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Leakage-induced soil erosion poses a major threat to dike failure, particularly during floods. Timely detection and notification of leakage outlets to dike management are crucial for ensuring dike safety. However, manual inspection, the current main approach for identifying leakage outlets, is costly, inefficient, and lacks spatial coverage. To achieve efficient and automatic localization of dike leakage outlets, an innovative strategy combining drones, infrared thermography, and deep learning is presented. Drones are employed for dikes' surface sensing. Real-time images from these drones are sent to a server where well-trained detectors are deployed. Once a leakage outlet is detected, alarming information is remotely sent to dike managers. To realize this strategy, 4 thermal imagers were employed to image leaking outlets of several models and actual dikes. 9,231 hand-labeled thermal images with 13,387 leaking objects were selected for analysis. 19 detectors were trained using transfer learning. The best detector achieved a mean average precision of 95.8 % on the challenging test set. A full-scale embankment was constructed for leakage outlet detection tests. Various field tests confirmed the efficiency of the proposed leakage outlet localization method. In some tough conditions, the trained detector also evidently outperformed manual judgement. Results indicate that under typical circumstances, the localization error of the proposed method is within 5 m, demonstrating its practical reliability. Finally, the influencing factors and limits of the suggested strategy are thoroughly examined. [ABSTRACT FROM AUTHOR]

This paper presents a laboratory study to investigate the wave overtopping over dike on the fringing reef with a large steep fore-reef slope. The experimented models were set up in wave flume, considering three different slopes of dike combined with various wave and still water levels and different roughness cases. The research results indicate that wave overtopping over a dike on the fringing reef depends not only on the relative crest freeboard but also on a synthetic parameter typical for the wave hydrodynamic properties of the fringing reef characteristics and the slope of the dike. An empirical equation of wave overtopping discharge for dike on the fringing reef was derived based on an equation in EurOtop2018 by adding new synthetic parameter, and the comparison of the data from the new empirical formulas with the measured data showed good agreement. The proposed equation of this paper has been applied to estimate wave overtopping discharge over dike on the fringing reef having a large steep fore-reef slope.

The basic purpose of the present research is to numerically elucidate the flow around a single dike in four different geometric configurations (CN: no cylinders, C5: 5 cylinders, C10: 10 cylinders, C15: 15 cylinders), under conditions of a constant flow rate and subcritical flow. This involved substituting the impermeable dike with varying numbers of piles to validate the observed experimental flow patterns, particularly the conditions leading to reverse flow formation. OpenFOAM, an open-source algorithm, was utilized for the simulation, incorporating the volume of fluid (VOF) method. Accurately depicting the reverse flow formation with minimal numerical diffusion, a strategy involving multizone meshing and the application of mesh refinement zones was utilized. These refinements were particularly focused on the section between 1.8 m and 2.2 m within the numerical domain. The water surface profile in front section of the dike and the averaged velocity at five different locations, which were then compared with the numerical results. The numerically predicted streamwise velocity showed a percentage error ranging between 0.5% and 4.5%. The numerical results from this study are pivotal in dike design, aiming to mitigate accelerated wear during flood events and to protect both the dike head and the adjacent bank from high energy flow failures. [ABSTRACT FROM AUTHOR]

In recent years, Erbil has faced an elevated risk of floods due to climate change and incorrect land development design and management. To tackle this issue, this study uses Hydrologic Engineering Center River Analysis System (HEC-RAS) software to address flood inundation and reduction by constructing dikes. This involved using a digital elevation model (DEM) in the study area (Mass Village) east of Erbil. The study delineated the catchment area and employed watershed modelling system (WMS) software. Furthermore, Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) software was used to create a flood hydrograph, which the HEC-RAS software used to estimate flood inundation areas, velocity, and water levels. The study identified water surface areas and velocities prone to flooding in the urbanised area, with water depths ranging from 0 to 5 m. The model was rerun after the construction of the dikes, resulting in water depths ranging from 0 to 7.2 m upstream of the dikes. The modelling results indicated a water depth of 0 m downstream of the dike (protected area), demonstrating that the dike's construction successfully reduced flooding in the urbanised area.

Abstract The temporal evolution of dike volume can help elucidate its propagation dynamics, however, such an estimation is possible only when there are geodetic observations available along the dike path. Here it is shown that dike volume history during eight eruptions can be reconstructed from seismic moment release using high resolution earthquake catalogs. The critical volume needed for each dike to reach the surface is simulated and compared to the accumulated volume prior to eruption in order to infer fracture toughness, a measure of resistance to fracture. It is found that fracture toughness varies between 123–833 MPa m 1/2, with larger values corresponding to longer dikes. Resistance to fracture dominates over viscous dissipation when the dikes propagate through unfractured heterogeneous material with large rigidity contrast, or when there is dike segmentation. These results can be utilized for real time monitoring of dike growth, forecasting eruption volume, and for constraining analog or numerical models of dike propagation.

This article revisits an ostensibly important monument in Classical Attic historiography: the so-called Tomb of Critias, as preserved in a scholium note in Aeschines' "Against Timarchus" (1.39). We survey prior scholarly positions on the realia of this monument, suggest it is a fiction, and consider the possible sources for the hexameter verse associated with it. We argue that the poetic composition from which the entire tradition derives, rather than being an inscription on a tomb, may in fact be an oligarchic commemoration, perhaps an encomium or epitaphios logos recited at Eleusis in the aftermath of the fall of the Thirty. As such, the verse composition may allude to a historiographical tradition that viewed the Thirty as a subversive hetaireia/kōmos group led out to govern the unruly dēmos. The reception of this composition generates a 'lieu de mémoire' in the historical imagination of later readers. The composition offers a piece of comparanda for the political views expressed by other Athenians with pro-oligarchic tendencies, an extreme formulation that strongly contrasts with the extant writings of Critias, Plato, and Xenophon. In revisiting this short anecdote we highlight the relevance of both scholia and monuments in our understanding of Attic historiography. [ABSTRACT FROM AUTHOR]

Geotextiles, as a type of common filtration material, have broad prospects in emergency rescue of dike backward erosion piping (BEP). To investigate the filtration performance of geotextile in BEP emergency rescue, several experiments were conducted using nonwoven and woven geotextiles to simulate the process of rescuing BEP with geotextiles. The influence of geotextile specifications and types on hydraulic compatibility of the filter system was analyzed, and the clogging mechanism of geotextile during dealing with BEP was revealed at a microscopic level. The results showed that the nonwoven geotextile filter with an equivalent pore size of 0.103 mm had a gradient ratio value of less than 3, and it had a highest flow rate of 260 mL/min. Increasing the thickness and pore size of nonwoven geotextiles within a certain range helped enhance their anti-clogging ability. The main mechanism of clogging in nonwoven geotextiles was the deposition of fine sand particles on their surface, forming a layer of low permeability soil. Plain woven geotextiles experienced severe clogging with a 42% reduction in flow rate, and it was not suitable for rescuing BEP. The clogging mechanism of woven geotextile involved the blocking of horizontal water passages by fine sand particles. [ABSTRACT FROM AUTHOR]

