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Margreth S.,WSL Institute for Snow and Avalanche Research SLF | Faillettaz J.,ETH Zurich | Funk M.,ETH Zurich | Vagliasindi M.,Fondation Montagne SUre | And 2 more authors.
Cold Regions Science and Technology

The Whymper glacier is a hanging glacier located on the south face of the Grandes Jorasses (Mont Blanc Massif, Italy). Combined snow and ice avalanches triggered by ice masses breaking off from the hanging glacier endanger the village of Planpincieux and its surroundings in the Val Ferret. In 1997, the SLF and the VAW developed the first safety concept for the village for several scenarios based on the monitoring of the glacier and an assessment of the local avalanche hazard. At the end of June 1998 almost the entire Whymper glacier (around 150,000m3) sheared off and the ice avalanche stopped only 500m above the valley road. The Whymper glacier has grown back and now has a similar surface topography as in 1998. The SLF and VAW improved the 1997 safety concept by considering several scenarios of falling ice volumes. The different ice avalanche scenarios were simulated using the 2-dimensional calculation model RAMMS. The necessary safety measures are defined in relation to the local avalanche danger level and the potential volume of an icefall. The hanging glacier is continuously monitored with a system consisting of a total station, GPS-stations, seismic sensors and visual observations. The improved safety concept has been operational since 2009. However, a dangerous icefall has not occurred yet. © 2011 Elsevier B.V.. Source

Ciarapica G.,University of Perugia | Passeri L.,University of Perugia | Bonetto F.,Regione Autonoma Valle dAosta | Piaz G.V.D.,Accademia Delle Science
Swiss Journal of Geosciences

The Roisan zone is a metamorphic cover unit exposed along the ductile shear zone between the Dent Blanche s.s. and Mont Mary-Cervino Upper Austroalpine outliers, Aosta Valley, north-western Italian Alps. It is characterized by the occurrence of dolostones, pure marbles, marbles with quartz, calcirudites and ophiolite-free calcschists. Locally, dolostones preserve alternances of thick massive beds and thinner levels of planar stromatolites and other sedimentary structures and textures typical of a carbonate platform. In Mt Grand Pays they contain Dasycladales and foraminifers referable to the Norian. Pure marbles and marbles with quartz grains are tentatively referred to the end of Triassic–Early Jurassic, thin-bedded marbles and calcirudites to the Early and Middle Jurassic, calcschists from Middle Jurassic to Late Cretaceous. This Roisan succession is quite similar to the one of Mt Dolin, in the Swiss part of the Dent Blanche nappe, where the same Triassic foraminifer association has been reported. There, the fossils were found only in reworked pebbles, contained in calcirudites of presumed Jurassic age. Some differences exist between the two successions: calcirudites are abundant in the Mt Dolin and sporadic in the Roisan zone, whereas calcschists are very thick in the Roisan zone. As consequence the Mt Dolin succession can be considered settled down in the proximity of the faults related to the pre-oceanic rifting of the Piedmont basin, whereas the Roisan zone could have been deposited in a more distal area. © 2016 Swiss Geological Society Source

Isotta F.A.,Federal Office of Meteorology and Climatology MeteoSwiss | Frei C.,Federal Office of Meteorology and Climatology MeteoSwiss | Weilguni V.,Bundesministerium fur Land und Forstwirtschaft | Percec Tadic M.,Meteorological and Hydrological Service of Croatia | And 14 more authors.
International Journal of Climatology

In the region of the European Alps, national and regional meteorological services operate rain-gauge networks, which together, constitute one of the densest in situ observation systems in a large-scale high-mountain region. Data from these networks are consistently analyzed, in this study, to develop a pan-Alpine grid dataset and to describe the region's mesoscale precipitation climate, including the occurrence of heavy precipitation and long dry periods. The analyses are based on a collation of high-resolution rain-gauge data from seven Alpine countries, with 5500 measurements per day on average, spanning the period 1971-2008. The dataset is an update of an earlier version with improved data density and more thorough quality control. The grid dataset has a grid spacing of 5 km, daily time resolution, and was constructed with a distance-angular weighting scheme that integrates climatological precipitation-topography relationships. Scales effectively resolved in the dataset are coarser than the grid spacing and vary in time and space, depending on station density. We quantify the uncertainty of the dataset by cross-validation and in relation to topographic complexity, data density and season. Results indicate that grid point estimates are systematically underestimated (overestimated) at large (small) precipitation intensities, when they are interpreted as point estimates. Our climatological analyses highlight interesting variations in indicators of daily precipitation that deviate from the pattern and course of mean precipitation and illustrate the complex role of topography. The daily Alpine precipitation grid dataset was developed as part of the EU funded EURO4M project and is freely available for scientific use. © 2013 Royal Meteorological Society. Source

