Geosciences

26 pages, 17693 KiB

Open AccessEditor’s ChoiceArticle

The Mw = 5.6 Kanallaki Earthquake of 21 March 2020 in West Epirus, Greece: Reverse Fault Model from InSAR Data and Seismotectonic Implications for Apulia-Eurasia Collision

by Sotiris Valkaniotis, Pierre Briole, Athanassios Ganas, Panagiotis Elias, Vassilis Kapetanidis, Varvara Tsironi, Anna Fokaefs, Helena Partheniou and Panagiotis Paschos

Geosciences 2020, 10(11), 454; https://doi.org/10.3390/geosciences10110454 - 11 Nov 2020

Cited by 19 | Viewed by 4234

Abstract

We identify the source of the Mw = 5.6 earthquake that hit west-central Epirus on 21 March 2020 00:49:52 UTC. We use Sentinel-1 synthetic aperture radar interferograms tied to one permanent Global Navigation Satellite System (GNSS) station (GARD). We model the source by [...] Read more.

We identify the source of the Mw = 5.6 earthquake that hit west-central Epirus on 21 March 2020 00:49:52 UTC. We use Sentinel-1 synthetic aperture radar interferograms tied to one permanent Global Navigation Satellite System (GNSS) station (GARD). We model the source by inverting the INSAR displacement data. The inversion model suggests a shallow source on a low-angle fault (39°) dipping towards east with a centroid depth of 8.5 km. The seismic moment deduced from our model agrees with those of the published seismic moment tensors. This geometry is compatible with reverse-slip motion along the west-verging Margariti thrust fault that accommodates part of the convergence within the collision zone between Apulia and Eurasia. We also processed new GNSS data and estimate a total convergence rate between Apulia and Eurasia of 8.9 mm yr⁻¹, of which the shortening of the crust between the Epirus coastal GNSS stations and station PAXO in the Ionian Sea (across the Ionian Thrust) is equivalent to ~50% of it or 4.6 mm yr⁻¹. By back-slip modelling we found that a 60-km wide deformation zone takes up nearly most of the convergence between Apulia-Eurasia, trending N318°E. Its central axis runs along the southwest coast of Corfu, along the northeast coast of Paxoi, heading toward the northern extremity of the Lefkada island. The island of Paxoi appears kinematically as part of the Apulian plate. Full article

(This article belongs to the Special Issue Seismotectonics, Active Deformation, and Structure of the Crust)

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25 pages, 6422 KiB

Open AccessEditor’s ChoiceArticle

Chinyero Volcanic Landscape Trail (Canary Islands, Spain): A Geotourism Proposal to Identify Natural and Cultural Heritage in Volcanic Areas

by Esther Beltrán-Yanes, Javier Dóniz-Páez and Isabel Esquivel-Sigut

Geosciences 2020, 10(11), 453; https://doi.org/10.3390/geosciences10110453 - 11 Nov 2020

Cited by 15 | Viewed by 5470

Abstract

The Chinyero Special Nature Reserve is located on the NW rift zone of Tenerife, between 600 and 1500 m above sea level. This natural setting is distinguished by a significant concentration of monogenetic basaltic volcanoes that have erupted in recent and historical times, [...] Read more.

The Chinyero Special Nature Reserve is located on the NW rift zone of Tenerife, between 600 and 1500 m above sea level. This natural setting is distinguished by a significant concentration of monogenetic basaltic volcanoes that have erupted in recent and historical times, including Garachico (1706) and Chinyero (1909). The volcanic landscapes of this protected area are part of the Canary Island pine forest ecosystem and, therefore, also feature beautiful forests colonising the newly formed layers of volcanic materials. The aim of this paper is to design a geographical route through the landscape for geotourism purposes, based on a global and coherent interpretation of the original physiognomy of a landscape that has been decisively shaped by volcanic phenomena. This nature trail represents a proposal for a new tourism product as an alternative to the traditional “sun and beach” coastal tourism product. This paper comprises a first stage, dedicated to the geographical study of the landscape, and a second stage focused on designing a geotourism route, which will identify and characterise the elements of the natural and cultural heritage of the area and its unique landforms. Full article

(This article belongs to the Special Issue Geomorphology, Geoheritage, Geoparks and Geotourism in Volcanic Areas)

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18 pages, 4135 KiB

Open AccessEditor’s ChoiceArticle

Detailed Geophysical Mapping and Hydrogeological Characterisation of the Subsurface for Optimal Placement of Infiltration-Based Sustainable Urban Drainage Systems

by Theis Raaschou Andersen

Geosciences 2020, 10(11), 446; https://doi.org/10.3390/geosciences10110446 - 08 Nov 2020

Cited by 5 | Viewed by 2978

Abstract

The continuous growth of cities in combination with future climate changes present urban planners with significant challenges, as traditional urban sewer systems are typically designed for the present climate. An easy and economically feasible way to mitigate this is to introduce a Sustainable [...] Read more.

The continuous growth of cities in combination with future climate changes present urban planners with significant challenges, as traditional urban sewer systems are typically designed for the present climate. An easy and economically feasible way to mitigate this is to introduce a Sustainable Urban Drainage System (SUDS) in the urban area. However, the lack of knowledge about the geological and hydrogeological setting hampers the use of SUDS. In this study, 1315 ha of high-density electromagnetic (DUALEM-421S) data, detailed lithological soil descriptions of 614 boreholes, 153 infiltration tests and 250 in situ vane tests from 32 different sites in the Central Denmark Region were utilised to find quantitative and qualitative regional relationships between the resistivity and the lithology, the percolation rates and the undrained shear strength of cohesive soils at a depth of 1 meter below ground surface (m bgs). The qualitative tests enable a translation from resistivity to lithology as well as a translation from lithology to percolation rates with moderate to high certainty. The regional cut-off value separating sand-dominated deposits from clay-dominated deposits is found to be between 80 to 100 Ωm. The regional median percolation rates for sand and clay till is found to be 9.9 × 10⁻⁵ m/s and 2.6 × 10⁻⁵ m/s, respectively. The quantitative results derived from a simple linear regression analysis of resistivity and percolation rates and resistivity and undrained shear strength of cohesive soils are found to have a very weak relationship on a regional scale implying that in reality no meaningful relationships can be established. The regional qualitative results have been tested on a case study area. The case study illustrates that site-specific investigations are necessary when using geophysical mapping to directly estimate lithology, percolation rates and undrained shear strength of cohesive soils due to the differences in soil properties and the surrounding environment from site to site. This study further illustrates that geophysical mapping in combination with lithological descriptions, infiltration tests and groundwater levels yield the basis for the construction of detailed planning maps showing the most suitable locations for infiltration. These maps provide valuable information for city planners about which areas may preclude the establishment of infiltration-based SUDS. Full article

(This article belongs to the Special Issue Urban Geophysics)

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28 pages, 18732 KiB

Open AccessEditor’s ChoiceReview

The New Seismotectonic Atlas of Greece (v1.0) and Its Implementation

by Ioannis Kassaras, Vasilis Kapetanidis, Athanassios Ganas, Andreas Tzanis, Chrysanthi Kosma, Andreas Karakonstantis, Sotirios Valkaniotis, Stylianos Chailas, Vasiliki Kouskouna and Panayotis Papadimitriou

Geosciences 2020, 10(11), 447; https://doi.org/10.3390/geosciences10110447 - 08 Nov 2020

Cited by 40 | Viewed by 9882

Abstract

Knowledge and visualization of the present-day relationship between earthquakes, active tectonics and crustal deformation is a key to understanding geodynamic processes, and is also essential for risk mitigation and the management of geo-reservoirs for energy and waste. The study of the complexity of [...] Read more.

Knowledge and visualization of the present-day relationship between earthquakes, active tectonics and crustal deformation is a key to understanding geodynamic processes, and is also essential for risk mitigation and the management of geo-reservoirs for energy and waste. The study of the complexity of the Greek tectonics has been the subject of intense efforts of our working group, employing multidisciplinary methodologies that include detailed geological mapping, geophysical and seismological data processing using innovative methods and geodetic data processing, involved in surveying at various scales. The data and results from these studies are merged with existing or updated datasets to compose the new Seismotectonic Atlas of Greece. The main objective of the Atlas is to harmonize and integrate the most recent seismological, geological, tectonic, geophysical and geodetic data in an interactive, online GIS environment. To demonstrate the wealth of information available in the end product, herein, we present thematic layers of important seismotectonic and geophysical content, which facilitates the comprehensive visualization and first order insight into seismic and other risks of the Greek territories. The future prospect of the Atlas is the incorporation of tools and algorithms for joint analysis and appraisal of these datasets, so as to enable rapid seismotectonic analysis and scenario-based seismic risk assessment. Full article

(This article belongs to the Special Issue Seismotectonics, Active Deformation, and Structure of the Crust)

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20 pages, 5560 KiB

Open AccessEditor’s ChoiceArticle

Discovery of Ancient Volcanoes in the Okhotsk Sea (Russia): New Constraints on the Opening History of the Kurile Back Arc Basin

by Reinhard Werner, Boris Baranov, Kaj Hoernle, Paul van den Bogaard, Folkmar Hauff and Igor Tararin

Geosciences 2020, 10(11), 442; https://doi.org/10.3390/geosciences10110442 - 06 Nov 2020

Cited by 7 | Viewed by 2596

Abstract

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern [...] Read more.

Here we present the first radiometric age and geochemical (major and trace element and isotope) data for samples from the Hydrographer Ridge, a back arc volcano of the Kurile Island Arc, and a newly discovered chain of volcanoes (“Sonne Volcanoes”) on the northwestern continental slope of the Kurile Basin on the opposite side of the arc. The ⁴⁰Ar/³⁹Ar age and geochemical data show that Hydrographer Ridge (3.2–3.3 Ma) and the “Sonne Volcanoes” (25.3–25.9 Ma) have very similar trace element and isotope characteristics to those of the Kurile Island Arc, indicating derivation from a common magma source. We conclude that the age of the “Sonne Volcanoes” marks the time of opening of the Kurile Basin, implying slow back arc spreading rates of 1.3–1.8 cm/y. Combined with published data from the Kurile fore arc, our data suggest that the processes of subduction, Kurile Basin opening and frontal arc extension occurred synchronously and that extension in the rear part and in the frontal part of the Kurile Island Arc must have been triggered by the same mechanism. Full article

(This article belongs to the Special Issue Tectonics and Morphology of Back-Arc Basins)

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30 pages, 8792 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Foraminifer and Ostracod Occurrence in a Cool-Water Carbonate Factory of the Cape Adare (Ross Sea, Antarctica): A Key Lecture for the Climatic and Oceanographic Variations in the Last 30,000 Years

by Romana Melis and Gianguido Salvi

Geosciences 2020, 10(10), 413; https://doi.org/10.3390/geosciences10100413 - 15 Oct 2020

Cited by 8 | Viewed by 3109

Abstract

Foraminifers and ostracods were studied in a gravity-core recovered near Cape Adare (Ross Sea, Antarctica) with the aim of identifying the climatic and oceanographic variations during the last 30 ka. The sedimentary sequence represents conditions of a cool-water carbonate factory, which evidences that [...] Read more.

Foraminifers and ostracods were studied in a gravity-core recovered near Cape Adare (Ross Sea, Antarctica) with the aim of identifying the climatic and oceanographic variations during the last 30 ka. The sedimentary sequence represents conditions of a cool-water carbonate factory, which evidences that during the Marine Isotope Stage 2 (MIS2) the area was ice-free and very productive. The overall preservation of delicate skeletal remains such as bryozoans and molluscs indicated moderate bottom currents. This carbonate factory was interrupted by some terrigenous levels, representing conditions of instability/retreat of the ice shelves southward. The younger levels were referred to the meltwater pulse (MWP)-1A and 1B events. The Holocene sequence comprised more terrigenous sediments, reflecting high bottom-currents similar to the present-day conditions. Very abundant and well preserved foraminifers and ostracods, representative of shelf-upper slope paleoenvironments, were recovered. Epistominella exigua, among the foraminifers, suggested the influence of the Circumpolar Deep Water during some periods of the late Quaternary. Heavy-test taxa, such as Cibicides refulgens, indicated strengthening bottom hydrodynamics. As for the ostracods, peaks in the presence of Australicythere devexa, Bairdoppilata simplex and Pseudocythere aff. caudata together with significant values of Polycope spp. allowed us to identify environments rich in nutrients with the influence of cold and deep water upwelling phenomena. Full article

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

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23 pages, 15466 KiB

Open AccessEditor’s ChoiceArticle

Structural and Stratigraphic Setting of Campagna and Giffoni Tectonic Windows: New Insights on the Orogenic Evolution of the Southern Apennines (Italy)

by Stefano Vitale, Ernesto Paolo Prinzi, Maria Monda, Francesco D’Assisi Tramparulo and Sabatino Ciarcia

Geosciences 2020, 10(10), 405; https://doi.org/10.3390/geosciences10100405 - 10 Oct 2020

Cited by 3 | Viewed by 2573

Abstract

We present a structural study on the tectonic windows of Giffoni and Campagna, located in the western sector of the southern Apennines (Italy). We analyzed thrusts, folds, and related minor deformation structures. Here, a major in-sequence E-verging thrust fault juxtaposes Meso-Cenozoic successions of [...] Read more.

