Geosciences

15 pages, 1365 KiB

Open AccessArticle

Concentration of Trace Elements in Cryoconites of Mountain and Polar Regions of the World

by Evgeny Abakumov, Rustam Tembotov, Vyacheslav Polyakov, Mikhail Ivanov, Bulat Mavlyudov, Ivan Kushnov, Timur Nizamutdinov, Rositsa Yaneva and Miglena Zhiyanski

Geosciences 2023, 13(6), 188; https://doi.org/10.3390/geosciences13060188 - 19 Jun 2023

Cited by 3 | Viewed by 1171

Abstract

The surface of mountain glaciers is a place of accumulation of various biogenic organomineral and mineral compounds. As a result of intensive mass deglaciation of glaciers due to climate change and anthropogenic activity, this material can significantly affect the transformation of the landscape [...] Read more.

The surface of mountain glaciers is a place of accumulation of various biogenic organomineral and mineral compounds. As a result of intensive mass deglaciation of glaciers due to climate change and anthropogenic activity, this material can significantly affect the transformation of the landscape in the periglacial zone. Thus, this work considers the contamination of the surface of the Arctic, Antarctic, and Caucasian glaciers by priority pollutants. Atomic absorption spectroscopy was used to analyze trace elements (Cu, Zn, Ni, Cd, Pb) from cryoconite deposits. It was revealed that the cryoconite dust on the Ray-Iz glacier (Polar Urals) has a high level of nickel contamination, which comes to the glacier from local rock materials as a result of their weathering. The lowest concentrations of trace elements are found in one of the Arctic plots located at Mushketov and Aldegonda glaciers, the Caucasus, and the Antarctic, which is due to their relatively low content in the composition of rocks and the relatively low contribution of long-range transport of matter to the polar regions. Contamination of moraine sediments in the periglacial zone can make a significant contribution to the formation of the soil cover of these territories, the pollution of water bodies near the glacier, as well as affect the quality of life of the people living in the immediate vicinity of the mountain areas. Full article

(This article belongs to the Section Geochemistry)

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22 pages, 7759 KiB

Open AccessArticle

Discrete Fracture Network (DFN) Analysis to Quantify the Reliability of Borehole-Derived Volumetric Fracture Intensity

by Pedro Ojeda, Davide Elmo, Steve Rogers and Andres Brzovic

Geosciences 2023, 13(6), 187; https://doi.org/10.3390/geosciences13060187 - 18 Jun 2023

Cited by 3 | Viewed by 2070

Abstract

Volumetric fracture intensity (P₃₂) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the [...] Read more.

Volumetric fracture intensity (P₃₂) is a parameter that plays a major role in the mechanical and hydraulic behaviour of rock masses. While methods such as Ground Penetrating Radar (GPR) are available to map the 3D geometrical characteristics of the fractures, the direct measurement of P₃₂ at a resolution compatible with geotechnical applications is not yet possible. As a result, P₃₂ can be estimated from the borehole and surface data using either simulation or analytical solutions. In this paper, we use Discrete Fracture Network (DFN) models to address the problem of estimating P₃₂ using information from boreholes (1D data). When calculating P₃₂ based on Terzaghi Weighting, it is common practice to use drill run lengths and limit the minimum angle between the borehole and the intersected fractures. The analysis presented in this paper indicated that limiting the minimum angle of intersection would result in an underestimation of the calculated P₃₂. Additionally, the size of the interval has a significant impact on the variability of the calculated P₃₂. We propose a methodology to calculate P₃₂ using variable lengths, depending on the angle between the fractures and the borehole. This methodology allows the capture of the spatial variation in intensity and simultaneously avoids artificially increasing or decreasing the intensity sampled along borehole intervals. Additionally, this work has addressed the impact of boundary effects in DFN models and proposes a methodology to mitigate them. Full article

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17 pages, 35429 KiB

Open AccessArticle

Micromorphological Characteristics of Soils in the Chernevaya Taiga (Western Siberia, Russia)

by Evgeny Abakumov, Timur Nizamutdinov, Alla Lapidus, Georgy Istigechev and Sergey Loiko

Geosciences 2023, 13(6), 186; https://doi.org/10.3390/geosciences13060186 - 18 Jun 2023

Viewed by 1014

Abstract

The Chernevaya taiga is a unique ecosystem formed under the influence of a complex of geogenic and bioclimatic factors located in the foothill border of the southeastern part of Western Siberia. The combination of local climatic conditions and the composition of parent material [...] Read more.

The Chernevaya taiga is a unique ecosystem formed under the influence of a complex of geogenic and bioclimatic factors located in the foothill border of the southeastern part of Western Siberia. The combination of local climatic conditions and the composition of parent material led to the formation of specific soil conditions on the territory of these habitats. The soils of the Chernevaya taiga have unique morphogenesis. They have a thick podzolized horizon and are fertile, unlike the typical soils of the oligotrophic pine forests of Siberia; however, the microstructure of these soils is poorly studied. The purpose of the research is to analyze the micromorphological organization and microstructure of three types of soils in Western Siberia (two typical soils from the Chernevaya taiga (Greyzemic Phaeozem (Albic) and Albic Stagnic Luvisol (Ochric)) and one from oligotrophic pine stand (Eutric Protoargic Arenosol)). It was found that the soils of the Chernevaya taiga differ greatly from the background (zonal) soils of the region on both the macro- and microlevels. In the Phaeozems and Luvisols of the Chernevaya taiga, there are actively formed organomineral aggregates and the quantity of porous media is more than 50%. At the bottom of the podzolized part of the soil profiles, we noted illuvial processes and a sharp change in the type of microstructure. The presence of pyrogenic materials (charcoal) and coprolitic (vermicular) materials in the humus-accumulative horizon indicates a high rate of material transformation and high biological activity and bioturbation in the soil. The skeleton part of the Chernevaya taiga soils is represented by a quartz–feldspar base with an admixture of sericite; augite; biotite; and a minimal admixture of tourmaline, zircon, and glauconite. Full article

(This article belongs to the Section Biogeosciences)

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12 pages, 2977 KiB

Open AccessArticle

Geological and Climatic Factors Affecting the Correlation between Electrical Resistivity and SPT N-Value in Sandy Soils of Phuket, Thailand

by Avirut Puttiwongrak, Solina Keo, Sakanann Vann, Tanwa Arpornthip, Thongchai Suteerasak and Piti Sukontasukkul

Geosciences 2023, 13(6), 185; https://doi.org/10.3390/geosciences13060185 - 17 Jun 2023

Viewed by 2051

Abstract

Understanding the technical properties of the subsurface soil is essential for carrying out any building project correctly. In sandy soils in Phuket, Thailand, a correlation between electrical resistivity and the SPT N-value should be established in design to cut down on the time [...] Read more.

Understanding the technical properties of the subsurface soil is essential for carrying out any building project correctly. In sandy soils in Phuket, Thailand, a correlation between electrical resistivity and the SPT N-value should be established in design to cut down on the time and expense of engineering field work for site investigation operations. Using the least squares method, the data of electrical resistivity and SPT N-values were fitted for regression analysis, and the behavior of the fitting coefficients was examined under various soil conditions found in the field. The factors affecting the link between electrical resistivity and the SPT N-value were found using data classifications of geology and climate. Phuket is located in a humid tropical region with frequent heavy rainstorms and extended periods of high temperatures and is composed of two main distinct geological areas: (1) igneous rock and (2) sedimentary and metamorphic rocks. According to the geological classification, the regression parameter (R²) of the relationship between the electrical resistivity and SPT N-values somewhat increased from a straightforward plot (R² = 0.0171) to 0.1721, and the geology and climate data categorization revealed the best fit which is an exponential model (R² = 0.6175). By re-examining the two VES lines under the identical bedrock and climate characteristics as the original model, the relative R² of 0.5519 validates the association between electrical resistivity and SPT N-values. It is important to emphasize that the geology and climate of the collected data have an impact on the correlation model. Furthermore, a geotechnical investigation should be used to confirm the findings of an electrical resistivity survey as a preliminary tool to assess any problematic subsurface zones. However, more field test data from diverse places must be acquired in order to establish the relationship between the SPT N-value and electrical resistivity of sandy soils. Full article

(This article belongs to the Topic Environmental Geology and Engineering)

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34 pages, 13983 KiB

Open AccessArticle

Water Erosion Risk Assessment for Conservation Planning in the East Hararghe Zone, Ethiopia

by Gezahegn Weldu Woldemariam, Kalid Hassen Yasin and Anteneh Derribew Iguala

Geosciences 2023, 13(6), 184; https://doi.org/10.3390/geosciences13060184 - 17 Jun 2023

Cited by 1 | Viewed by 1608

Abstract

Water erosion is accelerating soil loss rates in the East Hararghe Zone due to inappropriate human activities and their complex and intertwined interactions with natural factors, particularly in sensitive agroecosystems that lack soil and water conservation (SWC) measures. Although these dynamic processes cause [...] Read more.

