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Geosciences (ISSN 2076-3263; CODEN: GBSEDA) is an interdisciplinary, international peer-reviewed open access journal of geoscience, future earth and planetary science published monthly online by MDPI.
- Open Access free for readers, with article processing charges (APC) paid by authors or their institutions.
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- CiteScore 2017 (Scopus): 1.97, which equals rank 32/182 (Q1) in the category 'General Earth and Planetary Sciences'.
- Rapid publication: manuscripts are peer-reviewed and a first decision provided to authors approximately 18 days after submission; acceptance to publication is undertaken in 5.9 days (median values for papers published in the first six months of 2018).
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Latest Articles
Analysis of Damage Caused by Hydrometeorological Disasters in Texas, 1960–2016
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Geosciences 2018, 8(10), 384; https://doi.org/10.3390/geosciences8100384 (registering DOI) - 20 October 2018
Abstract
Property damages caused by hydrometeorological disasters in Texas during the period 1960–2016 totaled $54.2 billion with hurricanes, tropical storms, and hail accounting for 56%, followed by flooding and severe thunderstorms responsible for 24% of the total damages. The current study provides normalized trends
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Property damages caused by hydrometeorological disasters in Texas during the period 1960–2016 totaled $54.2 billion with hurricanes, tropical storms, and hail accounting for 56%, followed by flooding and severe thunderstorms responsible for 24% of the total damages. The current study provides normalized trends to support the assertion that the increase in property damage is a combined contribution of stronger disasters as predicted by climate change models and increases in urban development in risk prone regions such as the Texas Gulf Coast. A comparison of the temporal distribution of damages normalized by population and GDP resulted in a less statistically significant increasing trend per capita. Seasonal distribution highlights spring as the costliest season (March, April and May) while the hurricane season (June through November) is well aligned with the months of highest property damage. Normalization of property damage by GDP during 2001–2016 showed Dallas as the only metropolitan statistical area (MSA) with a significant increasing trend of the 25 MSAs in Texas. Spatial analysis of property damage per capita highlighted the regions that are at greater risk during and after a major disaster given their limited economic resources compared to more urbanized regions. Variation in the causes of damage (wind or water) and types of damage that a “Hurricane” can produce was investigated using Hazus model simulation. A comparison of published damage estimates at time of occurrence with simulation outputs for Hurricanes Carla, 1961; Alicia, 1983; and Ike, 2008 based on 2010 building exposure highlighted the impact of economic growth, susceptibility of wood building types, and the predominant cause of damage. Carla and Ike simulation models captured less than 50% of their respective estimates reported by other sources suggesting a broad geographical zone of damage with flood damage making a significant contribution. Conversely, the model damage estimates for Alicia are 50% higher than total damage estimates that were reported at the time of occurrence suggesting a substantial increase in building exposure susceptible to wind damage in the modeled region from 1983 – 2010.
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Efficiency of a Digital Particle Image Velocimetry (DPIV) Method for Monitoring the Surface Velocity of Hyper-Concentrated Flows
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Geosciences 2018, 8(10), 383; https://doi.org/10.3390/geosciences8100383 - 19 October 2018
Abstract
Digital particle image velocimetry records high resolution images and allows the identification of the position of points in different time instants. This paper explores the efficiency of the digital image-technique for remote monitoring of surface velocity and discharge measurement in hyper-concentrated flow by
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Digital particle image velocimetry records high resolution images and allows the identification of the position of points in different time instants. This paper explores the efficiency of the digital image-technique for remote monitoring of surface velocity and discharge measurement in hyper-concentrated flow by the way of laboratory experiment. One of the challenges in the application of the image-technique is the evaluation of the error in estimating surface velocity. The error quantification is complex because it depends on many factors characterizing either the experimental conditions or/and the processing algorithm. In the present work, attention is devoted to the estimation error due either to the acquisition time or to the size of the sub-images (interrogation areas) to be correlated. The analysis is conducted with the aid of data collected in a scale laboratory flume constructed at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospace and of Materials Engineering (DICAM)—University of Palermo (Italy) and the image processing is carried out by the help of the PivLab algorithm in Matlab. The obtained results confirm that the number of frames used in processing procedure strongly affects the values of surface velocity; the estimation error decreases as the number of frames increases. The size of the interrogation area also exerts an important role in the flow velocity estimation. For the examined case, a reduction of the size of the interrogation area of one half compared to its original size has allowed us to obtain low values of the velocity estimation error. Results also demonstrate the ability of the digital image-technique to estimate the discharge at given cross-sections. The values of the discharge estimated by applying the digital image-technique downstream of the inflow sections by using the aforementioned size of the interrogation area compares well with those measured.
