Geosciences

33 pages, 19994 KiB

Open AccessArticle

Convective Instability in Intraplate Oceanic Mantle Caused by Amphibolite-Derived Garnet-Pyroxenites—A Xenolith Perspective (Hyblean Plateau, Sicily)

by Vittorio Scribano and Serafina Carbone

Geosciences 2020, 10(9), 378; https://doi.org/10.3390/geosciences10090378 - 22 Sep 2020

Cited by 2 | Viewed by 2581

Abstract

Geochemical characteristics of middle ocean ridge basalts (MORBs) testify partial melting of spinel-peridotite mixed with a few amounts of garnet-pyroxenite. The latter can be considered either autochthonous products of the crystallization of partial melts in the sub-oceanic mantle or allocthonous recycled crustal materials [...] Read more.

Geochemical characteristics of middle ocean ridge basalts (MORBs) testify partial melting of spinel-peridotite mixed with a few amounts of garnet-pyroxenite. The latter can be considered either autochthonous products of the crystallization of partial melts in the sub-oceanic mantle or allocthonous recycled crustal materials originated in subduction contexts. Here we suggest the “autocthnous recycled” origin for garnet-pyroxenites. Such a hypothesis derives from the study of garnet-bearing pyroxenite xenoliths from the Hyblean Plateau (Sicily). These consist of Al-diopside, pyralspite-series garnet, Al-spinel and Al-rich orthopyroxene. Trace element distribution resembles an enriched MORB but lower chromium. Major-element abundances closely fit in a tschermakitic-horneblende composition. Assuming that a high-Al amphibolite was formed by hydrothermal metasomatism of a troctolitic gabbro in a slow-spreading ridge segment, a transient temperature increasing induced dehydroxilization reaction in amphiboles, giving Al-spinel-pyroxenite and vapor as products. Garnet partially replaced spinel during an isobaric cooling stage. Density measurements at room conditions on representative samples gave values in the range 3290–3380 kg m⁻³. In general, a density contrast ≥300 kg m⁻³ can give rise to convective instability, provided a sufficient large size of the heavy masses and adequate rheological conditions of the system. Garnet-pyroxenite lumps can therefore sink in the underlying mantle, imparting the “garnet geochemical signature” to newly forming basaltic magma. Full article

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30 pages, 6009 KiB

Open AccessArticle

Investigating the Correlation of Tectonic and Morphometric Characteristics with the Hydrological Response in a Greek River Catchment Using Earth Observation and Geospatial Analysis Techniques

by Emmanouil Psomiadis, Nikos Charizopoulos, Konstantinos X. Soulis and Nikolaos Efthimiou

Geosciences 2020, 10(9), 377; https://doi.org/10.3390/geosciences10090377 - 21 Sep 2020

Cited by 15 | Viewed by 3299

Abstract

Morphometric analysis can be used to investigate catchment dynamics and tectonic processes responsible for the development of drainage catchments and to support flood risk assessment. In this study, a comparative GIS-based morphometric analysis between the main southern and northern sub-catchments of the Sperchios [...] Read more.

Morphometric analysis can be used to investigate catchment dynamics and tectonic processes responsible for the development of drainage catchments and to support flood risk assessment. In this study, a comparative GIS-based morphometric analysis between the main southern and northern sub-catchments of the Sperchios River basin, Central Greece, was performed, using geospatial and remote sensing data. The goal was to investigate their correlation with the peculiar geotectonic activity and the frequent flash-flood events that occur in the river floodplain. All sub-catchments characteristics are linked with the geological formation types of the area, in combination with ongoing tectonic activity. The results indicate that drainage network development is significantly controlled by the region’s overall tectonic activity. The morphometric characteristics—i.e., bifurcation ratio, drainage density, circularity ratio, elongation ratio and water concentration–time values, reflect the flood-prone character of the southern part of Sperchios River catchment in comparison to the northern part, especially during intense rainfall events. The study can provide valuable insight into identifying how morphometric characteristics are associated with increased flood hazard. Full article

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13 pages, 1777 KiB

Open AccessArticle

Natural Radioactivity of Laterite and Volcanic Rock Sample for Radioactive Mineral Exploration in Mamuju, Indonesia

by Ilsa Rosianna, Eka Djatnika Nugraha, Heri Syaeful, Sugili Putra, Masahiro Hosoda, Naofumi Akata and Shinji Tokonami

Geosciences 2020, 10(9), 376; https://doi.org/10.3390/geosciences10090376 - 19 Sep 2020

Cited by 18 | Viewed by 5272

Abstract

Mamuju is a region of Indonesia with relatively high exposure to natural radiation. Since 2012, Mamuju has been a uranium and thorium exploration area. Several mapping studies of the region have been carried out to depict NORM (naturally occurring radioactive material) areas and [...] Read more.

Mamuju is a region of Indonesia with relatively high exposure to natural radiation. Since 2012, Mamuju has been a uranium and thorium exploration area. Several mapping studies of the region have been carried out to depict NORM (naturally occurring radioactive material) areas and areas with uranium anomalies. This paper is the first study to use radioactivity measurements of laterite and volcanic rocks to determine the characteristics of radionuclides and other mineral measurements, which are essential for categorising Mamuju rocks and exploring the region as a potential mining area. The radioactivity of the samples was measured using a high-purity germanium (HPGe) detector. Furthermore, we used X-ray fluorescence (XRF) to determine the rock mineral composition. Mamuju is anomalous due to its high content of ²³⁸U and ²³²Th concentrations of 539–128,699 Bq·kg⁻¹ (average: 22,882 Bq·kg⁻¹) and 471–288,639 Bq·kg⁻¹ (average: 33,549 Bq·kg⁻¹), respectively. The major elements are dominant, including Fe₂O₃, SiO₂, Al₂O₃, and Na₂O, with several other major elements such as MnO, TiO₂, and CaO. Full article

(This article belongs to the Special Issue Radioisotopes Studies in the Geosciences)

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19 pages, 2630 KiB

Open AccessReview

Heated Topics in Thermochronology and Paths towards Resolution

by Matthew Fox and Andrew Carter

Geosciences 2020, 10(9), 375; https://doi.org/10.3390/geosciences10090375 - 19 Sep 2020

Cited by 17 | Viewed by 3818

Abstract

Thermochronometry is widely used to track exhumation, the motion of rock towards Earth’s surface, and to gain fresh insights into geodynamic and geomorphic processes. Applications require models to reconstruct a rock’s cooling history as it is exhumed from higher temperatures at depth within [...] Read more.

