Morphometric and landsliding analyses in chain domain: the Roccella basin,NE Sicily,Italy

The dynamic interaction of endogenic and exogenic processes in active geodynamic context leads to the deterioration of the physico-mechanical characteristics of the rocks, inducing slopes instability. In such context, the morphometric parameters and the analysis of landslide distribution contribute to appraise the evolutive state of hydrographic basins. The aim of the study is the morphometric characterization of the Roccella Torrent basin (Rtb) located in South Italy. Landsliding and tectonic structure dynamically interact with the drainage pattern that records these effects and permits the definition of the evolutive geomorphic stage of the basin. The Air Photograph Investigation and field surveys permitted to draw the main geomorphic features, the drainage pattern of the Rtb, to calculate the morphometric parameters and to delimit the landslides’ bodies. Detailed analysis about the landslide distribution within a test site 17 km² wide were carried out to elaborate indicative indexes of the landslides type and to single out the lithotypes that are more involved in slope instability phenomena. The morphometric parameters indicate the rejuvenation state within the Rtb where the stream reaches show the effects of increased energy relief in agreement with the geological settings of this sector of the Apennine–Maghrebian Chain.     

Carbon dioxide degassing and thermal energy release in the Monte Amiata volcanic-geothermal area (Italy)

The quaternary volcanic complex of Mount Amiata is located in southern Tuscany (Italy) and represents the most recent manifestation of the Tuscan Magmatic Province. The region is characterised by a large thermal anomaly and by the presence of numerous CO₂-rich gas emissions and geothermal features, mainly located at the periphery of the volcanic complex. Two geothermal systems are located, at increasing depths, in the carbonate and metamorphic formations beneath the volcanic complex. The shallow volcanic aquifer is separated from the deep geothermal systems by a low permeability unit (Ligurian Unit). A measured CO₂ discharge through soils of 1.8 × 10⁹ mol a⁻¹ shows that large amounts of CO₂ move from the deep reservoir to the surface. A large range in δ¹³C_TDIC (−21.07 to +3.65) characterises the waters circulating in the aquifers of the region and the mass and isotopic balance of TDIC allows distinguishing a discharge of 0.3 × 10⁹ mol a⁻¹ of deeply sourced CO₂ in spring waters. The total natural CO₂ discharge (2.1 × 10⁹ mol a⁻¹) is slightly less than minimum CO₂ output estimated by an indirect method (2.8 × 10⁹ mol a⁻¹), but present-day release of 5.8 × 10⁹ mol a⁻¹ CO₂ from deep geothermal wells may have reduced natural CO₂ discharge. The heat transported by groundwater, computed considering the increase in temperature from the infiltration area to the discharge from springs, is of the same order of magnitude, or higher, than the regional conductive heat flow (>200 mW m⁻²) and reaches extremely high values (up to 2700 mW m⁻²) in the north-eastern part of the study area. Heat transfer occurs mainly by conductive heating in the volcanic aquifer and by uprising gas and vapor along fault zones and in those areas where low permeability cover is lacking. The comparison of CO₂ flux, heat flow and geological setting shows that near surface geology and hydrogeological setting play a central role in determining CO₂ degassing and heat transfer patterns.     

Structural control over equilibrium silicon and oxygen isotopic fractionation: A first-principles density-functional theory study

Isotopic fractionation factors for oxygen and silicon in selected silicates (quartz, enstatite, forsterite, lizardite, kaolinite) are calculated using first-principles methods based on density-functional theory. Good agreement between theory and experiment is found in the case of oxygen. In the case of silicon, agreement and differences with existing estimates of equilibrium fractionation factors are discussed. The relationship between silicon and oxygen fractionation factors, silicate polymerization degree and chemical composition is studied and compared with previous semi-empirical models.     