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Acid Neutralization by Mining Waste Dissolution under Conditions Relevant for Agricultural Applications
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Geosciences 2018, 8(10), 380; https://doi.org/10.3390/geosciences8100380 - 16 October 2018
Abstract
The acidification of agricultural soils in high rainfall regions is usually countered by the application of finely ground calcite or dolomite. As this carbonate dissolves, soil pH is raised, but CO2 is released. Mining activities often produce large quantities of very fine
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The acidification of agricultural soils in high rainfall regions is usually countered by the application of finely ground calcite or dolomite. As this carbonate dissolves, soil pH is raised, but CO2 is released. Mining activities often produce large quantities of very fine silicate rock-derived powders that are commonly deposited in stockpiles. However, the dissolution of such powders can also result in an increase in pH, without any direct release of CO2. Of particular interest are those silicate powders that have a high reactivity and higher capacity for raising pH. In this contribution, we report experimental work addressing the dissolution of various silicate rock-derived powders that were produced during mining activities in Norway under conditions that were representative of weathering in agricultural soils. Three different powders—derived from Åheim dunite, Stjernøya nepheline syenite, or Tellnes ilmenite norite—were exposed to different acids at pH 4 in unstirred flow cells, and dissolution or leaching kinetics were determined from the changes in the fluid composition. Based on these kinetics, pH neutralization rates were determined for the individual powders and compared to expected values for carbonates. Based on this comparison, it is concluded that the application of silicate rock-derived powder dissolution to replace carbonate-based liming may not be feasible due to slower reaction rates, unless larger quantities of a finer particle size than normal are used. The application of larger volumes of slower-reacting silicates may have the additional benefit of reducing the required frequency of liming.
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Where, What, When, and Why Is Bottom Mapping Needed? An On-Line Application to Set Priorities Using Expert Opinion
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Geosciences 2018, 8(10), 379; https://doi.org/10.3390/geosciences8100379 - 16 October 2018
Abstract
Globally, there is a lack of resources to survey the vast seafloor areas in need of basic mapping data. Consequently, smaller areas must be prioritized to address the most urgent needs. We developed a systematic, quantitative approach and on-line application to gather mapping
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Globally, there is a lack of resources to survey the vast seafloor areas in need of basic mapping data. Consequently, smaller areas must be prioritized to address the most urgent needs. We developed a systematic, quantitative approach and on-line application to gather mapping suggestions from diverse stakeholders. Participants are each provided with 100 virtual coins to place throughout a region of interest to convey their mapping priorities. Inputs are standardized into a spatial framework using a grid and pull-down menus. These enabled participants to convey the types of mapping products that they need, the rationale used to justify their needs, and the locations that they prioritize for mapping. This system was implemented in a proposed National Marine Sanctuary encompassing 2784 km2 of Lake Michigan, Wisconsin. We demonstrate key analyses of the outputs, including coin counts, cell ranking, and multivariate cluster analysis for isolating high priority topics and locations. These techniques partition the priorities among the disciplines of the respondents, their selected justifications, and types of desired map products. The results enable respondents to identify potential collaborations to achieve common goals and more effectively invest limited mapping funds. The approach can be scaled to accommodate larger geographic areas and numbers of participants and is not limited to seafloor mapping.