Thermochronometry is widely used to track exhumation, the motion of rock towards Earth’s surface, and to gain fresh insights into geodynamic and geomorphic processes. Applications require models to reconstruct a rock’s cooling history as it is exhumed from higher temperatures at depth within the crust to cooler shallower levels and eventually Earth’s surface. Thermochronometric models are dependent on the predictable accumulation and the temperature-dependent loss of radiogenic daughter products measured in the laboratory. However, there are many geologically reasonable scenarios that will yield very similar thermochronometric ages. This similarity hinders finding the actual scenario, so instead an approximate model is sought. Finding suitable model parameters is a potentially ill-posed inverse problem that requires making decisions about how best to extract information from the data and how to combine data to leverage redundant information and reduce the impact of data noise. Often these decisions lead to differences in conclusions of studies and such discrepancies have led to heated debates. Here, we discuss debates centred on the use of a variety of modelling approaches and potential sources of biases that lead to differences in the predicted exhumation rate. We also provide some suggestions about future research paths that will help resolve these debates. Full article

(This article belongs to the Special Issue Surface-Deep Earth Interactions: From Integrated Datasets to Landscape Evolution and Geodynamic Modeling)

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21 pages, 11258 KiB

Open AccessArticle

Storm-Induced Boulder Displacements: Inferences from Field Surveys and Hydrodynamic Equations

by Marco Delle Rose, Corrado Fidelibus, Paolo Martano and Luca Orlanducci

Geosciences 2020, 10(9), 374; https://doi.org/10.3390/geosciences10090374 - 19 Sep 2020

Cited by 6 | Viewed by 2380

Abstract

The storm of 12–13 November 2019 provoked the displacements of boulders on a central Mediterranean rocky coast; with reference to a selected area, prone to boulder production and geomorphologically monitored for years, a field-oriented study approach was applied for the phenomenon, by collating [...] Read more.

The storm of 12–13 November 2019 provoked the displacements of boulders on a central Mediterranean rocky coast; with reference to a selected area, prone to boulder production and geomorphologically monitored for years, a field-oriented study approach was applied for the phenomenon, by collating data concerning the pre-storm locations and kinematics of these boulders. The number of displaced boulders is 11, that is in terms of the morphological imprint of a specific storm, one of the major study cases for the Mediterranean. In addition, based on widely used hydrodynamic equations, the minimum wave height required to displace the boulders is assessed. The values conform with the expected values for the wave climate dominating during the causative meteorological event and give a measure of the energy of the storm slamming the coast. Boulder dislodgement usually plays a key role in determining the rate of the coastal recession, likely also in the investigated area. In view of an adverse climate evolution with a possible increase of the energy and frequency of severe storms, the results deriving from the study of this morphodynamics should be considered for hazard assessment and coastal management. Full article

(This article belongs to the Special Issue Geomorphological and Sedimentological Imprints of Storm Events)

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17 pages, 3300 KiB

Open AccessArticle

Combining Groundwater Flow Modeling and Local Estimates of Extreme Groundwater Levels to Predict the Groundwater Surface with a Return Period of 100 Years

by Hans Kupfersberger, Gerhard Rock and Johannes C. Draxler

Geosciences 2020, 10(9), 373; https://doi.org/10.3390/geosciences10090373 - 18 Sep 2020

Cited by 4 | Viewed by 2322

Abstract

Knowledge about extreme groundwater levels is needed to avoid structural or environmental damage by groundwater flooding. Typically, distributions of extreme groundwater levels are generated by interpolation between results derived from local extreme value analysis at groundwater observation wells. As an alternative methodology, we [...] Read more.

Knowledge about extreme groundwater levels is needed to avoid structural or environmental damage by groundwater flooding. Typically, distributions of extreme groundwater levels are generated by interpolation between results derived from local extreme value analysis at groundwater observation wells. As an alternative methodology, we propose to apply the Gumbel distribution to groundwater level time series, which are computed by a groundwater flow model. In the approach, model-based and observation-based extreme groundwater values are compared at every observation well using the model simulation period and the longest available observation period to calculate correction values that are regionalized over the model area. We demonstrate the applicability of the approach at the Südliches Wiener Becken (SWB) aquifer south of Vienna, where a groundwater flow model between 1993 to 2017 is available to compute the distribution of the groundwater levels with a hundred year return period (GLsWHYRP). We could show that the resulting GLsWHYRP are generally increased in regions of groundwater recharge and decreased in regions of groundwater discharge. The developed approach can also be used to assess the impact of changing boundary conditions on groundwater level and extreme highs and lows based on corresponding model scenarios. Full article

(This article belongs to the Special Issue Groundwater Flow Assessment)

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31 pages, 47684 KiB

Open AccessReview

A Review of Tsunami Hazards in the Makran Subduction Zone

by Amin Rashidi, Denys Dutykh, Zaher Hossein Shomali, Nasser Keshavarz Farajkhah and Mohammadsadegh Nouri

Geosciences 2020, 10(9), 372; https://doi.org/10.3390/geosciences10090372 - 18 Sep 2020

Cited by 16 | Viewed by 8147

Abstract

The uncertain tsunamigenic potential of the Makran Subduction Zone (MSZ) has made it an interesting natural laboratory for tsunami-related studies. This study aims to review the recent activities on tsunami hazard in the Makran subduction zone with a focus on deterministic and probabilistic [...] Read more.

The uncertain tsunamigenic potential of the Makran Subduction Zone (MSZ) has made it an interesting natural laboratory for tsunami-related studies. This study aims to review the recent activities on tsunami hazard in the Makran subduction zone with a focus on deterministic and probabilistic tsunami hazard assessments. While almost all studies focused on tsunami hazard from the Makran subduction thrust, other local sources such as splay faults and landslides can be also real threats in the future. Far-field tsunami sources such as Sumatra-Andaman and Java subduction zones, commonly lumped as the Sunda subduction zone, do not seem to pose a serious risk to the Makran coastlines. The tsunamigenic potential of the western segment of the MSZ should not be underestimated considering the new evidence from geological studies and lessons from past tsunamis in the world. An overview of the results of tsunami hazard studies shows that the coastal area between Kereti to Ormara along the shoreline of Iran-Pakistan and the coastal segment between Muscat and Sur along Oman’s shoreline are the most hazardous areas. Uncertainties in studying tsunami hazard for the Makran region are large. We recommend that future studies mainly focus on the role of thick sediments, a better understanding of the plates interface geometry, the source mechanism and history of extreme-wave deposits, the contribution of other local tsunamigenic sources and vulnerability assessment for all coastlines of the whole Makran region. Full article

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25 pages, 7529 KiB

Open AccessReview

Integrated Stratigraphy of the Marine Early Pleistocene in Umbria

by Roberto Bizzarri and Angela Baldanza

Geosciences 2020, 10(9), 371; https://doi.org/10.3390/geosciences10090371 - 17 Sep 2020

Cited by 12 | Viewed by 3189

Abstract

Through time, the wide area between southeastern Tuscany, northeastern Latium, and western Umbria has been revealed as a crucial area for understanding the evolution of Neogene basins in northern Apennine. In this study, the results of twenty years of research on the marine [...] Read more.

