Geosciences

26 pages, 35353 KiB

Open AccessArticle

New Insights into the Understanding of High-Pressure Air Injection (HPAI): The Role of the Different Chemical Reactions

by Dubert Gutiérrez, Gord Moore, Don Mallory, Matt Ursenbach, Raj Mehta and Andrea Bernal

Geosciences 2024, 14(10), 270; https://doi.org/10.3390/geosciences14100270 - 13 Oct 2024

High-pressure air injection (HPAI) is an enhanced oil recovery process in which compressed air is injected into deep, light oil reservoirs, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated [...] Read more.

High-pressure air injection (HPAI) is an enhanced oil recovery process in which compressed air is injected into deep, light oil reservoirs, with the expectation that the oxygen in the injected air will react with a fraction of the reservoir oil at an elevated temperature to produce carbon dioxide. The different chemical reactions taking place can be grouped into oxygen addition, thermal cracking, oxygen-induced cracking, and bond scission reactions. The latter reactions involve the combustion of a flammable vapor as well as the combustion of solid fuel, commonly known as “coke”. Since stable peak temperatures observed during HPAI experiments are typically below 300 °C, it has been suggested that thermal cracking and combustion of solid fuel may not be important reaction mechanisms for the process. The objective of this work is to assess the validity of that hypothesis. Therefore, this study makes use of different oxidation and combustion HPAI experiments, which were performed on two different light oil reservoir samples. Modeling of those tests indicate that thermal cracking is not an important reaction mechanism during HPAI and can potentially be ignored. The work also suggests that the main fuel consumed by the process is a flammable vapor generated by the chemical reactions. This represents a shift from the original in situ combustion paradigm, which is based on the combustion of coke. Full article

(This article belongs to the Topic Enhanced Oil Recovery Technologies, 3rd Volume)

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36 pages, 4601 KiB

Open AccessArticle

Investigating Sense of Place and Geoethical Awareness among Educators at the 4th Summer School of Sitia UNESCO Global Geopark: A Quasi-Experimental Study

by Alexandros Aristotelis Koupatsiaris and Hara Drinia

Geosciences 2024, 14(10), 269; https://doi.org/10.3390/geosciences14100269 - 12 Oct 2024

Abstract

Anthropogenic global challenges and environmental pressures are increasingly significant. Developing pro-environmental behavior and geoethics is crucial for enhancing awareness, action capability, and respect for natural systems. UNESCO Global Geoparks (UGGps) play a vital role in conserving geological and biological diversity while aligning with [...] Read more.

Anthropogenic global challenges and environmental pressures are increasingly significant. Developing pro-environmental behavior and geoethics is crucial for enhancing awareness, action capability, and respect for natural systems. UNESCO Global Geoparks (UGGps) play a vital role in conserving geological and biological diversity while aligning with the United Nations’ Sustainable Development Goals. This quasi-experimental study, conducted during the 4th Summer School of Environmental Education on Geotopes and Sustainability at the Sitia UGGp, uses a pre–post design and comprehensive questionnaire to explore changes in participants’ sense of place and geoethical awareness. Results indicate significant improvements in place attachment, place meaning, and geoethical awareness. These findings suggest that stronger emotional bonds and deeper personal meanings related to the Sitia UGGp correlate with increased geoethical awareness. This research highlights the role of psychological connections in influencing geoenvironmental ethics and underscores the importance of place-based emotional and cognitive bonds in fostering geoethical thinking. However, this study’s limited sample size and the specific geographic context of Sitia UGGp may limit the generalizability of the findings. Despite these limitations, this study provides insights into the interplay of emotions, meanings, and geoethics within the sustainability and resilience spectrum. Full article

(This article belongs to the Section Geoheritage, Geoparks and Geotourism)

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35 pages, 5053 KiB

Open AccessArticle

Simulating Compaction and Cementation of Clay Grain Coated Sands in a Modern Marginal Marine Sedimentary System

by James E. Houghton, Thomas E. Nichols and Richard H. Worden

Geosciences 2024, 14(10), 268; https://doi.org/10.3390/geosciences14100268 - 12 Oct 2024

Abstract

Reservoir quality prediction in deeply buried reservoirs represents a complex challenge to geoscientists. In sandstones, reservoir quality is determined by the extent of compaction and cementation during burial. During compaction, porosity is lost through the rearrangement and fracture of rigid grains and the [...] Read more.