Multiple Pool Fire (MPF) reasonably enhances the flame height, the rate of fuel combustion and irradiation due to cascading effect and flame merging of multiple pools. The distribution of temperature and radiative heat flux from the source is the key parameter in predicting safety distance. The current study's major objective is to develop a Computational Fluid Dynamics (CFD) model to calculate the safety distance of MPF and validate the predicted results (flame temperature, radiative heat flux, CO2 and O2 mass fraction) with the experimental data. The flame structure and its thermal properties have been evaluated using the Reynolds Averaged Navier Stokes (RANS) and the Large Eddy Simulation (LES) model. The CFD results are found to be in close agreement with the experimental findings. The LES turbulence model predicts more accurately the flame structures and the fluctuations with an error of less than 3%, while the Re-Normalization Group k-ε model predicts the average characteristics. This authenticates the accuracy of computational methodology and robustness of the LES turbulence model to predict MPF flame characteristics. Furthermore, this computational methodology can be utilised by the industries for quantitative risk assessment and the worst-case scenario of various pool fires to save the human and material of the workplace beforehand. [ABSTRACT FROM AUTHOR]

This paper investigates experimentally the changing of a hydraulic characteristic of combined hydraulic structure owing to the existence of dike structure. Different models of combined structures are used with rectangular gates and rectangular weirs, respectively. Also, the location of the dike structure is considered. A dike is located upstream, downstream, and on both sides of the combined hydraulic structure. Discharge quantity, average downstream water depth, discharge coefficient, and Reynolds number are adopted to describe the alteration in hydraulic behavior of a combined structure. While the relation between upstream Froude number and downstream Froude number, as well as the relation between downstream Froude number with distance, are employed to illustrate the interactive response between dike and combined structure, From the study, the relation between Froude number at downstream and non-dimensional downstream distance as well as the relation between non-dimensional downstream water depth and non-dimensional distance reveal how the dike location effects on water depth and flow velocity, which lead to a change in the type of flow. Here, the dike position is shared in the form of a hydraulic jump at downstream of the combined structure. The experimental data were statistically analyzed to ensure their validity and reliability. The importance of this study is concentrated on how the location of the dike structure is shared in the alteration in the hydraulic characteristics of the combined hydraulic structure, especially the rise in the water depth at downstream, in addition to the change in the hydraulic jump height and energy losses. [ABSTRACT FROM AUTHOR]

Prevention of river or coastal dikes from erosion failure has become more important than ever due to the increasing impact of climate change. A microbially induced carbonate precipitation-based approach was investigated as a possible more sustainable solution for sandy dikes erosion due to overtopping. A series of model tests in a hydraulic flume were carried out on biotreated sand dike models. The models were treated using either surface spray or percolation method and then subjected to flow under various flow rates ranging from 2 to 22 L/s. The erosion, stability, geotechnical parameters, and the amount of calcium carbonate precipitated in the models were measured to assess the effect of the biotreatment. The testing results showed that the untreated sandy dike can be eroded easily, while no erosion occurred after the biocementation using five treatments of 1.5 M of cementation solution through either percolation or surface spray method. Data suggest that in almost the equivalent calcium carbonate content, the percolation method allows soil in a relatively deeper layer to be treated, while the changes occurred just on the formed crust of the models treated with the surface spray method. [ABSTRACT FROM AUTHOR]

AbstractStorm surge-induced flooding (SSIF) is a major hazard for coastal areas under intensified typhoons. Therefore, it is essential to assess the potential impacts of SSIF (SSPIA). This study proposes a multidisciplinary framework for refined SSPIA using an ocean model and a refined exposure estimation method. First, a finite-volume coastal ocean model (FVCOM) and a typhoon model were developed and validated. Then, five scenarios of varying intensity were defined and combined with FVCOM to identify inundation scenarios. Subsequently, machine learning was used to obtain the fine-scale gridded population and gross domestic product (GDP) maps based on the census and geospatial data. Finally, we assessed the magnitude of the affected population and GDP based on the inundation scenarios and refined exposure datasets. We selected Zhoushan Island as a study area to implement this framework. Our assessment results show that the lowest scenario (955 hPa) affected 2587 people and 323.745 million CNY of GDP, while the highest scenario (915 hPa) affected 259,516 people and 20,178.898 million CNY of GDP. Therefore, it is imperative to implement effective mitigation and adaptation measures to address the threat of SSIF. This framework will apply to all flood-prone areas for a refined assessment of the potential impacts of SSIF.

The Fagradalsfjall eruption commenced on 19 March 2021 on a ~180-m-long eruptive fissure, following a 23-day dike intrusion. New eruptive fissures opened northeast of the initial eruption site on 5, 6–7, 10, and 13 April 2021. The northernmost eruption occurred on 5 April, approximately 1 km northeast of the initial fissure, with the other fissure openings between this and the initial eruptive vents. Still images from web cameras and time-lapse cameras are available for five of the fissure openings. These data show that the eruptions were preceded by steam emitted from cracks in the exact locations where the eruptions started. The time between the first steam observations and the visual appearance of glowing lava ranged between 15 s and 1.5 min during night observations and from 9 to 23 min during daytime observations. The difference in observation time is likely explained by the different lighting conditions. The eruptive vents are located where the north-easterly oriented dike intersected pre-existing north-south-oriented fractures, inferred to be strike-slip faults. These fractures could be identified on a high-resolution ICEYE interferogram as well as on pre-existing aerial photographs and digital elevation models. This interferogram spanned the first day of the eruption (19–20 March 2021). It not only displays deformation related to the pre-eruptive dike intrusion but also shows lineations in locations where eruptive vent openings occurred later in April 2021. These findings demonstrate how Interferometric Synthetic Aperture Radar Analysis (InSAR) can be used to forecast likely locations of subsequent eruptive vent openings, which is of great importance for hazard assessment and defining exclusion zones during fissure eruptions. [ABSTRACT FROM AUTHOR]

Frequent drought and worsening salinity intrusion challenge future land uses and livelihoods in the Vietnamese Mekong Delta. The central government is, therefore, formulating a new strategy premised on adaption to natural environmental dynamics. For an achievable strategy that bridges the gap between plans and practice, it is important to understand what drives land-use changes at the farm level. Previous research developed and applied a multi-scale drivers framework in the highly flooded zone of the delta. The current study uses that same framework to investigate the land-use history and drivers of change in the salinity intrusion zone of this delta from 1975 to 2016. We interviewed 32 farmers in Tra Vinh Province and used transcript analysis to quantify the influence of the drivers that the farmers mentioned. We then compared the drivers of land-use change with those found earlier in the highly flooded zone. Results show more diversification of land uses and land-use changes in the salinity intrusion zone. Farmers here followed three main pathways: rice intensification, integrated farming of rice and vegetables/aquaculture, or intensive shrimp farming. Land-use changes were conditional on the regional infrastructure construction to preserve freshwater conditions. However, household-scale drivers, especially natural and financial assets, were most frequently mentioned. Socio-economic context also emerged as an important driver, particularly trends and pressures from the community and markets. [ABSTRACT FROM AUTHOR]

Volcanic eruptions are often preceded by episodes of in ation and emplacement of magma along tensile fractures. Here we study the 2021 Tajogaite-Cumbre Vieja eruption on La Palma, Canary Islands, and present evidence for tensile fractures dissecting the new cone during the terminal stage of the eruption. We use synthetic aperture radar (SAR) observations, together with drone images and time-lapse camera data, to determine the timing, scale and complexities associated with a fracturing event, which is diverging at a topographic ridge. By comparing the field dataset with analogue models, we further explore the details of lens-shaped fractures that are characteristic for faults diverging at topographic highs and converging at topographic lows. The observations made at Cumbre Vieja and in our models are transferrable to other volcanoes and add further evidence that topography is substantially affecting the geometry and complexity of fractures and magma pathways, and the locations of eruptions.

