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This work reports on data on a moderate effusive-explosive eruption of a summit crater of Alaid volcano (Atlasova Island, Northern Kuril Islands) observed from September 10 to December 1, 2022. Based on satellite and visual data, it was determined that the strombolian-vulcanian activity resulted in two lava flows, 2.6- and 1-km long, that outflowed onto the southern slope of the volcano and at least 16 emissions occurred to heights of 2.5 to 6 km a.s.l. The ash plumes spread out mainly in the southeast and east-southeast directions with their maximum length reaching 300–530 km. The eruption posed a danger to local airlines. The lava outflow provoked the formation of lahars that descended along the southern slope of the volcano and reached the island coast. The alluvial fan formed from mudflow masses partially deposited beyond the coastline, causing accretion of the island land. [ABSTRACT FROM AUTHOR]

Stromboli is an open-conduit active volcano located in the southern Tyrrhenian Sea and is the easternmost island of the Aeolian Archipelago. It is known as "the lighthouse of the Mediterranean" for its continuous and mild Strombolian-type explosive activity, occurring at the summit craters. Sometimes the volcano undergoes more intense explosions, called "major explosions" if they affect just the summit above 500 m a.s.l. or "paroxysms" if the whole island is threatened. Effusive eruptions are less frequent, normally occurring every 3–5 years, and may be accompanied or preceded by landslides, crater collapses and tsunamis. Given the small size of the island (maximum diameter of 5 km, NE–SW) and the consequent proximity of the inhabited areas to the active craters (maximum distance 2.5 km), it is of paramount importance to use all available information to forecast the volcano's eruptive activity. The availability of a detailed record of the volcano's eruptive activity spanning some centuries has prompted evaluations on its possible short-term evolution. The aim of this paper is to present some statistical insights on the eruptive activity at Stromboli using a catalogue dating back to 1879 and reviewed for the events during the last two decades. Our results confirm the recent trend of a significant increase in major explosions, small lava flows and summit crater collapses at the volcano, and might help monitoring research institutions and stakeholders to evaluate volcanic hazards from eruptive activity at this and possibly other open-vent active basaltic volcanoes. [ABSTRACT FROM AUTHOR]

The topographic fabric of the rift valley floor has been analyzed using the multibeam echosounder data obtained by the autonomous underwater vehicle (AUV) Abyss at two locations over a short segment of the slow-spreading Central Indian Ridge between 10°18′ and 10°57′S. The region is influenced by hydrothermal venting in the near vicinity. Two AUV dives D51 and D52 were performed over this segment at two locations that are 30 km apart and covered 5 km2 and 8 km2 seafloor area, respectively. The dive D51 covered the off-axis part of the rift valley floor in the middle part of the segment, and the dive D52 is located near to the non-transform discontinuity that covered the terminal part of an oceanic core complex (OCC). High-resolution seafloor topography as revealed by the AUV-mounted multibeam echosounder system brought out several micro-bathymetric fabric features such as a lava lake, a cratered volcano, an OCC, and the foot wall volcanic complex at the distal part of the OCC. The valley floor imaged in the D51 is marked by a lava flow encompassing an area of 1 km2 and a volcano in the NE corner. The volcano has a diameter of about 800 m with an elevation of about 200 m from the adjacent seafloor, and the partially mapped volcano crater has a relief of about 60 m. A prominent linear fissure running parallel to the ridge axis has been identified; this feature joins with the volcano. Analysis of AUV-mounted CTD data indicated three distinct temperature spikes ranging 0.009 to 0.013 °C in the region of dive D51. The observed temperature spikes appear to be related to the linear fissure on the seafloor and probably represent leaky venting of fluids from the fissure. With respect to the dive D52, the foot wall volcanic features associated with the OCC are prominent. The volcanic seafloor feature covered an area of 3.45 km2 and is conspicuous with rugged topographic fabric at the base of the OCC. These inferences and the morphotectonics of the rift valley floor as revealed by the AUV data suggest moderate hydrothermal venting in this segment of the slow-spreading Central Indian Ridge. [ABSTRACT FROM AUTHOR]

