Volcanic Complex Research Articles

How residents and volcanoes co-produce risk knowledge: Ways of knowing and affective attunement to the rhythms of Lonquimay volcano, Chile

In this paper, we present our understanding of the importance of affects in people's sense-making of volcanic risk in everyday life. In doing so, we explore how local knowledge on volcanism is produced and circulated through communities' ongoing affective encounters with volcanoes. Through ethnographic fieldwork and semi-structured interviews, we draw on the heterogeneous experiences and narratives of Malalcahuello residents living next to the Lonquimay volcanic complex in the Southern Andes of Chile. Its last eruption in 1988–1990 formed a new cone on the NE flank, called Navidad (Christmas), which has allowed residents to experience active volcanism in a twofold sense: being affected by its impacts during the eruption, and responding affectively to the volcano in everyday life. The results pave the way for a typology of affect-based ways of knowing volcanism. These are constituted by multiple people's viewpoints: 1) knowing the ground, 2) knowing the territory, 3) knowing the risk, and 4) knowing the behaviour. These ways of knowing vary according to, and are in part determined by, the different rhythms of the volcano itself. Therefore, active volcanism becomes a more-than-human agent of knowledge through its rhythmic presence in people's everyday lives. Over time, the local population has become affectively attuned to both ‘hazardous situations’ related to volcanic eruption and ‘risk and safe situations’ during volcanic quiescence. These attributes of human-volcano encounters turn hazardous spaces into affect-laden spaces at different times, raising the need to rethink spatio-temporal dimensions in knowledge dialogue and disaster risk reduction. Overall, the paper underlines the importance of affect-oriented risk research in Chile and worldwide to account for the pre-existent viewpoints from which a volcano is at the heart of people's concerns.

Reassessing the origins of Near Eastern obsidian vessels: Not as simple as “Central Anatolia”

In the 1960s, Renfrew and colleagues tested an obsidian vessel from Tepe Gawra in northern Iraq. The vessel was attributed to their “Group 1e-f” chemical type, which matched obsidian from the Acıgöl volcanic complex in central Turkey as well as unclear locations in eastern Turkey and Armenia. Renfrew and colleagues favored an attribution of the vessel to Acıgöl, and consequently, an association between obsidian vessels and central Turkey became widely held in the literature. Given the destructive nature of chemical analysis until the 21st century, obsidian vessels and fragments were almost never tested, so there were few chances to overturn or support this association. Furthermore, such vessels have attracted much attention as likely prestige objects. To consider value and meanings derived from a material’s source, however, it is crucial to have the correct identification of its origin. First I consider the available sourcing data for previously studied vessel fragments. Second I report my new source identifications for a vessel with an uncertain provenience in the Metropolitan Museum of Art, fragments from Ur, and the same vessel from Tepe Gawra tested by Renfrew and colleagues. Only the site located in south-central Turkey (Domuztepe) had polished artifact fragments from the obsidian sources of Cappadocia. For Mesopotamian (Tepe Gawra, Ur, Kenan Tepe) and Zagros (Tal-e Malyan) sites, the vessels instead derived from four sources in eastern Turkey: Sarıkamış 2, Nemrut Dağ 2, Bingöl B, and Meydan Dağ. Thus, the association between obsidian vessels and central Turkey must be abandoned, as must narratives based on this association (e.g., exchange between early states or elites in Cappadocia and Mesopotamia).

Geomorphological evidence for volcano-tectonic deformation along the unstable western flank of Cumbre Vieja Volcano (La Palma)

In 2021, La Palma's southern volcanic complex Cumbre Vieja erupted for its longest period in historic times. Although the geological record shows no evidence for a collapse of Cumbre Vieja, ground deformation studies and field observations suggest that its western flank is moving seawards, following the direction of previous collapses of the island. To better estimate the hazard of a potential flank collapse of Cumbre Vieja, it is important to identify the lateral extent and depth of the mobile sector. Here, we analyse the volcano-tectonic deformation along Cumbre Vieja's western flank, based on geomorphological analysis of combined topographic and new ship-born bathymetric data as well as the analysis of shallow seismicity records associated with the 2021 eruption. In our interpretation, the shoreline-crossing Puerto Naos Ridge results from tectonic uplift accompanying transpressional deformation along the northern boundary of Cumbre Vieja's moving flank, therefore decoupling a stable sector in the north from the mobile sector farther south. The proposed moving sector is consistent in scale with previous ground deformation studies and documented flank collapses of structurally similar volcanoes. We present a workflow for semi-automatically detecting boundaries of unstable volcanic flanks based on morphological changes captured in digital elevation data. The method correctly delineated the known boundaries of the unstable flanks of Mt. Etna and Kilauea volcanoes. The ability to constrain potential boundaries of unstable volcanic flanks should inform the planning of future geophysical and geodetic campaigns aiming to identify precursory signals of potential flank failures.