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Simulations of Moisture Gradients in Wood Subjected to Changes in Relative Humidity and Temperature Due to Climate Change
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Geosciences 2018, 8(10), 378; https://doi.org/10.3390/geosciences8100378 - 15 October 2018
Abstract
Climate change is a growing threat to cultural heritage buildings and objects. Objects housed in historic buildings are at risk because the indoor environments in these buildings are difficult to control and often influenced by the outdoor climate. Hygroscopic materials, such as wood,
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Climate change is a growing threat to cultural heritage buildings and objects. Objects housed in historic buildings are at risk because the indoor environments in these buildings are difficult to control and often influenced by the outdoor climate. Hygroscopic materials, such as wood, will gain and release moisture during changes in relative humidity and temperature. These changes cause swelling and shrinkage, which may result in permanent damage. To increase the knowledge of climate-induced damage to heritage objects, it is essential to monitor moisture transport in wood. Simulation models need to be developed and improved to predict the influence of climate change. In a previous work, relative humidity and temperature was monitored at different depths inside wooden samples subjected to fluctuating climate over time. In this article, two methods, the hygrothermal building simulation software WUFI® Pro and the Simplified model, were compared in relation to the measured data. The conclusion was that both methods can simulate moisture diffusion and transport in wooden object with a sufficient accuracy. Using the two methods for predicted climate change data show that the mean RH inside wood is rather constant, but the RH minimum and maximum vary with the predicted scenario and the type of building used for the simulation.
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Landslide Disasters Triggered by Extreme Rainfall Events: The Case of Montescaglioso (Basilicata, Southern Italy)
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Geosciences 2018, 8(10), 377; https://doi.org/10.3390/geosciences8100377 - 15 October 2018
Abstract
We present the results of the study of a large and rapid landslide disaster event, which occurred in Montescaglioso, southern Italy, on 3 December 2013. The studied landslide developed following extreme rainfalls in a zone characterized by a stabilized paleo-landslide body and anthropized
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We present the results of the study of a large and rapid landslide disaster event, which occurred in Montescaglioso, southern Italy, on 3 December 2013. The studied landslide developed following extreme rainfalls in a zone characterized by a stabilized paleo-landslide body and anthropized in time, filling some streams of the original hydrographic network. The morpho-topographic setting characterizing the slope before the new landslide, has showed, in fact, a substantial stability confirmed also by the application of SINMAP (Stability Index MAPping) analysis. Nevertheless, heavy rains and floods caused a powerful and spectacular landslide event because of the anthropic removal of the old drainage network, which has caused the heaviness of the slope located upstream of the 20 collapsed buildings and along the ill-drained quick-road, built transversely to the slope.
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The Riding Trail as Geotourism Attraction: Evidence from Iceland
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Geosciences 2018, 8(10), 376; https://doi.org/10.3390/geosciences8100376 - 12 October 2018
Abstract
The geological aspects of tourism are much more extensive than just places to be viewed and/or experienced. The terrain traveled is also a geological phenomenon and an attraction in itself. For a hiker or a rider the type of trail is important. Features
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The geological aspects of tourism are much more extensive than just places to be viewed and/or experienced. The terrain traveled is also a geological phenomenon and an attraction in itself. For a hiker or a rider the type of trail is important. Features of the trail such as the gradient, altitude, the soil qualities, the length and the vistas it affords are important geological considerations. The trail as an experienced geological attraction, or should we say, the foundation for horse based tourism, particularly long rides, is the topic of this paper. The research is based on different sources. Existing data from earlier research on the Icelandic horse industry and equestrian tourism are used, as well as eight interviews conducted for this study. Further, the authors use their personal experiences as riders and horse tourists to reflect on the topic. Findings indicate that the riding trail and its surroundings can be defined as geosites and equestrian tourists as casual geotourists. The trails as geosites have different values for its stakeholders. The trails seem to have values such as scientific/educational, cultural/heritage, scenic and touristic values, just as other geosites. Furthermore, we argue that riding trails do have an economic value, as well as an emotional/romantic value.
