Tephra mantled terrain in the vicinity of active volcanic regions has been affected by catastrophic, regional distributed landslide clusters. Our study presents physical, mechanical, and mineralogy characterization of weathered Ta-d pumice (tephra from Tarumae volcano) from Asahi and Uryu landslides triggered by the 2018 Hokkaido Eastern Iburi Earthquake. Laboratory examination included grain-size distribution analysis, Atterberg limits, 1D consolidation tests, and static triaxial compression tests conducted on undisturbed and reconstituted samples. X-ray diffraction (XRD) examination and scanning electron microscopy (SEM) analysis was performed to identify the clay mineral proportion and micromorphology of clay minerals. Laboratory results indicated that yellowish-brown Ta-d pumices had low dry density and high natural water content, liquid limit values of 89.34% and 61.76%, plasticity index values of 24.13% and 17.52%, and permeability value of about cm/s, as well as peak effective cohesion of 11.2 kPa and 5.8 kPa and peak effective internal friction of 20.8 degrees and 23.1 degrees. XRD analysis shows that halloysite is the dominant clay mineral present in all samples and SEM observations revealed that it is dominantly present in "crinkly halloysite" habits, which is associated with the spherical halloysite that can facilitate saturation of the slip layer and a critical reduction in shear resistance.

The c. 86 Ma Jagersfontein kimberlite in the southern portion of the Kalahari craton in South Africa erupted a suite of refractory peridotite xenoliths with regionally anomalous rhenium+osmium (ReOs) isotope systematics and highly siderophile element (HSE) abundances. A portion of this suite comprises peridotites with 2.7 to 3.0 Ga Re- depletion Os-187/Os-188 model ages, refractory major elements and HSE abundances that represent some of the most depleted and least metasomatised known components of Archean cratonic nuclei. Other peridotites in the Jagersfontein suite show enrichment in Os, Ir, Pd, Pt and, especially, Ru, as well as having more radiogenic Os-187/Os-188. Ruthenium abundances reach up to similar to 22 times "Primitive Upper Mantle" levels and correspond to samples containing microscopic laurite plus pentlandite. The more radiogenic Os-187/Os-188 in HSE-enriched samples, along with the modern mantle like Ru isotope composition (epsilon(100)0.00 +/- 0.12, epsilon(102)-0.03 +/- 0.16), indicate that the prominent HSE enrichment is not related to an excess of unequilibrated Late Veneer material in the mantle source. Instead, the HSE characteristics and Os isotope ratios of these peridotites are inferred to have been caused by metasomatic addition of small volumes of HSE-rich sulfide/alloy to the refractory Archean peridotites. Although there is some variation in the metasomatic characteristics, the calculated Os-187/Os-188 of the contaminant causing the strongly Ru-enriched peridotites is similar to 0.116, which is equivalent to the convecting mantle composition in the early Mesoproterozoic. Unlike the erosion and Proterozoic replacement of older mantle interpreted to explain post-Archean Os-187/Os-188 mantle beneath the central Kaapvaal nucleus, the Archean mantle lithosphere beneath Jagersfontein therefore appears to have been modified by the passage of Proterozoic melts. The 2400 km(2) 1.9 Ga layered mafic Trompsburg Complex, less than 10 km southeast of Jagersfontein, indicates that the mantle lithosphere in the area has experienced substantive transfer of large volumes of post-Archean melt, and we suggest that the passage of those melts may have caused the mantle HSE enrichment.