Olivine Time-Capsules Constrain the Pre-Eruptive History of Holocene Basalts, Mount Meager Volcanic Complex, British Columbia, Canada

Abstract The Canadian segment of the Cascade Volcanic Arc (i.e. the Garibaldi Volcanic Belt) comprises more than 100 eruptive centres, spanning the entire Quaternary period (Pleistocene to Holocene in age), and with deposits ranging in composition from alkaline basalt to rhyolite. At least one of the volcanoes is currently active; Mount Meager / Q̓welq̓welústen erupted explosively 2360 years BP and has ongoing fumarolic activity. Long-term forecasting of eruption frequency and style depends on reconstruction of the history and timescales of magmatic processes preceding previous volcanic eruptions. Utilising diffusion chronometry, we investigate the Mount Meager Volcanic Complex focusing on Holocene olivine-phyric basalts (Lillooet Glacier basalts) exposed by the retreat of the Lillooet Glacier. We identify two distinct olivine populations in samples of quenched, glassy basalt lavas that record different magmatic processes and histories. Glomerocrysts of Fo83 olivine phenocrysts, entrained and transported by a hot mafic input, form Population 1. These exhibit resorption and normally zoned outermost rim compositions of Fo76–78; a third of them also show interior reverse compositional zoning. A second population of skeletal microphenocrysts have the same composition as the phenocryst rims (i.e. Fo76–78) and are in equilibrium with the adjacent matrix glass. We estimate the pre-eruptive temperature-fO2 conditions in a shallow reservoir (100 MPa; ~3 km) for a melt with H2O content of 0.5 to 1 wt % as ~1097°C to 1106°C (± 30°C), and NNO + 0.5 (±1.1), respectively. Using these input parameters, we report Fe-Mg diffusion chronometry results for 234 normally zoned profiles from 81 olivine phenocrysts. Diffusion modelling of compositional profiles in oriented crystals indicates pre-eruptive magmatic residence times of 1 to 3 months. These remarkably short residence times in shallow reservoirs prior to eruption suggest very short periods of unrest may precede future eruptions.

Miocene climate cooling and aridification of Antarctica may have enhanced syn-extensional magmatism in the western Ross Sea

Continental rift systems are commonly characterized by volcanism with parental basaltic magmas sourced from the mantle. Erosion of the rift shoulders and sedimentation in the adjacent basins can affect the stress and thermal fields at depth, thereby affecting partial mantle melting. However, the sensitivity of magmatic activity to such surface forcing is elusive. Geological observations from the western Ross Sea, Antarctica, suggest rift onset in the Cretaceous with a transition from wide-rifting to narrow-rifting at the boundary between the Antarctic craton and the Transantarctic Mountains. Miocene climate cooling during rifting in the western Ross Sea, in addition, leads to an abrupt decrease in sedimentation rate, synchronous to the emplacement of the McMurdo Volcanic Group. This represents the largest alkali province worldwide, extending both inland and offshore of Transantarctic Mountains and western Ross Sea, respectively. Here, we use coupled thermo-mechanical and landscape evolution numerical modeling to quantify melt production in slowly stretching rift basins due to changes in erosion/deposition rates. The model combines visco-elasto-plastic deformation of the lithosphere and underlying mantle during extension, partial rock melting, and linear hillslope diffusion of the surface topography. The parametric study covers a range of slow extension rates, crustal thicknesses, mantle potential temperatures and diffusion coefficients. Numerical simulations successfully reproduce the ∼150–200-km-wide extension of western Ross Sea and Miocene-to-present asthenospheric melt production (McMurdo Volcanic Group). Results further show that slow rifts magmatism is highly sensitive to sediment deposition within the basin, which inhibits mantle decompression melting and delays the crustal breakup. Regional climate-driven sedimentation rate changes are thus likely to have affected the syn-rift magmatic history of the western Ross Sea, Antarctica, supporting the relevance of interactions between surface and deep-seated processes across extensional settings.