Water erosion is accelerating soil loss rates in the East Hararghe Zone due to inappropriate human activities and their complex and intertwined interactions with natural factors, particularly in sensitive agroecosystems that lack soil and water conservation (SWC) measures. Although these dynamic processes cause prolonged impacts, a comprehensive assessment of the risk of soil erosion has not yet been undertaken at the zonal level. To bridge this gap, we employed the revised universal soil loss equation (RUSLE) prediction model, along with remote sensing and geographic information systems (GIS), to estimate annual soil erosion rates, analyze the temporal-spatial patterns of erosion risk, and evaluate the potential of standard conservation practices to reduce soil loss in croplands. Total soil erosion (in millions of tonnes/year; Mt yr⁻¹) was estimated to be 9 in 1990, 14 in 2000, 12 in 2010, and 11 in 2020, with average rates of 33, 50, 44, and 39 t ha⁻¹ yr⁻¹, respectively. This suggests an overall 18% increase in soil erosion from 1990 to 2020. Over 75% of the area showed a tolerable soil loss rate (<10 t ha⁻¹ yr⁻¹) and low susceptibility to erosion risk. A mountainous landscape in the northwest presents extremely high erosion (>120 t ha⁻¹ yr⁻¹), which accounts for more than 80% of soil loss, making SWC planning a priority. Analysis of land-use land-cover change (LULCC) confirmed a higher increase in soil loss for LULCC that involved conversion to croplands, with average rates of 36.4 t ha⁻¹ yr⁻¹ (1990–2000), 70 t ha⁻¹ yr⁻¹ (2000–2010), and 36 t ha⁻¹ yr⁻¹ (2010–2020). The results have further revealed that implementing supportive practices such as terracing, stripping, and contouring could reduce average soil erosion by approximately 87%, 65%, and 29%, respectively, compared to the baseline model’s prediction. Therefore, a rigorous cost–benefit analysis is essential to design and implement optimal location-specific practices that maximize investment returns in SWC efforts and ecological restoration. However, we acknowledge the limitations of this study, associated with an empirical model that does not account for all forms of erosion, as well as reliance mainly on secondary data, which may affect the accuracy of the predicted outcomes. Full article

(This article belongs to the Section Natural Hazards)

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16 pages, 1070 KiB

Open AccessArticle

Methane Concentration Forecasting Based on Sentinel-5P Products and Recurrent Neural Networks

by Theofani Psomouli, Ioannis Kansizoglou and Antonios Gasteratos

Geosciences 2023, 13(6), 183; https://doi.org/10.3390/geosciences13060183 - 16 Jun 2023

Viewed by 1429

Abstract

The increase in the concentration of geological gas emissions in the atmosphere and particularly the increase of methane is considered by the majority of the scientific community as the main cause of global climate change. The main reasons that place methane at the [...] Read more.

The increase in the concentration of geological gas emissions in the atmosphere and particularly the increase of methane is considered by the majority of the scientific community as the main cause of global climate change. The main reasons that place methane at the center of interest, lie in its high global warming potential (GWP) and its lifetime in the atmosphere. Anthropogenic processes, like engineering geology ones, highly affect the daily profile of gasses in the atmosphere. Should direct measures be taken to reduce emissions of methane, immediate global warming mitigation could be achieved. Due to its significance, methane has been monitored by many space missions over the years and as of 2017 by the Sentinel-5P mission. Considering the above, we conclude that monitoring and predicting future methane concentration based on past data is of vital importance for the course of climate change over the next decades. To that end, we introduce a method exploiting state-of-the-art recurrent neural networks (RNNs), which have been proven particularly effective in regression problems, such as time-series forecasting. Aligned with the green artificial intelligence (AI) initiative, the paper at hand investigates the ability of different RNN architectures to predict future methane concentration in the most active regions of Texas, Pennsylvania and West Virginia, by using Sentinel-5P methane data and focusing on computational and complexity efficiency. We conduct several empirical studies and utilize the obtained results to conclude the most effective architecture for the specific use case, establishing a competitive prediction performance that reaches up to a 0.7578 mean squared error on the evaluation set. Yet, taking into consideration the overall efficiency of the investigated models, we conclude that the exploitation of RNN architectures with less number of layers and a restricted number of units, i.e., one recurrent layer with 8 neurons, is able to better compensate for competitive prediction performance, meanwhile sustaining lower computational complexity and execution time. Finally, we compare RNN models against deep neural networks along with the well-established support vector regression, clearly highlighting the supremacy of the recurrent ones, as well as discuss future extensions of the introduced work. Full article

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20 pages, 30144 KiB

Open AccessArticle

Automated Delimitation of Rockfall Hazard Indication Zones Using High-Resolution Trajectory Modelling at Regional Scale

by Luuk Dorren, Christoph Schaller, Alexandra Erbach and Christine Moos

Geosciences 2023, 13(6), 182; https://doi.org/10.3390/geosciences13060182 - 16 Jun 2023

Cited by 3 | Viewed by 1024

Abstract

The aim of this study was to delimit potential rockfall propagation zones based on simulated 2 m resolution rockfall trajectories using Rockyfor3D for block volume scenarios ranging from 0.05–30 m³, with explicit inclusion of the barrier effect of standing trees, for [...] Read more.

The aim of this study was to delimit potential rockfall propagation zones based on simulated 2 m resolution rockfall trajectories using Rockyfor3D for block volume scenarios ranging from 0.05–30 m³, with explicit inclusion of the barrier effect of standing trees, for an area of approx. 7200 km² in Switzerland and Liechtenstein. For the determination of the start cells, as well as the slope surface characteristics, we used the terrain morphology derived from a 1 m resolution digital terrain model, as well as the topographic landscape model geodataset of swisstopo and information from geological maps. The forest structure was defined by individual trees with their coordinates, diameters, and tree type (coniferous or broadleaved). These were generated from detected individual trees combined with generated trees on the basis of statistical relationships between the detected trees, remote sensing-based forest structure type definitions, and stem numbers from field inventory data. From the simulated rockfall propagation zones we delimited rockfall hazard indication zones (HIZ), as called by the practitioners (because they serve as a basis for the Swiss hazard index map), on the basis of the simulated reach probability rasters. As validation, 1554 mapped past rockfall events were used. The results of the more than 89 billion simulated trajectories showed that 94% of the mapped silent witnesses could be reproduced by the simulations and at least 82% are included in the delimited HIZ. Full article

(This article belongs to the Special Issue Rockfall Protection and Mitigation)

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41 pages, 16865 KiB

Open AccessArticle

High-Latitude Depositional Systems, Provenance, and Basinal Setting of the Late Cretaceous Cantwell Basin, Denali National Park and Preserve, Alaska: A Stratigraphic Framework for Paleontological and Paleoclimatic Studies

by Brandon Keough and Kenneth Ridgway

Geosciences 2023, 13(6), 181; https://doi.org/10.3390/geosciences13060181 - 15 Jun 2023

Viewed by 1844

Abstract

The Cantwell Formation of the central Alaska Range provides a robust archive of high-latitude, Late Cretaceous depositional systems and paleo-floral/faunal assemblages. Our stratigraphic analysis defines two mappable members. The lower member (1500–2000 m thick) represents vegetated alluvial fan and braided fluvial systems that [...] Read more.