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Paleoenvironment Variability during Termination I at the Reykjanes Ridge, North Atlantic
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Geosciences 2018, 8(10), 375; https://doi.org/10.3390/geosciences8100375 - 11 October 2018
Abstract
The micropaleontological study (radiolarians and foraminifera) of the sediment core AMK-340, Reykjanes Ridge, North Atlantic, combined with the radiocarbon dating and oxygen and carbon isotopic record, provided data for the reconstruction of the summer paleotemperature across the upper 100 meters water depth range,
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The micropaleontological study (radiolarians and foraminifera) of the sediment core AMK-340, Reykjanes Ridge, North Atlantic, combined with the radiocarbon dating and oxygen and carbon isotopic record, provided data for the reconstruction of the summer paleotemperature across the upper 100 meters water depth range, and paleoenvironments during the Termination I in the age interval of 14.5–8 ka. The response of the main microfossil species to the paleoceanographic changes within the Bølling-Allerød (BA) warming, the Younger Dryas (YD) cold event and final transition to the warm Holocene, was different. The BA warming was well captured by the radiolarian and benthic foraminiferal records, but not the planktic one. The high abundances of the cold-water radiolarian species Amphimelissa setosa as a Greenland/Iceland Sea indicator marked a cooling at the end of the BA and at the start of the YD at 13.2–12.3 ka. The micropaleontological and isotopic data together with the paleotemperature estimates for the Reykjanes Ridge at 60°N document that, after the warm BA, the middle YD ca. 12.5–12.2 ka was the next significant step toward the Holocene warming. The start of the Holocene interglacial conditions was reflected in large representation of the microfossils being indicators of the open boreal North Atlantic environments indicating increasing warmth.
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The Role of Climate: 71 ka of Atmospheric Mercury Deposition in the Southern Hemisphere Recorded by Rano Aroi Mire, Easter Island (Chile)
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Geosciences 2018, 8(10), 374; https://doi.org/10.3390/geosciences8100374 - 11 October 2018
Abstract
The study of mercury accumulation in peat cores provides an excellent opportunity to improve the knowledge on mercury cycling and depositional processes at remote locations far from pollution sources. We analyzed mercury concentrations in 150 peat samples from two cores from Rano Aroi
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The study of mercury accumulation in peat cores provides an excellent opportunity to improve the knowledge on mercury cycling and depositional processes at remote locations far from pollution sources. We analyzed mercury concentrations in 150 peat samples from two cores from Rano Aroi (Easter Island, 27° S) and in selected vegetation samples of present-day flora of the island, in order to characterize the mercury cycling for the last ~71 ka BP. The mercury concentrations showed values ranging between 35 and 200 ng g−1, except for a large maxima (~1000 ng g−1) which occurred at the end of the Last Glacial Maximum (LGM, ~20 ka cal BP) in both peat cores. Low temperatures during the LGM would accelerate the atmospheric oxidation of Hg(0) to divalent mercury that, coupled with higher rainfall during this period, most likely resulted in a very efficient surface deposition of atmospheric mercury. Two exceptional short-lived Hg peaks occurred during the Holocene at 8.5 (350 ng g−1) and 4.7 (1000 ng g−1) ka cal BP. These values are higher than those recorded in most peat records belonging to the industrial period, highlighting that natural factors played a significant role in Hg accumulation—sometimes even more so than anthropogenic sources. Our results suggest that wet deposition, linked to atmospheric oxidation, was the main process controlling the short-lived Hg events, both in the mire and in the catchment soils.
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Graphical abstract
Gravity Data Inversion with Method of Local Corrections for Finite Elements Models
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Geosciences 2018, 8(10), 373; https://doi.org/10.3390/geosciences8100373 - 10 October 2018
Abstract
We present a new method for gravity data inversion for the linear problem (reconstruction of density distribution by given gravity field). This is an iteration algorithm based on the ideas of local minimization (also known as local corrections method). Unlike the gradient methods,
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We present a new method for gravity data inversion for the linear problem (reconstruction of density distribution by given gravity field). This is an iteration algorithm based on the ideas of local minimization (also known as local corrections method). Unlike the gradient methods, it does not require a nonlinear minimization, is easier to implement and has better stability. The algorithm is based on the finite element method. The finite element approach in our study means that the medium (part of a lithosphere) is represented as a set of equal rectangular prisms, each with constant density. We also suggest a time-efficient optimization, which speeds up the inversion process. This optimization is applied on the gravity field calculation stage, which is a part of every inversion iteration. Its idea is to replace multiple calculations of the gravity field for all finite elements in all observation points with a pre-calculated set of uniform fields for all distances between finite element and observation point, which is possible for the current data set. Method is demonstrated on synthetic data and real-world cases. The case study area is located on the Timan-Pechora plate. This region is one of the promising oil- and gas-producing areas in Russia. Note that in this case we create a 3D density model using joint interpretation of seismic and gravity data.