The 3‐D Density Structure of the Large Shield Volcanic Structure in the Gardner Region Revealed by a New Gravity Inversion

AbstractThe Gardner region is a well‐known shield volcanic complex on the Moon. Its magma origin and formation mechanism are of significant interest but still enigmatic. To reveal the subsurface structure of this volcanic complex, we propose a new 3‐D inversion method of the gravity field based on the regularizations of the L1 norm of the model and its gradients. The model test indicates that our proposed method can recover the density structures with high resolution. Subsequently, we apply it to the Bouguer gravity data in the Gardner region. Our result shows a large, dense body with a volume of about 45 × 45 × 13 km3 centered under the topographic bulge of the Gardner Plateau. We infer that this structure is most likely dense basalts trapped at the crust‐mantle boundary as a sill and acted as the magma reservoir that has fed the volcanic complex in the Gardner area.

New Data on Ages of the Basement of the Central Kamchatka Depression and the Base of the Klyuchevskaya Group of Volcanoes

New Data on Ages of the Basement of the Central Kamchatka Depression and the Base of the Klyuchevskaya Group of Volcanoes

Regional controls on fluid flow in geothermal systems of the Taupo Volcanic Zone, New Zealand

ABSTRACT The Taupo Volcanic Zone (TVZ) provides almost 20% of New Zealand’s electricity production through seven of its 23 high-temperature geothermal systems. Fluid circulation in geothermal systems is influenced by permeable pathways, heat sources, and topography. To explore influences on systems in the TVZ, we have created regional-scale heat and fluid flow models using TOUGH2. We modelled several potential influences individually and in combination: TVZ rift boundaries, the densely faulted Taupo Fault Belt, varying thickness of volcanic cover, topographic loading, and localised heat sources inferred from magnetotelluric data. The locations of seven of the nine geothermal systems in our study area can be explained by TVZ-scale convection influenced by localised deep heat sources and hydraulic gradients due to topography. Regional-scale geology appears to be an additional influence at Rotorua and Ngatamariki, where cold recharge within the Taupo Fault Belt pushes modelled upflow towards the rift margins. At Ohaaki, modelled upflow is northwest of the system unless a dipping contact between basement and more permeable cover rocks is included. Modelled upflow zones do not correspond to geothermal systems at Te Kopia and Haroharo Volcanic Complex, which we hypothesise is related to uplift along the Paeroa Fault and shallow impermeable lava domes respectively.

Using the pedogenic oxide ratio in distinguishing volcanic soil weathering intensity in subtropical region

Pedogenic oxide ratio (POR) helps identify and understand pedogenic processes. However, POR is seldom used to study and distinguish the weathering intensity of volcanic soils that are moderately weathered in the subtropical region. The research was conducted by collecting thirty-three subtropical volcanic soils from the northeastern Tatung Volcanic Group (TVG) region in Yangmingshan National Park, near Taipei, located in northern Taiwan. These volcanic soils could be grouped into two groups with different weathering intensities based on three weathering indices, pedogenic Fe-oxides ratios (PORs) - Feo/Fed, ((Fed-Feo)/Fet), and total reserve in bases (TRB): the highly weathered (HW) group and the lower weathered (LW) group. The two PORs show significant differences between the two groups, but not for TRB, which indicates the PORs are a good indicator for providing quantitative measurements of weathering intensity. Except for the soil bulk density (BD) meeting andic soil properties, the soils of the HW group have a lower content of Al plus 1/2 Fe content (by ammonium oxalate) (Alo + 1/2Feo) and phosphorus (P) retention, and soils of the LW group only have a lower P retention. Within those soil physicochemical properties and selective dissolution analysis results and index values, Alo + 1/2Feo, pyrophosphate extractable C (Cp), P retention, and dithionite-citrate-bicarbonate (DCB) extractable aluminum (Ald) are four critical factors for the discrimination of the soils. The soils in the study area still have relict volcanic soil properties after moderately weathered. Our research results indicate that the PO and POR are good indicators of moderately weathered volcanic soils in the subtropical region, allowing for a more precise assessment of the soil weathering process, in addition to quantitative measurements of weathering intensity.