We present a structural study on the tectonic windows of Giffoni and Campagna, located in the western sector of the southern Apennines (Italy). We analyzed thrusts, folds, and related minor deformation structures. Here, a major in-sequence E-verging thrust fault juxtaposes Meso-Cenozoic successions of the Apennine Platform (Picentini Mts unit) and the Lagonegro-Molise Basin (Frigento unit). However, out-of-sequence thrusts duplicated the tectonic pile with the interposition of the upper Miocene wedge-top basin deposits of the Castelvetere Group. We reconstructed the orogenic evolution of these two tectonic windows, including five deformation phases. The first (D1) was related to the in-sequence thrusting with minor thrusts and folds, widespread both in the footwall and the hanging wall. A subsequent extension (D2) has formed normal faults crosscutting the D1 thrusts and folds. All structures were subsequently affected by two shortening stages (D3 and D4), which also deformed the upper Miocene wedge top basin deposits of the Castelvetere Group. We interpreted the D3–D4 structures as related to an out-of-sequence thrust system defined by a main frontal E-verging thrust and lateral ramps characterized by N and S vergences. Low-angle normal faults were formed in the hanging wall of the major thrusts. Out-of-sequence thrusts are observed in the whole southern Apennines, recording a crustal shortening event that occurred in the late Messinian–early Pliocene. Finally, we suggest that the two tectonic windows are the result of the formation of an E–W trending regional antiform, associated with a late S-verging back-thrust, that has been eroded and crosscut by normal faults (D5) in the Early Pleistocene. 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, 4782 KiB

Open AccessEditor’s ChoiceArticle

Cemented on the Rock. A Pleistocene Outer Shelf Lithobiont Community from Sicily, Italy

by Antonietta Rosso, Agatino Reitano and Rossana Sanfilippo

Geosciences 2020, 10(9), 343; https://doi.org/10.3390/geosciences10090343 - 29 Aug 2020

Cited by 2 | Viewed by 2353

Abstract

The lithobiont community encrusting an early Pleistocene palaeocliff cropping out north of Augusta (SE Sicily, Italy) was investigated based on field observations and laboratory inspection of two rocky samples. Bryozoans, serpulids, brachiopods and bivalves encrusted part of the exposed surfaces that were bored [...] Read more.

The lithobiont community encrusting an early Pleistocene palaeocliff cropping out north of Augusta (SE Sicily, Italy) was investigated based on field observations and laboratory inspection of two rocky samples. Bryozoans, serpulids, brachiopods and bivalves encrusted part of the exposed surfaces that were bored mostly by clionaid sponges. Bryozoans, with at least 25 species detected on the rocky samples, are the most diversified skeletonized lithobionts also accounting for the highest number of colonies/specimens and highest coverage. Brachiopods, with the only species Novocrania anomala and a few but large cemented valves, cover wide surfaces. Serpulids, with two species identified on the sampled rocks and further two on the outcrop, were intermediate. A multiphase colonization is present, including a final epilithobiont community locally formed on eroded surfaces exposing a network of pervasive borings. The co-occurrence of very sciaphilic species having circalittoral to bathyal distributions suggests that the studied community thrived on a rocky substratum located near or at the shelf break, probably belonging to the shelf break (or RL) biocoenosis, also in agreement with observations on the fossil content of neighboring marly sediments. The observed relationships among colonizers largely represent mere superimpositions, and real interactions are not enough to state species competitiveness. Full article

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

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18 pages, 6343 KiB

Open AccessEditor’s ChoiceArticle

Validating Structural Styles in the Flysch Basin Northern Rif (Morocco) by Means of Thermal Modeling

by Achraf Atouabat, Sveva Corrado, Andrea Schito, Faouziya Haissen, Oriol Gimeno-Vives, Geoffroy Mohn and Dominique Frizon de Lamotte

Geosciences 2020, 10(9), 325; https://doi.org/10.3390/geosciences10090325 - 19 Aug 2020

Cited by 6 | Viewed by 3357

Abstract

Vitrinite reflectance and a micro-Raman spectroscopy parameters data set have been acquired on dispersed organic matter of the Maghrebian flysch basin and the Tangiers unit across a NE-SW section in the north-western Rif belt (North Morocco). Thermal maturity shows increasing values from the [...] Read more.

Vitrinite reflectance and a micro-Raman spectroscopy parameters data set have been acquired on dispersed organic matter of the Maghrebian flysch basin and the Tangiers unit across a NE-SW section in the north-western Rif belt (North Morocco). Thermal maturity shows increasing values from the hinterland to the external unit (from NE to SW). Paleo-thermal indicators show that the internal flysch basin (i.e., the Mauretanian unit) is less mature than the external one, (i.e., the Massylian unit), with R_o% and R_o eq. Raman values ranging from 0.64% to 1.02% (from early mature to late mature stages of hydrocarbon generation). 1D thermal modeling estimates the overburden now totally eroded ranging from 3.1 km to 6.0 km, and has been used as constraint to reconstruct the complete thrust wedge geometry in Miocene times. The reconstructed geometry accounts for high shortening (about 63%) due to the development of an antiformal stack in the frontal part of the wedge made up by the flysch succession. This stacking is interpreted as a consequence of the western translation of the Alboran Domain in the core of the Betic-Rif orogenic system. Full article

(This article belongs to the Special Issue Temperature in Sedimentary Basins)

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32 pages, 5502 KiB

Open AccessEditor’s ChoiceArticle

Sedimentation Patterns of Multiple Finnish Lakes Reveal the Main Environmental Stressors and the Role of Peat Extraction in Lake Sedimentation

by Tuija Vähäkuopus, Tommi Kauppila, Jari Mäkinen, Antti E. K. Ojala and Samu E. Valpola

Geosciences 2020, 10(8), 313; https://doi.org/10.3390/geosciences10080313 - 13 Aug 2020

Cited by 1 | Viewed by 5234

Abstract

Human land-use activities, especially in the peatlands, are under consideration as the mitigation and lowering of CO₂ emissions from land-use practices is needed to address climate change. In Finland, approximately one third of the land surface is covered by peatlands, and around [...] Read more.

Human land-use activities, especially in the peatlands, are under consideration as the mitigation and lowering of CO₂ emissions from land-use practices is needed to address climate change. In Finland, approximately one third of the land surface is covered by peatlands, and around 50% of peatlands are ditched for forestry. Another 3% of peatlands are used for agriculture and approximately 1% for peat extraction. The effects of these different land-use practices, including changes in sediment depositional rates and sediment quality, need to be identified. This study analyzed 51 lakes that were subdivided into two groups: (1) a group of impacted lakes in which peat was recently extracted from the catchments and (2) a reference group consisting of lakes where peat had not been extracted from the basin, but in which other land-use activities had occurred. The overall aim of the study was to investigate if peat extraction caused excessive delivery and deposition of dry and organic matter in lakes that are located in their immediate downstream catchment areas. Differences in sediment accumulation were defined by comparing the overall sediment thickness and recent (post 1986) sedimentation levels to identify if there were differences in the sediment chemical composition or rate of organic matter deposition between groups and to identify possible land-use stressors that could explain the possible differences in sediment chemical assemblages or sedimentation rates. The results show moderate (cm scale) sedimentation rates in both impacted and reference lakes after 1986, while sediment chemical assemblages indicated the erosion and input of mineral soils to all of the studied lakes, rather than the input of organic materials. No statistically significant correlations were observed between selected environmental variables and the recent accumulation rates of carbon and dry matter. Moreover, significant changes in the stressors potentially affecting the chemical assemblages of pre- and post-disturbance sediments were not observed. Full article

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25 pages, 11073 KiB

Open AccessEditor’s ChoiceArticle

Late Miocene-Early Pliocene Out-of-Sequence Thrusting in the Southern Apennines (Italy)

by Stefano Vitale, Ernesto Paolo Prinzi, Francesco D’Assisi Tramparulo, Claudio De Paola, Rosa Di Maio, Ester Piegari, Monia Sabbatino, Jacopo Natale, Pasqualino Notaro and Sabatino Ciarcia

Geosciences 2020, 10(8), 301; https://doi.org/10.3390/geosciences10080301 - 06 Aug 2020

Cited by 13 | Viewed by 3597

Abstract

We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine orogenic belt. The analyzed structures are exposed in the Campania region (southern Italy). Here, thrusts bound the N-NE side of the carbonate ridges that form the regional mountain [...] Read more.

We present a structural study on late Miocene-early Pliocene out-of-sequence thrusts affecting the southern Apennine orogenic belt. The analyzed structures are exposed in the Campania region (southern Italy). Here, thrusts bound the N-NE side of the carbonate ridges that form the regional mountain backbone. In several outcrops, the Mesozoic carbonates are superposed onto the unconformable wedge-top basin deposits of the upper Miocene Castelvetere Group, providing constraints to the age of the activity of this thrusting event. Moreover, a 4-km-long N-S oriented electrical resistivity tomography profile, carried out along the Caserta mountains, sheds light on the structure of this thrust system in an area where it is not exposed. Further information was carried out from a tunnel excavation that allowed us to study some secondary fault splays. The kinematic analysis of out-of-sequence major and minor structures hosted both in the hanging wall (Apennine Platform carbonates) and footwall (Castelvetere Group deposits and Lagonegro-Molise Basin units) indicates the occurrence of two superposed shortening directions, about E-W and N-S, respectively. We associated these compressive structures to an out-of-sequence thrusting event defined by frontal thrusts verging to the east and lateral ramp thrusts verging to the north and south. We related the out-of-sequence thrusting episode to the positive inversion of inherited normal faults located in the Paleozoic basement. These envelopments thrust upward to crosscut the allochthonous wedge, including, in the western zone of the chain, the upper Miocene wedge-top basin deposits. 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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19 pages, 6467 KiB

Open AccessEditor’s ChoiceArticle

Multi-Proxy Characterisation of the Storegga Tsunami and Its Impact on the Early Holocene Landscapes of the Southern North Sea

by Vincent Gaffney, Simon Fitch, Martin Bates, Roselyn L. Ware, Tim Kinnaird, Benjamin Gearey, Tom Hill, Richard Telford, Cathy Batt, Ben Stern, John Whittaker, Sarah Davies, Mohammed Ben Sharada, Rosie Everett, Rebecca Cribdon, Logan Kistler, Sam Harris, Kevin Kearney, James Walker, Merle Muru, Derek Hamilton, Matthew Law, Alex Finlay, Richard Bates and Robin G. Allaby Show full author list Hide full author list

Geosciences 2020, 10(7), 270; https://doi.org/10.3390/geosciences10070270 - 15 Jul 2020

Cited by 18 | Viewed by 19099

Abstract

Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in [...] Read more.

Doggerland was a landmass occupying an area currently covered by the North Sea until marine inundation took place during the mid-Holocene, ultimately separating the British landmass from the rest of Europe. The Storegga Event, which triggered a tsunami reflected in sediment deposits in the northern North Sea, northeast coastlines of the British Isles and across the North Atlantic, was a major event during this transgressive phase. The spatial extent of the Storegga tsunami however remains unconfirmed as, to date, no direct evidence for the event has been recovered from the southern North Sea. We present evidence of a tsunami deposit in the southern North Sea at the head of a palaeo-river system that has been identified using seismic survey. The evidence, based on lithostratigraphy, geochemical signatures, macro and microfossils and sedimentary ancient DNA (sedaDNA), supported by optical stimulated luminescence (OSL) and radiocarbon dating, suggests that these deposits were a result of the tsunami. Seismic identification of this stratum and analysis of adjacent cores showed diminished traces of the tsunami which was largely removed by subsequent erosional processes. Our results confirm previous modelling of the impact of the tsunami within this area of the southern North Sea, and also indicate that these effects were temporary, localized, and mitigated by the dense woodland and topography of the area. We conclude that clear physical remnants of the wave in these areas are likely to be restricted to now buried, palaeo-inland basins and incised river valley systems. Full article

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21 pages, 13263 KiB

Open AccessEditor’s ChoiceArticle

The Zagreb (Croatia) M5.5 Earthquake on 22 March 2020

by Snježana Markušić, Davor Stanko, Tvrtko Korbar, Nikola Belić, Davorin Penava and Branko Kordić

Geosciences 2020, 10(7), 252; https://doi.org/10.3390/geosciences10070252 - 01 Jul 2020

Cited by 51 | Viewed by 31899

Abstract

On 22 March 2020, Zagreb was struck by an M5.5 earthquake that had been expected for more than 100 years and revealed all the failures in the construction of residential buildings in the Croatian capital, especially those built in the first half of [...] Read more.