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Assessment of Leachate Production from a Municipal Solid-Waste Landfill through Water-Balance Modeling
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Geosciences 2018, 8(10), 372; https://doi.org/10.3390/geosciences8100372 - 10 October 2018
Abstract
Mineral temporary capping systems of landfills are required to accomplish the long-term coverage prerequisites or to use them as a basis layer prior to later permanent sealing. Such a capping system for a municipal waste landfill in Rastorf (Northern Germany) was developed and
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Mineral temporary capping systems of landfills are required to accomplish the long-term coverage prerequisites or to use them as a basis layer prior to later permanent sealing. Such a capping system for a municipal waste landfill in Rastorf (Northern Germany) was developed and tested for its sealing capability on the basis of observed and simulated water balance components for the period between 2008 and 2015, considering observed local weather data and complemented by the Hydraulic Evaluation of Landfill Performance (HELP 3.95 D) model. The modeling results of this case study could be improved by the correction of previously used global solar radiation data due to the consideration of exposure and inclination angle of landfill surface areas. The model could positively be validated by comparing observed and simulated outflow (surface runoff and lateral drainage) data with R2 values ranging between 0.95 and 0.99, as well as for the leachate rates with R2 values of 0.78–0.87. The statistical-empirical HELP model was found useful in predicting the leachate generation of a temporary landfill capping system for specific soil and site conditions, even if only a restricted set of observed data was available.
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Graphical abstract
A Novel Method for Evaluation of Flood Risk Reduction Strategies: Explanation of ICPR FloRiAn GIS-Tool and Its First Application to the Rhine River Basin
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Geosciences 2018, 8(10), 371; https://doi.org/10.3390/geosciences8100371 - 6 October 2018
Abstract
To determine the effects of measures on flood risk, the International Commission for the Protection of the Rhine (ICPR), supported by the engineering consultant HKV has developed a method and a GIS-tool named “ICPR FloRiAn (Flood Risk Analysis)”, which enables the broad-scale assessment
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To determine the effects of measures on flood risk, the International Commission for the Protection of the Rhine (ICPR), supported by the engineering consultant HKV has developed a method and a GIS-tool named “ICPR FloRiAn (Flood Risk Analysis)”, which enables the broad-scale assessment of the effectiveness of flood risk management measures on the Rhine, but could be also applied to other rivers. The tool uses flood hazard maps and associated recurrence periods for an overall damage and risk assessment for four receptors: human health, environment, culture heritage, and economic activity. For each receptor, a method is designed to calculate the impact of flooding and the effect of measures. The tool consists of three interacting modules: damage assessment, risk assessment, and measures. Calculations using this tool show that the flood risk reduction target defined in the Action Plan on Floods of the ICPR in 1998 could be achieved with the measures already taken and those planned until 2030. Upon request, the ICPR will provide this tool and the method to other river basin organizations, national authorities, or scientific institutions. This article presents the method and GIS-tool developed by the ICPR as well as first calculation results.
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A Methodology for Long-Term Monitoring of Climate Change Impacts on Historic Buildings
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Geosciences 2018, 8(10), 370; https://doi.org/10.3390/geosciences8100370 - 4 October 2018
Abstract
A new methodology for long-term monitoring of climate change impacts on historic buildings and interiors has been developed. This paper proposes a generic framework for how monitoring programs can be developed and describes the planning and arrangement of a Norwegian monitoring campaign. The
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A new methodology for long-term monitoring of climate change impacts on historic buildings and interiors has been developed. This paper proposes a generic framework for how monitoring programs can be developed and describes the planning and arrangement of a Norwegian monitoring campaign. The methodology aims to make it possible to establish a data-driven decision making process based on monitored decay related to climate change. This monitoring campaign includes 45 medieval buildings distributed over the entirety of Norway. Thirty-five of these buildings are dated to before 1537 and include wooden buildings as well as 10 medieval churches built in stone while the remaining 10 buildings are situated in the World Heritage sites of Bryggen, in Bergen on the west coast of Norway, and in Røros, which is a mining town in the inland of the country. The monitoring is planned to run for 30 to 50 years. It includes a zero-level registration and an interval-based registration system focused on relevant indicators, which will make it possible to register climate change-induced decay at an early stage.