Polymorphism of As4S3 (tris-(μ2-sulfido)-tetra-arsenic): accurate structure refinement on natural α- and β-dimorphites and inferred room temperature thermodynamic properties

An accurate structure refinement, using single-crystal X-ray diffraction data, on natural α- and β-dimorphites collected at Solfatara di Pozzuoli, in the Phlegraean Fields, near Naples and at Vesuvius (Italy) is reported. Theoretical calculations at various levels of sophistication have been used to calculate molecular vibrational frequencies and gas-phase specific heats, to analyze the crystal packing, and to estimate lattice energies of both phases. All computational methods contribute to demonstrate that the β-phase is the thermodynamically stable one at room temperature.     

Exploiting historical rainfall and landslide data in a spatial database for the derivation of critical rainfall thresholds

Critical rainfall thresholds for landslides are powerful tools for preventing landslide hazard. The thresholds are commonly estimated empirically starting from rainfall events that triggered landslides in the past. The creation of the appropriate rainfall–landslide database is one of the main efforts in this approach. In fact, an accurate agreement between the landslide and rainfall information, in terms of location and timing, is essential in order to correctly estimate the rainfall–landslide relationships. A further issue is taking into account the average moisture conditions prior the triggering event, which reasonably may be crucial in determining the sufficient amount of precipitation. In this context, the aim of this paper is exploiting historical landslide and rainfall data in a spatial database for the derivation of critical rainfall thresholds for landslide occurrence in Sicily, southern Italy. The hourly rainfall events that caused landslides occurred in the twentieth century were specifically identified and reconstructed. A procedure was proposed to automatically convert rain guages charts recorded on paper tape into digital format and then to provide the cumulative rainfall hyetograph in digital format. This procedure is based on a segmentation followed by signal recognition techniques which allow to digitalize and to recognize the hyetograph automatically. The role of rainfall prior to the landslide events was taken into account by including in the analysis the rainfall occurred 5, 15 and 30 days before each landslide. Finally, cumulated rainfall duration thresholds for different exceedance probability levels were determined. The obtained thresholds resulted in agreement with the regional curves proposed by other authors for the same area; antecedent rainfall turned out to be particularly important in triggering landslides.     

La nuova carta magnetica d'Italia (Isogone al 1° gennaio 1940) dell'Istituto Geografico Militare

Riassunto L'Autore, accennato alla carta del Palazzo del 1892 e dimostrata la necessità di una più precisa carta rispondente alle accresciute esigenze civili e militari, tratta del nuovo rilievo magnetico d'Italia basato su ben 1529 stazioni eseguite dall'Istituto Geografico Militare dal 1932 al 1937 e quindi della nuova carta magnetica con le isogone al 1° gennaio 1940 testé pubblicata dallo stesso Istituto.

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Zusammenfassung Der Verf., nach Erwähnung der erdmagnetischen Karte von Palazzo des Jahres 1892 hervorhebt die Notwendigkeit einer genaueren den vermehrten zivilen und militärischen Ansprüchen entsprechender Aufnahme; eine solche neue erdmagnetische Aufnahme Italiens ist vom Istituto Geografico Militare in den Jahren 1932–1937 durchgeführt worden und zwar mit zusammen 1529 Stationen. Diese Arbeit wird beschrieben und erörtet besonders in Zusammenhang mit der hier vorgestellten neuen Isogonen-Kart, bezogen auf dem 1. Januar 1940.

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Résumé L'Auteur, après avoir mentionné la carte magnétique du Prof. Palazzo (1892) et démontré la nécessité d'une carte plus précise et plus correspondante à l'accroissement des exigences civiles et militaires, s'entretient sur le nouveau levé magnétique d'Italie, qui se base sur les observations de 1529 stations, esecutées par l'Istituto Geografico Militare entre 1932 et 1937; ensuite il illustre la nouvelle carte magnétique des isogones, au l.er Janiver 1940, qui vient d'être publiée par le même Institut et qui est jointe au présent mémoire.

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Quest'articolo è in parte un riassunto di quanto io stesso ebbi a scrivere in alcune memorie precedenti edite dall'Istituto Geografico Militare e dalla Società Italiana per il Progresso delle Scienze.     