Lateral and vertical variations of seismic anisotropy in the lithosphere–asthenosphere system underneath Central Europe from long-term splitting measurements

SUMMARY Backazimuthal variations in the shear wave splitting of core-refracted shear waves (SKS, SKKS and PKS phases, jointly referred to as XKS) at the Black Forest Observatory (BFO, Southwest Germany) indicate small-scale lateral and partly vertical variations of the seismic anisotropy. However, existing anisotropy studies and models for the nearby Upper Rhine Graben (URG) area in the northern Alpine foreland are mostly based on short-term recordings and by this suffer from a limited backazimuthal coverage and averaging over a wide or the whole backazimuth range. To identify and delimit laterally confined anisotropy regimes in this region, we carry out XKS splitting measurements at six neighbouring (semi-)permanent broad-band seismological recording stations (interstation distance 10–80 km). We manually analyse long-term (partly > 20 yr) recordings to achieve a sufficient backazimuthal coverage to resolve complex anisotropy. The splitting parameters (fast polarization direction $\phi $, delay time $\delta t$) are determined in a single- and multi-event analysis. We test structural anisotropy models with one layer with horizontal or tilted symmetry axis and with two layers with horizontal symmetry axes (transverse isotropy). To account for lateral variations around a single recording site, modelling is compared for the whole and for limited backazimuth ranges. Based on this, we provide a 3-D block model with spatial variation of anisotropic properties. Based on delay times > 0.3 s and missing discrepancies between SKS and SKKS phases, which do not support lower mantle anisotropy, the found anisotropy is placed in the lithosphere and asthenosphere. The spatial distribution as well as the lateral and backazimuthal variations of the splitting parameters confirm lateral and partly vertical variations in anisotropy. On the east side of the URG, we suggest two anisotropic layers in the Moldanubian Zone (south) and one anisotropic layer in the Saxothuringian Zone (north). In the Moldanubian Zone, a change of the fast polarization directions is observed between the east and the west side of the URG, indicating different textures. At the boundary between the two terranes, an inclined anisotropy is modelled which may be related with deformation during Variscan subduction. Regarding the observation of numerous null measurements and inconsistent splitting parameters, especially (southwest of BFO) in the southern URG, different hypothesis are tested: scattering of the seismic wavefield due to small-scale lateral heterogeneities, a vertical a-axis due to a vertical mantle flow related to the Kaiserstuhl Volcanic Complex, as well as a different preferred orientation of the olivine crystals (not A-type, but C-type) due to specific ambient conditions (high temperature, water content).

Geochemical Evidence of Water-Fluxed Crustal Melting in the Northern Colombian Andes

Abstract The compositions of crustal magmas are powerful tools for understanding the formation and differentiation of continents. However, the geochemical fingerprints that distinguish the two dominant mechanisms of crustal melting, namely dehydration and water-fluxed melting, are still controversial. To provide new insights into this problem, we discuss the petrogenesis of the Paipa Volcanic Complex (PVC), an isolated Quaternary volcanic field in the Colombian Eastern Cordillera. The PVC is characterized by peraluminous trondhjemite-like rhyolites with exceptionally high Na2O contents (~6 wt %), super-chondritic Nb/Ta (~27), elevated Sr/Y ratios (~120), spoon-shaped REE patterns, and enriched isotopic compositions that overlap with those of the local basement. They also exhibit high pre-eruptive H2O contents (~up to 9.5 wt %) and abundant Paleozoic zircon inheritances. We demonstrate that these characteristics are inconsistent with a process of intra-crustal differentiation from a mafic or intermediate mantle-derived precursor. Instead, we propose that the origin of the PVC is best explained by melting the local (meta)sedimentary basement under H2O-saturated conditions, at middle-crustal pressures (~1.3 GPa) and relatively low temperatures (~690–740°C), following the complete breakdown of plagioclase and biotite, and the formation of reactive peritectic amphibole. This scenario differs from the high-temperature dehydration melting conditions that have been widely proposed for the Andes and globally, which result in the production of water undersaturated magmas in equilibrium with anhydrous lithologies rich in plagioclase and/or garnet. Accordingly, we speculate that an external H2O flux was ultimately sourced from a buoyant, cold, and hydrated mantle wedge that was extensively metasomatized by fluids derived from the Nazca and Caribbean flat-slab fronts. These conditions depressed the asthenospheric mantle potential temperature, likely inhibiting mantle melting. In turn, they facilitated the infiltration and ascent of mantle-derived H2O through pre-existing crustal faults and shear zones. Our results indicate that water-fluxed melting could be a plausible mechanism for generating crustal magmas in orogenic regions where the availability of free H2O has been difficult to confirm.