Arc volcanoes often show an alternating behaviour between explosive and effusive activity. Although considered an effusive phenomenon, emplacement of highly evolved lava domes is almost always accompanied by explosive activity and processes that initiate the formation of pyroclastic density currents. Lava dome forming eruptions have distinct hazard patterns and whether a specific volcano has produced lava domes during its history is important. While the presence of a lava dome is self-evident for modern (witnessed) eruptions-the question becomes more difficult for deposits in the stratigraphic record. We here review the most recent eruption of Sanbe Volcano, SW Japan, and highlight challenges in the discrimination between explosive and effusive eruption styles. The Taiheizan eruption produced a large number of deposits from pyroclastic density currents (PDC) of the block and ash flow type, leading to the undisputed interpretation that an active lava dome was present during this eruption about 4000 years ago. However, re-evaluation of the deposits suggests they formed by eruption column collapse during a Plinian eruption. The term "block and ash flow deposit" (a descriptive expression for a deposit with a bimodal grainsize distribution), is often tied to an interpretation (formed by lava dome collapse) in the volcanological literature. There are many processes around active volcanoes that can produce deposits with large blocks in a fine-grained matrix and a dominantly bimodal GSD. This makes recognition of dome forming eruptions in the eruptive record challenging but also gives room for misinterpretation. Beside our re-evaluation of the Taiheizan eruption style, we provide a list of features that can help to identify dome forming eruptions in the stratigraphic record.

Pyroclastic density currents (PDCs) are a major volcanic hazard, whose variability of triggering and deposition mechanisms suggests highly complex and different initial states to be considered. Here, we describe block and ash flow deposits from the March 2019 eruption of Bezymianny volcano, Kamchatka. Ash clouds from this eruption extended into the Pacific Ocean, while block and ash flow deposits were found widely across the slopes of the edifice. We use satellite and drone-based photogrammetry to show material dispersal and accumulation during the eruption. We also use these photogrammetric data to obtain basic granulometry, suggesting dominantly 60 cm block dimensions, some exceeding 2 m in scale, embedded in a fine ash matrix. In addition, we sampled the deposit and herein demonstrate how distinct petrographical features can be used to distinguish the type of block and ash flow. Deposit characteristics, density, dimension, and petrography suggest that PDC initiation occurred during an eruptive episode conventionally considered as a “boiling over” event. This activity is characterized by rapid magma volume expansion due to intense gas exsolution which is driving a frothed mass out of the vent leading to the formation of large but highly vesicular juvenile blocks. Such an eruption style is transitional between effusive (lava dome forming) and explosive activity, and we suggest a new term “effervescent fountaining” to replace the term “boiling over” as a more appropriate description of such an eruption. Material dispersal, density of juvenile material, and Fe-Ti mineralogy are useful features to distinguish different types of block and ash flow deposits. These characteristics are also applicable to deposits from eruptions and deposits within the prehistoric geological record, improving our understanding of historic eruption patterns.

The mineralogy of volcanic rocks is usually considered as a consecutive crystallisation path related to a liquid line of decent. Tephra and pyroclastic rocks hold a special status as their formation includes the physical disruption of the magma during an explosive eruption. We describe tuffisite samples (captured veins of pyroclastic material in coherent lava bombs) and concurrently ejected volcanic ash from the ongoing eruption of Ebeko Volcano, Russia. Our samples show that tridymite (a mineral, not present in the original phase assemblage of the magma) forms as a consequence of explosive eruptive activity, volatile exsolution and fluid flow following decompression and magma fragmentation. Vapour phase crystallisation (VPC) of cristobalite is well known from highly evolved, dome-forming eruptions due to gas flux through highly permeable and porous glassy dome rocks. At Ebeko volcano, increased permeability develops in the volcanic conduit during magma fragmentation and transient tephra storage. Magmas erupted at Ebeko are less evolved than those of typical (dome-forming) andesitic - dacitic Pel & eacute;an eruptions and show comparably higher eruption temperatures favouring the formation of tridymite over cristobalite during VPC.