On 22 March 2020, Zagreb was struck by an M5.5 earthquake that had been expected for more than 100 years and revealed all the failures in the construction of residential buildings in the Croatian capital, especially those built in the first half of the 20th century. Because of that, extensive seismological, geological, geodetic and structural engineering surveys were conducted immediately after the main shock. This study provides descriptions of damage, specifying the building performances and their correlation with the local soil characteristics, i.e., seismic motion amplification. Co-seismic vertical ground displacement was estimated, and the most affected area is identified according to Sentinel-1 interferometric wide-swath data. Finally, preliminary 3D structural modeling of the earthquake sequence was performed, and two major faults were modeled using inverse distance weight (IDW) interpolation of the grouped hypocenters. The first-order assessment of seismic amplification (due to site conditions) in the Zagreb area for the M5.5 earthquake shows that ground motions of approximately 0.16–0.19 g were amplified at least twice. The observed co-seismic deformation (based on Sentinel-1A IW SLC images) implies an approximately 3 cm uplift of the epicentral area that covers approximately 20 km². Based on the preliminary spatial and temporal analyses of the Zagreb 2020 earthquake sequence, the main shock and the first aftershocks evidently occurred in the subsurface of the Medvednica Mountains along a deep-seated southeast-dipping thrust fault, recognized as the primary (master) fault. The co-seismic rupture propagated along the thrust towards northwest during the first half-hour of the earthquake sequence, which can be clearly seen from the time-lapse visualization. The preliminary results strongly support one of the debated models of the active tectonic setting of the Medvednica Mountains and will contribute to a better assessment of the seismic hazard for the wider Zagreb area. Full article

(This article belongs to the Section Geophysics)

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20 pages, 4164 KiB

Open AccessEditor’s ChoiceArticle

Sea Level Trend and Fronts in the South Atlantic Ocean

by Laura A. Ruiz-Etcheverry and Martin Saraceno

Geosciences 2020, 10(6), 218; https://doi.org/10.3390/geosciences10060218 - 03 Jun 2020

Cited by 12 | Viewed by 4452

Abstract

The understanding of the physical drivers of sea level trend is crucial on global and regional scales. In particular, little is known about the sea level trend in the South Atlantic Ocean in comparison with other parts of the world. In this work, [...] Read more.

The understanding of the physical drivers of sea level trend is crucial on global and regional scales. In particular, little is known about the sea level trend in the South Atlantic Ocean in comparison with other parts of the world. In this work, we computed the South Atlantic mean sea level (SAMSL) trend from 25 years of satellite altimetry data, and we analyzed the contributions of steric height (thermosteric and halosteric components) and ocean mass changes for the period 2005–2016 when all the source data used (Argo, GRACE and satellite altimetry) overlap. The SAMSL trend is 2.65 ± 0.24 mm/yr and is mostly explained by ocean mass trend, which is 2.22 ± 0.21 mm/yr. However, between 50° S–33° S, the steric height component constitutes the main contribution in comparison with the ocean mass component. Within that latitudinal band, three regions with trend values higher than the SAMSL trend are observed when considering 25 years of satellite SLA. In the three regions, a southward displacement of the Subtropical, Subantarctic, and Polar Fronts is observed. The southward shift of the fronts is associated with the strengthening and polar shift of westerly winds and contributes to a clear thermosteric trend that translates to the SLA trend observed in those regions. Full article

(This article belongs to the Special Issue Satellite Observations of Sea Level and Ocean Circulation)

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16 pages, 6006 KiB

Open AccessEditor’s ChoiceArticle

Ground Deformation and Seismic Fault Model of the M6.4 Durres (Albania) Nov. 26, 2019 Earthquake, Based on GNSS/INSAR Observations

by Athanassios Ganas, Panagiotis Elias, Pierre Briole, Flavio Cannavo, Sotirios Valkaniotis, Varvara Tsironi and Eleni I. Partheniou

Geosciences 2020, 10(6), 210; https://doi.org/10.3390/geosciences10060210 - 01 Jun 2020

Cited by 31 | Viewed by 4426

Abstract

We identify the source of the M_w = 6.4 earthquake that rocked north-central Albania on November 26, 2019 02:54 UTC. We use synthetic aperture radar interferograms tied to the time series of coordinates of two permanent Global Navigation Satellite System (GNSS) stations [...] Read more.

We identify the source of the M_w = 6.4 earthquake that rocked north-central Albania on November 26, 2019 02:54 UTC. We use synthetic aperture radar interferograms tied to the time series of coordinates of two permanent Global Navigation Satellite System (GNSS) stations (DUR2 and TIR2). We model the source by inverting the displacement data. Assuming in our model a half-space elastic medium and uniform slip along a rectangular fault surface, we invert the 104 picked measurements on a couple of ascending and descending interferograms to calculate the parameters of the fault. All inversions made with different input parameters converge towards a stable and robust solution with root mean square (r.m.s.) residual of 5.4 mm, thus ~1/5 of a fringe. They reveal that the earthquake occurred deep in the crust on a low-angle fault (23°) dipping towards east with a centroid at 16.5 km depth. The best-fitting length and width of the fault are 22 and 13 km, and the reverse slip, 0.55 m. The seismic moment deduced from our model agrees with those of the published seismic moment tensors. This geometry is compatible with a blind thrust fault that may root on the main basal thrust, i.e., along the thrust front that separates Adria–Apulia from Eurasia. It is notable that there is a 123 ns yr⁻¹ active shortening of the crust between the GNSS stations DUR2-TIR2 (equivalent to a shortening rate of 3.6 mm yr⁻¹), and roughly in the east–west direction. Given this amount of strain the recurrence time of M6+ earthquakes along this fault should be of the order of 150 years. Full article

(This article belongs to the Special Issue Seismotectonics, Active Deformation, and Structure of the Crust)

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21 pages, 746 KiB

Open AccessEditor’s ChoiceReview

Previous, Current, and Future Trends in Research into Earthquake Precursors in Geofluids

by Giovanni Martinelli

Geosciences 2020, 10(5), 189; https://doi.org/10.3390/geosciences10050189 - 19 May 2020

Cited by 23 | Viewed by 5117

Abstract

Hazard reduction policies include seismic hazard maps based on probabilistic evaluations and the evaluation of geophysical parameters continuously recorded by instrumental networks. Over the past 25 centuries, a large amount of information about earthquake precursory phenomena has been recorded by scholars, scientific institutions, [...] Read more.

Hazard reduction policies include seismic hazard maps based on probabilistic evaluations and the evaluation of geophysical parameters continuously recorded by instrumental networks. Over the past 25 centuries, a large amount of information about earthquake precursory phenomena has been recorded by scholars, scientific institutions, and civil defense agencies. In particular, hydrogeologic measurements and geochemical analyses have been performed in geofluids in search of possible and reliable earthquake precursors. Controlled experimental areas have been set up to investigate physical and chemical mechanisms originating possible preseismic precursory signals. The main test sites for such research are located in China, Iceland, Japan, the Russian Federation, Taiwan, and the USA. The present state of the art about the most relevant scientific achievements has been described. Future research trends and possible development paths have been identified and allow for possible improvements in policies oriented to seismic hazard reduction by geofluid monitoring. Full article

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

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19 pages, 24752 KiB

Open AccessEditor’s ChoiceArticle

Mainshock Anticipated by Intra-Sequence Ground Deformations: Insights from Multiscale Field and SAR Interferometric Measurements

by Francesco Brozzetti, Alessandro Cesare Mondini, Cristina Pauselli, Paolo Mancinelli, Daniele Cirillo, Fausto Guzzetti and Giusy Lavecchia

Geosciences 2020, 10(5), 186; https://doi.org/10.3390/geosciences10050186 - 15 May 2020

Cited by 15 | Viewed by 3367

Abstract

The 2016 Central Italy seismic sequence was characterized by two main events: 24 August, Mw 6, and 30 October, Mw 6.5. We carried out high-resolution field sampling and DInSAR analysis of the coseismic and intra-sequence ground deformations along the Mt Vettore-Mt Bove causative [...] Read more.

The 2016 Central Italy seismic sequence was characterized by two main events: 24 August, Mw 6, and 30 October, Mw 6.5. We carried out high-resolution field sampling and DInSAR analysis of the coseismic and intra-sequence ground deformations along the Mt Vettore-Mt Bove causative fault (VBF). We found that during the intra-sequence period (24 August–30 October), the ground experienced some deformations whose final patterns seemed to be retraced and amplified by the following mainshock. We interpreted that (i) immediately after the 24 August earthquake, the deformation observed in the southern VBF expanded northwards and westwards over a Length of Deforming Ground (LDG) ranging between 28.7 and 36.3 km, and (ii) it extended to the whole portion of the hanging wall that was later affected by mainshock coseismic deformation. Assuming the LDG to be an indicator for an expected (=coseismic) surface rupture length and using known scaling functions, we obtained 6.4 ≤ Mw ≤ 6.7 for a possible incoming earthquake, which is consistent with the mainshock magnitude. We suggest that the evolution of the ground deformations after a significant seismic event might provide insights on the occurrence of new earthquakes with magnitudes comparable to or larger than the former. Full article

(This article belongs to the Special Issue Seismic Sequence in Mediterranean Region)

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16 pages, 5681 KiB

Open AccessEditor’s ChoiceArticle

A Gas-Emission Crater in the Erkuta River Valley, Yamal Peninsula: Characteristics and Potential Formation Model

by Evgeny Chuvilin, Julia Stanilovskaya, Aleksey Titovsky, Anton Sinitsky, Natalia Sokolova, Boris Bukhanov, Mikhail Spasennykh, Alexey Cheremisin, Sergey Grebenkin, Dinara Davletshina and Christian Badetz

Geosciences 2020, 10(5), 170; https://doi.org/10.3390/geosciences10050170 - 08 May 2020

Cited by 21 | Viewed by 15094

Abstract

Methane is a powerful greenhouse gas, and the abrupt degassing events that recently have formed large craters on the Russian Arctic Yamal and Gydan Peninsulas have caused major concern. Here we present field data on cover sediments and evolution of a gas-emission crater [...] Read more.

Methane is a powerful greenhouse gas, and the abrupt degassing events that recently have formed large craters on the Russian Arctic Yamal and Gydan Peninsulas have caused major concern. Here we present field data on cover sediments and evolution of a gas-emission crater discovered in the Erkuta–Yakha River valley in the southern Yamal Peninsula in June 2017. The crater is located south of other similar craters discovered over the past decade in northern West Siberia. Data were collected during a field trip to the Erkuta crater in December 2017 which included field observations and sampling of permafrost soil and ground ice from the rim of the crater. All soil and ice samples were measured for contents of methane and its homologs (ethane and propane) and carbon dioxide. The contents of carbon dioxide in some samples are notably higher than methane. The strongly negative δ13С of methane from ground ice samples (−72‰) is typical of biogenic hydrocarbons. The ratio of methane to the total amount of its homologs indicate a component of gases that have migrated from a deeper, thermogenic source. Based on obtained results, a potential formation model for Erkuta gas-emission crater is proposed, which considers the combined effect of deep-seated (deep gas migration) and shallow (oxbow lake evolution and closed talik freezing) causes. This model includes several stages from geological prerequisites to the lake formation. Full article

(This article belongs to the Special Issue Gas Emissions and Crater Formation in Arctic Permafrost)

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17 pages, 6701 KiB

Open AccessEditor’s ChoiceArticle

Soil–Structure Interaction Assessment of the 23 November 1980 Irpinia-Basilicata Earthquake

by Daniele Mina and Davide Forcellini

Geosciences 2020, 10(4), 152; https://doi.org/10.3390/geosciences10040152 - 22 Apr 2020

Cited by 22 | Viewed by 3458

Abstract

This paper aimed to present a systematic study of the effects caused by the strong earthquake that struck southern Italy on 23 November 1980 (Ms = 6.9) and affected the Campania and Basilicata regions. Two aspects are discussed here: The broadening of the [...] Read more.