Magma Differentiation, Contamination/Mixing and Eruption Modulated by Glacial Load—The Volcanic Complex of The Pleiades, Antarctica

AbstractThe Pleiades Volcanic Field is made up of some 20 monogenetic, partly overlapping scoria and spatter cones, erupted in the last 900 ka, cropping out from the ice close to the head of the Mariner Glacier in northern Victoria Land, Antarctica. Erupted products vary from hawaiite to trachyte, defining a complete mild Na‐alkaline differentiation trend. Mafic samples are characterized by multi‐elemental patterns typical of OIB magmas, moderately low 87Sr/86Sr (0.7037) and high 143Nd/144Nd (0.51284), with a clear within‐plate affinity, indicating a subcontinental lithospheric source. With increasing SiO2, 87Sr/86Sr ratios increase up to 0.7052 and 143Nd/144Nd decrease to 0.51277, supporting the hypothesis of open‐system evolution, with significant crustal assimilation during fractional crystallization. The erupted volume of most evolved products (∼7 km3), according to fractionation models, suggests that primitive magmas should have been more than 10 times larger, indicating the occurrence of a large magma plumbing system, unexpected for a volcanic field of monogenetic scoria cones. The occurrence of a complete fractionation trend with large magma chambers and large assimilation rate is unusual, if not unique, among the alkali basaltic volcanic fields and it is matched by a climax of activity during the last glacial maximum (30 ka), as indicated by new 40Ar‐39Ar ages (30 ± 3 ka and 25 ± 2 ka) for samples from the two most prominent edifices. Therefore, we hypothesize a role of a thick ice cap in suppressing eruptions and ultimately leading to prolonged magma residence time in the subsurface, favoring significant fractionation coupled with unusual high rates of crustal assimilation.

ORIGIN OF VOLCANIC-HOSTED MAGNETITE AT THE LAGUNA DEL MAULE COMPLEX, CHILE: A NEW EXAMPLE OF ANDEAN IRON OXIDE-APATITE MINERALIZATION

Abstract Iron oxide-apatite (IOA) deposits, also known as magnetite-apatite or Kiruna-type deposits, are a major source of iron and potentially of rare earth elements and phosphorus. To date, the youngest representative of this group is the Pleistocene (~2 Ma) El Laco deposit, located in the Andean Cordillera of northern Chile. El Laco is considered a unique type of IOA deposit because of its young age and its volcanic-like features. Here we report the occurrence of similarly young IOA-type mineralization hosted within the Laguna del Maule Volcanic Complex, an unusually large and recent silicic volcanic system in the south-central Andes. We combined field observations and aerial drone images with detailed petrographic observations, electron microprobe analysis (EMPA), and 40Ar/39Ar dating to characterize the magnetite mineralization—named here “Vetas del Maule”—hosted within andesites of the now extinct La Zorra volcano (40Ar/39Ar plateau age of 1.013 ± 0.028 Ma). Five different styles of magnetite mineralization were identified: (1) massive magnetite, (2) pyroxene-actinolite-magnetite veins, (3) magnetite hydrothermal breccias, (4) disseminated magnetite, and (5) pyroxene-actinolite veins with minor magnetite. Field observations and aerial drone imaging, coupled with microtextural and microanalytical data, suggest a predominantly hydrothermal origin for the different types of mineralization. 40Ar/39Ar incremental heating of phlogopite associated with the magnetite mineralization yielded a plateau age of 873.6 ± 30.3 ka, confirming that the emplacement of Vetas del Maule postdated that of the host andesite rocks. Our data support the hypothesis that the magnetite mineralization formed in a volcanic setting from Fe-rich fluids exsolved from a magma at depth. Ultimately, Vetas del Maule provides evidence that volcanic-related IOA mineralization may be more common than previously thought, opening new opportunities of research and exploration for this ore deposit type in active volcanic arcs.