The elemental and isotopic properties of garnet pyroxenites can yield information on lithospheric mantle composition, thermal state, and evolution. The 34Ma Kakanui Mineral Breccia in New Zealand contains spectacular but little-studied mantle peridotite and pyroxenite xenoliths that yield new insights into the evolution of a portion of the underlying mantle lithosphere of a former Gondwana margin. The moderately depleted and metasomatized spinel peridotites, as judged from spinel and olivine compositions and bulk rock major and platinum group element abundances, give mineral equilibration temperatures <1020 degrees C and are derived from the middle to shallow (similar to 35 to 50 km) lithospheric mantle when projected onto a 70 mW center dot m(-2) geotherm. These residues have low Re/Os and Re-depletion Os-187/Os-188 model ages that range from Eocene (0.05 Ga) to Paleoproterozoic (1.9 Ga), consistent with extraction from a lithospheric mantle comprising fragments with complex depletion histories. Although the peridotites have restricted delta O-18 (olivine +5.2 to 6.2), evidence for an isotopically heterogeneous mantle column in addition to the Os-187/Os-188 is seen in clinopyroxene Sr-87/Sr-86 (0.70244 to 0.70292), epsilon Nd (+4.1 to 18.8), Pb-206/Pb-204 (17.8 to 20.3), and epsilon Hf (+10 to +101). Higher metamorphic equilibrium temperatures of the garnet pyroxenites (Fe-Mg exchange of >1150 degrees C) compared to the peridotites indicate their Eocene extraction was from towards the base of this isotopically heterogeneous mantle lithosphere. Pyroxenite bulk compositions point to cumulate origins, and the mineral isotope ratios of Sr-87/Sr-86 (0.70282 to 0.70294), epsilon Nd (+5.5 to 8.0) and Pb-206/Pb-204 (18.1 to 19.3) match many of the Zealandia metasomatized mantle peridotite xenoliths as well as the primitive intraplate basalts but not the garnet pyroxenite host magmas. In contrast to many global pyroxenite studies, the garnet pyroxenite Sr-87/Sr-86 and delta O-18 (+5.2 to 5.8) data provide no evidence for subducted crustal material in the primary magma source region, and Sm-Nd and Lu-Hf isotope data yield mid-Cenozoic ages that are probably related to isotope closure during eruption. An exception is one sample that yields a Lu-Hf isochron age of 111.9 +/- 9.1 Ma, which corresponds to the convergence of the Lu-Hf isotope evolution curves of three other samples. Liquids calculated to have been in equilibrium with these cumulates have trace element compositions comparable to primitive alkaline intraplate basalts like those found at the surface of Zealandia. The new data, therefore, indicate that a pulse of intraplate magmatism occurred during or directly after the cessation of long-lived subduction on the former Zealandia Early Cretaceous forearc Gondwana margin, despite any volcanic surface exposure having been long eroded away. The lower lithospheric mantle emplacement of the garnet pyroxenites suggests that the source of the alkaline parent magmas was probably the convecting mantle, which supports conclusions that intraplate magmas in Zealandia have asthenospheric and lithospheric mantle sources.

Even though no basalts have erupted at Asama volcano, its large, felsic magma chamber standing beneath the summit is frequently replenished by cryptic injections of mafic magma of basalt-basaltic andesite composition. This mafic magma is preserved within melt inclusions trapped in olivine phenocrysts collected from the old Itabana pumice of the Kurofu stage and the Tenmei pumice of the current Maekake stage. The trapped mafic melts provide a detailed and vivid record of cryptic mafic magma injection into the felsic chamber where they admix to erupt andesite magma. The main phenocrysts of plagioclase, orthopyroxene, and clinopyroxene, commonly seen in the erupted products, are derived from the felsic magmas and trapped felsic melts of dacite-rhyolite compositions, containing low sulfur contents (0.3 wt% of SO3 or less; most are lower than 0.10 wt%). In contrast, the mafic melts, entrapped by olivine phenocrysts, show high concentrations of SO3, up to 1.06 wt% for Itabana and SO3 0.65 wt% for Tenmei. In addition, the olivine phenocryst commonly encloses early crystalline phases precipitated from the sulfur-rich mafic magma, such as Cr-spinel, Mg-rich orthopyroxene, Fe, Cu, and Ni-bearing sulfides, and often Al-rich clinopyroxene. The olivine-hosted mafic melt inclusions always contain numerous vesicles. Furthermore, they are often included as hourglass-shaped trapped melts, exhibiting snapshots of intense foaming and gas phase exsolution during the olivine growth and probably in the process of the cryptic injection into the felsic magma beneath the Asama summit. Our new data contributes to a better understanding of the magmatic system of the Asama volcano but also highlight the importance of the "Excess sulfur problem", especially concerning the 1783 Tenmai eruption, which was contemporary to the Laki Fires.