Reservoir quality prediction in deeply buried reservoirs represents a complex challenge to geoscientists. In sandstones, reservoir quality is determined by the extent of compaction and cementation during burial. During compaction, porosity is lost through the rearrangement and fracture of rigid grains and the deformation of ductile grains. During cementation, porosity is predominantly lost through the growth of quartz cement, although carbonate and clay mineral growth can be locally important. The degree of quartz cementation is influenced by the surface area of quartz available for overgrowth nucleation and thermal history. Clay grain coats can significantly reduce the surface area of quartz available for overgrowth nucleation, preventing extensive cementation. Using a coupled-effect compaction and cementation model, we have forward-modelled porosity evolution of surface sediments from the modern Ravenglass Estuary under different maximum burial conditions, between 2000 and 5000 m depth, to aid the understanding of reservoir quality distribution in a marginal marine setting. Seven sand-dominated sub-depositional environments were subject to five burial models to assess porosity-preservation in sedimentary facies. Under relatively shallow burial conditions (<3000 m), modelled porosity is highest (34 to 36%) in medium to coarse-grained outer-estuary sediments due to moderate sorting and minimal fine-grained matrix material. Fine-grained tidal flat sediments (mixed flats) experience a higher degree of porosity loss due to elevated matrix volumes (20 to 31%). Sediments subjected to deep burial (>4000 m) experience a significant reduction in porosity due to extensive quartz cementation. Porosity is reduced to 1% in outer estuary sediments that lack grain-coating clays. However, in tidal flat sediments with continuous clay grain coats, porosity values of up to 30% are maintained due to quartz cement inhibition. The modelling approach powerfully emphasises the value of collecting quantitative data from modern analogue sedimentary environments to reveal how optimum reservoir quality is not always in the coarsest or cleanest clastic sediments. Full article

26 pages, 8635 KiB

Open AccessReview

The Mundeck Salt Unit: A Review of Aptian Depositional Context and Hydrocarbon Potential in the Kribi-Campo Sub-Basin (South Cameroon Atlantic Basin)

by Mike-Franck Mienlam Essi, Eun Young Lee, Mbida Yem, Jean Marcel Abate Essi and Joseph Quentin Yene Atangana

Geosciences 2024, 14(10), 267; https://doi.org/10.3390/geosciences14100267 - 11 Oct 2024

Abstract

The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and [...] Read more.

The Kribi-Campo sub-basin, located in the Gulf of Guinea, constitutes the southeastern segment of the Cameroon Atlantic Margin. Drilling in the Aptian salt unit revealed a sparse hydrocarbon presence, contrasting with modest finds in its counterparts like the Ezanga Salt in Gabon and the Rio Muni Salt in Equatorial Guinea. This discrepancy prompted a reassessment of the depositional context and hydrocarbon potential of the Mundeck salt unit. By integrating 2D seismic reflection and borehole data analysis, this study established the structural and stratigraphic framework of the area, emphasizing the salt unit’s significance. Borehole data indicate a localized salt unit offshore Kribi, with seismic reflection data revealing distinct forms of diapir and pillow. This salt unit displays a substantial lateral extent with thicknesses ranging from 4000 m to 6000 m. The depositional context is linked to the following two major geological events: a significant sea-level drop due to margin uplift during the Aptian and thermodynamic processes driven by transfer faults related to mid-oceanic ridge formation. These events were crucial in forming and evolving the Mundeck Salt. Regarding hydrocarbon prospects, this study identifies the unit as being associated with potential petroleum plays, supported by direct hydrocarbon indicators and fault-related structures. The findings suggest that untapped hydrocarbon resources may still exist, underscoring the need for further exploration and analysis. Full article

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

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14 pages, 3655 KiB

Open AccessArticle

Analyzing Public Interest in Geohazards Using Google Trends Data

by Dmitry Erokhin and Nadejda Komendantova

Geosciences 2024, 14(10), 266; https://doi.org/10.3390/geosciences14100266 - 11 Oct 2024

Abstract

This study investigates public interest in geological disasters by analyzing Google Trends data from 2023. This research focuses on earthquakes, hurricanes, floods, tornadoes, and tsunamis to understand how search behaviors reflect public awareness and concern. This study identifies temporal and geographical patterns in [...] Read more.

This study investigates public interest in geological disasters by analyzing Google Trends data from 2023. This research focuses on earthquakes, hurricanes, floods, tornadoes, and tsunamis to understand how search behaviors reflect public awareness and concern. This study identifies temporal and geographical patterns in search trends. Key findings reveal that public interest spikes during significant disaster events, such as the February 2023 earthquake in Turkey and Syria and the August 2023 hurricanes in the United States. This study highlights the importance of timely and accurate information dissemination for disaster preparedness and response. Google Trends proves to be a valuable tool for monitoring public interest, offering real-time insights that can enhance disaster management strategies and improve community resilience. This study’s insights are essential for policymakers, disaster management agencies, and educational efforts aimed at mitigating the impacts of natural disasters. Full article

(This article belongs to the Section Natural Hazards)

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23 pages, 10461 KiB

Open AccessArticle

Effects of Anthropic Structures on Morphodynamic Beach Evolution along the Gulf of Roses (Northwestern Mediterranean, Spain)

by Antoni Calafat, Manel Salvador, Marta Guinau and José L. Casamor

Geosciences 2024, 14(10), 265; https://doi.org/10.3390/geosciences14100265 - 10 Oct 2024

Abstract

This study conducts a morphodynamic analysis of beaches located in the northern sector of the Gulf of Roses (NW Mediterranean, Spain). The primary objective is to investigate mid-short (2004–2020) term spatial and temporal variations in shoreline position and sedimentological behaviour. The study area [...] Read more.