Detecting Geothermal Phenomena at Sikidang Crater Area Based on Ground Penetrating Radar Method

Abstract Sikidang Crater (2000 masl) is one of the leading tourist sites in the Dieng area. However, not many people realise that Sikidang Crater is located in the Dieng Volcanic Complex where most of the volcanoes belong to the type A category. Sikidang Crater is one of the main geothermal manifestations occupied by mud pools, solfatara, fumaroles, and altered rocks. These manifestations have potential geological hazards such as toxic gases, base surge, and mud explosions. On the other hand, it has a high level of human activity that increases the risk of disasters. As an effort to prevent and mitigate disasters, it is necessary to know the subsurface geological conditions of the crater. This study aims to determine the subsurface geological conditions of the crater. This research uses the methods of detailed geological mapping, manifestation observation, and Ground Penetrating Radar (GPR) geophysical survey. The tool used is Akula Geoscanner 9000C running at 64.75 Hz frequency, capable of penetrating 50 meters deep, and has a vertical resolution of > 0.85 meters. Sikidang Crater is located at the southeastern foot of Mount Pangonan and it forms semicircular like a horseshoe. According to Van Zuidam, the crater is classified as a solfatara and fumarole field geomorphology unit. The lithology of this area is dominated by the eruption products of Mount Pangonan. In general, radargrams resulting from GPR surveys show various amplitudes of reflected electromagnetic waves. This is consistent when correlated with the variation in rock density of the research area. At some points, there is a decrease in electromagnetic wave velocity due to contrast in dielectric constant values, which is interpreted as geothermal fluid flow towards the surface. The potential level of geothermal fluid flow is classified into high, medium, low, and none based on the density of potential points seen in the radargram.

Investigation of the Extent of Hydrothermal Activities of the Sikidang Crater, Dieng Volcanic Complex (Central Java), Using Geomagnetic Method

Abstract The Sikidang Crater (± 2000 m asl) is one of the active craters in the Dieng Volcanic Complex (DVC). It is situated on the southeastern flank of Mt. Pangonan. The crater is significant for development of both tourism and energy sectors in Dieng. Thermal manifestations inside the crater which consist of boiling mud pools and pots, hot springs, fumaroles, gas vents, steaming and altered ground make the place a popular tourist attraction. They also serve as windows to the shallow subsurface processes and help better understand the dynamics of the Dieng geothermal system. However, the land use of the crater and its vicinity disregards the fact that the actual extent of the hydrothermal activity of the crater has not been figured out, and that the foci of the thermal fluid discharges in the crater often shift. Some agriculture plots, housing areas, as well as tourism and geothermal infrastructures are located within or near the morphological boundary of the crater. The inherent hydrothermal hazard of the crater therefore, must be well mitigated to minimize the negative impacts to the people, as well as their assets. Our research aims to delineate the lateral and vertical extent of the hydrothermal activity of the crater by geomagnetic method. Geomagnetic anomaly in geothermal field occurs due to the difference in the intensity of hydrothermal alteration of the rocks. The equipment used was a pair of Proton Precision Magnetometers GEOTRON G5. Our result shows that low geomagnetic anomaly (-2200 to -400 nT) correlated with demagnetized, hydrothermally altered andesitic rocks covers an area of ≥ 1.15 km2, i.e., more than seven times larger than the area outlined by morphological boundary of the crater. The anomalous zone extends N/NE - S/SW from beyond the areas of inter-volcanic plain between Pangonan and Igir Binem in the north, to the areas beyond Sikunang and Kendil cones in the south. Below the Sikidang mud pool the demagnetized rock mass reaches a maximum thickness of 2000 m. The supporting data, i.e., the fluctuations of the gas discharge, and the seismicity of the DVC indicate that the recent dynamics of the Sikidang Crater is mostly controlled by the internal processes within the crater.

