a semicircular pattern in the volcanic crater and provide an opportunity to (1) observe cave development over time, (2) identify low temperature fumaroles as the main driving force for cave formation, (3) verify the impact of seasonal snow accumulation on cave climate, and (4) assess heat distribution in subglacial and subaerial portions of the new lava dome. Glaciovolcanic cave systems on Mount St. Helens are comparatively young (<10 years) and the most dynamic in the Pacific Northwest. Observed cave expansion during the study suggests ongoing genesis and future formation of interconnected systems. However, further expansion may also be limited by increasing fumarole temperatures towards the upper parts of the lava dome, cave instability due to snow overload, or variable subglacial volcanic heat output. New glaciovolcanic cave system development provides a unique barometer of volcanic activity on glacier-mantled volcanoes and to study the subglacial environment. We present the results of eight years of initial study within this dynamic cave system, and discuss a pathway towards future longitudinal analyses. [ABSTRACT FROM AUTHOR]

• First detailed mapping of the hidden active crater of Lascar volcano by UAS. • Topographical changes of the active crater quantified by DEM of difference analysis. • Thermal orthomosaic helps to determine thermal anomalies and fumaroles. • Nested ring structures have been identified on the crater floor. • Ring structures imply a narrow conduit top less than 40 m in diameter. Details of ongoing changes in geomorphology and structure of nested volcanic craters are lacking due to the difficult and hazardous access. In this study, we present a novel unoccupied aircraft system (UAS) dataset collected at Lascar, northern Chile, one of the most active volcanoes in the Central Volcanic Zone of the Andes. Lascar features nested craters, the deepest crater of which has experienced repeated lava dome emplacement and numerous violent explosions in recent decades. We performed UAS surveys in 2017 and 2020 to collect the optical and thermal imaging data of the active crater. By applying the Structure-from-Motion (SfM) method, we obtained centimeter-scale optical and thermal orthomosaics as well as digital terrain models. We quantify the spatial and volumetric changes that occurred during the observation period. The results show material removal from the crater wall and a significant accumulation of volcanic material on the crater floor. The thermal orthomosaic helps identify thermal anomalies and the spatial distribution of fumaroles. The highest thermal anomaly was found on the crater floor and delimited by ring structures. Both the optical orthomosaics and DEMs from 2017 and 2020 showed a consistent ring structure, which remained stable following two explosive events. Possible localized subsidence was observed within the ring structure. Consequently, we hypothesize that the ring structure represents the surface expression of underlying concentric fracture systems and constrains a narrow conduit top. Our results provide important insights into an active crater's morphological, structural, and thermal features, with implications for understanding the formation mechanism and evolution of volcanic craters. [ABSTRACT FROM AUTHOR]

The seismic signatures, recorded during transition from passive degassing to slow growth of a new lava dome in January–February 2016 at Volcán de Colima, gave us the information allowing reconstruct this process. The study is based on seismic data collected by the seismic network of Colima University (RESCO). Processing of seismic signals was performed using the unfiltered records of vertical component of digital broadband station EZ5 situated at a distance of 4 km from the crater. Two types of seismic signals, with explosions followed by pyroclastic flows and incandescent rockfalls (PFIRs) (type 1) and without PFIRs (type 2), define the vent-clearing and a dome growing processes. Totally were selected 154 seismic signals which represented these two types of waveforms. Events of type 1 dominated during January and the first days of February. Events of type 2 began to appear actively beginning from 4 to 6 February. The process, generating Vulcanian explosions and corresponding seismic signals, is considered to follow two-stage conceptual model which consists of the ascent of fragmented magma to the surface (stage 1), and a subsequent explosion (stage 2). Explosive waveforms of the events of both types demonstrated the similarity in the range of seismic energy of the explosive phases and their spectral frequency. Similarity in distributions of durations of the phases, corresponding to the depths of initial ascent of fragmented magma to the surface before explosion, indicated the generation of both types of explosions at the same fragmentation zone within the conduit. Existence of two-phase and three-phase explosive waveforms showed the complex collection of the magma bubbles within fragmentation zone. It was noted a tendency of decreasing of the spectral amplitudes of PFIR signals in time during the period of study, which illustrated the development of the vent-clearing process and defined the period of a birth of new lava dome in the crater of volcano. Initial growth of a new lava dome may be considered within the time interval from 4 to 6 to 24 February, during a break in a vent-clearing process. The full filling of the crater with magma continued for about 8 months. • Seismic signals, produced by explosions during two months of transition from passive degassing to the lava dome growth were analyzed. • Two types of seismic signals, with explosions followed by PFIRs (type 1) and without PFIRs (type 2) were recorded. • Type 1 events were associated with vent-clearing process before the lava dome growth. • Waveforms of both types of events demonstrated the similarity in the range of seismic energy of the main phases and their spectral frequency. • Tendency of decreasing of the spectral amplitudes of PFIR signals of the events of type 1 during the total period of study was noted. [ABSTRACT FROM AUTHOR]