This study conducts a morphodynamic analysis of beaches located in the northern sector of the Gulf of Roses (NW Mediterranean, Spain). The primary objective is to investigate mid-short (2004–2020) term spatial and temporal variations in shoreline position and sedimentological behaviour. The study area covers the northern part of the gulf, spanning 9.86 km, and includes both natural beaches and heavily anthropized ones. The following GIS methodologies were employed to study the variations in the coastline: QGIS for areas and DSAS-ArcGIS for transects, quantifying coastal changes from 2004 to 2020. Sediment samples were collected from both the dry beach and swash areas for each profile. The results reveal minor discrepancies in shoreline evolution data, depending on the method used (transects or areas). Profile-based analysis shows an average annual rate of −0.11 m·y⁻¹ (ranging between 0.53 and −0.55 m·y⁻¹), while areal-based results (2004–2020) indicate a total loss of −20,810 m² (−1300 m²·y⁻¹). Sediment grain size decreases northward (from 745 to 264 µm in the swash zone). Changes in shoreline position and grain size illustrate the impact of various anthropogenic structures on morphodynamic behaviour. These structures preferentially deposit specific grain sizes and impede sediment transport, which will cause an advance in the position of the shoreline and sediment grain sizes upstream and a reverse process downstream. This study underscores the influence of coastal anthropization on beach morphology and sedimentology, generating distinct morphodynamic behaviour. Full article

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

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25 pages, 10202 KiB

Open AccessArticle

The Coefficient of Earth Pressure at Rest K₀ of Sands up to Very High Stresses

by Maurizio Ziccarelli

Geosciences 2024, 14(10), 264; https://doi.org/10.3390/geosciences14100264 - 7 Oct 2024

Abstract

The mechanical behaviour of soils subjected to any stress path in which deviatoric stresses are present is heavily characterised by non-linearity, irreversibility and is strongly dependent on the initial state of stress. The latter, for the majority of geotechnical applications, is normally determined [...] Read more.

The mechanical behaviour of soils subjected to any stress path in which deviatoric stresses are present is heavily characterised by non-linearity, irreversibility and is strongly dependent on the initial state of stress. The latter, for the majority of geotechnical applications, is normally determined by the at-rest earth pressure coefficient K₀, even though this state is valid, strictly speaking, for axisymmetric conditions and for zero-lateral deformations only. Many expressions are available in the literature for the determination of this coefficient for cohesive and granular materials both for normal consolidated and over-consolidated conditions. These relations are available for low to medium stress levels. Results of an extensive experimental investigation on two sands of different mineralogy up to very high stress (120 MPa) are reported in the paper. For reach very high vertical stresses, a special oedometer has been realised. In the loading phase (normal consolidated sands), the coefficient K_0n depends on the stress level. It passes from values of about 0.8 to values of about 0.45 in the range of effective vertical stress σ′_v = 0.5–4 MPa. Subsequently, K_0n is about constant and varies between 0.45 to 0.55 up to very high vertical effective stresses (120 MPa). For the sands employed in the tests, Jaki’s relation did not lead to reliable results at relatively low pressures, while at high pressures, the same relationship seems to lead to reliable predictions if it refers to the constant volume angle of shear strength. For the over-consolidated sands, K_0C strongly depends on the OCR, and for very high values of OCR, K_0C could be greater than Rankine’s passive coefficient of earth pressure, K_p. This result is due to the very locked structure of the sands caused by the grain crushing, with intergranular contact of sutured and sigmoidal, concavo-convex and inter-penetrating type, that confer to the sand a sort of apparent cohesion and make it similar to weak sandstone. Full article

(This article belongs to the Section Geomechanics)

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24 pages, 55271 KiB

Open AccessArticle

Santorini Volcanic Complex (SVC): How Much Has the Crustal Velocity Structure Changed since the 2011–2012 Unrest, and at What Point Are We Now?

by Andreas Karakonstantis and Filippos Vallianatos

Geosciences 2024, 14(10), 263; https://doi.org/10.3390/geosciences14100263 - 4 Oct 2024

Abstract

This study is focused on one of the most active features of the Hellenic Volcanic Arc Southern Aegean Sea, the Santorini Island Volcanic Complex (SVC). The recent volcano-tectonic crisis in the intracalderic area has emerged the need for closer monitoring of the region. [...] Read more.