Classifying zones of suitability for manual drilling using textural and hydraulic parameters of shallow aquifers: a case study in northwestern Senegal

A method is proposed that uses analysis of borehole stratigraphic logs for the characterization of shallow aquifers and for the assessment of areas suitable for manual drilling. The model is based on available borehole-log parameters: depth to hard rock, depth to water, thickness of laterite and hydraulic transmissivity of the shallow aquifer. The model is applied to a study area in northwestern Senegal. A dataset of boreholes logs has been processed using a software package (TANGAFRIC) developed during the research. After a manual procedure to assign a standard category describing the lithological characteristics, the next step is the automated extraction of different textural parameters and the estimation of hydraulic conductivity using reference values available in the literature. The hydraulic conductivity values estimated from stratigraphic data have been partially validated, by comparing them with measured values from a series of pumping tests carried out in large-diameter wells. The results show that this method is able to produce a reliable interpretation of the shallow hydrogeological context using information generally available in the region. The research contributes to improving the identification of areas where conditions are suitable for manual drilling. This is achieved by applying the described method, based on a structured and semi-quantitative approach, to classify the zones of suitability for given manual drilling techniques using data available in most African countries. Ultimately, this work will support proposed international programs aimed at promoting low-cost water supply in Africa and enhancing access to safe drinking water for the population.     

The relation between karst spring discharge and rainfall by cross-correlation analysis (Campania, southern Italy)

The relation between rainfall and the discharge from two springs, located at the base of different karst massifs in southern Italy, is investigated by cross-correlation analyses. Data are derived from a continuous time window of 13 years. The input signal involves multiple rainfall time series (cumulative rainfall over varying time windows), while the time series of daily spring discharges are used as the output signal. Analyses were first conducted on the unprocessed data and then on data for which linear trends and seasonal components had been removed, the latter by a spectral analysis. Analyses contributed to the investigation of the time required for water to flow through the karst aquifers at the two sites. Long time intervals of the cumulative rainfall (>60 days) appear to be the main component affecting the spring discharge hydrographs; shorter time intervals seem to be related to quick-flow paths. Some statistics about the linear regression and the meaning of the cross-correlation analysis are discussed. Cross-correlation analysis can provide strong support for identification of the main rainfall contribution and the travel time through the main infiltration pathways in aquifers.     

Rheological characteristics of debris-flow material in South-Gargano watersheds

In recent years, debris flows have represented a severe natural hazard in South-Gargano watersheds (Puglia Region, Southern Italy). Hill slopes erosion, caused by the inadequate protection of the degraded forests, produces large amounts of soil and debris that are conveyed downstream during heavy rainstorms. The involved material is characterized by limestone fragments and blocks in a sandy-silt matrix. In this paper, the rheological properties of such debris-flow materials have been investigated. Eight specimens of particulated sediments of particle diameter of d ≤ 4 mm have been analysed using a rheometric tool for large particle suspensions, the ball measuring system (BMS). The influence of sediment concentration on the bulk rheological behaviour has been evaluated at concentrations by volume obtained in fully water-saturated conditions (volumetric sediment concentration C _V ~ 0.8) and with fixed water content (C _V = 0.42). The rheological data were fitted to the Bingham, Herschel–Bulkley, and O’Brien and Julien models to define viscosity and yield stress dependency on sediment concentration, to provide viscosity information for hazard mitigation as well as for comparison to other debris-flow events.     

A low plain between arcadia and agronomy: Ippolito Nievo and the Friulan landscape

An analysis of the historical and cultural context of a large number of literary works illuminates the concept of landscape, a recurrent theme in contemporary humanistic geography. In this context, the works of Ippolito Nievo present an opportunity to look closer at the socio-economic circumstances of his time while also offering suggestive interpretative elements about the attitudes held concerning the wetlands of the lower Friulan plain.