Shallow, implosive non-double-couple (NDC) earthquakes have been detected beneath Unzen Volcano, Japan, by a routinely operated seismometer network. Here, we analyze the waveforms from 14 temporary seismic stations around Mt. Fugen (Fugendake) and Heisei-Shinzan Lava Dome, which formed during the 1990–1995 eruptions, to further investigate this shallow seismicity. We also estimate the subsurface electrical resistivity structure using broadband magnetotelluric observations and investigate its relationship to the shallow seismicity. We find that (1) implosive NDC earthquakes occur at the craters that were active during the 1990–1991 eruptions, which are currently buried by the approximately 200-m-thick Heisei-Shinzan Lava Dome; (2) the detected NDC earthquakes generally possess downward P-wave arrivals, although upward P-wave arrivals are observed at a few seismic stations; (3) the tensile axes of the NDC earthquakes show various slip directions; (4) repeated NDC earthquakes are in some cases detected within 20 s of the initial event; and (5) a high-resistivity zone exists beneath the NDC earthquakes. We conclude that the implosive NDC earthquakes were generated by the collapse of small, randomly oriented, vapor-filled voids at the two buried craters, with active volcanic conduits still present beneath these craters. The shallow DC earthquakes consist of two clusters that are located 2–3 km below the NDC earthquakes. The focal mechanisms of the shallower cluster (approximately 2 km depth) indicate various fault mechanism, whereas those of the deeper cluster (approximately 3 km depth) indicate strike-slip faulting. The top of the shallower cluster corresponds to the base of the conductive zone, which suggests that the DC earthquakes in the shallower cluster are generated in a zone of high pore pressure that is capped by a hydrothermally altered clay layer. • Implosive non-double-couple (NDC) earthquakes occur at buried volcanic craters. • A high-resistivity zone exists beneath the NDC earthquakes. • NDC earthquakes are generated by void collapse above active volcanic conduits. • DC earthquakes occur 2–3 km beneath the NDC earthquakes. • High-pore-pressure zone capped by a clay layer generates shallower DC earthquakes. [ABSTRACT FROM AUTHOR]

On 21 December 1994, Popocatépetl volcano reawakened after about 70 years of dormancy with a series of phreatic explosions. Considering that the eruptive history of Popocatépetl volcano indicates that past activity has included major Plinian phases, great concern raised about the possible outcomes of that activity. This prompted the implementation of seismic, geodetic and visual monitoring devices, and a hydrogeochemical follow-up of water samples collected at different sites near the volcano. On March 1996 the first lava dome of a series of at least 40 distinct episodes of dome emplacement and further destruction that continue to the present was confirmed growing on the crater floor. A main feature of this succession is that it has developed as a process showing regimes of high and low emplacement and lava production rates alternating around a long term mean. Another feature of the ongoing eruption is the spatial distribution of the volcano-tectonic (VT) seismicity which has concentrated in two regions since the earliest stages of the activity, one below the crater, and other beneath the SE sector of the volcano. The latter activity is probably related to predominately normal faulting in that sector, associated to the NE–SW direction of maximum distention stress that may have caused sector collapses in the past. Here, we focus on the role of boron as one of the key hydrogeochemical indicators of the volcanic activity level. Since 1996, water samples have been systematically collected from 6 springs and one well located at distances between 14 and 35 km from the volcano crater. All sites are located in the southern sector of Popocatépetl, since no permanent springs could be found on the northern sector. Routine chemical analyses include spectrophotometrical determination of boron concentration. The analysis of the dome emplacement series and boron concentrations reveals that higher concentrations of boron in spring waters occur mostly during the periods of low dome emplacement and lava production rates. This may be interpreted as a reduced diffusion of volcanic gases into the crustal rocks surrounding the volcano in periods of open conduit activity. In addition, the springs located in the region of higher volcano-tectonic activity, in the SE sector of the volcano show the highest boron concentrations, suggesting increased volcanic gas transport in the fractured crust of that sector. In conclusion, boron dissolved in spring waters is a relevant indicator of the level of volcanic activity even in samples collected in populated areas at considerable distances of the active crater. [ABSTRACT FROM AUTHOR]