This paper aimed to present a systematic study of the effects caused by the strong earthquake that struck southern Italy on 23 November 1980 (Ms = 6.9) and affected the Campania and Basilicata regions. Two aspects are discussed here: The broadening of the knowledge of the response site effects by considering several soil free-field conditions and the assessment of the role of the soil–structure interaction (SSI) on a representative benchmark structure. This research study, based on the state-of-the-art knowledge, may be applied to assess future seismic events and to propose new original code provisions. The numerical simulations were herein performed with the advanced platform OpenSees, which can consider non-linear models for both the structure and the soil. The results show the importance of considering the SSI in the seismic assessment of soil amplifications and its consequences on the structural performance. Full article

(This article belongs to the Special Issue The November 23rd, 1980 Irpinia-Lucania, Southern Italy Earthquake: Insights and Reviews 40 Years Later)

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13 pages, 5507 KiB

Open AccessEditor’s ChoiceArticle

‘Silent’ Dome Emplacement into a Wet Volcano: Observations from an Effusive Eruption at White Island (Whakaari), New Zealand in Late 2012

by Arthur Jolly, Corentin Caudron, Társilo Girona, Bruce Christenson and Roberto Carniel

Geosciences 2020, 10(4), 142; https://doi.org/10.3390/geosciences10040142 - 14 Apr 2020

Cited by 17 | Viewed by 3596

Abstract

The 2012–2016 White Island (Whakaari) eruption sequence encompassed six small explosive events that included one steam driven and five explosive phreato-magmatic eruptions. More enigmatic, a dome was observed at the back of the vent and crater lake in November 2012. Its emplacement date [...] Read more.

The 2012–2016 White Island (Whakaari) eruption sequence encompassed six small explosive events that included one steam driven and five explosive phreato-magmatic eruptions. More enigmatic, a dome was observed at the back of the vent and crater lake in November 2012. Its emplacement date could not be easily determined due to persistent steam from the evaporating crater lake and because of the very low levels of discrete volcanic earthquakes associated with its growth. During this period, seismicity also included persistent tremor with dominant frequencies in the 2–5 Hz range. Detailed assessment of the tremor reveals a very slow evolution of the spectral peaks from low to higher frequencies. These gliding spectral lines evolved over a three-month time period beginning in late September 2012 and persisting until early January 2013, when the tremor stabilised. As part of the dome emplacement episode, the crater lake progressively dried, leaving isolated pools which then promoted persistent mud/sulphur eruption activity starting in mid-January 2013. We interpret the emplacement of the dome as a non-explosive process where the hot, mostly degassed, magma intruded slowly through the hydrothermal system in late September 2012 and cooled in a relatively quiet state. The tremor evolution might reflect the slow contraction of subsurface resonant cavities, which increased the pitch of the peak resonant frequency through time. Alternatively, spectral evolution might reflect a ‘comb function’ due to clockwork beating of the slowly cooling dome, although direct evidence of clockwork beats is not seen in the waveform data. Finally, it might represent frothing of the hydrothermal system ahead of the slowly propagating magma. Full article

(This article belongs to the Special Issue Exploring and Modeling the Magma-Hydrothermal Regime)

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16 pages, 4525 KiB

Open AccessEditor’s ChoiceArticle

Spatial Landslide Risk Assessment at Phuentsholing, Bhutan

by Abhirup Dikshit, Raju Sarkar, Biswajeet Pradhan, Saroj Acharya and Abdullah M. Alamri

Geosciences 2020, 10(4), 131; https://doi.org/10.3390/geosciences10040131 - 07 Apr 2020

Cited by 40 | Viewed by 6133

Abstract

Landslides are one of the most destructive and most recurring natural calamities in the Himalayan region. Their occurrence leads to immense damage to infrastructure and loss of land, human lives, and livestock. One of the most affected regions is the Bhutan Himalayas, where [...] Read more.

Landslides are one of the most destructive and most recurring natural calamities in the Himalayan region. Their occurrence leads to immense damage to infrastructure and loss of land, human lives, and livestock. One of the most affected regions is the Bhutan Himalayas, where the majority of the landslides are rainfall-induced. The present study aims to determine the hazard and risk associated with rainfall-induced landslides for the Phuentsholing region located in the southwestern part of the Bhutan Himalayas. The work involves developing a landslide risk map using hazard and vulnerability maps utilizing landslide records from 2004 to 2014. The landslide hazard map was generated by determining spatial and temporal probabilities for the study region. The spatial probability was computed by analyzing the landslide contributing factors like geology, slope, elevation, rainfall, and vegetation based on comprehensive field study and expertise about the area. The contributing factors were divided into various classes and the percentage of landslide occurrence under each class was calculated to understand its contributing significance. Thereafter, a weighted linear combination approach was used in a GIS environment to develop the spatial probability map which was multiplied with temporal probabilities based on regional rainfall thresholds already determined for the region. Consequently, vulnerability assessment was conducted using key elements at risk (population, land use/land cover, proximity to road, proximity to stream) and the weights were provided based on expert judgment and comprehensive field study. Finally, risk was determined and the various regions in the study area were categorized as high, medium, and low risk. Such a study is necessary for low-economic countries like Bhutan which suffers from unavailability of extensive data and research. The study is conducted for a specific region but can be extended to other areas around the investigated area. The tool can serve as an indicator for the civil authorities to analyze the risk posed by landslides due to the rapid infrastructure development in the region. Full article

(This article belongs to the Special Issue Analysis and Prediction of Rainfall-Induced Landslides in a Changing Environment)

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29 pages, 21007 KiB

Open AccessEditor’s ChoiceArticle

Evaluating Rockfall Risk: Some Critical Aspects

by Claudio Scavia, Monica Barbero, Marta Castelli, Maddalena Marchelli, Daniele Peila, Giulia Torsello and Gianmarco Vallero

Geosciences 2020, 10(3), 98; https://doi.org/10.3390/geosciences10030098 - 03 Mar 2020

Cited by 55 | Viewed by 7349

Abstract

Rockfalls evolve rapidly and unpredictably in mountain environments and can cause considerable losses to human societies, structures, economical activities, and also natural and historical heritage. Rockfall risk analyses are complex and multi-scale processes involving several disciplines and techniques. This complexity is due to [...] Read more.

Rockfalls evolve rapidly and unpredictably in mountain environments and can cause considerable losses to human societies, structures, economical activities, and also natural and historical heritage. Rockfall risk analyses are complex and multi-scale processes involving several disciplines and techniques. This complexity is due to the main features of rockfall phenomena, which are extremely variable over space and time. Today, a considerable number of methods exists for protecting land, as well as assessing and managing the risk level. These methodologies are often very different from each other, depending on the data required, the purposes of the analysis, and the reference scale adopted, i.e., the analysis level of detail. Nevertheless, several questions still remain open with reference to each phase of the hazard and risk process. This paper is devoted to a general overview of existing risk estimation methodologies and a critical analysis of some open questions with the aim of highlighting possible further research topics. A typical risk assessment framework is exemplified by analyzing a real case study. Each step of the process is treated at both the detailed and the large scale in order to highlight the main characteristics of each level of detail. Full article

(This article belongs to the Special Issue Innovative Strategies for Sustainable Mitigation of Landslide Risk)

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24 pages, 7129 KiB

Open AccessEditor’s ChoiceArticle

The Effects of Slope Initialization on the Numerical Model Predictions of the Slope-Vegetation-Atmosphere Interaction

by Vito Tagarelli and Federica Cotecchia

Geosciences 2020, 10(2), 85; https://doi.org/10.3390/geosciences10020085 - 24 Feb 2020

Cited by 27 | Viewed by 3780

Abstract

Deep slope movements and, eventually, slope failure, have been often interpreted to be due to slope-vegetation-atmosphere interaction on slopes formed of clayey materials in the Italian Southern-Eastern Apennines, as reported in the literature. Such slopes are generally formed of flysch, within which clay [...] Read more.

Deep slope movements and, eventually, slope failure, have been often interpreted to be due to slope-vegetation-atmosphere interaction on slopes formed of clayey materials in the Italian Southern-Eastern Apennines, as reported in the literature. Such slopes are generally formed of flysch, within which clay is the main lithotype. Such clays are characterized by a disturbed meso-fabric, as an effect of the intense tectonics. The paper presents the results of coupled hydromechanical numerical analyses of the slope-vegetation-atmosphere interaction for a clay slope representative for the geomechanical scenario where such climate-induced deep slope movements have been repeatedly recorded. In the analyses, different model initialization procedures and parameter values were adopted. The comparison of the numerical results with the site data is aimed at assessing the effects of the soil-vegetation-atmosphere interaction taking place in the top strata of the slope, on the stress-strain conditions across the whole slope, and on the slope stability. The comparison between the numerical results of the analyses carried out entailing different initialization stages are intended to evaluate the influence of such a stage on the model predictions. It is found that only when the slope model initialization accounts for the slope loading history, developed over geological time, the numerical predictions get close to the site observations. In such case, the numerical results confirm that deep movements consequent to progressive failure may take place in clay slopes due to the slope-vegetation-atmosphere interaction. Full article

(This article belongs to the Special Issue Innovative Strategies for Sustainable Mitigation of Landslide Risk)

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19 pages, 14084 KiB

Open AccessEditor’s ChoiceArticle

Morphotectonic Kinematic Indicators along the Vigan-Aggao Fault: The Western Deformation Front of the Philippine Fault Zone in Northern Luzon, the Philippines

by Rolly E. Rimando and Jeremy M. Rimando

Geosciences 2020, 10(2), 83; https://doi.org/10.3390/geosciences10020083 - 22 Feb 2020

Cited by 9 | Viewed by 35340

Abstract

The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from [...] Read more.

The Vigan-Aggao Fault is a 140-km-long complex active fault system consisting of multiple traces in the westernmost part of the Philippine Fault Zone (PFZ) in northern Luzon, the Philippines. In this paper, its traces, segmentation, and oblique left-lateral strike-slip motion are determined from horizontal and vertical displacements measured from over a thousand piercing points pricked from displaced spurs and streams observed from Google Earth Pro satellite images. This work marks the first instance of the extensive use of Google Earth as a tool in mapping and determining the kinematics of active faults. Complete 3D image coverage of a major thoroughgoing active fault system is freely and easily accessible on the Google Earth Pro platform. It provides a great advantage to researchers collecting morphotectonic displacement data, especially where access to aerial photos covering the entire fault system is next to impossible. This tool has not been applied in the past due to apprehensions on the positional measurement accuracy (mainly of the vertical component). The new method outlined in this paper demonstrates the applicability of this tool in the detailed mapping of active fault traces through a neotectonic analysis of fault-zone features. From the sense of motion of the active faults in northern Luzon and of the major bounding faults in central Luzon, the nature of deformation in these regions can be inferred. An understanding of the kinematics is critical in appreciating the distribution and the preferred mode of accommodation of deformation by faulting in central and northern Luzon resulting from oblique convergence of the Sunda Plate and the Philippine Sea Plate. The location, extent, segmentation patterns, and sense of motion of active faults are critical in coming up with reasonable estimates of the hazards involved and identifying areas prone to these hazards. The magnitude of earthquakes is also partly dependent on the type and nature of fault movement. With a proper evaluation of these parameters, earthquake hazards and their effects in different tectonic settings worldwide can be estimated more accurately. Full article

(This article belongs to the Section Natural Hazards)

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43 pages, 11615 KiB

Open AccessEditor’s ChoiceArticle

Distinguishing between Deep-Water Sediment Facies: Turbidites, Contourites and Hemipelagites

by Dorrik Stow and Zeinab Smillie

Geosciences 2020, 10(2), 68; https://doi.org/10.3390/geosciences10020068 - 13 Feb 2020

Cited by 129 | Viewed by 26090

Abstract

The distinction between turbidites, contourites and hemipelagites in modern and ancient deep-water systems has long been a matter of controversy. This is partly because the processes themselves show a degree of overlap as part of a continuum, so that the deposit characteristics also [...] Read more.

The distinction between turbidites, contourites and hemipelagites in modern and ancient deep-water systems has long been a matter of controversy. This is partly because the processes themselves show a degree of overlap as part of a continuum, so that the deposit characteristics also overlap. In addition, the three facies types commonly occur within interbedded sequences of continental margin deposits. The nature of these end-member processes and their physical parameters are becoming much better known and are summarised here briefly. Good progress has also been made over the past decade in recognising differences between end-member facies in terms of their sedimentary structures, facies sequences, ichnofacies, sediment textures, composition and microfabric. These characteristics are summarised here in terms of standard facies models and the variations from these models that are typically encountered in natural systems. Nevertheless, it must be acknowledged that clear distinction is not always possible on the basis of sedimentary characteristics alone, and that uncertainties should be highlighted in any interpretation. A three-scale approach to distinction for all deep-water facies types should be attempted wherever possible, including large-scale (oceanographic and tectonic setting), regional-scale (architecture and association) and small-scale (sediment facies) observations. Full article

(This article belongs to the Special Issue Interacting Alongslope and Downslope Sedimentary Processes)

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27 pages, 5054 KiB

Open AccessEditor’s ChoiceReview

Review of Explosive Hydrovolcanism

by Károly Németh and Szabolcs Kósik

Geosciences 2020, 10(2), 44; https://doi.org/10.3390/geosciences10020044 - 24 Jan 2020

Cited by 68 | Viewed by 12113

Abstract

Hydrovolcanism is a type of volcanism where magma and water interact either explosively or non-explosively. The less frequently used term, hydromagmatism, includes all the processes responsible for magma and water interaction in a magmatic system. Hydrovolcanism is commonly used as a synonym for [...] Read more.