The Cantwell Formation of the central Alaska Range provides a robust archive of high-latitude, Late Cretaceous depositional systems and paleo-floral/faunal assemblages. Our stratigraphic analysis defines two mappable members. The lower member (1500–2000 m thick) represents vegetated alluvial fan and braided fluvial systems that transition up-section to fluvial–estuarine systems that drained into an inland continental seaway. The upper member (~2000 m thick) represents estuarine–marginal marine and lacustrine systems. Previous paleontological studies demonstrate that the Cantwell basin was populated by various dinosaurs, fishes, bivalves, birds, and marginal marine micro-organisms. Integration of new and published geologic mapping allows for reconstruction of depositional systems at the basin scale and provides additional paleogeographic context. The northern basin margin was defined by a previously unrecognized south-verging thrust belt, whereas the southern margin of the basin was defined by a north-verging thrust belt inboard of an active magmatic arc. Sediment sources interpreted from U-Pb detrital zircon geochronology included the coeval magmatic arc and older Cretaceous plutons, and Proterozoic–Mesozoic strata exhumed along the basin margins. Results of our study provide a depositional, stratigraphic, and structural framework that may serve as a guide for future paleontological and paleoclimatic investigations of Late Cretaceous Arctic environments of the Cantwell basin. Full article

(This article belongs to the Special Issue Reconstructing Past Arctic Environments: Climate, Ecosystems, and Depositional Systems)

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12 pages, 7317 KiB

Open AccessArticle

Numerical Modelling of Double-Twisted Wire Mesh for Low-Energy Rockfall Catch Fences

by Hassan Al-Budairi, Zhiwei Gao and Andrew Steel

Geosciences 2023, 13(6), 180; https://doi.org/10.3390/geosciences13060180 - 15 Jun 2023

Cited by 2 | Viewed by 1077

Abstract

Low-energy rockfall catch fences are designed to protect infrastructure such as railways and roads wherein the kinetic energy of falling rocks is less than 100 kJ. The typical design consists of a double-twisted steel wire mesh supported by ground posts and strengthened by [...] Read more.

Low-energy rockfall catch fences are designed to protect infrastructure such as railways and roads wherein the kinetic energy of falling rocks is less than 100 kJ. The typical design consists of a double-twisted steel wire mesh supported by ground posts and strengthened by anchoring wire ropes. The fence stops falling rocks by dissipating the impact energy mainly through elastoplastic stretching of steel wires in the mesh. In this study, a three-dimensional finite element model for double-twisted wire mesh was developed in Abaqus/Explicit. The model has been verified using both quasi-static loading and impact tests. It was found that proper geometrical representation is essential for accurate simulation of wire deformation modes and the interaction between double-twisted wires. The model also enables the application of the real stress–strain relationship of a single steel wire in constitutive models. Full article

(This article belongs to the Special Issue Rockfall Protection and Mitigation)

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34 pages, 43349 KiB

Open AccessArticle

Detecting and Predicting Archaeological Sites Using Remote Sensing and Machine Learning—Application to the Saruq Al-Hadid Site, Dubai, UAE

by Haïfa Ben-Romdhane, Diana Francis, Charfeddine Cherif, Kosmas Pavlopoulos, Hosni Ghedira and Steven Griffiths

Geosciences 2023, 13(6), 179; https://doi.org/10.3390/geosciences13060179 - 15 Jun 2023

Viewed by 1875

Abstract

In this paper, the feasibility of satellite remote sensing in detecting and predicting locations of buried objects in the archaeological site of Saruq Al-Hadid, United Arab Emirates (UAE) was investigated. Satellite-borne synthetic aperture radar (SAR) is proposed as the main technology for this [...] Read more.

In this paper, the feasibility of satellite remote sensing in detecting and predicting locations of buried objects in the archaeological site of Saruq Al-Hadid, United Arab Emirates (UAE) was investigated. Satellite-borne synthetic aperture radar (SAR) is proposed as the main technology for this initial investigation. In fact, SAR is the only satellite-based technology able to detect buried artefacts from space, and it is expected that fine-resolution images of ALOS/PALSAR-2 (L-band SAR) would be able to detect large features (>1 m) that might be buried in the subsurface (<2 m) under optimum conditions, i.e., dry and bare soil. SAR data were complemented with very high-resolution Worldview-3 multispectral images (0.31 m panchromatic, 1.24 m VNIR) to obtain a visual assessment of the study area and its land cover features. An integrated approach, featuring the application of advanced image processing techniques and geospatial analysis using machine learning, was adopted to characterise the site while automating the process and investigating its applicability. Results from SAR feature extraction and geospatial analyses showed detection of the areas on the site that were already under excavation and predicted new, hitherto unexplored archaeological areas. The validation of these results was performed using previous archaeological works as well as geological and geomorphological field surveys. The modelling and prediction accuracies are expected to improve with the insertion of a neural network and backpropagation algorithms based on the performed cluster groups following more recent field surveys. The validated results can provide guidance for future on-site archaeological work. The pilot process developed in this work can therefore be applied to similar arid environments for the detection of archaeological features and guidance of on-site investigations. Full article

(This article belongs to the Section Geophysics)

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20 pages, 37108 KiB

Open AccessEditor’s ChoiceArticle

Geologically-Driven Migration of Landmines and Explosive Remnants of War—A Feature Focusing on the Western Balkans

by Ivo Baselt, Adis Skejic, Budo Zindovic and Jens Bender

Geosciences 2023, 13(6), 178; https://doi.org/10.3390/geosciences13060178 - 14 Jun 2023

Cited by 1 | Viewed by 2518

Abstract

Landmines and explosive remnants of war are still present in the Western Balkans and remain a deadly legacy of the hostilities at the end of the 20th century. Over the years, several incidents have occurred in Bosnia and Herzegovina, in Serbia, and in [...] Read more.

Landmines and explosive remnants of war are still present in the Western Balkans and remain a deadly legacy of the hostilities at the end of the 20th century. Over the years, several incidents have occurred in Bosnia and Herzegovina, in Serbia, and in Croatia where intact ordnance has caused injuries and fatalities. Floods, torrential flows, and gravitational mass movements pose a particular threat. Landmines and explosive remnants of war are mobilized and displaced into previously uncontaminated areas. We first discuss the historical and technical background of this hazardous situation. We then show which hydro-morphological processes are responsible for the mobilization and displacement. We then illustrate how a prediction of the likely contaminated areas can be obtained. We show that the problem can only be tackled using a stochastic-deterministic model. However, for the eventual development of risk-hazard maps, preliminary work using laboratory experiments and field surveys is required. The article, therefore, proposes a novel approach to the problem in an international research project. The aim would be to produce risk-hazard maps that can be used by elected decision-makers, administrative authorities, and emergency personnel in affected municipalities. Full article

(This article belongs to the Section Natural Hazards)

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17 pages, 7075 KiB

Open AccessArticle

Integrated Schumann Resonance Intensity as an Indicator of the Global Thunderstorm Activity

by Masashi Hayakawa, Yuriy P. Galuk and Alexander P. Nickolaenko

Geosciences 2023, 13(6), 177; https://doi.org/10.3390/geosciences13060177 - 14 Jun 2023

Viewed by 3110

Abstract

This paper addresses the accuracy of estimates for the contemporary level of global thunderstorm activity found from the synchronous records of integrated Schumann resonance (SR) intensity at two high-latitude observatories in the Northern and Southern hemispheres. The results are based on numerical simulations [...] Read more.