Through time, the wide area between southeastern Tuscany, northeastern Latium, and western Umbria has been revealed as a crucial area for understanding the evolution of Neogene basins in northern Apennine. In this study, the results of twenty years of research on the marine early Pleistocene deposits are summarized, and the biological and physical events are presented and discussed in order to propose an integrated stratigraphic scheme. The proposed reconstruction is also included in a wider context, taking into account both the local and regional geological evolution. Full article

(This article belongs to the Special Issue Quaternary Sedimentary Successions)

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13 pages, 3635 KiB

Open AccessArticle

Headspace Isotope & Compositional Analysis for Unconventional Resources: Gas in Place, Permeability and Porosity Prediction and Completions Planning

by Sheng Wu, Yongchun Tang, Mian Lin and Andrew Sneddon

Geosciences 2020, 10(9), 370; https://doi.org/10.3390/geosciences10090370 - 17 Sep 2020

Cited by 3 | Viewed by 2121

Abstract

Cuttings/cores’ Headspace Isotope and Composition Analysis (HICA) provides an effective way to calculate the nano pore throat size and distributions much like nitrogen and CO₂ adsorption BET/BJH analysis, and it could also provide information about the original pore pressure or gas in [...] Read more.

Cuttings/cores’ Headspace Isotope and Composition Analysis (HICA) provides an effective way to calculate the nano pore throat size and distributions much like nitrogen and CO₂ adsorption BET/BJH analysis, and it could also provide information about the original pore pressure or gas in place. Tight gas and oil storage is different from conventional where a majority of oil and gas are stored in nanometer sized pores (nanopores). Therefore the nanofludics, i.e., nanometer scale capillary sealing and opening in nanopores of tight rocks, plays a key role in overpressure conservation and storage of oil and gas, and also the fracing process involves the opening of the nano pore capillary seals through rock-fluid interactions. The rock-fluid nanofluidics interactions during fracing could also be studied through HICA and the results could help the optimization of fracing designs. Full article

(This article belongs to the Special Issue Stable Isotope Systematics of Coalbed Gas and Shale Gas during Desorption and Production)

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20 pages, 11314 KiB

Open AccessArticle

Toward a High-Definition Remote Sensing Approach to the Study of Deserted Medieval Cities in the Near East

by Lenka Starková

Geosciences 2020, 10(9), 369; https://doi.org/10.3390/geosciences10090369 - 16 Sep 2020

Cited by 8 | Viewed by 3181

Abstract

The variability of currently available remote sensing datasets raises the question of which specific processing methods should be used for feature detection and feature extraction in both large and small-scale overhead images. In some cases, particular analyses allow us to carry out feature [...] Read more.

The variability of currently available remote sensing datasets raises the question of which specific processing methods should be used for feature detection and feature extraction in both large and small-scale overhead images. In some cases, particular analyses allow us to carry out feature detection much more easily and effectively. The high-definition approach enables enhanced analysis of remote sensing data using all the spectral and graphical potential of multi-temporal ordered components. The deserted urban site of Kona Makhmūr, Iraqi Kurdistan, is taken as a case study to demonstrate this fine-grained approach. The analysis described in this paper is based on the complementary use of a variety of overlayed imagery, augmented by data from terrestrial surveys. The resulting map substantially enhances our knowledge of the built environment and the economic and environmental conditions of this early Islamic-period site. Spectral analysis of raster images allowed us to detect the real shapes of features, and with the addition of digital elevation model (DEM) (created via unmanned aerial system (UAV)) we were also able to interpret the state of preservation of the overground relics and the diachronic dynamics of their degradation. Full article

(This article belongs to the Special Issue Satellite, Aerial and Ground-Based Remote Sensing for Archaeological and Heritage Research)

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21 pages, 1132 KiB

Open AccessArticle

Sediment Bed-Load Transport: A Standardized Notation

by Ulrich Zanke and Aron Roland

Geosciences 2020, 10(9), 368; https://doi.org/10.3390/geosciences10090368 - 16 Sep 2020

Cited by 8 | Viewed by 3005

Abstract

Morphodynamic processes on Earth are a result of sediment displacements by the flow of water or the action of wind. An essential part of sediment transport takes place with permanent or intermittent contact with the bed. In the past, numerous approaches for bed-load [...] Read more.

Morphodynamic processes on Earth are a result of sediment displacements by the flow of water or the action of wind. An essential part of sediment transport takes place with permanent or intermittent contact with the bed. In the past, numerous approaches for bed-load transport rates have been developed, based on various fundamental ideas. For the user, the question arises which transport function to choose and why just that one. Different transport approaches can be compared based on measured transport rates. However, this method has the disadvantage that any measured data contains inaccuracies that correlate in different ways with the transport functions under comparison. Unequal conditions also exist if the factors of transport functions under test are fitted to parts of the test data set during the development of the function, but others are not. Therefore, a structural formula comparison is made by transferring altogether 13 transport functions into a standardized notation. Although these formulas were developed from different perspectives and with different approaches, it is shown that these approaches lead to essentially the same basic formula for the main variables. These are shear stress and critical shear stress. However, despite the basic structure of these 13 formulas being the same, their coefficients vary significantly. The reason for that variation and the possible effect on the bandwidth of results is identified and discussed. A further result is the finding that not only shear stress affects bed-load transport rates as is expressed by many transport formulas. Transport rates are also significantly affected by the internal friction of the moving sediment as well as by the friction fluid-bed. In the case of not fully rough flow conditions, also viscous effects and thus the Reynolds number becomes of importance. Full article

(This article belongs to the Special Issue The Study and Monitoring of Geomorphic Processes in Geosciences and Engineering)

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21 pages, 4961 KiB

Open AccessArticle

Beach Gravels as a Potential Lithostatistical Indicator of Marine Coastal Dynamics: The Pogorzelica–Dziwnów (Western Pomerania, Baltic Sea, Poland) Case Study

by Cyprian Seul, Roman Bednarek, Tomasz Kozłowski and Łukasz Maciąg

Geosciences 2020, 10(9), 367; https://doi.org/10.3390/geosciences10090367 - 16 Sep 2020

Cited by 5 | Viewed by 2652

Abstract

The petrographic composition and grain shape variability of beach gravels in the Pogorzelica–Dziwnów coast section (363.0 to 391.4 km of coastline), southern Baltic Sea, Poland were analyzed herein to characterize the lithodynamics and trends of seashore development. Gravels were sampled at 0.25 km [...] Read more.