Hydrovolcanism is a type of volcanism where magma and water interact either explosively or non-explosively. The less frequently used term, hydromagmatism, includes all the processes responsible for magma and water interaction in a magmatic system. Hydrovolcanism is commonly used as a synonym for phreatomagmatism. However, in recent years phreatomagmatism appears more in association with volcanic eruptions that occur in shallow subaqueous or terrestrial settings and commonly involves molten fuel-coolant interaction (MFCI) driven processes. Here a revised and reviewed classification scheme is suggested on the basis of the geo-environment in which the magma-water interaction takes place and the explosivity plus mode of energy transfer required to generate kinetic energy to produce pyroclasts. Over the past decade researchers have focused on the role hydrovolcanism/phreatomagmatism plays in the formation of maar craters, the evolution of diatremes and the signatures of magma—water interaction in the geological record. In the past five years, lithofacies-characterization is the most common approach to studying hydrovolcanism. By far mafic monogenetic volcanic fields generated the greatest number of research results. Significant knowledge gaps are identified, especially in developing tools to identify the textural signatures hydrovolcanism leave behind on eruptive products and exploring the role of hydrovolcanism in the growth of intermediate and silicic small volume volcanoes. Full article

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77 pages, 12837 KiB

Open AccessEditor’s ChoiceReview

A Review of the Curculionoidea (Coleoptera) from European Eocene Ambers

by Andrei A. Legalov

Geosciences 2020, 10(1), 16; https://doi.org/10.3390/geosciences10010016 - 30 Dec 2019

Cited by 38 | Viewed by 4970

Abstract

All 142 known species of Curculionoidea in Eocene amber are documented, including one species of Nemonychidae, 16 species of Anthribidae, six species of Belidae, 10 species of Rhynchitidae, 13 species of Brentidae, 70 species of Curcuionidae, two species of Platypodidae, and 24 species [...] Read more.

All 142 known species of Curculionoidea in Eocene amber are documented, including one species of Nemonychidae, 16 species of Anthribidae, six species of Belidae, 10 species of Rhynchitidae, 13 species of Brentidae, 70 species of Curcuionidae, two species of Platypodidae, and 24 species of Scolytidae. Oise amber has eight species, Baltic amber has 118 species, and Rovno amber has 16 species. Nine new genera and 18 new species are described from Baltic amber. Four new synonyms are noted: Palaeometrioxena Legalov, 2012, syn. nov. is synonymous with Archimetrioxena Voss, 1953; Paleopissodes weigangae Ulke, 1947, syn. nov. is synonymous with Electrotribus theryi Hustache, 1942; Electrotribus erectosquamata Rheinheimer, 2007, syn. nov. is synonymous with Succinostyphlus mroczkowskii Kuska, 1996; Protonaupactus Zherikhin, 1971, syn. nov. is synonymous with Paonaupactus Voss, 1953. Keys for Eocene amber Curculionoidea are given. There are the first records of Aedemonini and Camarotini, and genera Limalophus and Cenocephalus in Baltic amber. Full article

(This article belongs to the Special Issue The Evolutionary History of the Coleoptera)

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20 pages, 22786 KiB

Open AccessEditor’s ChoiceArticle

Constraints on Entrainment and Deposition Models in Avalanche Simulations from High-Resolution Radar Data

by Matthias Rauter and Anselm Köhler

Geosciences 2020, 10(1), 9; https://doi.org/10.3390/geosciences10010009 - 25 Dec 2019

Cited by 12 | Viewed by 4581

Abstract

Depth-integrated simulations of snow avalanches have become a central part of risk analysis and mitigation. However, the common practice of applying different model parameters to mimic different avalanches is unsatisfying. In here, we analyse this issue in terms of two differently sized avalanches [...] Read more.

Depth-integrated simulations of snow avalanches have become a central part of risk analysis and mitigation. However, the common practice of applying different model parameters to mimic different avalanches is unsatisfying. In here, we analyse this issue in terms of two differently sized avalanches from the full-scale avalanche test-site Vallée de la Sionne, Switzerland. We perform depth-integrated simulations with the toolkit OpenFOAM, simulating both events with the same set of model parameters. Simulation results are validated with high-resolution position data from the GEODAR radar. Rather than conducting extensive post-processing to match radar data to the output of the simulations, we generate synthetic flow signatures inside the flow model. The synthetic radar data can be directly compared with the GEODAR measurements. The comparison reveals weaknesses of the model, generally at the tail and specifically by overestimating the runout of the smaller event. Both issues are addressed by explicitly considering deposition processes in the depth-integrated model. The new deposition model significantly improves the simulation of the small avalanche, making it starve in the steep middle part of the slope. Furthermore, the deposition model enables more accurate simulations of deposition patterns and volumes and the simulation of avalanche series that are influenced by previous deposits. Full article

(This article belongs to the Special Issue Snow Avalanche Dynamics)

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5 pages, 1790 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Early Observations of the Interstellar Comet 2I/Borisov

by Chien-Hsiu Lee

Geosciences 2019, 9(12), 519; https://doi.org/10.3390/geosciences9120519 - 17 Dec 2019

Cited by 1 | Viewed by 2605

Abstract

2I/Borisov is the second ever interstellar object (ISO). It is very different from the first ISO ’Oumuamua by showing cometary activities, and hence provides a unique opportunity to study comets that are formed around other stars. Here we present early imaging and spectroscopic [...] Read more.

2I/Borisov is the second ever interstellar object (ISO). It is very different from the first ISO ’Oumuamua by showing cometary activities, and hence provides a unique opportunity to study comets that are formed around other stars. Here we present early imaging and spectroscopic follow-ups to study its properties, which reveal an (up to) 5.9 km comet with an extended coma and a short tail. Our spectroscopic data do not reveal any emission lines between 4000–9000 Angstrom; nevertheless, we are able to put an upper limit on the flux of the C2 emission line, suggesting modest cometary activities at early epochs. These properties are similar to comets in the solar system, and suggest that 2I/Borisov—while from another star—is not too different from its solar siblings. Full article

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10 pages, 6726 KiB

Open AccessEditor’s ChoiceArticle

Formation of the Yamal Crater in Northern West Siberia: Evidence from Geochemistry

by Sergey Vorobyev, Andrey Bychkov, Vanda Khilimonyuk, Sergey Buldovicz, Evgeny Ospennikov and Evgeny Chuvilin

Geosciences 2019, 9(12), 515; https://doi.org/10.3390/geosciences9120515 - 14 Dec 2019

Cited by 9 | Viewed by 4736

Abstract

In the framework of this work, studies on the Yamal crater formed as a result of a cryogenic eruption of a water-gas fluid were carried out. The structure and variations of the composition of the geochemical field along the section of the upper [...] Read more.

In the framework of this work, studies on the Yamal crater formed as a result of a cryogenic eruption of a water-gas fluid were carried out. The structure and variations of the composition of the geochemical field along the section of the upper horizons of permafrost are considered on the basis of field work, including the drilling of boreholes near the crater. The obtained regularities of the distribution of chemical elements, and gases between the mineral component of the soil and meltwater, suggest that permafrost at the site of the funnel are the remains of a sub-lake paleo-talik, from which mineralized water and gases were expulsed into the yet unfrozen reservoir that previously existed at this place. The component composition of gases suggests that they are products of biochemical processes similar to those that occur in modern peatlands. The δ¹³C value for methane extracted from the sediments of the near-contact zone of the Yamal crater was found to be −76‰. The predominance of high molecular weight normal alkanes in frozen bitumen indicates that the original organic substrate which was buried contained remains of higher vegetation. The Yamal funnel was formed by the sediment’s “explosion” while the water-gas fluid was released. The volume of the ejected sediment amounted to about 220 thousand m³. Full article

(This article belongs to the Special Issue Gas and Gas Hydrate in Permafrost)

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20 pages, 714 KiB

Open AccessEditor’s ChoiceReview

The Fossil Record of Darkling Beetles (Insecta: Coleoptera: Tenebrionidae)

by Maxim V. Nabozhenko

Geosciences 2019, 9(12), 514; https://doi.org/10.3390/geosciences9120514 - 13 Dec 2019

Cited by 21 | Viewed by 4790

Abstract

The fossil record of Tenebrionidae (excluding the Quartenary) is presented. In total, 122 fossil species, clearly belonging to the family, are known; some beetles were determined only to genus; 78 genera are listed in the fossil record, including 29 extinct genera. The great [...] Read more.

The fossil record of Tenebrionidae (excluding the Quartenary) is presented. In total, 122 fossil species, clearly belonging to the family, are known; some beetles were determined only to genus; 78 genera are listed in the fossil record, including 29 extinct genera. The great diversity of tenebrionids occurs in the Lower Cretaceous Lagerstätte of China (Yixian Formation), Middle Paleocene of France (Menat), Lower Eocene deposits of Germany (Geiseltal), Upper Eocene Baltic amber (Eastern Europe), Upper Eocene deposits of Florissant Formation (USA) and Miocene (Dominican amber). Tenebrionids of the following major lineages, including seven subfamilies, are currently known in the fossil record. These include the lagrioid branch (Lagriinae, Nilioninae), pimelioid branch (Pimeliinae), and tenebrioid branch (Alleculinae, Tenebrioninae, Diaperinae, Stenochiinae). The importance of the fossil record for evolutionary reconstructions and phylogenetic patterns is discussed. The oldest Jurassic and Early Cretaceous darkling beetles of the tenebrionoid branch consist of humid-adapted groups from the extant tribes Alleculini, Ctenopodiini (Alleculinae), and Alphitobiini (Tenebrioninae). Thus, paleontological evidence suggests that differentiation of the family started at least by the Middle Jurassic but does not indicate that xerophilic darkling beetles differentiated much earlier than mesophilic groups. Full article

(This article belongs to the Special Issue The Evolutionary History of the Coleoptera)

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27 pages, 10968 KiB

Open AccessEditor’s ChoiceArticle

Undrained Cyclic Laboratory Behavior of Sandy Soils

by Francesco Castelli, Antonio Cavallaro, Salvatore Grasso and Valentina Lentini

Geosciences 2019, 9(12), 512; https://doi.org/10.3390/geosciences9120512 - 11 Dec 2019

Cited by 13 | Viewed by 3147

Abstract

The complex cyclic shear stress path experienced by the soil during an earthquake, which could also induce liquefaction phenomena, can be approximated in the laboratory only by using sophisticated testing apparatuses. Cyclic triaxial tests have been widely used, especially for coarse grained soils, [...] Read more.

The complex cyclic shear stress path experienced by the soil during an earthquake, which could also induce liquefaction phenomena, can be approximated in the laboratory only by using sophisticated testing apparatuses. Cyclic triaxial tests have been widely used, especially for coarse grained soils, as in this study. In the framework of the design for the seismic retrofitting of the ‘‘Ritiro viaduct’’ foundations along the A20 motorway connecting Messina with Palermo (Italy), a soil liquefaction study was also carried out. With this aim, a detailed geological and geotechnical characterization of the area was performed by in situ and laboratory tests, including seismic dilatometer Marchetti tests (SDMTs), the combined resonant column (RCT) and cyclic loading torsional shear tests (CLTSTs), and undrained cyclic loading triaxial tests (CLTxTs). In particular, the paper presents the results of cyclic triaxial tests carried out on isotropically consolidated specimens of a sandy soil. The seismic retrofitting works include the reinforcement of the foundation and replacement of the decks with newly designed type and structural schemes, mixed steel, and concrete with continuous girder. During the investigation, data were acquired for the characterization of materials, for the definition of degradation phenomena with the relative identification of possible causes, and for the estimation of the residual performance characteristics of the building. The structural campaign of investigations necessary to determine all of the key parameters useful for a correct definition of the residual performance capabilities of the work was divided into two phases: One in situ and one in the laboratory. Full article

(This article belongs to the Special Issue New Perspectives in the Definition/Evaluation of Seismic Hazard through Analysis of the Environmental Effects Induced by Earthquakes)

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23 pages, 6422 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Improvement of an Operational Forecasting System for Extreme Tidal Events in Santos Estuary (Brazil)

by Joana Mendes, Paulo Leitão, José Chambel Leitão, Sofia Bartolomeu, João Rodrigues and João Miguel Dias

Geosciences 2019, 9(12), 511; https://doi.org/10.3390/geosciences9120511 - 10 Dec 2019

Cited by 4 | Viewed by 3289

Abstract

Forecasting estuarine circulation is a hot topic, especially in densely populated regions, like Santos (Brazil). This paper aims to improve a water-level forecasting system for the Santos estuary, particularly the physical forcing determining the residual tide, which in extreme cases increase the predicting [...] Read more.