Analysis of the Impact Area of the 2022 El Tejado Ravine Mudflow (Quito, Ecuador) from the Sedimentological and the Published Multimedia Documents Approach

Quito (Ecuador) has a history of mudflow events from ravines that pose significant risks to its urban areas. Located close to the Pichincha Volcanic Complex, on 31 January 2022, the northwest and central parts of the city were hit by a mudflow triggered by unusual rainfall in the upper part of the drainage, with 28 fatalities and several properties affected. This research focuses on the affected area from collector overflow to the end, considering sedimentological characteristics and behavior through various urban elements. This study integrates the analysis of videos, images, and sediment deposits to understand the dynamics and impacts of the mudflow using a multidisciplinary approach. The methodology includes verifying multimedia materials using free software alongside the Large-Scale Particle Image Velocimetry (LSPIV) to estimate the kinematic parameters of the mudflow. The affected area, reaching a maximum distance of 3.2 km from the overflow point, was divided into four zones for a detailed analysis, each characterized by its impact level and sediment distribution. Results indicate significant variations in mudflow behavior across different urban areas, influenced by topographical and anthropogenic factors. Multimedia analysis provided insights into the mudflow’s velocity and evolution as it entered urban areas. The study also highlights the role of urban planning and infrastructure in modifying the mudflow’s distribution, particularly in the Northern and Southern Axes of its path, compared with a similar 1975 event, seven times larger than this. It also contributes to understanding urban mudflow events in Quito, offering valuable insights for disaster risk management in similar contexts.

Позднемеловые-раннепалеогеновые вулканические породы Восточной Камчатки (особенности состава и изотопно-геохимическая гетерогенность)

New and previously published isotope-geochemical material on the Upper Cretaceous-Lower Paleogene volcanic complexes of the Ozernovsky-Valaginsky segment of the Achaivayam-Valaginsky paleoarc are presented. It is found that composition of rocks composing separate volcanic fields within the Achayvayam-Valagin paleoarc (terrane) is different. On Karaginsky Island, volcanics of the moderate-potassium calc-alkaline and shoshonite series are widespread. On Ozernaya Peninsula, low-potassium basalts of the tholeiitic series are predominantly developed. The rocks of the Kumroch Ridge include low-potassium basalt-basaltic andesite, medium-potassium calc-alkaline and high-potassium shoshonitic. Volcanic rocks of the Tumrok Ridge are represented by low-potassium picrites and high-potassium trachybasalt-trachyandesites. In the Valaginsky Ridge, low-potassium tholeiitic, moderate-potassium calc-alkaline and shoshonite-latite series, as well as picrites and lamproitoids are distinguished. Isotopic (Sr, Nd and Pb) and geochemical composition of the rocks indicate their formation from a depleted mantle source within an ensimatic volcanic arc. It is shown that in the absence of significant differences in the material composition of rocks, regional differences are manifested. It is suggested that large-ion lithophile elements enrichment of volcanics may relate to fluids introduced into the melts during the melting of the supra-subduction mantle wedge. Issues of geodynamics of the region are considered.

The subsurface anatomy of a mid-upper crustal magmatic intrusion zone beneath the Boku volcanic complex, Main Ethiopian Rift inferred from gravity data

Strain accommodation in the Main Ethiopian Rift has been localized since the Quaternary in axial magmatic segments that contain magma intrusion, volcanic complexes, and fault zones. However, the crustal structure and magmatic plumbing features of the individual volcanic complexes within these magmatic segments are poorly constrained. In this study, gravity data from the Global Gravity Model plus2013 was used to interpret the crustal structure and subsurface volcanic network at and near the Boku Volcanic Complex (Boku VC). Two-dimensional gravity models and an upward continuation map analysis of the upper crust reveal a gravity maximum that is interpreted as mafic intrusion at depths between 5 and 10 km beneath the Boku VC. A circular gravity maximum on the upward continued and residual gravity anomaly maps over the Boku VC and adjacent segments suggest the shallow plumbing systems beneath the segments are discrete, but that they merge into the deeper crust. The gravity models suggest that below 5 km beneath the center of magmatic segments nearly all the extension over the last 2 My can be accounted for by magmatic intrusion. Our models require faults in the uppermost crust which likely contribute to extension and may serve locally as conduits for the conveying melts or hydrothermal fluids. Our gravity analysis supports petrological studies that indicate a two-level magmatic plumbing system beneath the Wonji fault belts in which a melt supply from the upper mantle moves to mid-crust and then to shallow upper crust where the magma fractionates into more siliceous magma within smaller magma chambers.