For a better understanding of plate dynamics such as the opening of Japan Sea back-arc basins, it is critical to know why and how back-arc spreading/rifting occurs adjacent to convergent plate boundaries. Two models have been proposed for the formation of Japan Sea back-arc basins: the "slab rollback model" and the "plume model". We report here on 12 spinel peridotite xenoliths in the alkali basalt of the Cenozoic Kawashimo volcano in southwest Japan. These xenoliths are dominantly harzburgite with some lherzolite. The harzburgites and lher-zolites show coarse-grained or porphyroclastic textures that record variable degrees of deformation. Olivine and spinel compositions indicate the samples are residual mantle peridotites formed under various degrees of partial melting. Olivine crystallographic preferred orientations in the xenoliths have orthorhombic patterns character-ized by a strong [010] maximum, and this orthorhombic pattern implies that the olivine deformed by dislocation creep on the (010)[100] slip system. Using a sub-grain size piezometer, the maximum differential stress varies from 3 to 13 MPa in the samples. We also found that the peridotite xenoliths deformed under relatively high strain-rates, such as 10-13 to 10-10 s- 1, using olivine flow laws and the obtained stress and grain size. The range of high strain-rates is comparable to that predicted using a thermomechanical model of back-arc spreading/ rifting. Therefore, it is probable that the peridotite xenoliths preserve textures that formed during the mantle deformation that accompanied the Japan Sea back-arc spreading/rifting. We estimated an equilibrium temper-ature of 1238 +/- 20 degrees C using the two-pyroxene geothermometer, and this temperature is higher than any tem-perature reported previously for peridotite xenoliths in southwest Japan. The obtained equilibrium P-T condition for the xenoliths implies that the hot mantle plume hypothesis best explains the mechanism of formation of Japan Sea back-arc basins.

A suite of samples was studied that represents the major explosive eruptions of Sanbe volcano, SW Japan. We demonstrate how rate of magma flux into the Trans‐Crustal Magmatic System (TCMS) presents a major control on the type and style of the subsequently forthcoming eruptions. Erupted products can be separated into two distinct groups. An older group is characterized by highly evolved, high‐K, LILE‐rich rhyolitic magmas, showing a supressed adakitic trace element signature (otherwise characteristic for the young stratovolcanoes in the SW Japan arc) with low Ca, Sr concentrations and a negative Eu anomaly. In contrast, the younger group (dominantly of andesitic—dacitic composition) displays a strong adakitic trace element signature with characteristic steep REE profiles and high Sr concentrations. An Eu anomaly is generally lacking here. The two groups are also distinct in their petrographic features, with the early group being almost aphyric showing simple log linear crystal size distributions and homogeneous, uniform mineral chemistries. In contrast, products of the younger group show complex crystal size distributions with diverse mineral compositions and abundant disequilibrium features. Our study shows that an initial high melt‐production rate allowed dehydration melting of lower crustal rocks leading to the formation of highly evolved K‐rich magmas. These magmas intruded into the shallow crust and produced two large Plinian rhyolitic, caldera forming eruptions. Subsequently the primary magma production rate decreased and the lower crust became too refractory for additional dehydration melting by these lower volume magma batches, causing the conventional adakitic magmatism to produced several additional eruptions of smaller magnitude, mainly of Sub‐Plinian or Pelean styles.