Comina C.,University of Turin | Forno M.G.,University of Turin | Gattiglio M.,University of Turin | Gianotti F.,University of Turin | And 2 more authors.
Italian Journal of Geosciences

One of the few examples of high mountain prehistorical archaeo-logical sites in northern Italy has been discovered within the so called Plan di Modzon area, at 2300 m a.s.l., in the Aosta Valley (Western Alps). This area shows interesting geological features and morphological evidence which have been recently linked to a wide Deep-Seated Gravitational Slope Deformation (DSGSD). A probable filled lake and the presence of buried landforms have been also hypno tized on the basis of geological observations, resulting in the need for new devoted surveys to confirm these hypotheses. A better and comprehensive understanding of the geological evolution of the area is indeed necessary to allow a precise reconstruction of the environments in which man has inhabited these territories. Combined Electric Resistivity Tomographies (ERT) and geological surveys have been therefore used to better define the occurrence and nature of morphological evidence along the western slope of the filled lake, in which one of the archaeological sites has been discovered and excavated. The outcomes of the integration of the two surveys is a more refined definition of the geological forms, in respect to the one previously assumed on the basis of surface surveys only. Indeed, ERT revealed buried zones with low resistivity associable to the presence of sliding surfaces and also showed the geometry and thickness of the sediments within the filled lake. Geological surveys also evidenced a DSGSD evolution in the area constrained to Lateglacial, because of the lack of particularly evident gravitative forms, i.e. remodeled by glacial abrasion. © 2015 Società Geologica Italiana, Roma. Source

Forno M.G.,University of Turin | Gattiglio M.,University of Turin | Gianotti F.,University of Turin | Guerreschi A.,University of Ferrara | Raiteri L.,Regione Autonoma Valle dAosta
Quaternary International

The Plan di Modzon is a mountain area (2300m) located in the Verrogne Valley, NW of Aosta (Western Alps). It occurs along the contact between the Middle Penninic (micaschist and gneiss from the Gran San Bernardo Nappe) and the overlying upper units of the Piedmont Zone (carbonate calcschist alternating with marble).This area, largely shaped by Pleistocene glaciers, was involved in a wide deep-seated gravitational slope deformation (Pointe Leysser DSGSD) on the western extension of the Becca France doubled ridges. Several ridges that were affected by glacial erosion, discontinuously covered by glacial sediments, are present throughout the area. Extremely fractured rocks and various gravitational forms (minor scarps and trenches) mark the DSGSD.Several archaeological sites (MF1-MF9) have recently been found between 2242 and 2292m asl. They have revealed artifacts of rock crystal (hyaline quartz) referred to the Sauveterrian stage of the Mesolithic. An ensemble of other archaeological evidence is referred to the Copper Age. The investigation in progress specifically concerns the systematic excavation of sites MF1 and MF3.Some concomitant morphological factors have created very favorable conditions for prehistoric settlements in the Plan di Modzon area, including the exceptionally wide valley floor directly perched on the main Dora Baltea Valley, in consequence of the Verrogne Glacier diversion promoted by the P. Leysser DSGSD. Easy and direct accessibility to this area is provided by the gently-dipping slope of the Dora Baltea Valley affected by the DSGSD. The ridged and grooved morphology as the result of the glacial and gravitational interaction, offered wide surfaces free from geological hazards (debris flow and avalanche processes). The DSGSD is, therefore, one of the primary causes of the archaeological settlement of this area, contributing to create a morphology adapted to prehistoric settlements. © 2013 Elsevier Ltd and INQUA. Source

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