This study is focused on one of the most active features of the Hellenic Volcanic Arc Southern Aegean Sea, the Santorini Island Volcanic Complex (SVC). The recent volcano-tectonic crisis in the intracalderic area has emerged the need for closer monitoring of the region. The 2011–2012 unrest has been attributed to the augmentation of fluid flow inside local mapped fracture zones. After March 2012, the seismic activity dropped significantly, raising questions about whether we would have a long period of quiescence or be on a break before the next period of unrest. In this research, a re-examination of the seismic outbreak of 2011–2012 was conducted by adding more travel-time data from 2013 while we further analyzed the waveform data from 2014 to May 2024 to explore the differences of the SVC body-wave velocity structure by performing seismic tomography in these two time windows. The new dataset serves to identify the state of the Santorini Volcanic Complex. The results show a significant reduction in Vp and Vs anomalies at shallow depths since the period of unrest. At the same time, the distribution of Vp/Vs ratio remains high (>1.87) in the area NNE of Kameni at a shallower depth (2 km). The areas of Christiana Islands and Columbo volcano are mainly characterized by negative body-wave anomalies and low Vp/Vs ratio (1.56–1.64) at shallow depths for the study period, while a possible explanation to results in the submarine volcano may be explained by dry steam/gas phases that may have resulted in the generation of the swarms that occurred in the region. Full article

(This article belongs to the Special Issue Earthquake Geology of Plate Margins and Plate Interiors: Integrating Classical Methods with New Approaches)

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34 pages, 10557 KiB

Open AccessArticle

Possible Indication of the Impact of the Storegga Slide Tsunami on the German North Sea Coast around 8150 cal BP

by Andreas Vött, Hanna Hadler, Timo Willershäuser, Aron Slabon, Lena Slabon, Hannah Wahlen, Peter Fischer, Friederike Bungenstock, Björn R. Röbke, Manfred Frechen, Alf Grube and Frank Sirocko

Geosciences 2024, 14(10), 262; https://doi.org/10.3390/geosciences14100262 - 3 Oct 2024

Abstract

The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, [...] Read more.

The Storegga slide tsunami (SST) at ca. 8100 ± 100–250 cal BP is known to be the largest tsunami that affected the North Sea during the entire Holocene. Geological traces of tsunami landfall were discovered along the coasts of Norway, Scotland, England, Denmark, the Faroes and Shetland Islands. So far, the German North Sea coast has been considered as being well protected due to the wide continental shelf and predominant shallow water depths, both assumed to dissipate tsunami wave energy significantly, thus hindering SST propagation dynamics. The objective of our research was to clarify if the SST reached the German Bight and if corresponding sediment markers can be found. Our research was based on the in-depth investigation of a 5 m long section of the research core Garding-2 from Eiderstedt Peninsula near Garding in North Frisia known from a previous study. For this, we newly recovered sediment core Garding-2A at exactly the same coring location as core Garding-2. Additionally, high-resolution Direct Push sensing data were collected to gain undisturbed stratigraphic information. Multi-proxy analyses of sediment material (grain size, geochemical, geochronological and microfaunal data) were carried out to reconstruct palaeoenvironmental and palaeogeographical conditions. We identified a high-energy event layer with sedimentological (e.g., erosional unconformity, rip-up clasts, fining-upward), microfaunal (e.g., strongly mixed foraminiferal assemblage) and other features typical of tsunami influence and identical in age with the SST, dated to ca. 8.15 ka cal BP. The event layer was deposited at or maximum ca. 1–1.5 m below the local contemporary relative sea level and several tens of kilometers inland from the coastline within the palaeo-Eider estuarine system beyond the reach of storm surges. Tsunami facies and geochronological data correspond well with SST signatures identified on the nearby island of Rømø. SST candidate deposits identified at Garding represent the southernmost indications of this event in the southeastern North Sea. They give evidence, for the first time, of high-energy tsunami landfall along the German North Sea coast and tsunami impact related to the Storegga slide. SST deposits seem to have been subsequently reworked and redeposited over centuries until the site was affected by the Holocene marine transgression around 7 ka cal BP (7.3–6.5 ka cal BP). Moreover, the transgression initiated energetically and ecologically stable shallow marine conditions within an Eider-related tidal channel, lasting several millennia. It is suggested that the SST was not essentially weakened across the shallow continental shelf of the North Sea, but rather caused tsunami run-up of several meters (Rømø Island) or largely intruded estuarine systems tens of kilometers inland (North Frisia, this study). We, therefore, assume that the southern North Sea coast was generally affected by the SST but sedimentary signals have not yet been identified or have been misinterpreted. Our findings suggest that the German North Sea coast is not protected from tsunami events, as assumed so far, but that tsunamis are also a phenomenon in this region. Full article

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10 pages, 3646 KiB

Open AccessArticle

Non-Destructive Methods for Assessing the Condition of Reinforcement Materials in Soil

by Naoki Tatta and Hideo Sakai

Geosciences 2024, 14(10), 261; https://doi.org/10.3390/geosciences14100261 - 1 Oct 2024

Abstract

A reinforced earth wall is a structure in which reinforcement materials are placed in an embankment to build a vertical or nearly vertical wall surface. Such walls have been widely used in roads and in developed land since around 1960. Reinforcement materials have [...] Read more.