The petrographic composition and grain shape variability of beach gravels in the Pogorzelica–Dziwnów coast section (363.0 to 391.4 km of coastline), southern Baltic Sea, Poland were analyzed herein to characterize the lithodynamics and trends of seashore development. Gravels were sampled at 0.25 km intervals, in the midpart of the berm, following an early-autumn wave storm and before beach nourishment. Individual variations in petrographic groups along the shore were investigated. Gravel data were compared and related to coastal morpholithodynamics, seashore infrastructure, and geology of the study area. The contribution of crystalline rock gravels (igneous and metamorphic) was observed to increase along all coast sections, whereas the amount of less resistant components (limestones, sandstones, and shales) usually declined. This effect is explained by the greater wave crushing resistance of igneous and metamorphic components, compared with sedimentary components. Similarly, the gravel grain shape (mainly elongation or flattening) was observed to change, depending on resistance to mechanical destruction, or due to the increased chemical weathering in mainly the limestones, marbles, and sandstones. Observed increase in contribution of discoid and ellipsoid grains is a potential indicator of depositional trends along the coast sections investigated. On the other hand, increased contents of spheroidal and spindle-shaped grains may be related to erosional trends, where intensive redeposition and mechanical reworking of gravels occurs. However, due to the great number of coastal embankments, the petrographic composition and shape parameters of beach gravels do not always clearly indicate the dominant direction of longshore bedload transport. Increased amount of eroded limestone located east of Pogorzelica indicate increased erosion of glacial tills. These sediments are deposited, building the shallow foreshore, with additional redeposition of morainic material towards the shore. Full article

(This article belongs to the Special Issue Shoreline Dynamics and Beach Erosion)

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18 pages, 5262 KiB

Open AccessReview

Evolutionary Models of the Cenozoic Basins of Central-Western Mediterranean Area: A Review of Methodological Approaches

by Francesco Guerrera, Manuel Martín-Martín and Mario Tramontana

Geosciences 2020, 10(9), 366; https://doi.org/10.3390/geosciences10090366 - 15 Sep 2020

Cited by 11 | Viewed by 3461

Abstract

In the last 40 years, several models based on very different methodological approaches have been proposed to interpret the complex geodynamic evolution of the central-western Mediterranean area and, in particular, of the Cenozoic basins. The persistence of numerous interpretations and still-open problems resulted [...] Read more.

In the last 40 years, several models based on very different methodological approaches have been proposed to interpret the complex geodynamic evolution of the central-western Mediterranean area and, in particular, of the Cenozoic basins. The persistence of numerous interpretations and still-open problems resulted in the proliferation of very different models. The reconstructions presented are highly influenced by difficulties often encountered in considering constraints introduced by models built by means of completely different methodological approaches. For example, major difficulties can arise in integrating data from individual classical disciplines (i.e., geology, stratigraphy, geophysics, tectonics, magmatology and plate kinematics) with those resulting from the use of modern technologies (i.e., digital processing, uses of software, field observations using drones, etc.) and generally aimed to support specific topics. These considerations lead researchers to believe that a multidisciplinary approach would always be auspicious for these studies, because a greater control of the reconstruction of geologic and geodynamic events, and, therefore, for resulting models, would be ensured. After some considerations about different types of literature models based on specific investigation methodologies, the updating of a recently presented evolutionary model is proposed by attempting to integrate as much data as possible about the Cenozoic basins of the central-western Mediterranean area. Full article

(This article belongs to the Special Issue Tectono-Sedimentary Evolution of Cenozoic Basins)

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13 pages, 4587 KiB

Open AccessArticle

Quantitative Analysis of Pore Space Structure in Dry and Wet Soil by Integral Geometry Methods

by Dmitriy Ivonin, Timofey Kalnin, Eugene Grachev and Evgeny Shein

Geosciences 2020, 10(9), 365; https://doi.org/10.3390/geosciences10090365 - 14 Sep 2020

Cited by 7 | Viewed by 2957

Abstract

We present a methodology for a numerical analysis of three-dimensional tomographic images in this paper. The methodology is based on integral geometry, topology, and morphological analysis methods. It involves calculating cumulative and non-cumulative pore size distributions of Minkowski functionals and Betti numbers. We [...] Read more.

We present a methodology for a numerical analysis of three-dimensional tomographic images in this paper. The methodology is based on integral geometry, topology, and morphological analysis methods. It involves calculating cumulative and non-cumulative pore size distributions of Minkowski functionals and Betti numbers. We investigated 13 samples in dry and wet (saturated beyond the field capacity) conditions within different horizons of the Phaeozem albic. For samples of the arable horizon, an increase in the Euler characteristic was observed in the process of wetting. For samples from the A2, AB and B2 horizons, the Euler-Poincare characteristic decreased during wetting. It has been proven that both Betti numbers (number of isolated pores and number of “tunnels”) decrease with swelling of the AB and B2 horizons at a depth of 20–90 cm. For samples from the arable horizon, another dependence was observed: A Betti number of zero increased first but decreased during wetting. Based on the change in topological characteristics, two methods of changing the topology of the void space of the soil were demonstrated. The above-described quantitative changes of proposed parameters of pore space tomographic images prove the possibility and progressiveness of their usage for the pore space transformation estimate. Full article

(This article belongs to the Special Issue Modern Surveying and Geophysical Methods for Soil and Rock)

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22 pages, 11234 KiB

Open AccessArticle

Application of ‘Estimation Procedures’ in Unsaturated Soil Mechanics

by Delwyn G. Fredlund and Murray D. Fredlund

Geosciences 2020, 10(9), 364; https://doi.org/10.3390/geosciences10090364 - 11 Sep 2020

Cited by 19 | Viewed by 7731

Abstract

The application of unsaturated soil mechanics in routine geotechnical engineering applications requires the determination of unsaturated soil properties. Unfortunately, the cost of direct measurement of unsaturated soil properties goes beyond the financial budget of most clients. A solution has arisen, however, that involves [...] Read more.

The application of unsaturated soil mechanics in routine geotechnical engineering applications requires the determination of unsaturated soil properties. Unfortunately, the cost of direct measurement of unsaturated soil properties goes beyond the financial budget of most clients. A solution has arisen, however, that involves the measurement of two less costly soil properties functions that can be used in conjunction with a series of assumptions and estimation methodologies. The two laboratory tests involve measurement of the: (i) gravimetric water content versus soil suction, referred to as the soil-water characteristic curve (w-SWCC) and (ii) water content versus void ratio, referred to as the shrinkage curve (SC). These two unsaturated soil property relationships can be used along with saturated soil properties to extend unsaturated soil properties over the full range of soil suctions. “Estimation procedures” have been developed and verified for all physical properties of interest in unsaturated soil mechanics. The use of estimation procedures has meant that the geotechnical engineer must operate within a new paradigm. The new paradigm provides sufficient accuracy for most geotechnical engineering applications. The net result is an increased decision-making capability for geotechnical engineers. Full article

(This article belongs to the Section Geomechanics)

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12 pages, 2646 KiB

Open AccessArticle

Mire Development and Disappearance due to River Capture as Hydrogeological and Geomorphological Consequences of LGM Ice-Marginal Valley Evolution at the Vistula-Neman Watershed

by Grzegorz Wierzbicki, Mateusz Grygoruk, Maria Grodzka-Łukaszewska, Piotr Bartold and Tomasz Okruszko

Geosciences 2020, 10(9), 363; https://doi.org/10.3390/geosciences10090363 - 11 Sep 2020

Cited by 8 | Viewed by 3699

Abstract

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type [...] Read more.