On the occurrence of kalsilite in melilite-bearing ultrapotassic lavas from the Roman Province (Vulsini Mts., central Italy)

The Montefiascone Volcanic Complex belongs to the Vulsini Mts. volcanic district, one of the several leucite-bearing ultrapotassic Pleistocene volcanoes of the Roman Province (Central Italy). It is characterized by abundant pyroclastic successions and minor lava flows emplaced during a caldera formation phase occurred ∼0.3–0.2 Ma. The volcanic products span from leucite-basanites and leucite-tephrites to rarer leucitites and melilitites, occasionally associated with very rare kalsilite melilitolite ejecta. Here we report for the first time the presence of primary kalsilite in two lava flows in Forcinella and Feltricci localities, identifying a kamafugitic component among the Montefiascone volcanics.Detailed petrographic, SEM and EPMA studies on ten samples from the two localities revealed, in addition to kalsilite, variable amounts of clinopyroxene, melilite, leucite and nepheline plus rarer olivine coupled with carbonate-bearing segregation pockets in the groundmass. Geochemical and isotopic data confirm the exotic nature of the analysed rocks, showing ultrabasic/basic (SiO2 = 42.15–45.94 wt%) and ultrapotassic (K2O = 6.17–8.48 wt%; K2O/Na2O = 5.3–8.7) compositions, as well as strongly radiogenic 87Sr/86Sr (0.71038–0.711068), poorly radiogenic 143Nd/144Nd (0.512057.512091) and uniform middle radiogenic 206Pb/204Pb (18.76–18.78). Boron isotopes (δ11B ranges from 7.36 to 8.82‰) almost overlaps the typical MORB-OIB range values.These geochemical features recall those of the nearby kamafugite rocks from the Intra-Apennine Province. Major oxide and trace element modelling support fractionation links among the Italian kamafugite types. The overall geochemical and isotopic signatures speak for a common strongly subduction-metasomatized and orthopyroxene-free lithospheric mantle source. As already proposed for some nearby kamafugite centres in central Italy, limestone assimilation during magma ascent is a viable option to explain the mineralogical and whole-rock composition of Montefiascone lavas (i.e., the presence of carbonate plagues in the lava groundmass). This is particularly relevant considering the thick sedimentary sequence pierced by the limited volume of the upwelling magma. On the other hand, many other key features (such as the general lack of crustal xenoliths, the overall incompatible element fractionation and the radiogenic Sr isotopic ratios) clearly require also derivation from subduction-modified mantle sources.

Evaluating signal bleaching of Al and Ti–Li centers in fluvio-lacustrine sediments of Datong, North China, and its implications for the volcanic eruption chronology

Assessing the adequate bleaching of quartz Electron Spin Resonance (ESR) signals at the time of deposition is essential for sediment ESR dating. In this study, we focus on the Datong volcanic group is situated in Datong City, Shanxi Province, and is among the most renowned volcanic groups in China. The eruption within the Datong volcanoes during a geological period resulted in extensive high-temperature lava flow that directly overlaid Quaternary lacustrine deposits and subjected the underlying lacustrine layers to high-temperature heating. Thus, an investigation of the field profile in the Yujiazhai area, southeast of the Datong Volcanic Group, shows a novel approach for assessing the bleaching extent of ESR centers. This is accomplished by comparison of the DE values of the Al and the Ti–Li centers in partly-heated layer sample. The result reveals that quartz Al and Ti–Li centers in the lacustrine sediments appear to undergo sufficient bleached during transportation and natural bleaching processes in the study area. Furthermore, this study provides insight into the chronology of volcanic eruption in the Yujiazhai area, estimating an eruption age of approximately 300 ka. This volcanic activity most likely corresponds to the third volcanic activity period in the Datong region.