Forecasting estuarine circulation is a hot topic, especially in densely populated regions, like Santos (Brazil). This paper aims to improve a water-level forecasting system for the Santos estuary, particularly the physical forcing determining the residual tide, which in extreme cases increase the predicting errors. The MOHID hydrodynamic model was implemented with a nested downscaling approach. All automatic procedures to provide a high-resolution real-time forecast system are managed by the AQUASAFE software. Water-level observation and prediction datasets (2016–2017) of five tide gauges in the Santos channel were analyzed, resulting in distinct model configurations, aiming to minimize forecasting inaccuracies. Current MOHID open boundary reference solutions were modified: the astronomical solution was updated from FES2012 to FES2014 whereas the meteorological component (Copernicus Marine Environment Monitoring Service (CMEMS) global solution) time resolution was altered from daily to hourly data. Furthermore, the correlation between significant wave height with positive residual tide events was identified. The model validation presented a minimum Root Mean Square Error (RMSE) of 12.5 cm. Despite FES2014 solution improvements at the bay entrance, errors increase in inner stations were maintained, portraying the need for better bathymetric data. The use of a CMEMS hourly resolution decreased the meteorological tide errors. A linear regression method was developed to correct the residual tide through post-processing, under specific wave height conditions. Overall, the newest implementation increased the water-level forecast accuracy, particularly under extreme events. Full article

(This article belongs to the Special Issue Numerical Modelling of Circulation and Biogeochemistry of Esturine-Coastal Continuums)

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33 pages, 7576 KiB

Open AccessEditor’s ChoiceReview

Antarctic Sea Ice Proxies from Marine and Ice Core Archives Suitable for Reconstructing Sea Ice over the Past 2000 Years

by Elizabeth R. Thomas, Claire S. Allen, Johan Etourneau, Amy C. F. King, Mirko Severi, V. Holly L. Winton, Juliane Mueller, Xavier Crosta and Victoria L. Peck

Geosciences 2019, 9(12), 506; https://doi.org/10.3390/geosciences9120506 - 04 Dec 2019

Cited by 37 | Viewed by 10081

Abstract

Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate [...] Read more.

Dramatic changes in sea ice have been observed in both poles in recent decades. However, the observational period for sea ice is short, and the climate models tasked with predicting future change in sea ice struggle to capture the current Antarctic trends. Paleoclimate archives, from marine sedimentary records and coastal Antarctic ice cores, provide a means of understanding sea ice variability and its drivers over decadal to centennial timescales. In this study, we collate published records of Antarctic sea ice over the past 2000 years (2 ka). We evaluate the current proxies and explore the potential of combining marine and ice core records to produce multi-archive reconstructions. Despite identifying 92 sea ice reconstructions, the spatial and temporal resolution is only sufficient to reconstruct circum-Antarctic sea ice during the 20th century, not the full 2 ka. Our synthesis reveals a 90 year trend of increasing sea ice in the Ross Sea and declining sea ice in the Bellingshausen, comparable with observed trends since 1979. Reconstructions in the Weddell Sea, the Western Pacific and the Indian Ocean reveal small negative trends in sea ice during the 20th century (1900–1990), in contrast to the observed sea ice expansion in these regions since 1979. Full article

(This article belongs to the Special Issue Climate Variability in Antarctica and the Southern Hemisphere over the Last Millennia)

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28 pages, 6662 KiB

Open AccessEditor’s ChoiceArticle

Late Orogenic Heating of (Ultra)High Pressure Rocks: Slab Rollback vs. Slab Breakoff

by Elena Sizova, Christoph Hauzenberger, Harald Fritz, Shah Wali Faryad and Taras Gerya

Geosciences 2019, 9(12), 499; https://doi.org/10.3390/geosciences9120499 - 27 Nov 2019

Cited by 35 | Viewed by 5682

Abstract

Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) [...] Read more.

Some (ultra)high-pressure metamorphic rocks that formed during continental collision preserve relict minerals, indicating a two-stage evolution: first, subduction to mantle depths and exhumation to the lower-crustal level (with simultaneous cooling), followed by intensive heating that can be characterized by a β-shaped pressure–temperature–time (P–T–t) path. Based on a two-dimensional (2D) coupled petrological–thermomechanical tectono-magmatic numerical model, we propose a possible sequence of tectonic stages that could lead to these overprinting metamorphic events along an orogenic β-shaped P–T–t path: the subduction and exhumation of continental crust, followed by slab retreat that leads to extension and subsequent asthenospheric upwelling. During the last stage, the exhumed crustal material at the crust–mantle boundary undergoes heating from the underlying hot asthenospheric mantle. This slab rollback scenario is further compared numerically with the classical continental collision scenario associated with slab breakoff, which is often used to explain the late heating impulse in the collisional orogens. The mantle upwelling occurring in the experiments with slab breakoff, which is responsible for the heating of the exhumed crustal material, is not related to the slab breakoff but can be caused either by slab bending before slab breakoff or by post-breakoff exhumation of the subducted crust. Our numerical modeling predictions align well with a variety of orogenic P–T–t paths that have been reported from many Phanerozoic collisional orogens, such as the Variscan Bohemian Massif, the Triassic Dabie Shan, the Cenozoic Northwest Himalaya, and some metamorphic complexes in the Alps. Full article

(This article belongs to the Special Issue Active Deformation and Rheology of the Continental Lithosphere)

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26 pages, 28006 KiB

Open AccessEditor’s ChoiceArticle

Landslide Susceptibility Assessment of Mauritius Island (Indian Ocean)

by Vincenzo Marsala, Alberto Galli, Giorgio Paglia and Enrico Miccadei

Geosciences 2019, 9(12), 493; https://doi.org/10.3390/geosciences9120493 - 23 Nov 2019

Cited by 26 | Viewed by 10568

Abstract

This work is focused on the landslide susceptibility assessment, applied to Mauritius Island. The study area is a volcanic island located in the western part of the Indian Ocean and it is characterized by a plateau-like morphology interrupted by three rugged mountain areas. [...] Read more.

This work is focused on the landslide susceptibility assessment, applied to Mauritius Island. The study area is a volcanic island located in the western part of the Indian Ocean and it is characterized by a plateau-like morphology interrupted by three rugged mountain areas. The island is severely affected by geo-hydrological hazards, generally triggered by tropical storms and cyclones. The landslide susceptibility analysis was performed through an integrated approach based on morphometric analysis and preliminary Geographical Information System (GIS)-based techniques, supported by photogeological analysis and geomorphological field mapping. The analysis was completed following a mixed heuristic and statistical approach, integrated using GIS technology. This approach led to the identification of eight landslide controlling factors. Hence, each factor was evaluated by assigning appropriate expert-based weights and analyzed for the construction of thematic maps. Finally, all the collected data were mapped through a cartographic overlay process in order to realize a new zonation of landslide susceptibility. The resulting map was grouped into four landslide susceptibility classes: low, medium, high, and very high. This work provides a scientific basis that could be effectively applied in other tropical areas showing similar climatic and geomorphological features, in order to develop sustainable territorial planning, emergency management, and loss-reduction measures. Full article

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15 pages, 8097 KiB

Open AccessEditor’s ChoiceArticle

An Analysis Applying InSAR of Subsidence Caused by Nearby Mining-Induced Earthquakes

by Ryszard Hejmanowski, Agnieszka A. Malinowska, Wojciech T. Witkowski and Artur Guzy

Geosciences 2019, 9(12), 490; https://doi.org/10.3390/geosciences9120490 - 21 Nov 2019

Cited by 16 | Viewed by 3149

Abstract

Earthquake occurrence is usually unpredictable apart from sites in the vicinity of volcanoes. It is not easy to measure displacements caused by seismic phenomena using classical geodetic methods, which are based on point survey. Therefore, the surveying of ground movements caused by seismic [...] Read more.

Earthquake occurrence is usually unpredictable apart from sites in the vicinity of volcanoes. It is not easy to measure displacements caused by seismic phenomena using classical geodetic methods, which are based on point survey. Therefore, the surveying of ground movements caused by seismic events should be carried out continuously. Nowadays, remote sensing data and InSAR are often applied to monitor ground displacements in areas affected by seismicity. The effects of severe nearby mining-induced earthquakes have been discussed in the paper. The earthquakes occurred in 2017 and had a magnitude of 4.7 and 4.8. The distance between the epicenters of the mining-induced earthquakes was around 1.6 km. The aim of the investigation has been to analyze the spatio-temporal distribution of ground movements caused by the two tremors using the InSAR technique. Superposition of surface displacement has been studied in time and space. The main scientific aim has been to prove that in the areas where high-energy tremors occur, ground movements overlap. Due to proximity between the epicenters, the mining-induced earthquakes caused the formation of a large subsidence trough with the dimension of approximately 1.2 km × 4.2 km and total subsidence of ca. 116 mm. Two-time phases of subsidence were determined with temporal overlapping. The subsidence analysis has enhanced the cognition of the impact of mining-induced seismicity on the kinematics of surface changes. Moreover, the present work supports the thesis that InSAR is a valuable and adequately accurate technique to monitor ground displacements caused by mining induced earthquakes. Full article

(This article belongs to the Section Geophysics)

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25 pages, 5168 KiB

Open AccessEditor’s ChoiceArticle

Spatio-Temporal Relationships between Fumarolic Activity, Hydrothermal Fluid Circulation and Geophysical Signals at an Arc Volcano in Degassing Unrest: La Soufrière of Guadeloupe (French West Indies)

by Giancarlo Tamburello, Séverine Moune, Patrick Allard, Swetha Venugopal, Vincent Robert, Marina Rosas-Carbajal, Sébastien Deroussi, Gaëtan-Thierry Kitou, Tristan Didier, Jean-Christophe Komorowski, François Beauducel, Jean-Bernard De Chabalier, Arnaud Le Marchand, Anne Le Friant, Magali Bonifacie, Céline Dessert and Roberto Moretti

Geosciences 2019, 9(11), 480; https://doi.org/10.3390/geosciences9110480 - 15 Nov 2019

Cited by 26 | Viewed by 3637

Abstract

Over the past two decades, La Soufrière volcano in Guadeloupe has displayed a growing degassing unrest whose actual source mechanism still remains unclear. Based on new measurements of the chemistry and mass flux of fumarolic gas emissions from the volcano, here we reveal [...] Read more.

Over the past two decades, La Soufrière volcano in Guadeloupe has displayed a growing degassing unrest whose actual source mechanism still remains unclear. Based on new measurements of the chemistry and mass flux of fumarolic gas emissions from the volcano, here we reveal spatio-temporal variations in the degassing features that closely relate to the 3D underground circulation of fumarolic fluids, as imaged by electrical resistivity tomography, and to geodetic-seismic signals recorded over the past two decades. Discrete monthly surveys of gas plumes from the various vents on La Soufrière lava dome, performed with portable MultiGAS analyzers, reveal important differences in the chemical proportions and fluxes of H₂O, CO₂, H₂S, SO₂ and H_2, which depend on the vent location with respect to the underground circulation of fluids. In particular, the main central vents, though directly connected to the volcano conduit and preferentially surveyed in past decades, display much higher CO₂/SO₂ and H₂S/SO₂ ratios than peripheral gas emissions, reflecting greater SO₂ scrubbing in the boiling hydrothermal water at 80–100 m depth. Gas fluxes demonstrate an increased bulk degassing of the volcano over the past 10 years, but also a recent spatial shift in fumarolic degassing intensity from the center of the lava dome towards its SE–NE sector and the Breislack fracture. Such a spatial shift is in agreement with both extensometric and seismic evidence of fault widening in this sector due to slow gravitational sliding of the southern dome sector. Our study thus provides an improved framework to monitor and interpret the evolution of gas emissions from La Soufrière in the future and to better forecast hazards from this dangerous andesitic volcano. Full article

(This article belongs to the Special Issue Exploring and Modeling the Magma-Hydrothermal Regime)

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20 pages, 2861 KiB

Open AccessEditor’s ChoiceArticle

On-Site Water and Wind Erosion Experiments Reveal Relative Impact on Total Soil Erosion

by Miriam Marzen, Thomas Iserloh, Wolfgang Fister, Manuel Seeger, Jesus Rodrigo-Comino and Johannes B. Ries

Geosciences 2019, 9(11), 478; https://doi.org/10.3390/geosciences9110478 - 14 Nov 2019

Cited by 22 | Viewed by 5307

Abstract

The relative impact of water and wind on total erosion was investigated by means of an experimental-empirical study. Wind erosion and water erosion were measured at five different sites: (1) Mediterranean fallow, (2) Mediterranean orchard, (3) wheat field, (4) vineyard and (5) sand [...] Read more.