A short-lived but violent explosive eruption occurred on the small volcanic island Raikoke in June 2019 (central Kuril Islands). The culmination of the eruption lasted 3.5 h and the ash cloud rose to a height of 13 km. An analysis of a sequence of satellite images in combination with ground-based observations gave information on the pyroclastic deposits of the eruption and allowed us to estimate the associated impact on the island ecosystems. We found that this eruption had a phreatomagmatic, sub-Plinian to Plinian character. The phreatomagmatic mechanism of the eruption occurred due to interaction between the rising basaltic andesite magma and ground waters, which were mostly represented by sea water that percolated through the permeable rocks of the volcanic island. The eruption produced numerous pyroclastic flows. The hot deposits of the pyroclastic flows and tephra covered the entire island, destroying the vegetation and the habitat of birds and sea mammals. Much of the pyroclasts was deposited in the form of fans of pyroclastic flows at the base of the volcanic slopes, considerably displacing the shoreline seaward. As a result, the island area increased by 15%. The pyroclastic deposits were intensely eroded and redeposited during the first year after the eruption, making new areas of the island coast. The recovery of Raikoke’s ecosystems will be enhanced by erosion of the pyroclastic deposits and gradual resettling of birds, which would bring new plant species to the island. The succession would be accelerated by areas of survived vegetation. Overall, we see periodic dramatic disruptions in the island ecosystems caused by violent explosive eruptions with subsequent rapid recovery that with high probability will be interrupted by new eruption.

The increase in number and intensity of earthquakes during a pre-eruptive crisis is the main basis of seismic volcano monitoring. However, a strong understanding of how these seismic signals relate to magmatic processes in the magma plumbing systems prior to volcanic eruptions is crucial for these efforts. Here we compare the characteristics of a seismo-volcanic crisis prior to the 2010–2013 explosive-extrusive eruption of Kizimen volcano, Kamchatka with the timescales of processes in the magma plumbing system. These timescales are inferred from the numerical modelling of iron-magnesium intracrystalline interdiffusion in 88 zoned orthopyroxene crystals from dacites and silica-rich andesites collected after the eruption. We find that the eruptible magmas were assembled rapidly during a magma mixing process beginning around 1.5 years before the eruption, which is well correlated with the onset of the seismic crisis. We conclude that the observed seismic re-activation marked the onset of magma mixing and led to destabilization of the reservoir, followed by the eruption.

Abstract The increase of number and intensity of earthquakes during a pre-eruptive crisis is the main basis of seismic volcano monitoring. However, the exact relationship between the seismic activity and the volcano-magmatic processes remains unclear. Here we present a direct comparison between characteristics of a seismo-volcanic crisis recorded prior to the 2010-2013 eruption of Kizimen volcano (Kamchatka, Russia) and the timescales of processes in the magma plumbing system. These timescales are inferred from the modelling of Fe-Mg intracrystalline interdiffusion in 88 zoned orthopyroxene crystals from dacites and silica-rich andesites samples collected after the eruption. We show that the eruptible magmas were assembled rapidly during a magma mixing episode ~1.5 years before the eruption, which is well correlated with the onset of a seismic crisis. We conclude that the observed seismic re-activation marks the onset of magma mixing leading to destabilization of the reservoir followed by the eruption after ~1.5 years.