A reinforced earth wall is a structure in which reinforcement materials are placed in an embankment to build a vertical or nearly vertical wall surface. Such walls have been widely used in roads and in developed land since around 1960. Reinforcement materials have a set service life of 100 years and fall into two types: steel and geosynthetics. To ensure long-term durability, steel reinforcement materials are plated, while geosynthetics are designed with a limit strength designed to resist fracture for 100 years under the conditions of a given load placed on the reinforcement materials. However, owing to the difficulty of assessing the condition of reinforcement materials in soil, this paper proposes solutions based on non-destructive methods. Specifically, it proposes a method of assessing the amount of strain through an embedded optical fiber in the case of geosynthetic reinforcement materials, or magnetic surveying to investigate the degree of corrosion in the case of steel reinforcement materials. This paper demonstrates that it is possible to non-destructively assess the state of either type of reinforcement material. Full article

(This article belongs to the Special Issue Computational Geodynamic, Geotechnics and Geomechanics)

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31 pages, 83141 KiB

Open AccessArticle

The Relationships between the Internal Nappe Zone and the Regional Mylonitic Complex in the NE Variscan Sardinia (Italy): Insight from a New Possible Regional Interpretation?

by Franco Marco Elter and Federico Mantovani

Geosciences 2024, 14(10), 260; https://doi.org/10.3390/geosciences14100260 - 28 Sep 2024

Abstract

This study presents an updated interpretation of geological data collected between 1984 and 2022. The area under consideration holds significant regional importance as it is located between the Internal Nappe Zone (INZ) and the Regional Mylonitic Complex (RMC). Re-evaluation of the geological data [...] Read more.

This study presents an updated interpretation of geological data collected between 1984 and 2022. The area under consideration holds significant regional importance as it is located between the Internal Nappe Zone (INZ) and the Regional Mylonitic Complex (RMC). Re-evaluation of the geological data has highlighted a more intricate structural framework than what is currently documented in the existing literature. This paper aims to illustrate, through structural analysis, that the Posada Valley Shear Zone (PVSZ) does not serve as the transitional boundary between the Inner Nappe Zone and the Regional Mylonitic Complex or High-Grade Metamorphic Complex (HGMC) as traditionally thought. Instead, the authors’ findings indicate that the transition boundary is confined to a shear band with a variable thickness ranging from 10 to 70 m at its widest points. The development of the Posada Valley Shear Zone is characterized by a series of transitions from mylonite I S-C to mylonite II S-C, extending over approximately 5 km. The formation of the Posada Valley Shear Zone is chronologically confined between the development of the East Variscan Shear Zone (EVSZ) and the emplacement of the Late Variscan granites. The differing orientations of Sm and S3 observed in the mylonitic events of the Posada Valley Shear Zone and the Regional Mylonitic Complex, respectively, are likely attributable to an anticlockwise rotation of the shortening directions during the upper Carboniferous period. Furthermore, this study proposes that the Condensed Isogrades Zone (CIZ), despite its unclear formation mechanism, should be recognized as the true transition zone between the Inner Nappe Zone and the Regional Mylonitic Complex or High-Grade Metamorphic Complex. This new interpretation challenges the previously accepted notion of increasing Variscan metamorphic zonation toward the northeast. This conclusion is supported by the identification of the same NE–SW orientation of the D2 tectonic event in both the Old Gneiss Complex (OGC in the Regional Mylonitic Complex) and the lithologies of the Inner Nappe Zone and the Condensed Isogrades Zone. The comprehensive analysis and new insights provided in this paper contribute to a refined understanding of the geological relationships and processes within this region, offering significant implications for future geological studies and interpretations. Full article

(This article belongs to the Special Issue Metamorphism and Tectonic Evolution of Metamorphic Belts)

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23 pages, 6593 KiB

Open AccessArticle

Multitemporal Quantification of the Geomorphodynamics on a Slope within the Cratère Dolomieu at the Piton de la Fournaise (La Réunion, Indian Ocean) Using Terrestrial LiDAR Data, Terrestrial Photographs, and Webcam Data

by Kerstin Wegner, Virginie Durand, Nicolas Villeneuve, Anne Mangeney, Philippe Kowalski, Aline Peltier, Manuel Stark, Michael Becht and Florian Haas

Geosciences 2024, 14(10), 259; https://doi.org/10.3390/geosciences14100259 - 28 Sep 2024

Abstract

In this study, the geomorphological evolution of an inner flank of the Cratère Dolomieu at Piton de La Fournaise/La Réunion was investigated with the help of terrestrial laser scanning (TLS) data, terrestrial photogrammetric images, and historical webcam photographs. While TLS data and the [...] Read more.

In this study, the geomorphological evolution of an inner flank of the Cratère Dolomieu at Piton de La Fournaise/La Réunion was investigated with the help of terrestrial laser scanning (TLS) data, terrestrial photogrammetric images, and historical webcam photographs. While TLS data and the terrestrial images were recorded during three field surveys, the study was also able to use historical webcam images that were installed for the monitoring of the volcanic activity inside the crater. Although the webcams were originally intended to be used only for visual monitoring of the area, at certain times they captured image pairs that could be analyzed using structure from motion (SfM) and subsequently processed to create digital terrain models (DTMs). With the help of all the data, the geomorphological evolution of selected areas of the crater was investigated in high temporal and spatial resolution. Surface changes were detected and quantified on scree slopes in the upper area of the crater as well as on scree slopes at the transition from the slope to the crater floor. In addition to their quantification, these changes could be assigned to individual geomorphological processes over time. The webcam photographs were a very important additional source of information here, as they allowed the observation period to be extended further into the past. Besides this, the webcam images made it possible to determine the exact dates at which geomorphological processes were active. Full article