Diked and drained coastal lowlands rely on hydraulic and protective infrastructure that may not function as designed in areas with relative sea-level rise. The slow and incremental loss of the hydraulic conditions required for a well-drained system make it difficult to identify if and when the flow structures no longer discharge enough water, especially in tidal settings where two-way flows occur through the dike. We developed and applied a hydraulic mass-balance model to quantify how water levels in the diked and tidally restricted coastal wetlands and water bodies dynamically respond to sea-level rise, specifically applied to the Herring River Estuary in MA, USA, from 2020 to 2100. Sensitivity testing of the model parameters indicated that primary outcomes were not sensitive to many of the chosen input values, though the terrestrial water input rate to the estuary and the flow coefficient for the hydraulic infrastructure were important. The relative importance of parameters, however, is expected to be site specific. We introduced a drainability metric that quantifies the net water volume drained over every tidal cycle to monitor and forecast how rising water levels on either side of the dike affected the net draining or impounding conditions of the system. Ensembles of model results across parameter and sea-level scenario uncertainties indicated that substantial impoundment of the Herring River Estuary was expected within ~ 20 years with the existing flow structures, a sluice and two flap gates. Simulations with up to three additional gates did not dampen this trend toward impoundment, suggesting that rising impounded water levels are likely even with major construction upgrades. Increasingly impounded diked coastal waterbodies present a hydrologic challenge with socioecological implications due to projected flooding and ecosystem impacts. Solutions to this challenge may be to allow coastal wetland restoration pathways or require substantial and recurring infrastructure improvement projects. [ABSTRACT FROM AUTHOR]

The Koshi, one of the biggest tributaries of the Ganges River, has been renowned for centuries for its erratic behaviour and destructive flooding of the Indo-Nepalese plain. Based on the Tennessee Valley Authority model’s success and in order to develop the region, the river was totally dammed in 1959, radically transforming the way local communities relate to water in the wetlands of the Koshi plain. Since then, embankments have been built extensively in this plain both in India and Nepal. Devastating incidents, such as the spectacular disaster in 2008, are still vivid in inhabitants’ memories. Despite a questioning of the himalayan region’s management paradigm, the model continues to be applied extensively, with gradual development having recently been achieved in Nepal on secondary rivers in the Tarai plain. This article sets out to analyse the impact of this programme of embanking Koshi affluents in the villages of Tilathi and Narsingh, on the right and the left banks of the Koshi respectively. It shows that in recent decades, floods have become more frequent, often prolonging water removal time, and that the causes of floods are multiplying. These two case studies are emblematic of a demonstration of how floods are transformed into socio-environmental disasters and are vital for studying the structural dimensions of who wins and who loses in this new water-balance configuration where areas are exposed or protected.

This study aimed to assess the suitability of lime treatment for use in dikes in the Netherlands. The effect of this technique on the behavior of a Dutch clay was addressed by comparing the detailed response of lime-treated and natural samples at different lime contents (1.25% and 2.25%) and curing periods. A series of laboratory tests consisting of index classification, constant rate of strain, and triaxial and hole erosion tests were performed. The results demonstrated that lime treatment altered the soil response. Differences were observed in the physical, compressibility, strength, and erodibility properties. It was found that lime improved considerably the resistance to compression and erosion, but the effect on hydraulic conductivity was limited. The triaxial test results showed that lime treatment was particularly effective at low stress (<25 kPa) and low strain levels (<10%). During shearing, lime-treated samples exhibited dilative tendencies and enhanced effective strength properties until a stress-strain state was reached that was believed to be related to the breakage of the bonding structure of the sample. The findings of this study demonstrate that the merits of lime treatment can be of particular benefit in dike applications, particularly when the focus is on improving soil erosion resistance. [ABSTRACT FROM AUTHOR]

Leaks refer to seepage holes running through a dike body or foundation, the formation of which may pose dire threats to dike safety and cause dike breaching due to a large flow rate and strong scouring force. Once the water inlet of a leak is detected, sealing and rescue measures should be taken in accordance with the principle of "inlet plugging and outlet anti-filtration". The key is the quick filling and stability of the plugging materials. Herein, the rescue technology of dike leaks is systematically laid out; the formation causes and development mechanism of the leaks are analyzed; the dike leak detection, plugging, and sealing technology is summarized; and the future research direction is clarified. Existing plugging technology and equipment are complicated and time-consuming. Hence, plugging methods should be innovated and improved to effectively improve the efficiency and success rate of emergency rescues. A new concept of "grade-by-grade plugging and sealing" is correspondingly proposed for dike leaks, changing leak rescues from "single-level plugging and sealing at the leak inlet" to "grade-by-grade plugging and sealing at the portal and inside the leak". A tandem closed space is formed in the leak. The hydrodynamic pressure is changed from the independent bearing of the portal to the gradual bearing of the plugging materials at the portal and inside the leak. [ABSTRACT FROM AUTHOR]

The Nanggulan Formation sediments form a weakly undulating hill and range in age from the Middle Eocene to the Late Oligocene. In Samigaluh and Sermo areas, a series of sedimentary rocks with small dimensions resembling fragments and forming a steep hilly morphology is exposed. Outcrops are mainly made up of sandstone and claystone interbedded with lignite intercalation. An outcrop in Sermo-2 found andesite intruding claystone. Claystone is found near rock contact, where it is an alteration to metasediment and chlorite is formed. Petrographic data showed the presence of chlorite, pyrite, and kaolinite. Andesite dike is one factor that contributes to the Nanggulan Formation being exposed to the surface. The Nanggulan Formation is a roof pendant above a dike. The implications of the roof pendant are related to the propylitic to argillic of hydrothermal alteration, which produce chlorite, pyrite, illite, and kaolinite minerals.

O objetivo é analisar a tensão entre duas formas díke na tragédia de Sófocles Édipo rei. Como as tragédias ocupavam um papel privilegiado na pólis, as encenações constituíam uma instituição política. Devido a isso, as tragédias representavam certos conflitos sociais e políticos entre uma tradição arcaica e uma nova ordem democrática, tensões estas que podem ser evidenciadas na investigação promovida por Édipo. Neste inquérito há um conflito entre duas formas de justiça, uma divina (tradicional) e outra humana (democrática e institucional). O artigo, primeiramente, descreve a relação entre tragédia e pólis; em seguida, assinala o conflito que se desenhava na pólis democrática e que se refletia, de certo modo, nas peças trágicas; por fim, examina, em Édipo rei, a articulação antagônica entre a díke tradicional e a humana.