In December 2018, Mount Etna (Italy) experienced a period of increased eruptive activity that culminated in a fissure eruption on the southeast flank. After the onset of the flank eruption, the peak frequency of the summit infrasound signals decreased while resonance increased. We invert infrasound observations for crater geometry and show that crater depth and radius increased during the eruption, which suggests that the flank eruption drained magma from the summit and that eruptive activity led to erosion of the crater wall. By inverting the entire infrasound amplitude spectra rather than just the peak frequency, we are able to place additional constraints on the crater geometry and invert for, rather than assume, the crater shape. This work illustrates how harmonic infrasound observations can be used to obtain high‐temporal‐resolution information about crater geometry and can place constraints on complex processes occurring in the inaccessible crater region during eruptive activity. Plain Language Summary: Volcanoes generate low‐frequency sound waves in the atmosphere (infrasound) that can be recorded by specialized microphones. Much like giant musical instruments, the character of the sound can depend upon the shape and size of the crater. Mount Etna erupted in December 2018 with lava flowing out a fissure on the flank of the volcano. The character of the sound changed after the flank eruption. We study the change in the character of the sound in order to estimate how the shape of the volcanic crater at the summit of Mount Etna changed. Our results show that the crater got deeper and wider, which suggests that the eruption of lava on the flank of the volcano drained magma from the summit area. This work shows how infrasound observations can track changes in crater geometry and provide insight about the magma plumbing systems beneath volcanoes. Key Points: Eruptive activity at Mount Etna's summit generated harmonic infrasound signals due to crater resonancePeak frequency of infrasound signal decreased and resonance increased after fissure eruption on flankInfrasound amplitude spectra can be inverted for crater shape and used to track changes in morphology [ABSTRACT FROM AUTHOR]

Sunset Crater volcano, located ~25 km northeast of downtown Flagstaff (Arizona, USA) in the San Francisco volcanic field, represents an interesting case of highly explosive monogenetic volcanism. Sunset Crater is a young (ca. 1085 CE) scoria cone, ~290 m high, that produced 0.52 km³ dense rock equivalent (DRE) of basaltic magma (0.16, 0.12, and 0.24 km³ DRE for the scoria cone, lava flows, and tephra deposit, respectively). The activity developed in three distinct phases: an initial fissure phase, followed by a highly explosive phase, and a final low-explosivity waning phase. The first phase was characterized by the opening of a 10-kmlong fissure, which produced the Gyp Crater spatter mounds and the Vent 512 lava flow ~10 km SE of the main scoria cone, followed by lava fountaining activity that produced the first tephra layer (unit 1, 0.01 km³ DRE). During the second highly explosive phase, the activity migrated to the northwest to evolve into a single-vent eruption, which formed the main scoria cone. The central vent activity was initially characterized by variable eruptive styles, which started the process of cone building, including deposition of a second tephra layer (unit 2, 0.01 km³ DRE), and the effusion of the two main lava flows (Bonito and Kana'a). Following the initiation of effusive activity, the eruption increased in explosivity to produce three subplinian tephra layers from the central vent (units 3, 4, and 5), which emitted more than 0.22 km³ DRE of basalt, with associated eruption columns >20 km high. By the end of this phase, the Kana'a lava flow was almost completely emplaced, but the Bonito flow continued to grow, forming a 3-km-diameter flow field. A final waning phase produced several tephra units, commonly discontinuous and reworked, with <0.01 km3 DRE cumulative volume. The comparatively large volume of tephra, the high eruptive columns, and high mass eruption rates make Sunset Crater the most explosive monogenetic eruption studied to date (volcano explosivity index [VEI] 3-4). Sunset Crater volcano represents an interesting case of monogenetic volcanism in that its activity was characterized by highly explosive eruptive phases up to subplinian in scale and intermittent episodes of lava effusion that heavily affected prehistoric communities in the area. Explosive basaltic volcanism should be considered when assessing volcanic hazards in continental settings, such as in the western United States. [ABSTRACT FROM AUTHOR]

Mafic to intermediate shield volcanoes with multi-cubic-kilometer eruptive volumes are common in the Cascades Volcanic Arc, but little is known about their eruptive histories as either singular or sustained episodes, or the total time required for their construction. Paleomagnetic data were collected from the lava flows of Ash Creek Butte (17 sites) and Crater Mountain (14 sites) in northern California; both volcanoes are large shields with total volumes of ∼11 km3 each. Tightly clustered paleomagnetic results at both volcanoes, when coupled with analysis of geomagnetic secular variation, suggest that each edifice was built in only a few centuries, possibly in as little time as 50–90 years, indicating sub-century to century scale eruptive durations for two sizeable regional shield volcanoes within the Cascades Arc. These rapidly built shield volcanoes are substantially larger than typically defined monogenetic volcanoes, yet both are wholly formed within a single 'episode' at the limits of temporal resolution. Paleomagnetic methods provide a high-resolution tool that can be applied to understanding the tempo of regional volcanism in arcs. • Two 11 km3 shield volcanoes in northern California were erupted in under a few centuries • Paleomagnetic sampling and secular variation analysis tightly defines volcanic episodes • Effusion rate calculations support a brief volcanic episode at Crater Mountain [ABSTRACT FROM AUTHOR]