(This article belongs to the Section Natural Hazards)

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27 pages, 39557 KiB

Open AccessArticle

Application of Experimental Configurations of Seismic and Electric Tomographic Techniques to the Investigation of Complex Geological Structures

by Vasileios Gkosios, John D. Alexopoulos, Konstantinos Soukis, Ioannis-Konstantinos Giannopoulos, Spyridon Dilalos, Dimitrios Michelioudakis, Nicholas Voulgaris and Thomas Sphicopoulos

Geosciences 2024, 14(10), 258; https://doi.org/10.3390/geosciences14100258 - 28 Sep 2024

Abstract

The main purpose of this study is the subsurface investigation of two complex geological environments focusing on the improvement of data acquisition and processing parameters regarding electric and seismic tomographic techniques. Two different study areas, in central–east Peloponnese and SE Attica, were selected, [...] Read more.

The main purpose of this study is the subsurface investigation of two complex geological environments focusing on the improvement of data acquisition and processing parameters regarding electric and seismic tomographic techniques. Two different study areas, in central–east Peloponnese and SE Attica, were selected, where detailed geological mapping and surface geophysical survey were carried out. The applied geophysical survey included the application of electrical resistivity tomography (ERT), seismic refraction tomography (SRT) and ground penetrating radar (GPR). The geoelectrical measurements were acquired with different arrays and electrode configurations. Moreover, various types of seismic sources were used at seventeen shot locations along the seismic arrays. For the processing of geoelectrical data, clustered datasets were created, increasing the depth of investigation and discriminatory capability. The seismic data processing included the following: (a) the creation of synthetic models and seismic records to determine the effectiveness and capabilities of the technique, (b) spectral analysis of the seismic records to determine the optimal seismic source type and (c) inversion of the field data to create representative subsurface velocity models. The results of the two techniques successfully delineated the complex subsurface structure that characterizes these two geological environments. The application of the ERT combined with the SRT are the two dominant, high-resolution techniques for the elucidation of complex subsurface structures. Full article

(This article belongs to the Section Geophysics)

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16 pages, 54958 KiB

Open AccessArticle

Seismotectonic Setting of the Andes along the Nazca Ridge Subduction Transect: New Insights from Thermal and Finite Element Modelling

by Sara Ciattoni, Stefano Mazzoli, Antonella Megna and Stefano Santini

Geosciences 2024, 14(10), 257; https://doi.org/10.3390/geosciences14100257 - 28 Sep 2024

Abstract

The structural evolution of Andean-type orogens is strongly influenced by the geometry of the subducting slab. This study focuses on the flat-slab subduction of the Nazca Ridge and its effects on the South American Plate. The process of flat slab subduction impacts the [...] Read more.

The structural evolution of Andean-type orogens is strongly influenced by the geometry of the subducting slab. This study focuses on the flat-slab subduction of the Nazca Ridge and its effects on the South American Plate. The process of flat slab subduction impacts the stress distribution within the overriding plate and increases plate coupling and seismic energy release. Using the finite element method (FEM), we analyse interseismic and coseismic deformation along a 1000 km transect parallel to the ridge. We examine stress distribution, uplift patterns, and the impact of megathrust activity on deformation. To better define the crust’s properties for the model, we developed a new thermal model of the Nazca Ridge subduction zone, reconstructing the thermal structure of the overriding plate. The results show concentrated stress at the upper part of the locked plate interface, extending into the Coastal and Western Cordilleras, with deeper stress zones correlating with seismicity. Uplift patterns align with long-term rates of 0.7–1 mm/yr. Cooling from flat-slab subduction strengthens the overriding plate, allowing far-field stress transmission and deformation. These findings provide insights into the tectonic processes driving stress accumulation, seismicity, and uplift along the Peruvian margin. Full article

(This article belongs to the Special Issue New Trends in Earthquake Engineering and Seismotectonics)

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34 pages, 40857 KiB

Open AccessArticle

Application of the Coastal and Marine Ecological Classification Standard (CMECS) to Create Benthic Geologic Habitat Maps for Portions of Acadia National Park, Maine, USA

by Bryan Oakley, Brian Caccioppoli, Monique LaFrance Bartley, Catherine Johnson, Alexandra Moen, Cameron Soulagnet, Genevieve Rondeau, Connor Rego and John King

Geosciences 2024, 14(10), 256; https://doi.org/10.3390/geosciences14100256 - 28 Sep 2024

Abstract

The Coastal and Marine Ecological Classification Standard (CMECS) was applied to four portions of Acadia National Park, USA, focusing on intertidal rocky and tidal flat habitats. Side-scan sonar coupled with multi-phase echo sounder bathymetry are the primary data sources used to map the [...] Read more.