The advances and retreats of ice sheets during Pleistocene significantly changed high- and mid-latitude landscapes and hydrological systems, albeit differently, in North America and Europe. On the southern margin of the Last Glacial Maximum (LGM) in the Baltic Sea basin, a specific type of valley has developed between glacial margins and upland or mountain slopes. We studied new geological data (boreholes, electrical resistivity imaging (ERI) from this geomorphic setting in Northeast Poland to understand: (1) how the landscape and river network evolved to eventually produce peat mires during the Holocene, and (2) the nature of groundwater recharge to fens in the upper Biebrza Valley. We present the results on a geological cross-section with hydrogeological interpretation. We also discuss regional geomorphology. In addition, we present the LGM extent derived from a spatial distribution of Vistulian (Weichselian) terminal moraines. These end moraines are also interpreted as Saalian kames. Thus, we additionally present another method of LGM extent delineation from a physicogeographical division. We link the steep slopes of the studied valley walls (kame terrace fronts) with thermokarst erosion in the periglacial zone. We then document the hydrogeological window (DISCONTINUITY in the till layer over the confined aquifer), which enables the outflow of groundwater into the peat bog. Although minerotrophic fen mire development in the study area is likely to be sustained in the near future through sufficient groundwater supply, the projected capture of the Biebrza River by the Neman River will not allow for sustaining peatland development. Full article

(This article belongs to the Special Issue Hydrological Systems and Models Applied in Permafrost)

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13 pages, 3007 KiB

Open AccessArticle

Investigation of Spatial and Temporal Changes in the Land Surface Albedo for the Entire Chinese Territory

by Jihui Yuan

Geosciences 2020, 10(9), 362; https://doi.org/10.3390/geosciences10090362 - 10 Sep 2020

Cited by 4 | Viewed by 1958

Abstract

Currently, global climate change (GCC) and the urban heat island (UHI) phenomena are becoming serious problems, partly due to the artificial construction of the land surface. When sunlight reaches the land surface, some of it is absorbed and some is reflected. The state [...] Read more.

Currently, global climate change (GCC) and the urban heat island (UHI) phenomena are becoming serious problems, partly due to the artificial construction of the land surface. When sunlight reaches the land surface, some of it is absorbed and some is reflected. The state of the land surface directly affects the surface albedo, which determines the magnitude of solar radiation reflected by the land surface in the daytime. In order to better understand the spatial and temporal changes in surface albedo, this study investigated and analyzed the surface albedo from 2000 to 2016 (2000, 2008, and 2016) in the entire Chinese territory, based on the measurement database obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument, aboard NASA’s Terra satellite. It was shown that the Northeast China exhibited the largest decline in surface albedo and North China showed the largest rising trend of surface albedo from 2000 to 2016. The correlation between changes in surface albedo and the Normalized Difference Vegetation Index (NDVI) indicated that the change trend of surface albedo was opposite to that of NDVI. In addition, in order to better understand the distribution of surface albedo in the entire Chinese territory, the classifications of surface albedo in three years (2000, 2008, and 2016) were implemented using five classification methods in this study. Full article

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26 pages, 17807 KiB

Open AccessArticle

The Capo Castello Shear Zone (Eastern Elba Island): Deformation at the Contact between Oceanic and Continent Tectonic Units

by Caterina Bianco

Geosciences 2020, 10(9), 361; https://doi.org/10.3390/geosciences10090361 - 10 Sep 2020

Cited by 1 | Viewed by 3106

Abstract

Low-grade mylonitic shear zones are commonly characterized by strain partitioning, with alternating low strain protomylonite and high strain mylonite and ultramylonite, where the shearing is most significant. In this paper the capo Castello shear zone is analyzed. It has developed along the contact [...] Read more.

Low-grade mylonitic shear zones are commonly characterized by strain partitioning, with alternating low strain protomylonite and high strain mylonite and ultramylonite, where the shearing is most significant. In this paper the capo Castello shear zone is analyzed. It has developed along the contact between continental quartzo-feldspathic, in the footwall, and oceanic ophiolitic units, in the hangingwall. The shear zone shows, mostly within the serpentinites, a heterogeneous strain localization, characterized by an alternation of mylonites and ultramylonites, without a continuous strain gradient moving from the protolith (i.e., the undeformed host rock) to the main tectonic contact between the two units. The significance of this mylonitic shear zone is examined in terms of the dominant deformation mechanisms, and its regional tectonic frame. The combination of the ultramafic protolith metamorphic processes and infiltration of derived fluids caused strain softening by syntectonic metamorphic reactions and dissolution–precipitation processes, leading to the final formation of low strength mineral phases. It is concluded that the strain localization, is mainly controlled by the rock-fluid interactions within the ophiolitic level of the Capo Castello shear zone. Regarding the regional setting, this shear zone can be considered as an analogue of the initial stage of the post-collisional extensional fault, of which mature stage is visible along the Zuccale fault zone, a regional structure affecting eastern Elba Island. Full article

(This article belongs to the Special Issue The Apennines: Tectonics, Sedimentation, and Magmatism from the Palaeozoic to the Present)

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18 pages, 9803 KiB

Open AccessArticle

Mineralogical and Geotechnical Characterization of the Clay Layers within the Basal Shear Zone of the 1963 Vajont Landslide

by Alberto Bolla, Paolo Paronuzzi, Daniela Pinto, Davide Lenaz and Marco Del Fabbro

Geosciences 2020, 10(9), 360; https://doi.org/10.3390/geosciences10090360 - 06 Sep 2020

Cited by 10 | Viewed by 3461

Abstract

The 1963 Vajont landslide is a reference example of large rockslides involving clay interbeds emplaced in sedimentary rock masses in correspondence with the basal rupture zone (thinly stratified cherty limestone of the Fonzaso Formation dated to Middle–Upper Jurassic). The basal shear zone of [...] Read more.