Osmium isotopes, whole rock and mineral geochemical data from peridotite xenoliths from two Miocene McMurdo Volcanic Group cinder cones in the Transantarctic Mountains (TAM) in Southern Victoria Land, Antarctica, reveal that the underlying mantle preserves evidence for major mid-Proterozoic lithosphere formation despite the crust being dominated by late Neoproterozoic-Ordovician (~0.65–0.47 Ga) rocks. The Hooper Crags xenolith suite is dominated by harzburgites with highly refractory olivine Mg# (up to 92.3) and depleted bulk rock major and platinum group element + Re abundances, with 187Os/188Os ratios indicating depletion in the mid-Proterozoic. Pipecleaner Glacier xenoliths, 18 km distant, are lherzolites with olivine Mg# (<91) and fertile major and platinum group element abundances, with Os isotope abundances defining an aluminochron that also indicates mid-Proterozoic depletion. Although exposed crust along this portion of Antarctica reveals only minor evidence for Proterozoic magmatism, the major episode of lithosphere formation indicated by the Os isotope data is supported by published bulk rock Sm-Nd isotope and zircon εHf mantle model ages of Neoproterozoic to Ordovician plutonic rocks. The heterogeneous circum-cratonic mid-Proterozoic mantle under Southern Victoria Land has therefore persisted on a Ga timescale, including through the formation and destruction of Rodinia and Gondwana supercontinents as well as extensive crustal melting and emplacement of the Ferrar large igneous province. This longevity may be due to the thick (>250 km) East Antarctic Craton lithosphere shielding the immediately adjacent circum-cratonic mantle from being affected by convective asthenosphere-driven erosion. This contrasts with mantle lithosphere accreted distally to the East Antarctic Craton (represented by the now-detached Zealandia continent), which did not attain extreme thickness and has therefore been more susceptible to tectonic reworking and lateral translation.

Ebeko is one of the most active volcanoes of the Kurile island arc, producing frequent mild Vulcanian explosions with eruption clouds up to 5 km high. The volcano poses a serious threat to the Severo-Kurilsk town with a population of around 2500 inhabitants, located at a distance of only 7 km on a fan of the volcano’s laharic deposits. Here, we report an overview of the activity of the volcano in the 20th–21st centuries and the results of our geological and petrological investigations of the ongoing Vulcanian eruption that started in 2016. We have found that eruptions of Ebeko span a range of mechanisms from purely magmatic to phreatic/hydrothermal. Three of its historical eruptions (the 1934–1935, 1987–1991, and the 2016–ongoing) involved fresh magma, while during the others (1967–1971, 2009–2011) fresh magma was not erupted. Juvenile material of the ongoing eruption represents highly crystalline and highly viscous (more than 108 pa s) low-silica (56–58 wt% SiO2) andesite. Historical data and our observations of the ongoing eruption allowed us to suggest a functional model of the volcano where Vulcanian explosions are caused by shallow intrusions of small diapir-like batches of strongly crystallized and highly viscous andesitic magma ascending into water-saturated, hydrothermally altered rocks composing the volcano summit. We suggest that the diapir’s ascent is governed by their positive buoyancy. Some of the diapirs reach and breach the ground surface producing magmatic eruptions of Ebeko, while the others are stuck at the shallow subsurface level and feed intensive hydrothermal activity as well as phreatic eruptions of the volcano. Positive buoyancy of the diapirs is too weak to allow them to extrude high above the ground surface to form lava domes.

The research presented in this paper is part of the international research project VARI-SPEED, which aims to invent a mass optimized speed variable drivetrain comprising a main gearbox with variable transmission ratio and a rotor suitable for rotor speed variation. A performance and cost simulation model was set up for the Sikorsky UH-60A. Three different types of drivetrains were investigated: The Standard drivetrain, a 2 Speed gearbox and a continuously variable transmission (CVT). Flight missions of 3 industry sectors- Oil and Gas, Construction and Search and Rescue with a total of 33 different missions were simulated. The simulation was performed to evaluate the effects of the variable rotor speed technologies on performance and costs in the context of missions. It could be shown that rotor speed variation in a range of 50% can lead to less fuel consumption and mission costs in every industry sector and the performance of the helicopter can be increased. The CVT seems to be the better solution for multi purpose helicopters. In single missions the results can be different, therefore it is important to have a look on more different missions in an industry sector. The mass of the transmission system has an significant impact on the results. The results of the investigation can give an idea about the boundary conditions for the usage of rotor speed variation and show the critical points of rotor speed variation. The technology increases the efficiency, decreases fuel consumption and CO2emission and reduces noise and environmental impact of rotorcraft. Furthermore it can have also economic advantages for the operator.