The marshes and coastal areas of the river Dives, Calvados (France), are threatened both by water and sea level rises, coastal floodings and submersions as consequences of the global and local climate changes. The river Dives crosses this dyked marshland which covers nearly 10000 ha and whose impoldering dates since the 12th century. Local stakeholders are much concerned by the global decay of the dikes and wish to benefit from the expertise of a national research program (National Research Agency 2019-2023 DIGUES for Dikes, Interactions, Management, Uses, Environment and Scenario) in order to identify potential adaptation strategies. This exploratory research program aims at identifying natural and man-made habitats that cover the dikes and giving a better understanding of the evolutionary processes of this at-risk territory. The use of drone surveys and of a transect method over the landscape help determine disturbing elements that could have an impact on these flood protection structures. In addition to this alternative approach of habitat monitoring, this research gives the opportunity to establish different trend scenarios for the dikes of the river Dives that represent a central challenge in climate change issues.

Normal stress on dikes is one of the most critical parameters for a sound dike design. With more rapidly rising sea levels due to global warming, dikes are seriously threatened by overtopping induced by the combination of wave and storm surge. Compared with wave overtopping on positive freeboard, the curling breaking wave on dikes induced by the combined wave and surge overtopping may destroy the weakly protected dike crest and landward slope. Thus, in order to prevent severe damage to dikes, it is necessary to fully understand the normal stress induced by the combined wave and surge overtopping. In this paper, physical model tests were carried out to study the normal stress on dike induced by the combined wave and surge overtopping. Two characteristics of normal stress on dike were observed. The spatial distribution of normal stress on dike was also analyzed. It was found that the Weibull distribution can be used to effectively describe the statistical distribution of peak normal stresses. Furthermore, by curve fitting of the laboratory measured data, the Weibull factors on the part of the crest and the upper part of the landward slope were obtained.

Frequent drought and worsening salinity intrusion challenge future land uses and livelihoods in the Vietnamese Mekong Delta. The central government is, therefore, formulating a new strategy premised on adaption to natural environmental dynamics. For an achievable strategy that bridges the gap between plans and practice, it is important to understand what drives land-use changes at the farm level. Previous research developed and applied a multi-scale drivers framework in the highly flooded zone of the delta. The current study uses that same framework to investigate the land-use history and drivers of change in the salinity intrusion zone of this delta from 1975 to 2016. We interviewed 32 farmers in Tra Vinh Province and used transcript analysis to quantify the influence of the drivers that the farmers mentioned. We then compared the drivers of land-use change with those found earlier in the highly flooded zone. Results show more diversification of land uses and land-use changes in the salinity intrusion zone. Farmers here followed three main pathways: rice intensification, integrated farming of rice and vegetables/aquaculture, or intensive shrimp farming. Land-use changes were conditional on the regional infrastructure construction to preserve freshwater conditions. However, household-scale drivers, especially natural and financial assets, were most frequently mentioned. Socio-economic context also emerged as an important driver, particularly trends and pressures from the community and markets.

We present analog experiments on dike propagation, followed by a numerical model of horizontal and vertical growth, which is partially analytical and partially based on empirical observations. Experimental results show that the growth rates are similar until buoyancy becomes significant and, afterward, vertical growth dominates. The numerical model is defined for different conditions in a homogeneous medium: (a) constant flux, fracture‐limited propagation; (b) constant flux, viscous‐limited propagation; and (c) variable flux dependent on the driving pressure and dike dimensions. These conditions distinguish between cases when the influx depends on the deeper source of magma (e.g., a conduit, independent of the dike geometry) and when it depends on the dike, so the influx can change as it grows. In all cases, the ratio of vertical to horizontal propagation is proportional to the ratio of buoyancy pressure to source pressure, in which buoyancy drives vertical propagation. We test the numerical model on dikes observed at Piton de la Fournaise, in which the dimensions were estimated using geodetic and seismic data. The results show that the final dimensions can be reproduced using magma‐crust density differences of 50–300 kg/m3, viscosities of 30–300 Pa·s, influxes of 50–750 m3/s and shear moduli of ∼10 GPa. The modeled magma and host rock parameters agree with previous studies of the volcano, while the flux is higher than what is typically observed during eruption. This implies a variable injection condition, in which the flux peaks during propagation and diminishes by the onset of eruption. Plain Language Summary: Magma‐filled cracks, or "dikes," grow through the Earth's crust and can feed volcanic eruptions. Building reliable models of how they grow is important for forecasting future eruptions. Mathematical models of dike growth commonly consider growth in length only, which allows for simplifications that make it efficient to run simulations. More‐complex 3D simulations tend to require powerful computers and can take a long time to complete. We present a new model that simplifies the dike to an ellipsoidal shape, like a flattened sphere. This model allows dikes to grow in a way that matches experiments and shows that the growth depends on physical forces like buoyancy. When dikes have a low buoyancy, they can grow both vertically and horizontally, but as they become more buoyant, they grow primarily vertically. We test our model against past eruptions at Piton de la Fournaise, a highly active volcano located off the eastern coast of Madagascar. We find that under certain conditions, the model can reproduce the sizes of the dikes. These conditions help us to understand what happens at this volcano specifically, but also how other volcanoes can behave in general. Key Points: Analog experiments indicate that dike propagation in the vertical and horizontal directions depends on the buoyancy and source pressureWe define a numerical model in which growth depends on influx and different pressure ratios, which evolve with timeThe model reproduces the geometries and velocities for nine dikes in nature, using plausible values for magma and host rock rheology [ABSTRACT FROM AUTHOR]

Cotopaxi is a large, ice-capped stratovolcano located in the Ecuadorian Andes. After 72 years of repose, Cotopaxi erupted on August 14, 2015. The precursory activity included long-period (LP) events followed by volcano-tectonic (VT) earthquakes, very-long-period events accompanying LP signals (VLP/LP events), tremor, deformation and SO 2 emissions. VLP/LP events were first observed at Cotopaxi in 2002, and persistently occurred from 2009 to 2014 and during the 2015 eruptions. Previous studies of the VLP/LP seismicity suggested that these events originated by repetitive volume changes in a crack due to degassing of water from magma at a depth of 2–3 km beneath the NE flank. Based on this interpretation, we estimated the magma volumes related to individual VLP/LP events from 2009 to 2015, which were systematically extracted from continuous seismic records of the Cotopaxi broadband seismic network. Based on the accumulated magma volume and the VLP/LP activity, our study is divided into seven periods (phases A − G), during which the magma supply rate significantly fluctuated. In phase E (June 1–July 27, 2015), before the eruptions, the magma supply rate increased. Degassing at the VLP source generated gas flows in the conduit and pre-eruptive tremor, gradually drying out a shallow hydrothermal system. In phase F (July 28–September 15, 2015), we estimated the highest magma supply rate, leading to magma fragmentation at the VLP source and eruptions accompanied by tremor. In phase G (September 16–December 29, 2015), the magma supply rate decreased, and overall eruptive activity, VLP/LP events, and tremor gradually waned. These results indicate that the VLP/LP events were likely generated by degassing from magma supplied to the VLP source through an intruded dike before and during the eruptions. The VLP/LP activity provides critical useful information about the magma supply rates that controlled eruptive and gas emission activity at Cotopaxi during this period and may help to constrain magma volumes during future reactivations. • VLP/LP events are related to the overall seismic activity and SO 2 emissions during pre-eruptive and eruptive periods. • Seismic patterns indicating heightened activity and impending eruptions. • New methodology to quantify magma volume using a non-destructive VLP source at the volcano. • Degassing changes occur during passive and active states, and when the volcanic system's conduit becomes more open. [ABSTRACT FROM AUTHOR]