This paper addresses the accuracy of estimates for the contemporary level of global thunderstorm activity found from the synchronous records of integrated Schumann resonance (SR) intensity at two high-latitude observatories in the Northern and Southern hemispheres. The results are based on numerical simulations of electromagnetic fields in the frequency band of the global (Schumann) resonance in the Earth–ionosphere cavity characterized by a realistic conductivity profile in the middle atmosphere. The credible distribution is used for global thunderstorm activity in space and time. The paired observatory locations are considered either at the geographic poles or at Svalbard and the Antarctic Peninsula. The seasonal variations in the spatial distribution of global thunderstorms are adopted from the OTD satellite observations. The diurnal variations imply the spatial and temporal distribution of lightning strokes measured by the WWLLN network for an arbitrarily chosen date of 18 January 2022. The results obtained suggest that simultaneous records of the integrated SR intensity at Svalbard and in Antarctica provide errors below 3% in the diurnal variations of global thunderstorm activity with a temporal resolution of 10 min. The seasonal changes in global thunderstorm intensity are estimated with an error of ~10%. Since the level of global thunderstorm activity varies by a factor of two on the both time scales, the estimates confirm the appropriate accuracy of the estimate of thunderstorm activity from the concurrent measurements at the high-latitude SR observatories in the Arctic and Antarctic. Full article

(This article belongs to the Topic Advances in Environmental Remote Sensing)

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19 pages, 9092 KiB

Open AccessArticle

A Spatiotemporal Characterization of Water Resource Conditions and Demands as Influenced by the Hydrogeologic Framework of the Willcox Groundwater Basin, Southeastern Arizona, USA

by Carl Job, Carlos G. Ochoa, W. Todd Jarvis and Robert E. Kennedy

Geosciences 2023, 13(6), 176; https://doi.org/10.3390/geosciences13060176 - 11 Jun 2023

Viewed by 1022

Abstract

In the Willcox Groundwater Basin (WGB), increasing rates of agricultural groundwater withdrawal have led to significant regional groundwater level decline, threatening the basin’s long-term water resource security. Updated characterization of the basin’s water resource conditions and agricultural water demand is critically important for [...] Read more.

In the Willcox Groundwater Basin (WGB), increasing rates of agricultural groundwater withdrawal have led to significant regional groundwater level decline, threatening the basin’s long-term water resource security. Updated characterization of the basin’s water resource conditions and agricultural water demand is critically important for informing groundwater resource management efforts. We developed the hydrogeologic framework of the WGB and linked groundwater level data with land cover classification data to provide a spatiotemporal assessment of water resource conditions and agricultural development in the WGB. A correlation analysis evaluated the degree of association between the basin’s mean annual depth-to-groundwater and agricultural land cover extent. Results of this study indicate that between 2008 and 2021, agricultural land cover in the WGB increased by 29%. The average rate of groundwater level change in the basin’s measured wells was calculated at −13.8 m between 2006 and 2021. We found a strong correlation between the basin’s mean annual measured depth-to-groundwater and the annual agricultural land cover extent, further reinforcing the understanding of agricultural water use in the basin as a principal driver of groundwater level decline. The methodological framework employed proved a simple and effective way to assess groundwater resources as influenced by geology and land use. The outcomes of this study provide critical information toward improved water resources management by providing an integrated understanding of local hydrogeology, groundwater level variability, and changes in agricultural land cover in arid inland basins such as those found in Arizona, USA. Full article

(This article belongs to the Section Hydrogeology)

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20 pages, 17830 KiB

Open AccessArticle

Characterization of Gold of the Murcielago Fluvial Placer (Central Honduras) and Its Possible Primary Sources

by Sabrina Nazzareni, Simona Alunno, Federica Zaccarini, Michele Mattioli, Alessandro Murroni, Alessandro Di Michele and Alberto Renzulli

Geosciences 2023, 13(6), 175; https://doi.org/10.3390/geosciences13060175 - 10 Jun 2023

Viewed by 1069

Abstract

The Murcielago gold placer is located in the Lepaguare Valley, Olancho Department (Central Honduras). The placer mineralogy includes silicates (quartz, garnets, amphibole, Ca-pyroxene, micas, epidote, and tourmaline); calcite; and in the heavy fraction, zircon, ilmenite–rutile, magnetite, hematite, cassiterite, and cinnabar. Gold grains recovered [...] Read more.

The Murcielago gold placer is located in the Lepaguare Valley, Olancho Department (Central Honduras). The placer mineralogy includes silicates (quartz, garnets, amphibole, Ca-pyroxene, micas, epidote, and tourmaline); calcite; and in the heavy fraction, zircon, ilmenite–rutile, magnetite, hematite, cassiterite, and cinnabar. Gold grains recovered from the Murcielago placer production plant are mainly flattened grains with a moderately to high elliptical shape. The composition of the gold grains varies continuously in the range Au

_{46}

Ag

_{54}

to Au

_{88}

Ag

_{12}

. Few of them are characterized by Au-rich rims of a few microns in size (Ag 3-1 atoms percent (at%)). Gold from the Canan lode deposit, a nearby hydrothermal Au mineralization area, has a composition (from Au

_{54}

Ag

_{44}

to Au

_{81}

Ag

_{19}

) overlapping the composition of the Murcielago grains. Inclusions in the alluvial gold particles are arsenopyrite, pyrite, acanthite, sphalerite, and hematite. On the basis of the placer mineralogy and the gold grains analyses, possible gold source(s) include the Canan lode and skarn gold deposits in the area. We obtained new data on the Murcielago gold placer that will be the basis for an exploration of the potential sources of gold in the area. Full article

(This article belongs to the Special Issue Geochemistry and Geochronology of Mineral Deposits)

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16 pages, 4506 KiB

Open AccessArticle

Centrifuge Modelling of Vertical and Horizontal Drains to Mitigate Earthquake-Induced Liquefaction

by Daniela Giretti and Vincenzo Fioravante

Geosciences 2023, 13(6), 174; https://doi.org/10.3390/geosciences13060174 - 10 Jun 2023

Viewed by 974

Abstract

This paper reports the results of dynamic centrifuge tests carried out on sandy models alternatively equipped with vertical or horizontal drains. The main aim of the experimentation was to investigate the use of horizontal drains to mitigate the liquefaction susceptibility of sandy deposits [...] Read more.

This paper reports the results of dynamic centrifuge tests carried out on sandy models alternatively equipped with vertical or horizontal drains. The main aim of the experimentation was to investigate the use of horizontal drains to mitigate the liquefaction susceptibility of sandy deposits and to validate their applicability as a remediation technique applicable in urban and industrial areas to protect existing buildings from liquefaction. The assessment and validation were carried out by comparing the seismic behavior of models treated with horizontal drains with that of the untreated model and models equipped with vertical drains. Full article

(This article belongs to the Special Issue Advances in Earthquake Geotechnical Engineering)

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20 pages, 2431 KiB

Open AccessArticle

Toward a Geodesy and Time Reference in Space (GETRIS): A Study of Apparent Satellite Clocks of a Future GNSS Satellite Constellation

by Stefan Marz, Anja Schlicht and Urs Hugentobler

Geosciences 2023, 13(6), 173; https://doi.org/10.3390/geosciences13060173 - 08 Jun 2023

Cited by 2 | Viewed by 909

Abstract

Today, concepts within the Global Geodetic Observing System (GGOS) aim a Terrestrial Reference System (TRS) with 1 mm accuracy and long-term stability of 0.1 mm/year. GETRIS (Geodesy and Time Reference In Space) is a concept that aims to realize a relativistic reference system [...] Read more.