The 1963 Vajont landslide is a reference example of large rockslides involving clay interbeds emplaced in sedimentary rock masses in correspondence with the basal rupture zone (thinly stratified cherty limestone of the Fonzaso Formation dated to Middle–Upper Jurassic). The basal shear zone of the 1963 Vajont landslide was made up of a chaotic assemblage of displaced rock masses, limestone angular gravel, and spread clay lenses. The mineralogical investigations showed that the clays are characterized by complex assemblages of illite/smectite mixed layers (36–96%) admixed with variable amounts of calcite (4–64%) and quartz (0–6%). The clay layers show highly variable plasticity properties and shear strength characteristics. The samples with a large prevalence of clay mineral content (CM) (CM > 79%) are characterized by low values of the residual friction angle (6.7–14.9°), whereas clay materials characterized by a higher content of granular minerals (calcite and quartz) clearly show greater friction angle values (19.5–26.7°). The high permeability of the limestone angular gravel, which caused a rapid reservoir-induced inflow (1960–1963), together with the low friction angle of the clay layers were responsible for the overall shear strength reduction in correspondence with the basal rupture zone, thus favoring the huge sliding on 9 October 1963. Full article

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27 pages, 94114 KiB

Open AccessArticle

Characteristics of Atmospheric Circulation Associated with Variability of Sea Ice in the Arctic

by Gennady Platov, Dina Iakshina and Vladimir Krupchatnikov

Geosciences 2020, 10(9), 359; https://doi.org/10.3390/geosciences10090359 - 06 Sep 2020

Cited by 5 | Viewed by 2000

Abstract

The paper investigates the role of atmospheric circulation in the surface layer in forming the Arctic ice structure. For the analysis, the empirical orthogonal function (EOF) method of decomposition of the surface wind field is used, and the reaction of ice to changes [...] Read more.

The paper investigates the role of atmospheric circulation in the surface layer in forming the Arctic ice structure. For the analysis, the empirical orthogonal function (EOF) method of decomposition of the surface wind field is used, and the reaction of ice to changes in the principal components of leading EOF modes is investigated using statistical methods. Analyzing the rate of ice change in the Arctic associated with the Arctic ocean oscillation mode, we concluded that this mode’s variability leads to the formation of a seesaw in the ice field between two regions. From the one side, it is the region of the central deep-water part of the Arctic, including the East Siberian Sea, and from the other side, it is all other marginal seas. The second (“dipole”) mode is most associated with an increase/decrease in the ice thickness at the Arctic exit through the Fram Strait, as well as the formation of the so-called “ice factory” in the coastal region of the Beaufort Sea in the positive phase of this mode. There is also a significant relationship between the variability of third mode and the arrival of Atlantic waters with a high heat content into the Arctic through the Barents opening, which creates preconditions for ice formation in this region. Full article

(This article belongs to the Special Issue Geophysical Modeling of the Arctic Environment under Climate Changes)

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50 pages, 13746 KiB

Open AccessReview

Fossil History of Curculionoidea (Coleoptera) from the Paleogene

by Andrei A. Legalov

Geosciences 2020, 10(9), 358; https://doi.org/10.3390/geosciences10090358 - 06 Sep 2020

Cited by 33 | Viewed by 4601

Abstract

Currently, some 564 species of Curculionoidea from nine families (Nemonychidae—4, Anthribidae—33, Ithyceridae—3, Belidae—9, Rhynchitidae—41, Attelabidae—3, Brentidae—47, Curculionidae—384, Platypodidae—2, Scolytidae—37) are known from the Paleogene. Twenty-seven species are found in the Paleocene, 442 in the Eocene and 94 in the Oligocene. The greatest diversity [...] Read more.

Currently, some 564 species of Curculionoidea from nine families (Nemonychidae—4, Anthribidae—33, Ithyceridae—3, Belidae—9, Rhynchitidae—41, Attelabidae—3, Brentidae—47, Curculionidae—384, Platypodidae—2, Scolytidae—37) are known from the Paleogene. Twenty-seven species are found in the Paleocene, 442 in the Eocene and 94 in the Oligocene. The greatest diversity of Curculionoidea is described from the Eocene of Europe and North America. The richest faunas are known from Eocene localities, Florissant (177 species), Baltic amber (124 species) and Green River formation (75 species). The family Curculionidae dominates in all Paleogene localities. Weevil species associated with herbaceous vegetation are present in most localities since the middle Paleocene. A list of Curculionoidea species and their distribution by location is presented. Full article

(This article belongs to the Special Issue 2020: A 10 Years Journey-Advances in Geosciences)

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23 pages, 4651 KiB

Open AccessArticle

Characteristics of Sedimentary Organic Matter and Phosphorus in Minor Rivers Discharging into Zhejiang Coast, China

by Pei Sun Loh, Long-Xiu Cheng, Shi-Yuan Lin and Selvaraj Kandasamy

Geosciences 2020, 10(9), 357; https://doi.org/10.3390/geosciences10090357 - 05 Sep 2020

Cited by 1 | Viewed by 2074

Abstract

In this study, the spatial distribution of lignin-derived phenols, bulk elemental composition and different phosphorus (P) species in surface sediments along six rivers discharging into Zhejiang coast, Southeast China, were investigated to improve the understanding of the carbon and P dynamics in these [...] Read more.

In this study, the spatial distribution of lignin-derived phenols, bulk elemental composition and different phosphorus (P) species in surface sediments along six rivers discharging into Zhejiang coast, Southeast China, were investigated to improve the understanding of the carbon and P dynamics in these small river systems. The Shuang, Jiao, Ximen, Feiyun and Ao Rivers have total organic carbon (TOC) ranging from 0.29% to 2.77% and Λ (total lignin in mg/100 mg TOC) ranging from 0.24 to 4.24; Qiantang River has the lowest Λ (0.08–0.19) but the highest TOC (1.05%–6.46%). Jiao, Ximen, Feiyun and Ao Rivers have mean the total P (TP) and bioavailable P (BAP) of 34 to 124 mg/kg and 29 to 89 mg P/kg, and mean OC/OP molar ratio of 397–917. Qiantang River has the lowest mean TP and BAP of 13 mg P/kg and 7 mg P/kg, and highest OC/OP of 18,753; whereas Shuang River has the highest mean TP and BAP of 645 mg P/kg and 559 mg P/kg, and lowest mean OC/OP of 90. The lowest Λ, TP and BAP, but highest OC/OP, in the Qiantang River could be due to tidal bore causing rapid cycling of carbon and P. Trends of slight decrease in abundance of OC, Λ, TP and BAP, but increasing ratios of vanillic acid to vanillin [(Ad/Al)v], syringic acid to syringaldehyde [(Ad/Al)s] and OC/OP farther downstream of the rivers indicate a continuous decomposition of organic matter during transport along the rivers. Full article

(This article belongs to the Section Geochemistry)

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26 pages, 15050 KiB

Open AccessArticle

Applications of Geophysical Surveys for Archaeological Studies in Urban and Rural Areas in Czech Republic and Armenia

by Jaroslav Bárta, Tomáš Belov, Jan Frolík and Jaroslav Jirků

Geosciences 2020, 10(9), 356; https://doi.org/10.3390/geosciences10090356 - 05 Sep 2020

Cited by 2 | Viewed by 4151

Abstract

The authors of the presented paper tested the possible use of geophysical methods in the field of archaeological and constructional-historical research. It focused on the historical center of Prague, where we took measurements in the built-up areas covered by cobble stones and asphalt. [...] Read more.