Saline tidal wetlands are important sites of carbon sequestration and produce negligible methane (CH4) emissions due to regular inundation with sulfate‐rich seawater. Yet, widespread management of coastal hydrology has restricted tidal exchange in vast areas of coastal wetlands. These ecosystems often undergo impoundment and freshening, which in turn cause vegetation shifts like invasion by Phragmites, that affect ecosystem carbon balance. Understanding controls and scaling of carbon exchange in these understudied ecosystems is critical for informing climate consequences of blue carbon restoration and/or management interventions. Here, we (1) examine how carbon fluxes vary across a salinity gradient (4–25 psu) in impounded and natural, tidally unrestricted Phragmites wetlands using static chambers and (2) probe drivers of carbon fluxes within an impounded coastal wetland using eddy covariance at the Herring River in Wellfleet, MA, United States. Freshening across the salinity gradient led to a 50‐fold increase in CH4 emissions, but effects on carbon dioxide (CO2) were less pronounced with uptake generally enhanced in the fresher, impounded sites. The impounded wetland experienced little variation in water‐table depth or salinity during the growing season and was a strong CO2 sink of −352 g CO2‐C m−2 year−1 offset by CH4 emission of 11.4 g CH4‐C m−2 year−1. Growing season CH4 flux was driven primarily by temperature. Methane flux exhibited a diurnal cycle with a night‐time minimum that was not reflected in opaque chamber measurements. Therefore, we suggest accounting for the diurnal cycle of CH4 in Phragmites, for example by applying a scaling factor developed here of ~0.6 to mid‐day chamber measurements. Taken together, these results suggest that although freshened, impounded wetlands can be strong carbon sinks, enhanced CH4 emission with freshening reduces net radiative balance. Restoration of tidal flow to impounded ecosystems could limit CH4 production and enhance their climate regulating benefits. [ABSTRACT FROM AUTHOR]

Post‐rifting ground deformation may be driven by viscoelastic relaxation of stresses generated by dike intrusions. The single‐dike intrusion of the 2014–2015 Bárðarbunga eruption in Iceland presents an opportunity for a detailed study of this process. We use continuous Global Navigation Satellite System (GNSS) and Interferometric Synthetic Aperture Radar (InSAR) velocity fields to analyze the 2015–2020 post‐rifting deformation, showing uplift on both sides of the dike and horizontal displacement away from the dike after correcting for background deformation. Two GNSS stations experience baseline lengthening at a rate of 19 mm/yr in the direction perpendicular to the strike of the dike. A two‐layer viscoelastic model with a 0.4 × 1019 Pa s viscoelastic half‐space overlain by an 18 km thick elastic layer best explains the observed horizontal and vertical InSAR and GNSS displacements. The model misfit space shows a second regime of good fit, likely driven by deformation near the dike that may result from cooling compaction of the emplaced dike. Plain Language Summary: Surface displacement can continue for years after a fissure eruption ends. This has been found at some volcanoes, such as in Afar (Ethiopia) and Krafla (Iceland). The 2014–2015 Bárðarbunga eruption in Iceland created a 48 km long dike, that led to an eruption to the northeast of the Bárðarbunga caldera outside the Vatnajökull ice cap. Here, we focus on exploring an explanation for the surface movement in the dike area after the eruption. Other non‐volcanic processes cause surface movements in the area, including glacial isostatic adjustment caused by the ice retreat and plate spreading due to the divergence of the Eurasian plate and North American plate. We first correct for deformation due to these processes. The remaining deformation signal shows uplift on both sides of the dike and horizontal displacement away from the dike. We test if a two‐layer model consisting of an elastic layer on top of a viscoelastic half‐space can explain our observations. Our results suggest that material properties similar to other nearby areas explain the observations well. Systematic difference between observed and modeled deformation near the dike feeding the eruption is likely due to its cooling. Key Points: Interferometric Synthetic Aperture Radar (InSAR) & Global Navigation Satellite System (GNSS) velocities indicate ∼19 mm/yr widening across a dike after its formation interpreted as post‐rifting viscoelastic relaxationA two‐layer viscoelastic model with 0.4 × 1019 Pa s viscoelastic half‐space below 18 km depth best explains the GNSS and InSAR observationsElastic thickness of ∼18 km provides best fit, but a comparable fit is at ∼2 km, most likely due to unmodeled processes [ABSTRACT FROM AUTHOR]

Summary: The increase in the number of hydrogen (H2) fuel cell vehicles necessitates the swift installation of requisite infrastructure such as H2 refueling stations (HRSs). However, the use and storage of high‐pressure gaseous H2 in conventional HRSs limits inventory and poses safety risks. In this regard, ammonia (NH3) is a potential solution as an H2 carrier with high storage capacity that can be stored as a liquid. However, NH3 is toxic and accidental exposure to it is fatal for humans. Therefore, this study aims to develop a process and safety design for HRSs using NH3 as the H2 carrier. The operation of ammonia‐derived H2 refueling stations comprises dehydrogenation and refueling processes, for which quantitative risk assessment was performed based on process design data. Consequently, it was determined that NH3 leakage from the storage tank was the dominant accident scenario and that the associated risk exceeded the acceptable risk criteria. Therefore, we proposed a risk mitigation strategy that involves installing a dike to guarantee safe design and operation. [ABSTRACT FROM AUTHOR]

Abstract We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which has been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4200 m occurred at Minami-dake. During the 3 min following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC + 9); the same hereinafter), phase 1, a large strain with changes up to 120 nstrain was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations, whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes at all stations and small strain changes at the Harutayama observation tunnel (HVOT) and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake, which turned inflation after the deflation that occurred during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source M D, but also the Kita-dake source deflated due to the Minami-dake explosion.

Habitable ocean environments on Europa require an influx of reactants to maintain chemical disequilibrium. One possible source of reactants is seafloor volcanism. Modeling has shown that dissipation of tidal energy in Europa's asthenosphere can generate melt, but melt formation cannot be equated with volcanism. Melt must also be transported through Europa's cold lithosphere to erupt at the seafloor. Here, we use two models of dike propagation to show that dikes can only traverse the lithosphere if either the fracture toughness of the lithosphere or the flux into the dike is large (>500 MPa m1/2 or ∼1 m2 s−1, respectively). We conclude that cyclic volcanic episodes might provide reactants to Europa's ocean if magma accumulates at the base of the lithosphere for several thousand years. However, if dikes form too frequently, or are too numerous, the magma flux into each will be insufficient, and volcanism cannot support a habitable ocean environment. Plain Language Summary: Beneath the icy crust of Jupiter's moon Europa lies a deep, liquid‐water ocean that might provide an environment suitable for life. In the absence of sunlight, organisms must extract energy from chemical reactions within the ocean. Over time, organisms would use up all the chemical ingredients needed for these reactions, leading to extinction unless new ingredients were added to the environment. Because the ocean is closed‐off from Europa's surface by the thick ice crust, seafloor volcanism has been proposed as a source of chemical ingredients. Europa's deep rock interior can get hot enough to form small amounts of magma that will rise upward; however, the magma must also travel across the outer cold portion of the rock interior, which requires the formation and growth of magmatic dikes. Here we determine that dikes long enough to supply magma to Europa's seafloor only form if the rock is either very strong, or the amount of magma entering the dike is very large. In those cases, volcanism could occur on Europa's seafloor every few thousand years, supplying the necessary life‐sustaining chemical ingredients. NASA's upcoming Europa Clipper mission will provide new data that helps clarify whether the conditions needed for seafloor volcanism are met. Key Points: For volcanism to provide life‐sustaining reactants to Europa's ocean, asthenospheric‐formed melt must traverse the cold thick lithosphereDikes can propagate across the entire lithosphere if either the fracture toughness or the flux into the dike is largeVolcanism plausibly provides reactants to Europa's ocean every several thousand years, but seafloor volcanism is far from assured [ABSTRACT FROM AUTHOR]