Today, concepts within the Global Geodetic Observing System (GGOS) aim a Terrestrial Reference System (TRS) with 1 mm accuracy and long-term stability of 0.1 mm/year. GETRIS (Geodesy and Time Reference In Space) is a concept that aims to realize a relativistic reference system based on satellites as an extension to the TRS. This helps with another goal of the GGOS, namely, the connection of different satellite layers with the TRS. For a valuable contribution to the GGOS’s goals, we would expect to achieve precise determined satellite orbits at the level of 1–3 mm and satellite clocks with a picosecond accuracy. The use of increasingly precise links helps to improve the satellite precise orbit determination (POD) and is necessary to synchronize the clocks in the satellite/station network. We analyze a complementary use of high-precision optical dual one-way links at the level of 1 mm precision together with the L-band. In previous studies, we analyzed the benefit for satellite POD, achieving Medium Earth Orbit (MEO) as well as geosynchronous orbit (GSO) accuracies at the low-millimeter level. In this work, we analyze the capabilities for clock synchronization. We compare two different clock types for estimation and prediction. We analyze different satellite constellations and different combinations of measurement links. Full article

(This article belongs to the Section Geophysics)

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38 pages, 19437 KiB

Open AccessEditor’s ChoiceReview

A Critical Review of Current States of Practice in Direct Shear Testing of Unfilled Rock Fractures Focused on Multi-Stage and Boundary Conditions

by Nicholas R. MacDonald, Timothy R. M. Packulak and Jennifer J. Day

Geosciences 2023, 13(6), 172; https://doi.org/10.3390/geosciences13060172 - 08 Jun 2023

Cited by 1 | Viewed by 3912

Abstract

Direct shear (DS) is a common geotechnical laboratory test used to determine strength and deformation properties of rock discontinuities, such as normal and shear stiffness, peak and residual shear strength, and dilation. These are used as inputs for discontinuous geomechanical numerical models to [...] Read more.

Direct shear (DS) is a common geotechnical laboratory test used to determine strength and deformation properties of rock discontinuities, such as normal and shear stiffness, peak and residual shear strength, and dilation. These are used as inputs for discontinuous geomechanical numerical models to simulate discontinuities discretely and shear strength is often expressed by Mohr–Coulomb, Patton, or Barton–Bandis constitutive models. This paper presents a critical review of the different boundary conditions and procedural techniques currently used in practice, summarizes previous contributions, addresses their impacts on interpreted results for rock engineering design, and introduces clarifying terminology for shear strength parameters. Based on the review, the authors advise that constant normal stress is best suited for discrete numerical-model-based rock engineering design in dry conditions, but constant normal stiffness should be considered where fluid permeability is of interest. Multi-stage testing should not be used to obtain peak shear strength values except for stage 1, because of accumulating asperity damage with successive shear stages. Nevertheless, if multi-stage testing must be employed due to limited budget or specimen availability, guidance is presented to improve shear strength results with limited displacement techniques. Full article

(This article belongs to the Section Geomechanics)

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34 pages, 33492 KiB

Open AccessArticle

Large Earthquakes in Subduction Zones around the Polar Regions as a Possible Reason for Rapid Climate Warming in the Arctic and Glacier Collapse in West Antarctica

by Leopold I. Lobkovsky, Alexey A. Baranov, Igor A. Garagash, Mukamay M. Ramazanov, Irina S. Vladimirova, Yurii V. Gabsatarov, Dmitry A. Alekseev and Igor P. Semiletov

Geosciences 2023, 13(6), 171; https://doi.org/10.3390/geosciences13060171 - 08 Jun 2023

Cited by 2 | Viewed by 2924

Abstract

A correlation is observed between changes in the level of Earth’s seismic activity and increments of the atmospheric methane concentration over the past 40 years. Trigger mechanisms are proposed for methane emissions and glacier collapse in polar regions. These mechanisms are due to [...] Read more.

A correlation is observed between changes in the level of Earth’s seismic activity and increments of the atmospheric methane concentration over the past 40 years. Trigger mechanisms are proposed for methane emissions and glacier collapse in polar regions. These mechanisms are due to deformation waves caused by large earthquakes in subduction zones located near the polar regions: the Aleutian and Kuril–Kamchatka subduction zones, closest to the Arctic, and the Antarctica–Chilean and Tonga–Kermadec–Macquarie subduction zones. Disturbances of the lithosphere are transmitted over the distances of 3000–4000 km and more at a speed of about 100 km/year. Additional associated stresses come to the Arctic and Antarctica several decades after the occurrence of large earthquakes. In the Arctic zone, additional stresses affect the low-permeability structure of gas bearing sedimentary strata, causing increased methane emission and climate warming. In West Antarctica, deformation waves could trigger the acceleration and intensive collapse of West Antarctic glaciers, which has been observed since the 1970s. These waves are also capable of activating dormant volcanoes located under the sheet glaciers of West Antarctica, leading to an increase in heat flux, to the melting of ice at the glaciers’ base, and to their accelerated sliding towards the ocean, as is happening with the Thwaites Glacier. Full article

(This article belongs to the Special Issue Advances in Marine Geology—Selected Papers from P.P. Shirshov Institute of Oceanology, Russian Academy of Sciences)

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25 pages, 2886 KiB

Open AccessArticle

Study of the Mineralogical and Chemical Compositions of the Weakly Magnetic Fractions of the Egyptian Black Sand Altered Ilmenite

by Mohamed Ismail Moustafa

Geosciences 2023, 13(6), 170; https://doi.org/10.3390/geosciences13060170 - 07 Jun 2023

Cited by 1 | Viewed by 1009

Abstract

One of the most extensively studied topics in dozens of studies is the alteration process of ilmenite, the formation of leucoxene, and the presence of some impurity oxides: SiO₂ and Al₂O₃. The altered Egyptian black sand ilmenite grains [...] Read more.

One of the most extensively studied topics in dozens of studies is the alteration process of ilmenite, the formation of leucoxene, and the presence of some impurity oxides: SiO₂ and Al₂O₃. The altered Egyptian black sand ilmenite grains of relatively lower magnetic characters are studied using the binocular microscope and the Cameca SX-100 microprobe instrument. Both individual brown- and black-altered grains separated at 0.5 and 1 ampere values are investigated. The detection of the various alteration phases, their molecular formulas and limits, and the role of SiO₂ and Al₂O₃ in alteration mechanisms are detected. The alteration phases include pseudorutile (psr) and leached pseudorutile (lpsr) of different phases in addition to rutile. Few analyzed spots are detected to be leached ilmenite (lilm). Several Excel software are adopted to calculate the chemical formulas of each alteration phase. The contents of TiO₂ and Fe₂O₃ of all the investigated psr/lpsr in the study are in the range of 59.16–86.56% and 37.3–6.68%, respectively. The Ti/(Ti + Fe) ratio for these formulas ranges between 0.60 and 0.88. The psr/lpsr chemical formulas of all the investigated grains range as follows: Fe_2.01-0.50Ti₃O_8.97-4.50(OH)_0.03-4.50. The concluded lowest cationic iron content of the well-defined accepted lpsr phase is 0.5 with a corresponding molecular formula of Fe_0.50Ti₃O_4.5(OH)_4.5. The results revealed that in the region of 68–70 TiO₂%, the mechanism of ilmenite alteration may be changed where neither all the analyzed TiO₂ of the spot nor all the calculated structural water are contained within the molecular formula of lpsr. There are other associated mineral phases containing some TiO₂ and also some structural water which most probably are removed from the lpsr phase. As the analyzed spots are located at highly fissured locations, the alteration process is relatively faster and the lpsr phase can be broken into rutile and hematite. Additionally, as the analyzed TiO₂ and structural and/or molecular water contents increase, the darkness of the BSE image areas of the grain increases; this may reflect the existence of an individual TiO₂ phase, most probably rutile, mixed in homogeneity with the existed lpsr component. As the content of TiO₂ increases, within a definite TiO₂ range (80–85%), the associated contents of Al₂O₃ and SiO₂ increase. When the contents of the structural and/or molecular water contained within the lpsr phases decreases, the total oxides sum is more than 98%, the contents of Al₂O₃ are highly depleted. In the late alteration stages, the lpsr structure does not suddenly collapse but gradually produces other associated mineral phases. The relatively enriched contents of SiO₂ and/or Al₂O₃ in some secondary rutile grains can be explained as most of the SiO₂% is associated with mol water or bearing for mol and/or str water necessary for the leachability of Fe³⁺ from the psr structure. The XRD patterns of the investigated grains before and after roasting at 1100 °C for one hour are detected and interpreted. Full article

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14 pages, 2864 KiB

Open AccessArticle

Analytical Relation between b-Value and Electromagnetic Signals in Pre-Macroscopic Failure of Rocks: Insights into the Microdynamics’ Physics Prior to Earthquakes

by Patricio Venegas-Aravena and Enrique G. Cordaro

Geosciences 2023, 13(6), 169; https://doi.org/10.3390/geosciences13060169 - 07 Jun 2023

Cited by 2 | Viewed by 915

Abstract

Field measurements in subduction regions have revealed the presence of non-seismic pre-earthquake signals such as electromagnetic or acoustic emission, gas liberation, changes in Earth’s surface temperature, changes at the ionospheric level, or fluid migration. These signals are commonly associated with impending earthquakes, even [...] Read more.