The authors of the presented paper tested the possible use of geophysical methods in the field of archaeological and constructional-historical research. It focused on the historical center of Prague, where we took measurements in the built-up areas covered by cobble stones and asphalt. The works were carried out mainly at the Old Town Square, Hradčany Square, Charles Square and Lesser Town Square. Field conditions were completely different at the Armenia sites (intact agricultural areas). We used the methods of shallow geophysical survey, namely geoelectrical methods, gravimetry, seismics and magnetometry. Measurement results from the built-up areas were affected by presence of engineering networks, transportation and field obstacles. Working in the rural areas is generally less demanding in terms of implementation and evaluation, but our results show that proper selection of geophysical methods brings positive results even in urban areas. The research proved that good results can be expected if one uses multiple geophysical methods measuring various physical properties of an environment. The application of only one, albeit sophisticated method, is usually not enough. There is a necessity to improve interpretational software for the purposes of archaeological object detection. The objects are mainly buried within the first meters and are relatively small. Contrast of physical properties between searched objects and their surrounding environment does exist but typically is small and, therefore, it is necessary to measure multiple physical parameters simultaneously. The presented projects aimed not only to archaeology, but the results also had practical outputs for public administration and development. Full article

(This article belongs to the Special Issue Selected papers from the SAGA Workshop 1)

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17 pages, 2210 KiB

Open AccessArticle

Soil Heating at High Temperatures and Different Water Content: Effects on the Soil Microorganisms

by Ana Barreiro, Alba Lombao, Angela Martín, Javier Cancelo-González, Tarsy Carballas and Montserrat Díaz-Raviña

Geosciences 2020, 10(9), 355; https://doi.org/10.3390/geosciences10090355 - 05 Sep 2020

Cited by 16 | Viewed by 3396

Abstract

Soil properties determining the thermal transmissivity, the heat duration and temperatures reached during soil heating are key factors driving the fire-induced changes in soil microbial communities. The aim of the present study is to analyze, under laboratory conditions, the impact of the thermal [...] Read more.

Soil properties determining the thermal transmissivity, the heat duration and temperatures reached during soil heating are key factors driving the fire-induced changes in soil microbial communities. The aim of the present study is to analyze, under laboratory conditions, the impact of the thermal shock (infrared lamps reaching temperatures of 100 °C, 200 °C and 400 °C) and moisture level (0%, 25% and 50% per soil volume) on the microbial properties of three soil mixtures from different sites. The results demonstrated that the initial water content was a determinant factor in the response of the microbial communities to soil heating treatments. Measures of fire impact included intensity and severity (temperature, duration), using the degree-hours method. Heating temperatures produced varying thermal shock and impacts on biomass, bacterial activity and microbial community structure. Full article

(This article belongs to the Special Issue Wildfires Hazards)

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11 pages, 1529 KiB

Open AccessArticle

Ionosonde Data Analysis in Relation to the 2016 Central Italian Earthquakes

by Alessandro Ippolito, Loredana Perrone, Angelo De Santis and Dario Sabbagh

Geosciences 2020, 10(9), 354; https://doi.org/10.3390/geosciences10090354 - 05 Sep 2020

Cited by 6 | Viewed by 3214

Abstract

Ionospheric characteristics and crustal earthquakes that occurred in 2016 next to the town of Amatrice, Italy are studied together with the previous events that took place from 1984 to 2009 in Central Italy. The earthquakes with M larger than 5.5 and epicentral distances [...] Read more.

Ionospheric characteristics and crustal earthquakes that occurred in 2016 next to the town of Amatrice, Italy are studied together with the previous events that took place from 1984 to 2009 in Central Italy. The earthquakes with M larger than 5.5 and epicentral distances from the ionosonde less than 150 km were selected for the analysis. A multiparametric approach was applied using variations of sporadic E-layer parameters (the height and the transparency frequency) together with variations of the F2 layer critical frequency foF2 at the Rome ionospheric observatory. Only ionospheric data under quiet geomagnetic conditions were considered. The inclusion of new 2016 events has allowed us to clarify the earlier-obtained seismo-ionospheric empirical relationships linking the distance in space (km) and time (days) between the ionospheric anomaly and the impending earthquake, with its magnitude. The improved dependencies were shown to be similar to those obtained in previous studies in different parts of the world. The possibility of using the obtained relationships for earthquake predictions is discussed. Full article

(This article belongs to the Special Issue Detecting Geospace Perturbations Caused by Earth)

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10 pages, 3141 KiB

Open AccessArticle

Stress–Dilatancy Relationship of Erksak Sand under Drained Triaxial Compression

by Katarzyna Dołżyk-Szypcio

Geosciences 2020, 10(9), 353; https://doi.org/10.3390/geosciences10090353 - 05 Sep 2020

Cited by 4 | Viewed by 2734

Abstract

Analyzing the results of triaxial compression tests under drained conditions for Erksak sand published in the literature, the stress–dilatancy relationships were described using the frictional state concept. At all phases of shearing, the linear stress ratio–plastic dilatancy relationship can be expressed by the [...] Read more.

Analyzing the results of triaxial compression tests under drained conditions for Erksak sand published in the literature, the stress–dilatancy relationships were described using the frictional state concept. At all phases of shearing, the linear stress ratio–plastic dilatancy relationship can be expressed by the critical frictional state angle and two parameters of the frictional state concept. At failure, dense sand exhibits purely frictional behavior (α = 0, β = 1) and the stress ratio–dilatancy relationship may be correctly described by the Rowe, Bolton, and frictional state concept relationships. Very loose Erksak sand sheared under drained triaxial compression at the ultimate state reaches a stable condition, but the reached stress ratio is significantly smaller than the one at a critical state. Full article

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22 pages, 4665 KiB

Open AccessArticle

Evaluation of Satellite Rainfall Estimates for Meteorological Drought Analysis over the Upper Blue Nile Basin, Ethiopia

by Mintesinot Taye, Dejene Sahlu, Benjamin F. Zaitchik and Mulugeta Neka

Geosciences 2020, 10(9), 352; https://doi.org/10.3390/geosciences10090352 - 04 Sep 2020

Cited by 21 | Viewed by 3065

Abstract

The objective of this study was to evaluate the performance of satellite rainfall estimates (Climate Hazards Group Infrared Precipitation with Stations version 2 (CHIRPSv2) and Multi-Source Weighted-Ensemble Precipitation version 2 (MSWEPv2) from 1981 to 2018 for monthly meteorological drought analysis over the Upper [...] Read more.