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Application of Radial Basis Functions for Height Datum Unification
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Geosciences 2018, 8(10), 369; https://doi.org/10.3390/geosciences8100369 - 2 October 2018
Abstract
Local gravity field modelling demands high-quality gravity data as well as an appropriate mathematical model. Particularly in coastal areas, there may be different types of gravity observations available, for instance, terrestrial, aerial, marine gravity, and satellite altimetry data. Thus, it is important to
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Local gravity field modelling demands high-quality gravity data as well as an appropriate mathematical model. Particularly in coastal areas, there may be different types of gravity observations available, for instance, terrestrial, aerial, marine gravity, and satellite altimetry data. Thus, it is important to develop a proper tool to merge the different data types for local gravity field modelling and determination of the geoid. In this study, radial basis functions, as a commonly useful tool for gravity data integration, are employed to model the gravity potential field of the southern part of Iran using terrestrial gravity anomalies, gravity anomalies derived from re-tracked satellite altimetry, marine gravity anomalies, and gravity anomalies synthesized from an Earth gravity model. Reference GNSS/levelling (geometric) geoidal heights are used to evaluate the accuracy of the estimated local gravity field model. The gravimetric geoidal heights are in acceptable agreement with the geometric ones in terms of the standard deviation and the mean value which are 4.1 and 12 cm, respectively. Besides, the reference benchmark of the national first-order levelling network of Iran is located in the study area. The derived gravity model was used to compute the gravity potential difference at this point and then transformed into a height difference which results in the value of the shift of this benchmark with respect to the geoid. The estimated shift shows a good agreement with previously published studies.
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Geotourism Perspectives for Transhumance Routes. Analysis, Requalification and Virtual Tools for the Geoconservation Management of the Drove Roads in Southern Italy
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Geosciences 2018, 8(10), 368; https://doi.org/10.3390/geosciences8100368 - 1 October 2018
Abstract
The article illustrates the interest in transhumance routes, the ancient paths connecting high and lowland pastures in Southern Italy and other Mediterranean regions, as elements of particular importance for sustainable geotourism management. As a contribution to the needs of requalification of the drove
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The article illustrates the interest in transhumance routes, the ancient paths connecting high and lowland pastures in Southern Italy and other Mediterranean regions, as elements of particular importance for sustainable geotourism management. As a contribution to the needs of requalification of the drove roads, we propose a method of analysis for their preservation and their reuse for geotourism purposes, showing the steps and instruments necessary to organize, enhance and communicate transhumance routes as integrated cultural landscapes. Results are presented as applied to a specific case study (Molise, IT) of a geoconservation management proposal for the assessment of the state of conservation of the drove roads, of their cultural heritage and of their potential reuse for geotourism. This methodological proposal uses geographical information systems, historical sources, cartography and remote sensing techniques and includes 3D virtual reconstructions of the transhumance landscape. The article is meant to contribute to a non-stereotyped image of transhumance geoheritage, reflecting on communication and learning strategies supported by geo-historical analyses, in order to promote a greater awareness of landscapes genesis and evolution for visitors and local communities. It is argued that future challenges of geotourism relate to the ability to recompose nature and culture to an interpretive unity, both from a theoretical and operative point of view, and that the goal is to reach an integrated tourist offer focused on the relationship between man and environment with the signs of territorialisation processes expressed through economic vocations, traditional production chains, cultural values and territorial identity. To this purpose, the valorisation of the transhumance routes—for their historical-economic, ecological, landscape, patrimonial and identity meanings—seems to respond perfectly.