This study aimed to (i) select endophytic bacteria in maize root for its phosphorus solubilization ability and (ii) evaluate the efficacy of selected indigenous bacterial strains on soil fertility, phosphorus (P) uptake, growth, and maize yield. A total of 31 maize root samples were collected from An Phu District, An Giang Province, to isolate the bacteria. In addition, the pot experiment was conducted with nine treatments of (i) 100% P of the recommended fertilizer formula (RFF), (ii) 75% P of the RFF, (iii) 50% P of the RFF, (iv) 25% P of the RFF, (v) 75% P of the RFF plus a mixture of the 3 selected strains, (vi) 50% P of the RFF plus a mixture of the 3 selected strains, (vii) 25% P of the RFF plus a mixture of the 3 selected strains, (viii) 0% P of the RFF plus a mixture of the 3 selected strains, and (ix) 0% P of the RFF plus none of the 3 selected strains. The results identified 72 isolates from LGI medium. All isolates were screened in a broth medium at pH 5.0, but only 16 isolates obtained OD660 > 0.5. All 16 isolates were able to solubilize various insoluble P fractions. Of those, strain ASD-21 had the highest P solubilization ability for the insoluble Al-P compound. Strains ASD-08 and ASD-21 had the highest Fe-P concentration at 39.8-41.5 mg P L-1. Strains ASD-08 and ASD-21 had the highest Ca-P concentration (46.6-51.3 mg P L-1) for 48 h of incubation. They were identified as Enterobacter spp. Results also showed the application of a mixture of strains ASD-08, ASD-10, and ASD-21 increased soil fertility by increasing phosphorus content by 13.7 mg P kg-1 and replacing 25% of P fertilizer, but this mixture did not change maize yield. [ABSTRACT FROM AUTHOR]

Using remote sensing extended on geological and topographical maps and verified by the field work, we present the flood management and study the geomorphic features of the floodplain of a large, sand bed, untrained but embanked river in order to determine the flood hazard and to predict future flood scenarios. In geomorphological mapping, we focus on the landforms: crevasse channels and splays, flood basin, chute channels, side arms, floodplain channels, dunes and fields of aeolian sand. We base the flood risk assessment on consultations with environmental engineers who design new technical structures that control inundation (cut-off walls and lattice levees). We describe a levee breach as a result of piping (inner erosion) in a high hydraulic gradient condition and its effect (scour hole) as an erosional landform consistent with the repetitive pattern of erosion and deposition formed by an overbank flow on a floodplain. We reveal an existence of homogenous morphodynamic reaches in the river valley.

It is still common practice in Europe to dike salt marshes for agricultural use. This impacts both the vegetation and physical environment of the marsh. We studied the plant community, environmental conditions, and determined correlations between vegetation cover and diversity with environmental factors on an enclosed marsh, which has been behind a dike since 1890. Vegetation data from both salt marshes without dikes and fresh meadows are routinely sampled by the Danish Environmental Protection Agency and were here used to assess whether the plant community of the shielded marsh resembled that of either salt marshes or fresh meadows. The century-long elimination of tidal and storm flooding has resulted in low salinity levels (0.4–5.13 ppt), low available P (0.36–4.90 mg/100 g soil), and high total N (0.68–28.82 g/kg). The plant community of the shielded marsh demonstrated a mean species richness (11.4) similar to that of other salt marshes but was no longer characterized by the same composition of halophytes (ANOSIM, p < 0.001). However, despite the century-long shielding the vegetation does not resemble that of the nearby fresh meadow community (ANOSIM, p < 0.001). Therefore, prohibiting tidal floodings by dikes does not protect the salt marsh habitat but instead results in a habitat that contains both halophytes and glycophytes. [ABSTRACT FROM AUTHOR]

Thrust fault-related landforms, smooth plains units, and impact craters and basins have all been observed on the surface of Mercury. While tectonic landforms point to a long-lived history of global cooling and contraction, smooth plains units have been inferred to represent more punctuated periods of effusive volcanism. The timings of these processes are inferred through impact cratering records to have overlapped, yet the stress regimes implied by the processes are contradictory. Effusive volcanism on Mercury is believed to have produced flood basalts through dikes, the propagation of which is dependent on being able to open and fill vertical tensile cracks when horizontal stresses are small. On the contrary, thrust faults propagate when at least one horizontal stress is very large relative to the vertical compressive stress. We made sense of conflicting stress regimes through modeling with frictional faulting theory and Earth analogue work. Frictional faulting theory equations predict that the minimum and maximum principal stresses have a predictable relationship when thrust faulting is observed. The Griffith Criterion and Kirsch equations similarly predict a relationship between these stresses when tensile fractures are observed. Together, both sets of equations limit the range of stresses possible when dikes and thrusts are observed and permitted us to calculate deviatoric stresses for regions of Earth and Mercury. Deviatoric stress was applied to test a physical model for dike propagation distance in the horizontally compressive stress regime of the Columbia River Flood Basalt Province, an Earth analogue for Borealis Planitia, the northern smooth plains, of Mercury. By confirming that dike propagation distances from sources observed in the province can be generated with the physical model, we confidently apply the model to confirm that dikes on Mercury can propagate in a horizontally compressive stress regime and calculate the depth to the source for the plains materials. Results imply that dikes could travel from ∼89 km depth to bring material from deep within the lithosphere to the surface, and that Mercury’s lithosphere is mechanically layered, with only the uppermost layer being weak.