The relative impact of water and wind on total erosion was investigated by means of an experimental-empirical study. Wind erosion and water erosion were measured at five different sites: (1) Mediterranean fallow, (2) Mediterranean orchard, (3) wheat field, (4) vineyard and (5) sand substrate. Mean erosion rates ranged from 1.55 to 618 g·m⁻²·h⁻¹ for wind and from 0.09 to 133.90 g·m⁻²·h⁻¹ for rain eroded material over all tested sites. Percentages (%) of eroded sediment for wind and rain, respectively, were found to be 2:98 on Mediterranean fallow, 11:89 on Mediterranean orchard, 3:97 on wheat field, 98:2 on vineyard and 99:1 on sand substrate. For the special case of soil surface crust destroyed by goat trampling, the measured values emphasize a strong potential impact of herding on total soil erosion. All sites produced erosion by wind and rain, and relations show that both erosive forces may have an impact on total soil erosion depending on site characteristics. The results indicate a strong need to focus on both wind and water erosion particularly concerning soils and substrates in vulnerable environments. Measured rates show a general potential erosion depending on recent developments of land use and climate change and may raise awareness of scientist, farmers and decision makers about potential impact of both erosive forces. Knowledge about exact relationship is key for an adapted land use management, which has great potential to mitigate degradation processes related to climate change. Full article

(This article belongs to the Special Issue Capture the Process! Dynamic Approaches in Geomorphology, Hydrology and Soil Physics)

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21 pages, 12005 KiB

Open AccessEditor’s ChoiceArticle

Atmospheric Dynamics from Synoptic to Local Scale During an Intense Frontal Dust Storm over the Sistan Basin in Winter 2019

by Dimitris G. Kaskaoutis, Diana Francis, Alireza Rashki, Jean-Pierre Chaboureau and Umesh C. Dumka

Geosciences 2019, 9(10), 453; https://doi.org/10.3390/geosciences9100453 - 22 Oct 2019

Cited by 29 | Viewed by 4270

Abstract

The Sistan Basin has been recognized as one of the most active dust sources and windiest desert environments in the world. Although the dust activity in Sistan maximizes during the summer, rare but intense dust storms may also occur in the winter. This [...] Read more.

The Sistan Basin has been recognized as one of the most active dust sources and windiest desert environments in the world. Although the dust activity in Sistan maximizes during the summer, rare but intense dust storms may also occur in the winter. This study aims to elucidate the atmospheric dynamics related to dust emission and transport, dust-plume characteristics, and impacts on aerosol properties and air quality during an intense dust storm over Sistan in February 2019. The dust storm was initiated by strong northerly winds (~20 ms⁻¹) associated with the intrusion of a cold front from high latitudes. The upper-level potential vorticity (PV)-trough evolved into a cut-off low in the mid and upper troposphere and initiated unstable weather over Afghanistan and northern Pakistan. At the surface, density currents emanating from deep convective clouds and further strengthened by downslope winds from the mountains, caused massive soil erosion. The passage of the cold front reduced the temperature by ~10 °C and increased the atmospheric pressure by ~10 hPa, while the visibility was limited to less than 200 m. The rough topography played a major role in modulating the atmospheric dynamics, wind field, dust emissions, and transport pathways. Meso-NH model simulates large amounts of columnar mass dust loading (> 20 g m⁻²) over Sistan, while the intense dust plume was mainly traveling below 2 km and increased the particulate matter (PM₁₀) concentrations up to 1800 µg m⁻³ at Zabol. The dust storm was initially moving in an arc-shaped pathway over the Sistan Basin and then it spread away. Plumes of dust covered a large area in southwest Asia, reaching the northern Arabian Sea, and the Thar desert one to two days later, while they strongly affected the aerosol properties at Karachi, Pakistan, by increasing the aerosol optical depth (AOD > 1.2) and the coarse-mode fraction at ~0.7. Full article

(This article belongs to the Special Issue Observing Atmospheric Dynamics and Dust Activity)

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15 pages, 2051 KiB

Open AccessEditor’s ChoiceArticle

Quantification of Modelling Uncertainties in Bridge Scour Risk Assessment under Multiple Flood Events

by Alonso Pizarro and Enrico Tubaldi

Geosciences 2019, 9(10), 445; https://doi.org/10.3390/geosciences9100445 - 18 Oct 2019

Cited by 25 | Viewed by 3118

Abstract

Local scour is a dynamic process evolving during the lifetime of bridges as a result of the changes in hydrologic and hydraulic conditions. Current approaches for scour risk assessment are generally based on the evaluation of the equilibrium scour depth for a flood [...] Read more.

Local scour is a dynamic process evolving during the lifetime of bridges as a result of the changes in hydrologic and hydraulic conditions. Current approaches for scour risk assessment are generally based on the evaluation of the equilibrium scour depth for a flood event with a prefixed return period. The temporal evolution of the bridge-pier scour process is usually disregarded, by assuming that equilibrium conditions are always attained, regardless of the flood properties. However, recent studies have highlighted the importance of accounting for the contribution of multiple flood events and their exact hydrograph shape. This study aims at quantifying the epistemic uncertainty related to the modelling of the temporal evolution of scour under multiple consecutive flood events in clear-water conditions. A simple numerical case study is considered, using a Markovian framework to describe probabilistically the progression of scour. Well-known time-dependent scour models are used to estimate the temporal evolution of the scour-depth under each flood hydrograph, and the scour estimates are compared with those obtained using widely employed equilibrium scour formulas. Results show that the expected scour depth is influenced by the parameters used to describe the flood hydrograph and that the probability distribution of the scour depth is highly sensitive to the choice of the time-dependent scour model. The uncertainty in the scour estimation stemming from the formula adopted in this study for describing the temporal evolution of the scour depth can be higher than those related to the formula adopted for equilibrium scour. Full article

(This article belongs to the Special Issue Impacts of Compound Hydrological Hazards or Extremes)

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18 pages, 8537 KiB

Open AccessEditor’s ChoiceArticle

Comparison of Earthquake-Triggered Landslide Inventories: A Case Study of the 2015 Gorkha Earthquake, Nepal

by Sansar Raj Meena and Sepideh Tavakkoli Piralilou

Geosciences 2019, 9(10), 437; https://doi.org/10.3390/geosciences9100437 - 10 Oct 2019

Cited by 23 | Viewed by 4507

Abstract

Despite landslide inventories being compiled throughout the world every year at different scales, limited efforts have been made to critically compare them using various techniques or by different investigators. Event-based landslide inventories indicate the location, distribution, and detected boundaries of landslides caused by [...] Read more.

Despite landslide inventories being compiled throughout the world every year at different scales, limited efforts have been made to critically compare them using various techniques or by different investigators. Event-based landslide inventories indicate the location, distribution, and detected boundaries of landslides caused by a single event, such as an earthquake or a rainstorm. Event-based landslide inventories are essential for landslide susceptibility mapping, hazard modeling, and further management of risk mitigation. In Nepal, there were several attempts to map landslides in detail after the Gorkha earthquake. Particularly after the main event on 25 April 2015, researchers around the world mapped the landslides induced by this earthquake. In this research, we compared four of these published inventories qualitatively and quantitatively using different techniques. Two principal methodologies, namely the cartographical degree of matching and frequency area distribution (FAD), were optimized and applied to evaluate inventory maps. We also showed the impact of using satellite imagery with different spatial resolutions on the landslide inventory generation by analyzing matches and mismatches between the inventories. The results of our work give an overview of the impact of methodology selection and outline the limitations and advantages of different remote sensing and mapping techniques for landslide inventorying. Full article

(This article belongs to the Special Issue New Perspectives in the Definition/Evaluation of Seismic Hazard through Analysis of the Environmental Effects Induced by Earthquakes)

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21 pages, 4618 KiB

Open AccessEditor’s ChoiceArticle

Monitoring Groundwater Change in California’s Central Valley Using Sentinel-1 and GRACE Observations

by Zhen Liu, Pang-Wei Liu, Elias Massoud, Tom G Farr, Paul Lundgren and James S. Famiglietti

Geosciences 2019, 9(10), 436; https://doi.org/10.3390/geosciences9100436 - 09 Oct 2019

Cited by 49 | Viewed by 6847

Abstract

The San Joaquin Valley and Tulare basins in California’s Central Valley have intensive agricultural activity and groundwater demand that has caused significant subsidence and depletion of water resources in the past. We measured groundwater pumping-induced land subsidence in the southern Central Valley from [...] Read more.

The San Joaquin Valley and Tulare basins in California’s Central Valley have intensive agricultural activity and groundwater demand that has caused significant subsidence and depletion of water resources in the past. We measured groundwater pumping-induced land subsidence in the southern Central Valley from March 2015 to May 2017 using Sentinel-1 interferometric synthetic aperture radar (InSAR) data. The InSAR measurements provided fine spatial details of subsidence patterns and displayed a superposition of secular and seasonal variations that were coherent across our study region and correlated with precipitation variability and changes in freshwater demand. Combining InSAR and Global Positioning System (GPS) data, precipitation, and in situ well records showed a broad scale slowdown/cessation of long term subsidence in the wetter winter of 2017, likely reflecting the collective response of the Central Valley aquifer system to heavier-than-usual precipitation. We observed a very good temporal correlation between the Gravity Recovery and Climate Experiment (GRACE) satellite groundwater anomaly (GWA) variation and long-term subsidence records, regardless of local hydrogeology and mechanical properties. This indicates the subsidence from satellite geodesy is a very useful indicator for tracking groundwater storage change. With the continuing acquisition of Sentinel-1 and other satellites, we anticipate decadal-scale subsidence records with a spatial resolution of tens to hundreds of meters will be available in the near future to be combined with basin-averaged GRACE measurements to improve our estimate of time-varying groundwater change. Full article

(This article belongs to the Special Issue Earth Observations to Support the Management of Groundwater Level Changes Impacts)

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16 pages, 1415 KiB

Open AccessEditor’s ChoiceReview

Landfill Impacts on the Environment—Review

by Magdalena Daria Vaverková

Geosciences 2019, 9(10), 431; https://doi.org/10.3390/geosciences9100431 - 03 Oct 2019

Cited by 149 | Viewed by 56699

Abstract

Waste management (WM) is a demanding undertaking in all countries, with important implications for human health, environmental preservation, sustainability and circular economy. The method of sanitary landfilling for final disposal of waste remains a generally accepted and used method but the available scientific [...] Read more.

Waste management (WM) is a demanding undertaking in all countries, with important implications for human health, environmental preservation, sustainability and circular economy. The method of sanitary landfilling for final disposal of waste remains a generally accepted and used method but the available scientific evidence on the waste-related environmental and health effects is not conclusive. Comparative studies of various WM methods (landfilling, incineration, composting etc.) show that among the municipal solid waste (MSW) treatment and disposal technological options, sanitary landfilling or open dumping is popular in most countries because of the relative low cost and low-technical requirement. The European Union (EU) Directive on waste landfills has introduced specific goals for reducing the volume of disposed waste and very strict requirements for landfilling and landfill sites. Evaluation of the impact of landfills on the environment is a crucial topic in the literature and has received increased attention recently, given growing environmental concerns. The main goal of this survey was to conduct a comprehensive assessment of possible impacts of MSW landfills on the environment. The main conclusion of the overall assessment of the literature is that the disposal of MSW in landfills entails a number of environmental risks but with respect to the current situation and rich style of living adopted in industrially developed countries, the idea of WM systems functioning without landfilling—at least in the foreseeable future within one generation—seems to be somewhat unreal. The results also provided important information of landfills as a source of environmental risk. Results of this research may have an important impact on landfill management and the disposal of waste. From the literature review, it is evident that even if high levels of waste avoidance, reuse and recycling are achieved, some waste materials will always need to be forwarded for disposal. Full article

(This article belongs to the Special Issue Waste Management and Environmental Remediation)

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31 pages, 3363 KiB

Open AccessEditor’s ChoiceArticle

Evaluating GRACE Mass Change Time Series for the Antarctic and Greenland Ice Sheet—Methods and Results

by Andreas Groh, Martin Horwath, Alexander Horvath, Rakia Meister, Louise Sandberg Sørensen, Valentina R. Barletta, René Forsberg, Bert Wouters, Pavel Ditmar, Jiangjun Ran, Roland Klees, Xiaoli Su, Kun Shang, Junyi Guo, C. K. Shum, Ernst Schrama and Andrew Shepherd

Geosciences 2019, 9(10), 415; https://doi.org/10.3390/geosciences9100415 - 25 Sep 2019

Cited by 28 | Viewed by 6453

Abstract

Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment (GRACE) allows to derive the temporal evolution in ice mass for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). Various algorithms have been used in a wide range [...] Read more.

Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment (GRACE) allows to derive the temporal evolution in ice mass for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). Various algorithms have been used in a wide range of studies to generate Gravimetric Mass Balance (GMB) products. Results from different studies may be affected by substantial differences in the processing, including the applied algorithm, the utilised background models and the time period under consideration. This study gives a detailed description of an assessment of the performance of GMB algorithms using actual GRACE monthly solutions for a prescribed period as well as synthetic data sets. The inter-comparison exercise was conducted in the scope of the European Space Agency’s Climate Change Initiative (CCI) project for the AIS and GIS, and was, for the first time, open to everyone. GMB products generated by different groups could be evaluated and directly compared against each other. For the period from 2003-02 to 2013-12, estimated linear trends in ice mass vary between −99 Gt/yr and −108 Gt/yr for the AIS and between −252 Gt/yr and −274 Gt/yr for the GIS, respectively. The spread between the solutions is larger if smaller drainage basins or gridded GMB products are considered. Finally, findings from the exercise formed the basis to select the algorithms used for the GMB product generation within the AIS and GIS CCI project. Full article

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15 pages, 4677 KiB

Open AccessEditor’s ChoiceArticle

Wildfire Impacts on Slope Stability Triggering in Mountain Areas

by Andrea Abbate, Laura Longoni, Vladislav Ivov Ivanov and Monica Papini

Geosciences 2019, 9(10), 417; https://doi.org/10.3390/geosciences9100417 - 25 Sep 2019

Cited by 24 | Viewed by 6213

Abstract

Landslides over steep slopes, floods along rivers plains and debris flows across valleys are hydrogeological phenomena typical for mountain regions. Such events are generally triggered by rainfall, which can have large variability in terms of both its intensity and volume. Furthermore, terrain predisposition [...] Read more.

Landslides over steep slopes, floods along rivers plains and debris flows across valleys are hydrogeological phenomena typical for mountain regions. Such events are generally triggered by rainfall, which can have large variability in terms of both its intensity and volume. Furthermore, terrain predisposition and the presence of some disturbances, such as wildfires, can have an adverse effect on the potential risk. Modelling the complex interaction between these components is not a simple task and cannot always be carried out using instability thresholds that only take into account the characteristics of the rainfall events. In some particular cases, external factors can modify the existing delicate equilibrium on the basis of which stability thresholds are defined. In particular, events such as wildfires can cause the removal of vegetation coverage and the modification of the soil terrain properties. Therefore, wildfires can effectively reduce the infiltration capacity of the terrain and modify evapotranspiration. As a result, key factors for slope stability, such as the trend of the degree of saturation of the terrain, can be strongly modified. Thus, studying the role of wildfire effects on the terrain’s hydrological balance is fundamental to establish the critical conditions that can trigger potential slope failures (i.e., shallow landslides and possible subsequent debris flows). In this work, we investigate the consequences of wildfire on the stability of slopes through a hydrological model that takes into account the wildfire effects and compare the results to the current stability thresholds. Two case studies in the Ardenno (IT) and Ronco sopra Ascona (CH) municipalities were chosen for model testing. The aim of this paper is to propose a quantitative analysis of the two cases studies, taking into account the role of fire in the slope stability assessment. The results indicate how the post-fire circumstances strongly modify the ability of the terrain to absorb rainfall water. This effect results in a persistently drier terrain until a corner point is reached, after which the stability of the slope could be undermined by a rainfall event of negligible intensity. Full article

(This article belongs to the Special Issue Sediment Transport and Soil Erosion—Modelling, Monitoring and Experimental Methods)

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34 pages, 18165 KiB

Open AccessEditor’s ChoiceReview

Surface-Rupturing Historical Earthquakes in Australia and Their Environmental Effects: New Insights from Re-Analyses of Observational Data

by Tamarah R. King, Mark Quigley and Dan Clark

Geosciences 2019, 9(10), 408; https://doi.org/10.3390/geosciences9100408 - 20 Sep 2019

Cited by 45 | Viewed by 8847

Abstract

We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied [...] Read more.

We digitize surface rupture maps and compile observational data from 67 publications on ten of eleven historical, surface-rupturing earthquakes in Australia in order to analyze the prevailing characteristics of surface ruptures and other environmental effects in this crystalline basement-dominated intraplate environment. The studied earthquakes occurred between 1968 and 2018, and range in moment magnitude (Mw) from 4.7 to 6.6. All earthquakes involved co-seismic reverse faulting (with varying amounts of strike-slip) on single or multiple (1–6) discrete faults of ≥ 1 km length that are distinguished by orientation and kinematic criteria. Nine of ten earthquakes have surface-rupturing fault orientations that align with prevailing linear anomalies in geophysical (gravity and magnetic) data and bedrock structure (foliations and/or quartz veins and/or intrusive boundaries and/or pre-existing faults), indicating strong control of inherited crustal structure on contemporary faulting. Rupture kinematics are consistent with horizontal shortening driven by regional trajectories of horizontal compressive stress. The lack of precision in seismological data prohibits the assessment of whether surface ruptures project to hypocentral locations via contiguous, planar principal slip zones or whether rupture segmentation occurs between seismogenic depths and the surface. Rupture centroids of 1–4 km in depth indicate predominantly shallow seismic moment release. No studied earthquakes have unambiguous geological evidence for preceding surface-rupturing earthquakes on the same faults and five earthquakes contain evidence of absence of preceding ruptures since the late Pleistocene, collectively highlighting the challenge of using mapped active faults to predict future seismic hazards. Estimated maximum fault slip rates are 0.2–9.1 m Myr⁻¹ with at least one order of uncertainty. New estimates for rupture length, fault dip, and coseismic net slip can be used to improve future iterations of earthquake magnitude—source size—displacement scaling equations. Observed environmental effects include primary surface rupture, secondary fracture/cracks, fissures, rock falls, ground-water anomalies, vegetation damage, sand-blows/liquefaction, displaced rock fragments, and holes from collapsible soil failure, at maximum estimated epicentral distances ranging from 0 to ~250 km. ESI-07 intensity-scale estimates range by ± 3 classes in each earthquake, depending on the effect considered. Comparing Mw-ESI relationships across geologically diverse environments is a fruitful avenue for future research. Full article

(This article belongs to the Special Issue New Perspectives in the Definition/Evaluation of Seismic Hazard through Analysis of the Environmental Effects Induced by Earthquakes)

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10 pages, 2502 KiB

Open AccessEditor’s ChoiceArticle

Monitoring Coastline Dynamics of Alakol Lake in Kazakhstan Using Remote Sensing Data

by Adilet Valeyev, Marat Karatayev, Ainagul Abitbayeva, Saule Uxukbayeva, Aruzhan Bektursynova and Zhanerke Sharapkhanova

Geosciences 2019, 9(9), 404; https://doi.org/10.3390/geosciences9090404 - 19 Sep 2019

Cited by 17 | Viewed by 3870

Abstract

Alakol Lake is one of the largest hydrologically closed lake located in Balkash-Alakol River Basin in southeast Kazakhstan. Having a coastline approximately at 490 km, Alakol Lake has faced multiple threats due to both natural and anthropogenic factors as a result of tectonic [...] Read more.

Alakol Lake is one of the largest hydrologically closed lake located in Balkash-Alakol River Basin in southeast Kazakhstan. Having a coastline approximately at 490 km, Alakol Lake has faced multiple threats due to both natural and anthropogenic factors as a result of tectonic movements, geology, wind-wave conditions, growing tourism activities, fishing, and transport, etc. The present study aims to investigate the historical trends in coastline changes along Alakol Lake in Kazakhstan and estimate its change rate by using remote sensing data in particular scale-space images Landsat-5 TM, 7 ETM+, 8 OLI, and Sentinel-2A. Based on Landsat and Sentinel data, the modified normalized difference water index was calculated to demonstrate the coastline changes along Alakol Lake between 1990 and 2018. Moreover, the monitoring and analysis of coastline dynamics is based on the main morphometric characteristics of Alakol Lake including water surface area, coastline length, geomorphology of the coast, etc. Our results reveal that there is a continuous coastline retreat, depending on the coast types. For example, in the case of the denudation coasts, a land inundation was from 120 to 270 m between 1990 and 2018. In the case of the accumulative coast (mainly northeast, north, and northwest coasts) a land inundation was from 200 to 900 m. A vast area of agricultural land around Alakol Lake become flooded and lost. This study demonstrates the importance of monitoring coastline dynamics because it provides essential information for understanding the coastal response to contemporary nature and anthropogenic impacts. Full article

(This article belongs to the Special Issue Image processing and satellite imagery analysis in environments)

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24 pages, 4160 KiB

Open AccessEditor’s ChoiceReview

Periodicity in Volcanic Gas Plumes: A Review and Analysis

by Tom D. Pering, Tehnuka Ilanko and Emma J. Liu

Geosciences 2019, 9(9), 394; https://doi.org/10.3390/geosciences9090394 - 10 Sep 2019

Cited by 21 | Viewed by 5687

Abstract

Persistent non-explosive passive degassing is a common characteristic of active volcanoes. Distinct periodic components in measurable parameters of gas release have been widely identified over timescales ranging from seconds to months. The development and implementation of high temporal resolution gas measurement techniques now [...] Read more.

Persistent non-explosive passive degassing is a common characteristic of active volcanoes. Distinct periodic components in measurable parameters of gas release have been widely identified over timescales ranging from seconds to months. The development and implementation of high temporal resolution gas measurement techniques now enables the robust quantification of high frequency processes operating on timescales comparable to those detectable in geophysical datasets. This review presents an overview of the current state of understanding regarding periodic volcanic degassing, and evaluates the methods available for detecting periodicity, e.g., autocorrelation, variations of the Fast Fourier Transform (FFT), and the continuous wavelet transform (CWT). Periodicities in volcanic degassing from published studies were summarised and statistically analysed together with analyses of literature-derived datasets where periodicity had not previously been investigated. Finally, an overview of current knowledge on drivers of periodicity was presented and discussed in the framework of four main generating categories, including: (1) non-volcanic (e.g., atmospheric or tidally generated); (2) gas-driven, shallow conduit processes; (3) magma movement, intermediate to shallow storage zone; and (4) deep magmatic processes. Full article

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10 pages, 3137 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on the Influence of Polypropylene Fiber on the Swelling Pressure Expansion Attributes of Silica Fume Stabilized Clayey Soil

by Nitin Tiwari and Neelima Satyam

Geosciences 2019, 9(9), 377; https://doi.org/10.3390/geosciences9090377 - 29 Aug 2019

Cited by 43 | Viewed by 5760

Abstract

Expansive soil shows dual swell–shrink which is not suitable for construction. Several mitigating techniques exist to counteract the problem promulgated by expansive clayey soils. This paper explored the potential mecho-chemical reinforcement of expansive clayey soil to mitigate the effect of upward swelling pressure [...] Read more.

Expansive soil shows dual swell–shrink which is not suitable for construction. Several mitigating techniques exist to counteract the problem promulgated by expansive clayey soils. This paper explored the potential mecho-chemical reinforcement of expansive clayey soil to mitigate the effect of upward swelling pressure and heave. The polypropylene fiber is randomly distributed in the soil for mechanical stabilization, and the industrial residual silica fume is used as a chemical stabilizer. The experimental analysis was made in three phases which involved tests on mechanically-reinforced expansive soil, using randomly distributed polypropylene fibers with different percentages (0.25%, 0.50%, and 1.00%), and which were 12 mm length. The second phase of experiments was carried out on chemical stabilized expansive soil with different percentages (2%, 4%, and 8%) of silica, and the next phase of the experiment focused on the combination of mecho-chemical stabilization of the expansive soil with different combinations of silica (i.e., 2%, 4%, and 8%) and polypropylene fibers (i.e., 0.25%, 0.50%, and 1.00%). Maximum dry density (MDD), optimum moisture content (OMC), liquid limit (LL), plastic limit (PL), plastic index (PI), grain size, and constant volume swelling pressure tests were performed on unreinforced and reinforced expansive soil, to investigate the effects of polypropylene fiber and silica fume on the engineering properties of expansive clayey soil. The experimental results illustrate that the inclusion of polypropylene fiber has a significant effect on the upward swelling pressure and expansion property of expansive soil. The reduction in the upward swelling pressure and expansion is a function of fiber content. These results also indicated that the use of silica fume caused a reduction in upward swelling potential, and its effect was considerably more than the influence of fiber. Full article

(This article belongs to the Special Issue Behavior of Expansive Soils and its Shrinkage Cracking)

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