Field measurements in subduction regions have revealed the presence of non-seismic pre-earthquake signals such as electromagnetic or acoustic emission, gas liberation, changes in Earth’s surface temperature, changes at the ionospheric level, or fluid migration. These signals are commonly associated with impending earthquakes, even though they often rely solely on temporal and spatial correlations in impending earthquake zones without a comprehensive understanding of the underlying lithospheric processes. For example, one criticism is the measurement of increasing electromagnetic signals even in the absence of observable macroscopic stress changes, which challenges the conventional understanding that macroscopic stress changes are the primary energy source for non-seismic pre-earthquake signals. To address this gap, rock experiments provide valuable insights. Recent experiments have shown that rocks can become electrified under constant macroscopic stress changes, accompanied by a decrease in the b-value, indicating multiscale cracking. This suggests the existence of small-scale dynamics that generate electromagnetic signals independently of large-scale stress variations. In that sense, multiscale thermodynamics offers a valuable perspective in describing this multiscale phenomenon. That is why the main goal of this work is to demonstrate that the electromagnetic signals before macroscopic failures are not independent of the cracking generation because the origin of both phenomena is the same. In particular, we present analytical equations that explain the physical connection between multiscale cracking, the generation of electromagnetic signals, and its negative correlation with acoustic emission before the macroscopic failure of rocks even when the macroscopic load is constant. In addition, we also show that the thermodynamic fractal dimension, which corresponds to the global parameter that controls the cracking process, is proportional to the b-value when the large-scale crack generation is considerably larger than the small-scale cracks. Thus, the decreases in the b-value and the increases in the electromagnetic signals indicate that rocks irreversibly prepare to release energy macroscopically. These findings could be related to the dynamics at lithospheric scales before earthquakes. Full article

(This article belongs to the Special Issue Natural Hazards and Geological Risks in Subduction Zones)

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17 pages, 3291 KiB

Open AccessArticle

Geochemical Behavior of Lanthanides and Actinides in an Old Uranium Mine, Portugal

by Andrés Cardenas, Maria I. Dias, Catarina Diamantino, Edgar Carvalho, Dulce Russo and Rosa Marques

Geosciences 2023, 13(6), 168; https://doi.org/10.3390/geosciences13060168 - 06 Jun 2023

Cited by 1 | Viewed by 1241

Abstract

New insights about the geochemical behavior of actinides and lanthanides in an old uranium mine are provided for the first time in this work. Fifteen samples (water, soil, and sediments) were collected inside and outside the Quinta do Bispo old mine (Portugal) in [...] Read more.

New insights about the geochemical behavior of actinides and lanthanides in an old uranium mine are provided for the first time in this work. Fifteen samples (water, soil, and sediments) were collected inside and outside the Quinta do Bispo old mine (Portugal) in order to better understand the lanthanide and actinide behavior in the soil–water system. The chemical and mineralogical composition was obtained via ICP-MS, INAA, and XRD. The water sample from the open pit exhibits a higher U and REE dissolved concentration when compared to the other water samples. A positive Eu anomaly is found in this sample. The soil samples collected inside the mine area, including mine waste rocks and the minesoils surrounding the open pit, show uranium mineral phases, higher U contents, an enrichment of LREE relative to HREE, and a lower Th/U. This heterogeneity may be due to the open pit extraction and ore processes, as well as the percolation and water infiltration through the waste rock piles. Soils from outside the mine area have a similar mineralogical and chemical composition, despite their different geological context, which could be related to the influence of the granitic geological unit during the alluvial unit deposition. The sediments have similar REE patterns, negative Eu anomaly, and a high (La/Yb)_N. Full article

(This article belongs to the Special Issue Mineralogy and Geochemistry of Critical Metal-Bearing Mineral Deposits)

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14 pages, 7277 KiB

Open AccessArticle

Distribution and Morphometry of Thermocirques in the North of West Siberia, Russia

by Marina Leibman, Nina Nesterova and Maxim Altukhov

Geosciences 2023, 13(6), 167; https://doi.org/10.3390/geosciences13060167 - 03 Jun 2023

Cited by 1 | Viewed by 1069

Abstract

The Arctic zone of West Siberia (Yamal and Gydan peninsulas) is an area with continuous permafrost and tabular ground ice close to the surface, active thermodenudation, and related landforms: retrogressive thaw slumps (RTS); in Russian referred to as thermocirques (TC). The dimensions of [...] Read more.

The Arctic zone of West Siberia (Yamal and Gydan peninsulas) is an area with continuous permafrost and tabular ground ice close to the surface, active thermodenudation, and related landforms: retrogressive thaw slumps (RTS); in Russian referred to as thermocirques (TC). The dimensions of most TCs have not been determined so far. We use Sentinel 2 imagery to measure each TC area ranging from 0.55 to 38 ha with a median of 2.5 ha. Around 95% of TCs have an area of less than 10 ha. The largest areas are gained due to the merging of several neighboring TCs. The ArcticDEM is used to determine TC edge elevation and slope angle. In general, the Median TC of the Yamal peninsula has an area of 1.8 ha, an elevation of the edge of 17.7 m, and a slope angle of 2.5°. The Median TC of the Gydan peninsula has an area of 2.6 ha, elevation of the edge of 29.4 m, and slope angle of 3°. TCs of the Gydan peninsula occupy higher positions and slightly steeper slopes compared to TCs of the Yamal peninsula. The ranges of the median and the largest TC areas are consistent with the reported RTS dimensions in North America. Full article

(This article belongs to the Topic Landslide Detection and Monitoring Using Multisource Remote Sensing Data)

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13 pages, 3715 KiB

Open AccessArticle

Radionuclide Transport Simulations Supporting Proposed Borehole Waste Disposal in Israel

by Katherine Carol Swager, Suzanne Michelle Bourret, Gilles Y. Bussod, Noa Balaban, Hakim Boukhalfa, Ran Calvo, Ofra Klein-BenDavid, Dolan Lucero, Itay J. Reznik, Ravid Rosenzweig and Philip H. Stauffer

Geosciences 2023, 13(6), 166; https://doi.org/10.3390/geosciences13060166 - 03 Jun 2023

Viewed by 1363

Abstract

A scientific collaboration between the U.S. and Israel is underway to assess the suitability of a potential site for subsurface radioactive waste disposal in the Negev Desert, Israel. The Negev Desert has several favorable attributes for geologic disposal, including an arid climate, a [...] Read more.