The state-of-the-art formulas for mean wave overtopping (q) assessment typically require wave conditions at the toe of the structure as input. However, for structures built either on land or in very shallow water, obtaining accurate estimates of wave height and period at the structure toe often proves difficult and requires the use of either physical modeling or high-resolution numerical wave models. Here, we follow Goda's method to establish an accurate prediction methodology for both vertical and sloping structures based entirely on deep-water characteristics—where the influence of the foreshore is captured by directly incorporating the foreshore slope and the relative water depth at the structure toe (htoe/Hm0,deep). Findings show that q decreases exponentially with htoe/Hm0,deep due to the decrease of the incident wave energy; however, the rate of reduction in q decreases for structures built on land or in extremely shallow water (htoe/Hm0,deep ≤ 0.1) due to the increased influence of wave-induced setup and infragravity waves—which act as long-period fluctuations in mean water level—generated by nonlinear wave transformation over the foreshore. [ABSTRACT FROM AUTHOR]

[Display omitted] • A transition from 695 Ma I-type, convergent margin magmatism in the north to 635 Ma alkalic, within magmatism in the south is recorded. • Our results thus document a chronologic and tectonic transition from synorogenic, intra-oceanic arc to post-collision within-plate magmatism in the Ediacaran. • Our results also illustrate the viability of dikes as markers of orogénesis. The tectonic evolution of the Arabian-Nubian Shield began with formation of intra-oceanic arcs followed by collisions between these in Tonian-Cryogenian time and culminated in Ediacaran continental collision to form Gondwana. We provide new insights into the middle stage of this tectonic evolution by focusing on two Neoproterozoic dike swarms of different age in northern Arabia. The 695–700 Ma Za'am dikes were emplaced about the time of collision between the Midyan and Hijaz terranes whereas the 635 Ma Bayda dikes were emplaced ∼ 60 million years after collision. These record a shift from relatively unfractionated 695 Ma arc-type magmas in the south to fractionated 635 Ma within-plate alkaline magmas in the north. Our results document mantle source and crustal evolution beneath the Midyan terrane during and after terrane accretion, revealing a tectono-magmatic transition from SSZ-type magmas accompanying arc collision to post-terrane accretion within-plate magmatism through Cryogenian time. In addition, our results confirm the potential of dike studies for reconstructing the tectono-magmatic-metallogenic evolution of orogens. [ABSTRACT FROM AUTHOR]

Objective. The objective of our research was to search for manifestations of ore mineralization on the Roca and Cruls islands in the Argentine Islands, West Antarctica. Methods. Samples of rocks with the manifestation of ore mineralization were taken in the field routes. Silicate analysis of the rocks was carried out using the wet chemistry method in M.P. Semenenko Institute of Geochemistry, Mineralogy and Ore Formation of the National Academy of Sciences of Ukraine (IGMOF of NAS of Ukraine). The X-ray diffraction analysis of samples was carried out using a DRON-2 diffractometer, with copper radiation (СuКα = 1.54178 Å). The samples were surveyed in the 4—65° 2θ interval of angles, with a scan step of 0.1 degr. / min. For mineral diagnostics, the catalog of reference samples of the PDF-2 database (International Diffraction Data Center, ICDD) 2003. The chemical composition of minerals was examined using a JXA-733 X-ray microanalyzer (Jeol, Japan) using wave and energy-dispersion spectrometers. Contents of trace elements in the rocks were determined using the ICP-MS and quantitative spectral analysis methods. The validity of analyses was checked by means of determination of international and Russian reference samples GSP-2, VM, SGD-1А, ST-1. Concentration measuring errors were 3 to 5 wt. % for most elements. The quantitative spectrum analysis was carried out in IGMOF of NAS of Ukraine. Petrographic studies of rock sections were carried out using a MIN-8 polarized-light microscope. Results. Wolfram, copper, zinc, and lead were found in the minor intrusion of lamprophyres in the Andes complex granodiorites, on a small island of the Roca Islands. This semi-ring-shaped minor intrusion up to 0.5 m thick rooted in the not yet crystallized granodiorite intrusion. The dip angle of the minor intrusion is about 70°. It showed tungsten (28.7 g/t), copper (445 g/t), zinc (207 g/t), and lead (123 g/t) mineralization. In the eastern part of one of the Cruls Islands, a steep (dip azimuth NW 345°, angle 82°) tectonic zone up to 10 m wide was studied. Three metasomatic belts, one of which is up to 0.5 m thick, are associated with this zone. Metasomatites include pyrite-plagioclase rocks, epidosites and pyrite-epidote rocks, which have been formed due to hydrothermal and metasomatic changes of granodioritic tectonic breccia. The occurrence of cobalt (800 g/t), copper (200 g/t) and gold (up to 0.3 g/t) has been discovered. In these metasomatites, magnetite, pyrite, copper pyrite and pyrrhotite are available. Cobalt is present as magnetitic and pyritic impurities. Conclusions. During geological surveys in 2010 and 2012 the mineralization of wolfram, copper, lead, cobalt and gold was first discovered. The ore mineralization of such genesis was previously unknown in this area. The data obtained allow clarifying of perspectives of exploration activities in West Antarctica.

The contribution is dealing with run-off conditions on the lower part of the Ondava River as the capacity of the river bed is insufficient at high flow rates. The reason for the proposed research was the flood situations when protection dikes were breached. For mathematical modeling of flood wave progress, the HEC-RAS software has been applied coupling 1D and 2D modeling procedures. Results of the mathematical model of the surface water level regime in the Ondava River were compared with measured values and afterwards it was used to design further flood protection measures utilizing the existing drainage channel system and pumping stations, as well. [ABSTRACT FROM AUTHOR]

Sea levels will rise, even with stringent climate change mitigation. Mitigation will slow the rate of rise. There is limited knowledge on how the costs of coastal protection vary with alternative global warming levels of 1.5 to 4.0 °C. Analysing six sea-level rise scenarios (0.74 to 1.09 m, 50th percentile) across these warming levels, and five Shared Socioeconomic Pathways, this paper quantifies the economic costs of flooding and protection due to sea-level rise using the Dynamic Interactive Vulnerability Assessment (DIVA) modelling framework. Results are presented for World Bank income groups and five selected countries from the present to 2100. Annual sea flood damage costs without additional adaptation are more influenced by socio-economic development than sea-level rise, indicating that there are opportunities to control risk with development choices. In contrast, annual sea dike investment costs are more dependent on the magnitude of sea-level rise. In terms of total costs with adaptation, upper middle, low middle and low income groups are projected to have higher relative costs as a proportion of GDP compared with high income groups. If low income countries protected now, flood costs could be reduced after 2050 and beyond. However, without further adaptation, their coasts will experience growing risks and costs leaving them increasingly reliant on emergency response measures. Without mitigation or adaptation, greater inequalities in damage costs between income groups could result. At country level, annual sea flood damage costs without additional adaptation are projected to rapidly increase with approximately 0.2 m of sea-level rise, leaving limited time to plan and adapt. [ABSTRACT FROM AUTHOR]

Purpose. To present the model of tectonic development of the Irtysh shear zone, based on recent uranium-lead dating for zircon. Methodology. The authors analyzed the results of studies of foreign and domestic scientists, conducted field research, sample preparation, carried out iso-tope studies using SHRIMP-2 and LA-ICP-MS technology; determined small elements by the fusion method using ICP. Findings. Based on more than ten uranium-lead dating for zircon using the local method and the given geological and structural data, model of the Irtysh shear zone tectonic development has been proposed Originality. A tectonic model has been developed and the age and structural relationships of the Irtysh shear zone with the Kalba-Narym zone based on uranium-lead zircon dating have been established. Practical value. The article considers the structural and age relationships of the Irtysh crush zone which prove its formation along the deep Irtysh fault in the course of a long multi-stage tectogenesis. [ABSTRACT FROM AUTHOR]