The Coastal and Marine Ecological Classification Standard (CMECS) was applied to four portions of Acadia National Park, USA, focusing on intertidal rocky and tidal flat habitats. Side-scan sonar coupled with multi-phase echo sounder bathymetry are the primary data sources used to map the seafloor, coupled with underwater video imagery and surface grab samples for grain size and macrofaunal analysis. The CMECS Substrate, Geoform, and Biotic components were effective in describing the study areas. However, integrating the CMECS components to define Biotopes was more challenging due to the limited number of grab samples available and because the dominant species within a given map unit is largely inconsistent. While Biotopes ultimately could not be defined in this study, working within the CMECS framework to create statistically significant biotopes revealed the complexity of these study areas that may otherwise have been overlooked. This study demonstrates the effectiveness of the CMECS classification, including the framework’s ability to be flexible in communicating information. Full article

(This article belongs to the Special Issue Progress in Seafloor Mapping)

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16 pages, 757 KiB

Open AccessReview

Deterministic Physically Based Distributed Models for Rainfall-Induced Shallow Landslides

by Giada Sannino, Massimiliano Bordoni, Marco Bittelli, Claudia Meisina, Fausto Tomei and Roberto Valentino

Geosciences 2024, 14(10), 255; https://doi.org/10.3390/geosciences14100255 - 27 Sep 2024

Abstract

Facing global warming’s consequences is a major issue in the present times. Regarding the climate, projections say that heavy rainfalls are going to increase with high probability together with temperature rise; thus, the hazard related to rainfall-induced shallow landslides will likely increase in [...] Read more.

Facing global warming’s consequences is a major issue in the present times. Regarding the climate, projections say that heavy rainfalls are going to increase with high probability together with temperature rise; thus, the hazard related to rainfall-induced shallow landslides will likely increase in density over susceptible territories. Different modeling approaches exist, and many of them are forced to make simplifications in order to reproduce landslide occurrences over space and time. Process-based models can help in quantifying the consequences of heavy rainfall in terms of slope instability at a territory scale. In this study, a narrative review of physically based deterministic distributed models (PBDDMs) is presented. Models were selected based on the adoption of the infinite slope scheme (ISS), the use of a deterministic approach (i.e., input and output are treated as absolute values), and the inclusion of new approaches in modeling slope stability through the ISS. The models are presented in chronological order with the aim of drawing a timeline of the evolution of PBDDMs and providing researchers and practitioners with basic knowledge of what scholars have proposed so far. The results indicate that including vegetation’s effects on slope stability has raised in importance over time but that there is still a need to find an efficient way to include them. In recent years, the literature production seems to be more focused on probabilistic approaches. Full article

(This article belongs to the Section Natural Hazards)

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15 pages, 5438 KiB

Open AccessArticle

The Relationships between Greenstone Belts and the Kryvyi Rih–Kremenchuk Basin in the Middle Dnieper Domain of the Ukrainian Shield Revealed by Detrital Zircon

by Hennadii Artemenko, Leonid Shumlyanskyy, David Chew, Foteini Drakou, Bruno Dhuime, Hugo Moreira and Valeryi Butyrin

Geosciences 2024, 14(10), 254; https://doi.org/10.3390/geosciences14100254 - 27 Sep 2024

Abstract

Detrital zircons from two samples of metasandstones from the Lykhmanivka Syncline, Middle Dnieper Domain of the Ukrainian Shield (Skelevate Formation of the Kryvyi Rih Group), have been dated by the LA-ICP-MS U-Pb method. Metasandstones from the northern part of the syncline yield zircons [...] Read more.

Detrital zircons from two samples of metasandstones from the Lykhmanivka Syncline, Middle Dnieper Domain of the Ukrainian Shield (Skelevate Formation of the Kryvyi Rih Group), have been dated by the LA-ICP-MS U-Pb method. Metasandstones from the northern part of the syncline yield zircons belonging to four age groups: 3201 ± 12 Ma, 3089 ± 11 Ma, 2939 ± 8 Ma, and 2059 ± 4 Ma. All three Archean groups originated from similar rock types that crystallized at different times from the same mafic source (lower crust) with a ¹⁷⁶Lu/¹⁷⁷Hf ratio of about 0.020. In contrast, zircon from metasediments from the southern end of the Lykhmanivka Syncline fall within two age groups: 3174 ± 13 Ma, and 2038 ± 9 Ma. In terms of Hf isotope compositions, the detrital zircons from the two oldest age groups in both samples are very similar. The source area was dominated by rocks of the Auly Group (3.27–3.18 Ga) and the Sura Complex (3.17–2.94 Ga). The proportion of zircons dated at 2.07–2.03 Ga, which reflects the timing of metamorphism, is 5%. The metamorphic nature of the Paleoproterozoic zircon allows us to define the maximum depositional age of the metasandstones of the Lykhmanivka Syncline at ca. 2.9 Ga, which is in good agreement with the earlier results from the metaterrigenous rocks of the Kryvyi Rih–Kremenchuk Basin. Our data also indicate the local nature of sedimentation and the absence of significant transport and mixing of detrital material within the basin. Full article

(This article belongs to the Section Geochemistry)

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25 pages, 3229 KiB

Open AccessReview

Evaluation of Strength Anisotropy in Foliated Metamorphic Rocks: A Review Focused on Microscopic Mechanisms

by Umer Waqas, Mohsin Usman Qureshi, Shahab Saqib, Hafiz Muhammad Awais Rashid and Ali Murtaza Rasool

Geosciences 2024, 14(10), 253; https://doi.org/10.3390/geosciences14100253 - 26 Sep 2024

Abstract

This review paper addresses the recent and past advancements in investigating the anisotropic behavior of foliated metamorphic rock strength subjected to uniaxial or triaxial compression loading, direct or indirect tensile loading, and shear loading. The experimental findings published in the literature show that [...] Read more.