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Pressure–Temperature History of the >3 Ga Tartoq Greenstone Belt in Southwest Greenland and Its Implications for Archaean Tectonics
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Geosciences 2018, 8(10), 367; https://doi.org/10.3390/geosciences8100367 - 30 September 2018
Abstract
The Tartoq greenstone belt of southwest Greenland represents a well-preserved section through >3 Ga old oceanic crust and has the potential to provide important constraints on the composition and geodynamics of the Archaean crust. Based on a detailed structural examination, it has been
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The Tartoq greenstone belt of southwest Greenland represents a well-preserved section through >3 Ga old oceanic crust and has the potential to provide important constraints on the composition and geodynamics of the Archaean crust. Based on a detailed structural examination, it has been proposed that the belt records an early style of horizontal convergent plate tectonics where elevated temperatures, compared to the modern-day, led to repeated aborted subduction and tonalite–trondhjemite–granodiorite (TTG) type melt formation. This interpretation hinges on pressure–temperature (P–T) constraints for the belt, for which only preliminary estimates are currently available. Here, we present a detailed study of the pressure–temperature conditions and metamorphic histories for rocks from all fragments of the Tartoq belt using pseudosection modelling and geothermobarometry. We show that peak conditions are predominantly amphibolite facies, but range from 450 to 800 °C at up to 7.5 kbar; reaching anatexis with formation of TTG-type partial melts in the Bikuben segment. Emplacement of the Tartoq segments into the host TTG gneisses took place at approximately 3 Ga at 450–500 °C and 4 kbar as constrained from actinolite–chlorite–epidote–titanite–quartz parageneses, and was followed by extensive hydrothermal retrogression related to formation of shear zone-hosted gold mineralisation. Tourmaline thermometry and retrograde assemblages in mafic and ultramafic lithologies constrain this event to 380 ± 50 °C at a pressure below 1 kbar. Our results show that the convergent tectonics recorded by the Tartoq belt took place at a P–T gradient markedly shallower than that of modern-day subduction, resulting in a hot, weak and buoyant slab unable to generate and transfer ‘slab pull’, nor sustain a single continuous downgoing slab. The Tartoq belt suggests that convergence was instead accomplished by under-stacking of slabs from repeated aborted subduction. The shallow P–T path combined with thermal relaxation following subduction stalling subsequently resulted in partial melting and formation of TTG melts.
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The Use of High-Resolution Historical Images to Analyse the Leopard Pattern in the Arid Area of La Alta Guajira, Colombia
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Geosciences 2018, 8(10), 366; https://doi.org/10.3390/geosciences8100366 - 29 September 2018
Abstract
A recent review of global arid areas supports the idea that there are two patterns to vegetation in arid lands. Patches of thick vegetation alternate with those with much less vegetation or none at all. There is a specific size, shape and spatial
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A recent review of global arid areas supports the idea that there are two patterns to vegetation in arid lands. Patches of thick vegetation alternate with those with much less vegetation or none at all. There is a specific size, shape and spatial distribution that characterizes vegetation patterns in arid land ecosystems. In some places, the patches have irregular shapes; these are called spots or Leopard bush. This research project is based on a biophysical approach that integrates information collected in the field, high resolution historical satellite images and Geographical Information System technology. The results revealed that there were certain places in the landscape that facilitate the singular development of the vegetation. The Leopard pattern results from the interaction of various factors (fertility island, fragmentation of vegetation, anthropic influence, herbivorism). Specific characteristics that limit plant life forms are found in the area; since only certain resistant species develop, these form associations and in turn generate strategies to optimize resources. Eventually, this equilibrium is disturbed by human activities in the shape of ungulate livestock breeding and anthropogenic activities, resulting in a heterogeneity of soils and vegetation whose interaction generates the pattern.
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Microlensing Searches for Exoplanets
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Geosciences 2018, 8(10), 365; https://doi.org/10.3390/geosciences8100365 - 29 September 2018
Abstract
Gravitational microlensing finds planets through their gravitational influence on the light coming from a more distant background star. The presence of the planet is then inferred from the tell-tale brightness variations of the background star during the lensing event, even if no light
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Gravitational microlensing finds planets through their gravitational influence on the light coming from a more distant background star. The presence of the planet is then inferred from the tell-tale brightness variations of the background star during the lensing event, even if no light is detectable from the planet or the host foreground star. This review covers fundamental theoretical concepts in microlensing, addresses how observations are performed in practice, the challenges of obtaining accurate measurements, and explains how planets reveal themselves in the data. It concludes with a presentation of the most important findings to-date, a description of the method’s strengths and weaknesses, and a discussion of the future prospects of microlensing.
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