The assessment of the length-weight relationship and condition factors was carried out for three commercial fish species, Esomus metallicus Ahl, 1923, Anabas testudineus (Bloch, 1792) and Trichopodus trichopterus (Pallas, 1770). The survey was carried out in habitats influenced by human activities associated with rice paddy fields in three areas situated in An Giang Province, Vietnam: Luong Phi, islets in An Thanh Trung and Hau riverside in Vinh Thanh Trung. The relationship between length and weight showed the slope values (b) of the three species between 2.75 and 3.29; the growth patterns in them (negative allometry, positive allometry and isometry) varied depending on site and time of sampling. The b values in the three species were close to the critical isometric value (3), which could indicate that these species were highly fit for these conditions. No significant difference in the condition factors were observed in Anabas testudineus and Trichopodus trichopterus sampled from areas inside dike systems and outside them as well as from periods of the three consecutive rice crops produced annually in this region. Variations in this effect were more evident for Esomus metallicus. The condition factors of these species were close to the well-being value, showing the prospective for culturing them in rice paddy fields. The three species were impacted by the dike-site × crop interaction, showing that they are well adapted to the habitats and the seasonal conditions. [ABSTRACT FROM AUTHOR]

We herein propose an alternative model for deformation caused by an eruption at Sakurajima, which has been previously interpreted as being due to a Mogi-type spherical point source beneath Minami-dake. On November 13, 2017, a large explosion with a plume height of 4200 m occurred at Minami-dake. During the 3 min following the onset of the explosion (November 13, 2017, 22:07–22:10 (Japan standard time (UTC + 9); the same hereinafter), phase 1, a large strain with changes up to 120 nstrain was detected at the Arimura observation tunnel (AVOT) located approximately 2.1 km southeast from the Minami-dake crater. After the peak of the explosion (November 13, 2017, 22:10–24:00), phase 2, a large deflation was detected at every monitoring station due to the continuous Strombolian eruption. Subsidence toward Minami-dake was detected at five out of six stations, whereas subsidence toward the north of Sakurajima was detected at the newly installed Komen observation tunnel (KMT), located approximately 4.0 km northeast from the Minami-dake crater. The large strain change at AVOT as well as small tilt changes at all stations and small strain changes at the Harutayama observation tunnel (HVOT) and KMT during phase 1 can be explained by a very shallow deflation source beneath Minami-dake at 0.1 km below sea level (bsl). For phase 2, a deeper deflation source beneath Minami-dake at a depth of 3.3 km bsl was found in addition to the shallow source beneath Minami-dake, which turned inflation after the deflation that occurred during phase 1. However, this model cannot explain the tilt change of KMT. Adding a spherical deflation source beneath Kita-dake at a depth of 3.2 km bsl can explain the tilt and strain change at KMT and the other stations. The Kita-dake source was also found in a previous study of long-term ground deformation. Not only the deeper Minami-dake source MD, but also the Kita-dake source deflated due to the Minami-dake explosion. [ABSTRACT FROM AUTHOR]

Abstract Magmatic intrusions play a vital role not only in accommodating extensional stresses in continental rifts but also in feeding volcanic systems. The location, orientation, and timescale of dike intrusions are dictated by the interaction of regional and local stresses, the effect of pre‐existing weaknesses, and the composition of magma. Observing active intrusions can provide important information regarding the interaction between magmatic processes and the tectonic stress field during continental rifting. We focus on a seismic swarm that occurred in 2015 to the northeast of Fentale volcano, in the Main Ethiopian Rift (MER), and use radar interferometry to study surface deformation associated with the seismic swarm. Interferograms show a pattern of dike‐induced deformation, with a model estimate of volume change of 33×106±0.6×106m3 at a depth range of 5.4 to 8 km. We use a small baseline subset algorithm to calculate line of sight time series and find that the displacements decay exponentially with a decay constant of ∼83 days. Coupled source‐sink models suggest that such slow dike intrusions require a high viscosity rhyolitic magma. The difference in behavior between Fentale and other caldera systems in the MER, which show multi‐year cycles of inflation and deflation, suggests fundamental differences in magma composition and architecture of the plumbing system. This is the first direct observation of a dike intrusion in the MER and provides new constraints on the temporal‐spatial patterns of stress and strain that occur during continental rifting. Whether this activity is transient or a long‐term feature associated with rift evolution is an open question.

This paper presents the first results of the geostructural and tectonophysical studies of the crustal stress state in the Catoca kimberlite pipe area at the southwestern flank of the Kasai Shield in the northeasternAngola. In the evolution of the crustal stress state, six main stages are distinguished by analyzing the displacements of markers, fold hinges, long axes of boudins, granite dikes of various intrusion phases and kimberlites, as well as fractures with striations. For each of these stages, a dominating horizontal tectonic stress and its orientation is identified. During stage 1 (NW extension and shearing) and at the beginning of stage 2 (NW compression), structures formed in the host rocks in brittle-plastic conditions. The replacement of plastic deformation by faulting could occur about 530–510 Ma ago, when the continental crust ofAfricahad completely formed. Stage 3 (radial, mainly NW extension) and stage 4 (shearing, NW extension, and NE compression) were the most important for kimberlite occurrence: in the Early Cretaceous, radial extension was replaced by shearing. Both stages are related to opening of the central segment of theSouth Atlantic. The main kimberlite magmas occurred during the break-up of the Angola-Brazilian segment of Gondwana. In the course of all the four stages, stress was mainly released by the NE- and E-NE-striking faults and, to a lesser extent, by the NW-striking and latitudinal faults. The initial stage of kimberlite magmatism is associated with the NE- and E-NE-striking faults due to the presence of the Precambrian zones of flow and schistosity, which facilitated the NW-trending subhorizontal extension. Stage 5 (NE compression) began in the second half of the Cretaceous and possibly lasted until the end of the Paleogene, and compression occurred mainly along the NW-striking faults. Regionally, it corresponds to two stages of inversion movements in the southern regions of Africa, during which theAngoladome-shaped uplift emerged and the shoulders of the East African rifts began to take shape. Stage 6 (horizontal extension, mainly in the N-NE direction) is related to the processes that took place in the southern segment of theTanganyikarift and the eastern coast of theAtlantic. Based on the results of our studies, it became for the first time possible to get an idea of the main stages in the evolution of the studied region. Further geostructural measurements and dating of the host rocks will provide for a more precise definition of the proposed stages.

Flow overtopping can lead to the initiation of breaching and failure of fluvial dikes, causing severe inundations and damage in the protected areas. For flood risk management and prevention, the accurate estimate of flow discharge across the fluvial dike breach is paramount, requiring precise understanding of the breach expansion. Laboratory experiments were conducted to analyse the effects of fine sand, inducing apparent cohesion in the dike material, on breach development and outflow. Tests were conducted under controlled inflow discharge and dike material composed of either homogeneous non-cohesive coarse sand or heterogeneous fine sand/coarse sand mixtures. Based on the non-intrusive laser profilometry technique, high temporal and spatial resolution of the three-dimensional breach geometry evolution was measured, indicating a small effect of the fine material on the overall breach dynamics. A detailed analysis revealed, however, that fine sand induces less frequent slope collapses but larger sliding/failing lumps compared to homogenous non-cohesive coarse sand. [ABSTRACT FROM AUTHOR]