This review paper addresses the recent and past advancements in investigating the anisotropic behavior of foliated metamorphic rock strength subjected to uniaxial or triaxial compression loading, direct or indirect tensile loading, and shear loading. The experimental findings published in the literature show that the strength of foliated rocks is significantly affected by varying the angle β between weak planes and major principal stress. A higher value of strength is reported at β = 0° or 90°; whereas a low strength value is noted at intermediate angles between β = 0° and 90°. The strength anisotropy depends on the degree of schistosity or gneissosity, which is the result of the preferred arrangement of phyllosilicate minerals under differential pressures. The failure of foliated rocks starts at the microscopic scale because of the dislocation slip, plastic kinking, and fracturing in phyllosilicate minerals such as mica. Tensile wing cracks at the tip of the mica propagate parallel to the deviatoric stress. Then, intergranular and intragranular shear-tensile cracks coalesce and lead to rock failure. The weak planes’ orientation controls the mode of failure such that tensile splitting, slip failure, and shear failure across foliations are observed at β = 0°–30°, β = 30°–60°, β = 60°–90° respectively. In the past, several attempts have been made to formulate failure criteria to estimate rock strength using different mathematical and empirical approaches. Over the years, the trend has shifted towards discontinuum modeling to simulate rock failure processes and to solve problems from laboratory to upscaled levels. Full article

(This article belongs to the Section Geomechanics)

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23 pages, 103238 KiB

Open AccessArticle

Miocene Petit-Spot Basanitic Volcanoes on Cretaceous Alba Guyot (Magellan Seamount Trail, Pacific Ocean)

by Igor S. Peretyazhko, Elena A. Savina and Irina A. Pulyaeva

Geosciences 2024, 14(10), 252; https://doi.org/10.3390/geosciences14100252 - 25 Sep 2024

Abstract

New data obtained from core samples of two boreholes and dredged samples in the Alba Guyot in the Magellan Seamount Trail (MST), Western Pacific, including the ⁴⁰Ar/³⁹Ar age of basanite, mineralogy of basanite, tuff, tuffite, mantle-derived inclusions in basanite and [...] Read more.

New data obtained from core samples of two boreholes and dredged samples in the Alba Guyot in the Magellan Seamount Trail (MST), Western Pacific, including the ⁴⁰Ar/³⁹Ar age of basanite, mineralogy of basanite, tuff, tuffite, mantle-derived inclusions in basanite and tuff (lherzolite xenolith and Ol, Cpx, and Opx xenocrysts), and calcareous nannofossil biostratigraphy, have implications for the guyot′s history. Volcanics in the upper part of the Alba Guyot main edifice and its Oma Vlinder satellite, at sea depths between 3600 and 2200 m, were deposited during the Cretaceous 112 to 86 Ma interval. In the following ~60 myr, the Alba Guyot became partly submerged and denuded with the formation of a flat summit platform while the respective fragment of the Pacific Plate was moving to the Northern Hemisphere. Volcanic activity in the northeastern part of the guyot summit platform was rejuvenated in the Miocene (24–15 Ma) and produced onshore basanitic volcanoes and layers of tuff in subaerial and tuffite in shallow-water near-shore conditions. In the Middle-Late Miocene (10–6 Ma), after the guyot had submerged, carbonates containing calcareous nannofossils were deposited on the porous surfaces of tuff and tuffite. Precipitation of the Fe-Mn crust (Unit III) recommenced during the Pliocene-Pleistocene (<1.8 Ma) when the guyot summit reached favorable sea depths. The location of the MST guyots in the northwestern segment of the Pacific Plate near the Mariana Trench, along with the Miocene age and alkali-basaltic signatures of basanite, provide first evidence for petit-spot volcanism on the Alba Guyot. This inference agrees with the geochemistry of Cenozoic petit-spot basaltic rocks from the Pacific and Miocene basanite on the Alba Guyot. Petit-spot volcanics presumably originated from alkali-basaltic melts produced by decompression partial melting of carbonatized peridotite in the metasomatized oceanic lithosphere at the Lithosphere–Asthenosphere Boundary level. The numerous volcanic cones reaching up to 750 m high and 5.1 km in base diameter, which were discovered on the Alba summit platform, provide the first evidence of voluminous Miocene petit-spot basanitic volcanism upon the Cretaceous guyots and seamounts of the Pacific. Full article

(This article belongs to the Section Geochemistry)

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