The Siberian Traps large igneous province comprises lava flows, volcaniclastic and hyaloclastite deposits, and a network of sills and dikes that were emplaced into the sediments beneath the volcanics. Spectacular examples of these intrusions are found in the Tunguska Basin sediments in Eastern Siberia. Hundreds of diatremes have been identified, rooted above sill intrusions, linking the contact metamorphic aureoles around the intrusive complexes in the Tunguska Basin with the paleo-surface. The diatremes in the southern part of the basin have been proposed as the main conduits for metamorphic gas release to the atmosphere, and thus a trigger leading to the end-Permian terrestrial mass extinction. The content of these diatremes has yet to be presented in detail in English-language literature, and fundamental questions remain regarding the content and formation history of these structures. This study examines the geochemistry and petrography of crater sediments within the uppermost portion of the Oktyabrsk diatreme complex in the southern Tunguska Basin, Eastern Siberia. We focus primarily on 505 m of lacustrine sediments within the western crater. The sediments are tuffaceous silt- and sandstones intercalated with conglomerates and cemented by calcite. The major element composition of the bulk crater sediments indicates a mixture of basalt and carbonate. The sedimentary mineral assemblages do not reflect primary basaltic rock, but rather altered volcaniclastic material comprising clays, zeolites, calcite, and pyrite with minor detrital magnetite, fluorite, apatite, and garnets originating from hydrothermal diatreme deposits. The western crater sediments contain no evidence of allochthonous sediment sources and were subjected to only low-temperature diagenesis following burial, making this deposit a prime locale for further investigations of in situ processes and biologic activity in Siberia at the end-Permian. The Oktyabrsk complex formed via multiple episodes of mineral deposition and eruption events and the diatremes represent a likely source of the thick volcaniclastic deposits in the southern Tunguska Basin. This system enables further investigation of the connection between the Siberian Traps magma-sediment interaction and the end-Permian terrestrial environment. [ABSTRACT FROM AUTHOR]

The first historical eruption of Kambalny volcano began on March 24, 2017 with the powerful ash emission from the summit crater reaching as high as 6 km above sea level. The explosive activity continued without interruption from March 24 to March 30. The most powerful ash emission was registered on March 25-26, when the ash plume drifted several thousand kilometers SW, S, and SE from the volcano. On April 2 and April 9, after several calm days, powerful ash explosions occurred generating ash plumes up to 7 km high. The area of the land and sea over which the ash plume drifted during the day of March 25, was 650000 km2; the area of the ash accumulation on the land that was formed from March 24 to April 9, exceeded 1500 km2. These parameters were measured using the satellite-based data in the VolSatView information system. Domination of the silty fraction and the presence of secondary minerals (pyrite, gypsum, sulfur, and others) in the ash point to the phreatic character of the volcanic eruption. [ABSTRACT FROM AUTHOR]

• The 2.1 kyr Blue Dragon lava flow is one of the largest Holocene basaltic flows in the contiguous U.S. (280 km2/3.4 km3). • Satellite imagery shows the flow is divided into five large sub-areas deposited at different times during the eruption. • Major and trace elements and Pb isotopes show the lava composition changed over the course of the eruption. • The compositional data are consistent eruption of the Blue Dragon flow from a zoned magma chamber. • The changes in composition are consistent with changing magnitudes of fractional crystallization and crustal assimilation. The Blue Dragon lava flow in southern Idaho is one of the largest Holocene basaltic flows in the contiguous U.S. Multispectral remote sensing and field mapping of the flow have revealed its 280 km2 surface is divided into five large sub-areas with different spectral reflectance and morphology that correspond with distinct periods of the eruption. The flow grew outward from its source fissures primarily via a complex system of lava tubes, and stratigraphic relations at the boundaries of the mapped sub-areas provide temporal information about their order of emplacement. This offers a unique opportunity to reconstruct chemical and mineralogical changes in the source magmas as the eruption progressed. In this first comprehensive study of the compositional diversity of the Blue Dragon flow, geochemical data from 28 rock samples show that over the course of the eruption the lavas became progressively more primitive and depleted in incompatible trace elements, and Pb isotopes show subtle increases. These observations are best explained by eruption from a zoned magma source due to variable assimilation-fractional crystallization (AFC), with the initial eruption of more evolved and enriched magmas that may have been residual from the previous eruption, followed by progressively higher proportions of a more primitive and depleted component from deeper in the system. Differences in lava surface color and morphology among the five mapped eruptive phases may indicate changes in eruptive temperature, flow rate, or both as the Blue Dragon eruption progressed. The results support a growing body of evidence that systematic studies of geochemical variations in monogenetic and short-duration lava flows can reveal the relative influence of processes that affect single batches of magma. [ABSTRACT FROM AUTHOR]

Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) imaging system onboard NASA's (National Aeronautics and Space Administration's) Terra satellite is capable of measuring multispectral reflectance of the earth's surface targets in visible and infrared (VNIR) to shortwave infrared (SWIR) (until 2006) as well as multispectral thermal infrared (TIR) regions. ASTER VNIR stereo imaging technique can provide high-resolution digital elevation models (DEMs) data. The DEMs data, three-dimensional (3D) perspective, and ratio images produced from the ASTER multispectral data are employed to analyze the geomorphologic and lithologic features of Wudalianchi volcanoes in the northeastern China. Our results indicate that the 14 major conical volcanic craters of Wudalianchi volcanoes are arranged as three sub-parallel zones, extending in a NE (Northeast) direction, which is similar to the direction of regional fault system based on the ASTER DEMs data. Among the 14 volcanic craters in Wudalianchi, the Laoheishan, and Huoshaoshan lavas flows, after the historic eruptions, pouring down from the crater, partially blocked the Baihe River, which forms the Five Large Connected Pools, known as the Wudalianchi Lake. Lithologic mapping shows that ASTER multispectral ratio imagery, particularly, the Lava Flow Index (LFI) (LFI = B10/B12) imagery, can clearly distinguish different lava flow units, and at least four stages of volcanic eruptions are revealed in the Wudalianchi Quaternary volcano cluster. Thus, ASTER multispectral TIR data can be used to determine relative dating of Quaternary volcanoes in the semi-arid region. Moreover, ASTER 3D perspective image can present an excellent view for tracking the flow directions of different lavas of Wudalianchi Holocene volcanoes. [ABSTRACT FROM AUTHOR]

Unmanned Aerial Systems for image acquisition have revolutionized the study and monitoring of volcanic activity where field access is complex or impossible. Through a series of 3 examples in the Virunga Volcanic Province (Eastern Democratic Republic of Congo), the present work shows how times-series of photogrammetric products (i.e., point clouds, digital elevation models and orthophotos) allow the detection, quantification and interpretation of topographic changes associated with ground deformation, lava accumulation and erosion processes in volcanic craters. All these case studies of applied 4D photogrammetry also illustrate the solutions found to compensate the lack of ground control points and adapt the image acquisition strategies to the complexity of such a tropical volcanic environment.The two first examples focus on the summit crater of Nyiragongo. (1) The low level of the Nyiragongo's persistent lava lake observed during the 2012-2015 period was accompanied with the subsidence of the surrounding platform and the appearance of ring fissures. This subsidence was also detected using SAR interferometry. The modelling of that subsidence points towards a shallow source associated with the 2002-2012 accumulation of lava in the crater due to lava lake overflows. (2) On February 29, 2016, at the same time as the rise of the lava lake level, a new eruptive vent developed east of the lava lake, producing lava flows that accumulated in the crater and, for some of them, felt into the lava lake. From March 2016 to March 2018, at least 10.5 106 m3 of lava accumulated in the Nyiragongo crater, according to the comparison of digital elevation models. This volume corresponds to half of the lava flow volume emitted during the last disastrous flank eruption of the volcano, in January 2002.The final example concerns Nyamulagira volcano, where the collapse and enlargement of the pit crater located in the summit caldera was followed by the appearance of lava fountains in April and June-September 2014, and the development of a new intermittent lava lake activity starting from November 2014. From June 2014 to October 2018, about 19 106 m3 of lava accumulated in the pit crater. This summit activity at Nyamulagira seems to have inhibited the occurrence of flank eruptions, which used to occur every 1-4 years between 1938 and 2012. [ABSTRACT FROM AUTHOR]