A scientific collaboration between the U.S. and Israel is underway to assess the suitability of a potential site for subsurface radioactive waste disposal in the Negev Desert, Israel. The Negev Desert has several favorable attributes for geologic disposal, including an arid climate, a deep vadose zone, interlayered low-permeability lithologies, and carbonate rocks with high uranium-sorption potential. These features may provide a robust natural barrier to radionuclide migration. Geologic and laboratory characterization data from the Negev Desert are incorporated into multiphase flow and transport models, solved using PFLOTRAN, to aid in site characterization and risk analysis that will support decision-making for waste disposal in an intermediate-depth borehole design. The lithology with the greatest uranium sorption potential at the site is phosphorite. We use modeling to evaluate the ability of this layer to impact uranium transport around a proposed disposal borehole. The current objective of the simulations is focused on characterizing hypothetical leakage from waste canisters and subsequent uranium migration under three infiltration scenarios. Here, we describe a hydrogeologic model based on data from a local exploratory borehole and present results for uranium flow and transport simulations under varying infiltration scenarios. We find that under the current climate conditions, it is likely that uranium will remain in the near-field of the borehole for thousands of years. However, under a hypothesized extreme climate scenario representing an increase in infiltration by a factor of 300x above present-day values, uranium may break through the phosphorite layer and exit the base of the model domain (~200 m above the water table) within 1000 years. Simulation results have direct implications for the planning of nuclear waste disposal in the Negev Desert, and specifically in intermediate-depth boreholes. Full article

(This article belongs to the Special Issue Groundwater in Arid and Semiarid Areas II)

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21 pages, 10742 KiB

Open AccessArticle

Stochastic Approach for 2D Superficial Seismic Amplification Based on Quad4M; City of L’Aquila (Italy) Test Case

by Antonio Pasculli, Nicola Sciarra and Massimo Mangifesta

Geosciences 2023, 13(6), 165; https://doi.org/10.3390/geosciences13060165 - 03 Jun 2023

Cited by 1 | Viewed by 1138

Abstract

The values of the physical–mechanical properties of any soil are affected by uncertainties both due to experimental measurements and the impossibility of knowing them, in detail, at every point of the spatial domain. Accordingly, this work focuses on uncertainty in shear wave velocity [...] Read more.

The values of the physical–mechanical properties of any soil are affected by uncertainties both due to experimental measurements and the impossibility of knowing them, in detail, at every point of the spatial domain. Accordingly, this work focuses on uncertainty in shear wave velocity (V_s) and its impact on the seismic response. The Monte Carlo method, based on pseudo-random number generation, was selected. To understand which random distributions could identify the site’s real conditions, the Fourier spectrum frequencies were calculated for each realization and were compared with the predominant natural site frequency. The experimental range data were used to calculate the spectral average acceleration and the horizontal amplification factors. The simulations were performed and interpreted by a modified version of VisualQ4M software based on 2D Quad4M, including the generation of pseudo-random numbers and pre- and post-data processing. A site at a small scale, in the territory of the city of L’Aquila (Italy), was selected as the test case. This paper demonstrates, from a numerical point of view, that both a simple local topographic modification due to excavation and the uncertainties of the numerical values, even of the shear wave velocity alone, can have an important impact on the local seismic amplification. Full article

(This article belongs to the Special Issue Advances in Seismic Hazard Assessment)

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21 pages, 15066 KiB

Open AccessEditor’s ChoiceArticle

Sea Caves and Other Landforms of the Coastal Scenery on Gozo Island (Malta): Inventory and New Data on Their Formation

by Stefano Furlani, Fabrizio Antonioli, Emanuele Colica, Sebastiano D’Amico, Stefano Devoto, Pietro Grego and Timmy Gambin

Geosciences 2023, 13(6), 164; https://doi.org/10.3390/geosciences13060164 - 02 Jun 2023

Cited by 2 | Viewed by 2279

Abstract

Sea caves are a type of cave formed primarily by the wave action of the sea. The coastal scenery of the Gozitan coast is very interesting in that sea caves and other coastal landforms, such as sea arches, develop at the sea level. [...] Read more.

Sea caves are a type of cave formed primarily by the wave action of the sea. The coastal scenery of the Gozitan coast is very interesting in that sea caves and other coastal landforms, such as sea arches, develop at the sea level. We mapped seventy-nine semi-submerged sea caves opening at the sea level, five completely submerged sea caves, seven sea arches, one sea stack, and one shelter around the coast of Gozo, mainly in the Western and Eastern parts of the island, due to favorable lithological and topographical conditions. Additionally, we surveyed the topography of the emerged part of nine sea caves using the iPhone build-in LiDAR sensor, and eight sea caves in the submerged part using SCUBA equipment. This inventory represents the most detailed example of a database of coastal caves and related forms in the Mediterranean, mainly sourced from a swimming survey along the entire island. Thanks to the combination of outputs of the above-water emerged and submerged surveys, we defined three types of semi-submerged sea caves: (i) box caves, (ii) joint caves, and (iii) complex caves. Moreover, we added a cave-like landform above the sea level on calcarenites called shelter, or a little extended notch deeply carved into the cliff. The shape mainly depends on the structural and lithological setting of sea cliffs. In the Western sector of the island, we also discovered the only sea cave in Gozo, measuring 122 m in length and 10 m in width, with its floor developing above the mean sea level. This cave base is of interest due to rounded landforms related to marine erosion. In the innermost part of the cave, there is also a beach with rounded pebble at an elevation of about 7 m asl. Considering the tectonic stability of the island, it could be possibly related to the MIS 5.5 highstand. Full article

(This article belongs to the Special Issue Relative Sea-Level Rise)

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20 pages, 7962 KiB

Open AccessArticle

Early Pleistocene River-Fed Paleocoast in Western Umbria (Central Italy): Facies Analysis and Coastal Models

by Roberto Bizzarri and Angela Baldanza

Geosciences 2023, 13(6), 163; https://doi.org/10.3390/geosciences13060163 - 01 Jun 2023

Viewed by 1315

Abstract

Pliocene (?)—early Pleistocene shallow marine deposits, varying from gravel to sand to clay, characterize the southernmost sector of the Valdichiana Basin, between Orte and Città della Pieve, across Tuscany, Umbria and Latium (Central Italy). Facies associations, referring to the evolution of a river-fed [...] Read more.

Pliocene (?)—early Pleistocene shallow marine deposits, varying from gravel to sand to clay, characterize the southernmost sector of the Valdichiana Basin, between Orte and Città della Pieve, across Tuscany, Umbria and Latium (Central Italy). Facies associations, referring to the evolution of a river-fed coast, with a sensible facies heteropy, and a sub-environment articulation, both across and alongshore, have been recently described. Although the main part of the territory responds to a wave-dominated coastal model, a clear fluvial sediment origin and the presence of localized river mouths have also been documented. Nearshore is mainly represented by interbedded sand and gravel beachface to upper shoreface deposits, in which both a mouth bar organization and a lateral distribution of gravel beaches are recognizable. Sediment origins largely depend ondebris flow processes, related to small alluvial fans/fan deltas. In constrained areas, debris flow and current continental deposits occur, referring to coalescent alluvial fans, organized as a smoothly seaward-dipping piedmont band, drained by shallow braided channels. This roughly organized fluvial system feeds a coastal area, with a fandeltabuild-up. The as-described fan delta and beach systems are characterized by a smooth seaward morphology, according to models resembling, on a coast-transverse profile, the shelf-type fan delta. Although the proposed models differ from each other’s, with respect tothe shelf-type one, this is mainly on a lateral facies distribution. Full article

(This article belongs to the Special Issue Quaternary Coastal Paleoenvironments)

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19 pages, 5939 KiB

Open AccessArticle

Analysis of Dispersivity in Marine Clays of Cartagena de Indias, Colombia

by Cristian Acuña, Juan Betancur, Jair Arrieta Baldovino, Guilliam Barboza and Manuel Saba

Geosciences 2023, 13(6), 162; https://doi.org/10.3390/geosciences13060162 - 01 Jun 2023

Cited by 2 | Viewed by 1036

Abstract

This study assessed the dispersivity of soils extracted from the northern region of Cartagena de Indias (Colombia) using the pinhole test, crumb test, and chemical–microstructural analyses. Dispersive soils are susceptible to erosive phenomena upon contact with water, yet they have not been adequately [...] Read more.