The objective of this study was to evaluate the performance of satellite rainfall estimates (Climate Hazards Group Infrared Precipitation with Stations version 2 (CHIRPSv2) and Multi-Source Weighted-Ensemble Precipitation version 2 (MSWEPv2) from 1981 to 2018 for monthly meteorological drought analysis over the Upper Blue Nile (UBN) basin. The reference for the performance evaluation was rainfall measured in situ selected with reference to the elevation zones of the basin: Highland, midland, and lowland. Both the measured and estimated rainfall datasets were aggregated by month at a spatial resolution of 10 km × 10 km with a temporal coverage of 38 years from 1981 to 2018 and evaluated with respect to raw precipitation statistics and the standardized precipitation index (SPI). The values of SPI were validated with reference to documented meteorological drought records of the country. The mean bias, correlation coefficient, probability of bias (PBias, %), mean error (ME, mm), and root mean square error (RMSE, mm) values across the elevation zones for CHIRPSv2 were found to be 1.07, 0.91, 6.75, 7.74, and 122.34, respectively. The corresponding values were 1.19, 0.87, 18.56, 19.54, and 130.26 for MSWEPv2. Based on this result, CHIRPSv2 was employed to analyze the magnitude of drought in the different elevation zones of the UBN. The magnitude (SPI) of monthly meteorological drought over the entire UBN basin from 1981 to 2018 ranged from 0 to −3.74. The strongest negative SPI value (−3.74) was observed in August 1984 in midland areas. The highest magnitude of drought was −3.0 in July 2015 over the highland and −3.03 in June 2015 over the lowland during 2014–2017. The observed drought was characterized by extreme, severe, and moderate levels. The mean frequency of severe/extreme meteorological drought in the 38-year period over the highland, midland, and lowland parts of the UBN ranged from 7% to 11%. The average of severe/extreme drought events in each of the elevation zones of the basin was 9%, that is, drought occurred almost every 10 years for all elevation zones of the basin. Over the 38-year period, severe/extreme drought occurred at the onset and/or offset time of rainy season over all elevation zones of the basin. The UBN is characterized as a drought-prone basin. However, the frequency and magnitude of drought could neither be described as a decreasing nor as an increasing linear trend. Thus, the farming practices in the basin need to be enhanced with an improved early warning system and drought-resistant seed technologies. Full article

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23 pages, 8288 KiB

Open AccessArticle

Adaptive Numerical Modeling of Tsunami Wave Generation and Propagation with FreeFem++

by Georges Sadaka and Denys Dutykh

Geosciences 2020, 10(9), 351; https://doi.org/10.3390/geosciences10090351 - 04 Sep 2020

Cited by 1 | Viewed by 2437

Abstract

A simplified nonlinear dispersive Boussinesq system of the Benjamin–Bona–Mahony (BBM)-type, initially derived by Mitsotakis (2009), is employed here in order to model the generation and propagation of surface water waves over variable bottom. The simplification consists in prolongating the so-called Boussinesq approximation to [...] Read more.

A simplified nonlinear dispersive Boussinesq system of the Benjamin–Bona–Mahony (BBM)-type, initially derived by Mitsotakis (2009), is employed here in order to model the generation and propagation of surface water waves over variable bottom. The simplification consists in prolongating the so-called Boussinesq approximation to bathymetry terms, as well. Using the finite element method and the FreeFem++ software, we solve this system numerically for three different complexities for the bathymetry function: a flat bottom case, a variable bottom in space, and a variable bottom both in space and in time. The last case is illustrated with the Java 2006 tsunami event. This article is designed to be a pedagogical paper presenting to tsunami wave community a new technology and a novel adaptivity technique, along with all source codes necessary to implement it. Full article

(This article belongs to the Special Issue Interdisciplinary Geosciences Perspectives of Tsunami Volume 3)

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11 pages, 2919 KiB

Open AccessArticle

Fast Sampling Field Deployable Mud Gas Carbon Isotope Analyzer

by Sheng Wu, Andrei Deev, Yan Zhuang, Le Lu, Zhengyou Wang, Yongchun Tang and Andrew Sneddon

Geosciences 2020, 10(9), 350; https://doi.org/10.3390/geosciences10090350 - 04 Sep 2020

Cited by 4 | Viewed by 2371

Abstract

We report the details of a field deployable mud gas carbon isotope analyzer for mud gas analysis based on coupling a gas chromatograph with a mid-infrared spectrometer using a quantum cascade laser and hollow waveguide. The GC–IR² (gas chromatograph–infrared isotope ratio) system [...] Read more.

We report the details of a field deployable mud gas carbon isotope analyzer for mud gas analysis based on coupling a gas chromatograph with a mid-infrared spectrometer using a quantum cascade laser and hollow waveguide. The GC–IR² (gas chromatograph–infrared isotope ratio) system features a fast sampling cycle as short as 123 s for analyzing all three components, i.e., methane, ethane and propane. The samples are automatically diluted so the system could carry out effective measurements while sample concentrations vary from 400 ppm to 100% purity. The accuracy is guaranteed through periodic reference calibration, and variations due to field temperature changes are minimized. Full article

(This article belongs to the Special Issue Stable Isotope Systematics of Coalbed Gas and Shale Gas during Desorption and Production)

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11 pages, 5343 KiB

Open AccessArticle

Seawater Intrusion on the Arctic Coast (Svalbard): The Concept of Onshore-Permafrost Wedge

by Marek Kasprzak

Geosciences 2020, 10(9), 349; https://doi.org/10.3390/geosciences10090349 - 03 Sep 2020

Cited by 13 | Viewed by 3943

Abstract

Numerous hydrogeological studies on the coastal zone describe the intrusion of sea water inland, salting underground aquifers. The phenomenon is commonly observed in the coasts outside polar areas. However, the impact of sea water has so far not been an object of detailed [...] Read more.

Numerous hydrogeological studies on the coastal zone describe the intrusion of sea water inland, salting underground aquifers. The phenomenon is commonly observed in the coasts outside polar areas. However, the impact of sea water has so far not been an object of detailed investigation in a periglacial environment devoid of subsea permafrost. Geophysical measurements at the west coast of the Wedel-Jarlsberg Land in Svalbard indicate that the border between the unfrozen seabed and the frozen ground onshore is not delimited by the shoreline. A zone of coastal unfrozen ground is located under a thin layer of permafrost reaching toward the sea. This state was observed with the use of electrical resistivity tomography under rocky headlands and capes, uplifted marine terraces located at the foot of mountain massifs and valley mouths as well as in the marginal zone of the Werenskiold Glacier. This short article presents the results of such a measurement, supplemented with electromagnetic detection. The measurements are unique in that they were conducted not only on the land surface, but also at the floor of the sea bay during the low water spring tide. The author proposes name structures detected in the coastal zone as a “permafrost wedge”, extending an identification of the permafrost base between the coast and the glaciers of Svalbard. However, in the absence of boreholes that would allow determining the thermal state of the ground in the study sites, the concept is based only on the interpretation of the geophysical imaging. Therefore, further discussion is required on whether the identified contrasts in electrical resistivity indeed result from thermal differences between the rocks or if they only indicate the cryotic state of the ground (saline cryopeg) within the range of seawater intrusion. Full article

(This article belongs to the Special Issue Permafrost and Glaciers: Perspectives for the Earth and Planetary Sciences)

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