Coseismic landslides generated by strong earthquakes can substantially increase the devastation imposed on society and humanity, especially when such seismic events occur in unconsolidated pyroclastic fall deposits that are prone to destabilization. The catastrophic 2018 Hokkaido Eastern Iburi Earthquake triggered thousands of shallow liquefied landslides in pyroclastic fall deposits, 1 day after the passage of Typhoon Jebi. The landslides were highly mobile and had long runouts. We here report novel findings pertaining to distinctive properties of the widely distributed, weathered Plinian Ta-d tephra deposit from Tarumae volcano, and their impact on the spatial clustering of the Iburi landslides. Distribution of the landslides is positively correlated with the dispersal of Ta-d. Liquefaction occurred in the weathered Ta-d pumice, despite the absence of unconfined groundwater. The Ta-d pumice also has lower soil strength than other local pumice units. The volumetric soil moisture content of weathered Ta-d pumice is very high (>90%) and exceeds other soil layers, regardless of precipitation variation. The presence of hydrated halloysite was confirmed by X-ray diffraction. The halloysite enhances the shaking-triggered liquefaction, because it maintains weathered Ta-d pumice in a highly saturated and exceedingly loose state, even in the absence of unconfined groundwater. This is inconsistent with the traditional concept of liquefaction that generally occurs in sandy soils below the groundwater level.

Vulcanian explosions are hazardous and are often spontaneous and direct observations are therefore challenging. Ebeko is an active volcano on Paramushir Island, northern Kuril Islands, showing characteristic Vulcanian-type activity. In 2019, we started a comprehensive survey using a combination of field station records and repeated unoccupied aircraft system (UAS) surveys to describe the geomorphological features of the edifice and its evolution during ongoing activity. Seismic data revealed the activity of the volcano and were complemented by monitoring cameras, showing a mean explosion interval of 34 min. Digital terrain data generated from UAS quadcopter photographs allowed for the identification of the dimensions of the craters, a structural architecture and the tephra deposition at cm-scale resolution. The UAS was equipped with a thermal camera, which in combination with the terrain data, allowed it to identify fumaroles, volcano-tectonic structures and vents and generate a catalog of 282 thermal spots. The data provide details on a nested crater complex, aligned NNE-SSW, erupting on the northern rim of the former North Crater. Our catalog of thermal spots also follows a similar alignment on the edifice-scale and is also affected by topography on a local scale. This paper provides rare observations at Ebeko volcano and shows details on its Vulcanian eruption style, highlighting the relevance of structural and morphologic control for the geometry of craters and tephra fallout as well as for structurally controlled geothermal activity.

Spectacular reactions textures developed during the non-isochemical breakdown of orthopyroxene and spinel in peridotite mantle xenoliths in intraplate alkaline basalts from the Auckland Volcanic Field and the Dunedin Volcano in New Zealand, and Jeju Island in South Korea. Mantle orthopyroxene is replaced by symplectitic intergrowths of silica-rich glass and olivine (± clinopyroxene ± orthopyroxene) with individual minerals showing large diffusion gradients at their margins proximal to the host melt. The glasses are basaltic to trachytic and formed by incongruent melting of orthopyroxene and subsequent re-equilibration by diffusion and mixing during changing boundary conditions with the host magma. Although the glass composition is strongly dependent on the alkalinity of the host magma, the distance to the reacting contact and the respective phase assemblage that develops in the reaction zone (melt + ol ± clinopyroxene ± orthopyroxene), the most evolved melts converge at trachytic composition. Diffusion-driven Fe enrichment for mantle olivine indicates residence timescales within the host magma on the order of weeks to several months.