This study assessed the dispersivity of soils extracted from the northern region of Cartagena de Indias (Colombia) using the pinhole test, crumb test, and chemical–microstructural analyses. Dispersive soils are susceptible to erosive phenomena upon contact with water, yet they have not been adequately characterized in the city. To evaluate the dispersivity degree of different deformed and undisturbed soil samples, soil characterization tests included particle size analysis, chemical composition, Atterberg limits, specific gravity, and compaction. The results showed that the soils are highly plastic clays (i.e., CH) with a slight to moderate dispersivity level (i.e., ND3) according to the pinhole test and a moderate degree of dispersivity confirmed by the crumb test. The extracted soil sample sodium levels ranged from 0.72% to 1.94%, and the soil had an optimal moisture content of 26% and a maximum apparent dry unit weight of 13.87 kN/m³. According to standards and results, Cartagena de Indias’s studied marine clays are unsuitable for civil construction due to the degree of uncertainty in their behavior. Full article

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15 pages, 6827 KiB

Open AccessArticle

Mathematical Simulation of Honeycomb Weathering via Moisture Transport and Salt Deposition

by Alexander Safonov and Kirill Minchenkov

Geosciences 2023, 13(6), 161; https://doi.org/10.3390/geosciences13060161 - 31 May 2023

Viewed by 2435

Abstract

Honeycomb weathering is a common phenomenon found on various rock surfaces all around the world. However, honeycomb formation mechanisms are still poorly understood. In this study, we propose a model describing moisture transport within the sandstone and erosion resulting from salt deposition during [...] Read more.

Honeycomb weathering is a common phenomenon found on various rock surfaces all around the world. However, honeycomb formation mechanisms are still poorly understood. In this study, we propose a model describing moisture transport within the sandstone and erosion resulting from salt deposition during evaporation of moisture off the rock surface. The moisture transport model is based on the non-linear diffusion equation, where the volumetric moisture content is a combined parameter accounting for the moisture and gas (vapor) content. The moisture transport model accounts for the several-orders-of-magnitude decrease in moisture diffusivity, observed during drying. It was assumed that erosion occurs when the evaporation front is located close to the rock surface. The depth of erosion is proportional to the moisture flow rate through the drying surface. The ABAQUS finite-element software suite was used for numerical solution of the non-linear diffusion equation. The iterative scheme of erosion simulation for different drying cycles was implemented using the Python programming language. Computations were conducted in the 2D setting for the square model with dimensions of 50 mm × 50 mm. Simulation results demonstrate the possibility of obtaining various landform shapes (honeycombs, tafoni) by varying only the value of the distribution of moisture content at the bottom side, simulating the rate of internal wetting of rock. Full article

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25 pages, 5753 KiB

Open AccessEditor’s ChoiceArticle

Factors Contributing to the Long-Term Sea Level Trends in the Iberian Peninsula and the Balearic and Canary Islands

by Manuel Vargas-Yáñez, Elena Tel, Marta Marcos, Francina Moya, Enrique Ballesteros, Cristina Alonso and M. Carmen García-Martínez

Geosciences 2023, 13(6), 160; https://doi.org/10.3390/geosciences13060160 - 31 May 2023

Cited by 1 | Viewed by 3430

Abstract

We present an attempt to estimate the long-term changes in Relative Sea Level (RSL), in addition to the different factors contributing to such trends on a local and regional scale, using a statistical linear model. The time series analysis corresponded to 17 tide-gauges, [...] Read more.

We present an attempt to estimate the long-term changes in Relative Sea Level (RSL), in addition to the different factors contributing to such trends on a local and regional scale, using a statistical linear model. The time series analysis corresponded to 17 tide-gauges, grouped in three different areas: the northern and western Atlantic coasts of the Iberian Peninsula, the Canary Islands, and the southern and eastern coasts of the Iberian Peninsula and Balearic Islands. The analysis was performed for two periods: 1948–2019, using tide-gauge data; and 1993–2019, using both tide-gauge and altimetry data for comparison. The trends for the period 1948–2019 ranged between 1.09 ± 0.14 (Canary Islands) and 2.05 ± 0.21 mm/yr for the northern and western Atlantic Iberian Peninsula. Altimetry data during the period 1993–2019 yielded quite homogeneous results for all the locations and regions, ranging between 2.7 ± 0.4 and 3.0 ± 0.3 mm/yr. In contrast, the results obtained from tide-gauge data for this recent period showed a large dispersion, very likely due to local effects, or perhaps even to levelling or instrumental errors. Nevertheless, when the results were averaged for each area, the observed trends were comparable to the altimetry results, with values of 2.3 ± 0.8, 2.7 ± 0.5, and 2.8 ± 0.8 mm/yr for the three regions of study. A stepwise forward linear regression was used to relate the observed RSL variability to the atmospheric forcing and the thermosteric and halosteric components of the sea level. Surprisingly, the thermosteric and halosteric contributions were not significantly correlated to the observed RSL in many cases; consequently, the steric, the total addition of mass, the mass of salt, and the freshwater contributions to the observed sea level trends could not be reliably estimated. This result seems to have been the consequence of the scarcity of temperature and salinity data; this hypothesis was confirmed, with the exception of the tide-gauge data for L’Estartit. This location is close to a well sampled region. In this case, the atmospheric variables and the thermosteric and halosteric terms accounted for 80% of the observed RSL variance, and the contributions of these terms could be estimated. The freshwater contribution for this location was between 1.3 and 1.4 mm/yr, consistent with recent estimations of the contributions of glaciers and Greenland and Antarctica Ice Sheets. These results highlight the importance of monitoring programs and routine sampling for the determination of the different factors contributing to the sea level variability. Full article

(This article belongs to the Special Issue Relative Sea-Level Rise)

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20 pages, 11013 KiB

Open AccessArticle

Cenozoic Clastic Deposits in the Thermaikos Basin in Northern Greece and Their Reservoir Potential

by Georgios Makrodimitras, Anastasios Nikitas, Dimitrios Ktenas, Angelos G. Maravelis, Niki Marina Rokana, Nikolaos Pasadakis, Efthimios Tartaras and Aristofanis Stefatos

Geosciences 2023, 13(6), 159; https://doi.org/10.3390/geosciences13060159 - 27 May 2023

Cited by 1 | Viewed by 1182

Abstract

The Epanomi gas field discovery during the 1980s at the eastern fringe of the Thermaikos Basin in Northern Greece proved the existence of an active petroleum system in the area. Seismic and drilling exploration programs in the area provide data to study the [...] Read more.

The Epanomi gas field discovery during the 1980s at the eastern fringe of the Thermaikos Basin in Northern Greece proved the existence of an active petroleum system in the area. Seismic and drilling exploration programs in the area provide data to study the Cenozoic clastic sequence in the Thermaikos Basin. This study aims to recognize, through core and well-log data, the wide range of facies associations from different depositional environments, which contribute to the basin fill. Additional wells from the Kassandra and Epanomi onshore areas support the conclusions of this study. A detailed core description, a cuttings evaluation, and a log analysis of selected wells were the main tools for the facies association analysis. Seismic data from the area were used to identify the lateral extension of the depositional environments in the areas between and around the wells. The Eocene–Oligocene part of the stratigraphic succession corresponds to deep-water turbidites in the middle of the basin, passing laterally to a shallow marine and locally to fluvial, alluvial, and deltaic settings. The dominant (in terms of thickness) Miocene interval consists of fluvial and shallow marine sediments, while deltaic deposits are also present. The Quaternary deposits are mostly shallow marine, with local lagoonal sediments. The reservoir properties were integrated at the last stages of the study in order to identify the most interesting facies. The outcome of this study can be useful for hydrocarbon exploration or for potential future CO₂ storage. Full article

(This article belongs to the Section Sedimentology, Stratigraphy and Palaeontology)

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Geosciences, Volume 13, Issue 6 (June 2023) – 36 articles

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