The Goli d'Aget Member: Early Permian volcanoclastic and volcanic rocks within the Briançonnais Grand St-Bernard Nappe (Valais, Switzerland)

Abstract.: The well-preserved sedimentary structures of the Goli d'Aget Member (Early Permian) allow to distinguish four successive environments of deposition: 1) An alluvial plain with important channeling and evidence of volcanic activity; 2) A shallow lacustrine environment with a low water level, deposition of massive carbonates and an increasing contribution of volcanic materials; 3) A fluviatile plain with the deposition of volcanic tuffs; 4) A deltaic to lacustrine environment occasionally covered by pyroclastic flows. An ignimbritic rhyolite from the upper part of the Goli d'Aget Member has an age of 267-282 Ma (U-Pb on zircon). Major and trace elements, as well as zircon typology point to a calc-alkaline and volcanic-arc affinity for that high-silica rhyolite. The Goli d'Aget Member may be the best-preserved unit among the Permian units from the Swiss Penninic Western Alps. This series provides an important point of comparison with other local Permian units (Dent de Nendaz and Cleuson Members) and with similar series in the Western Alps including the Melogno porphyroids in the Ligurian Alps and the Rochachille Series near Briançon (France

An Open-Source WebGIS Platform for Rapid Disaster Impact Assessment

Natural disaster impacts have increased worldwide in the past decades. Earthquake is one of the disasters that have been studied for real-time analysis and crisis management. Disaster-related losses have been examined by the damage extent of the houses, infrastructures, fatalities and injuries converted to financial losses. WebGIS technologies provide a wide range of solutions to map those damages, analyse data and publish the results. Open-Source tools and data have been widely used today because they stay free and facilitate access to data especially significant in developing countries. This research presents a WebGIS prototype using Open-Source Geo-Spatial technologies such as PostGIS, Geoserver, Geoexplorer and OpenStreetMap (OSM) to evaluate the rapid impact of naturally produced disasters for the total damages. For this purpose, expert knowledge, such as earthquake intensities and vulnerability inputs are imported into the system and the loss of the damage is rapidly estimated. This work is part of a project for catastrophe modeling based on Open-Source data and software. We hope that applying Open-Source knowledge and solutions will decrease the time and efforts needed for rapid disaster and catastrophe management

Urban risks and resilience in the rwandan context

The rapid urbanization in Rwanda, a country with a disrupted habitat culture has led to a congestion of the capital, which concentrates all services. This has, among other things, a particular form of nature and impacts of natural hazards. Within the context of the natural hazards of Rwanda, we address the problems of the natural hazards due to rains in a watershed of Kigali (natural hazards analysis database and GIS data problematics) and Ruhengeri. Debris flows / landslides modelling are performed including source areas identification and potential propagation zones, with regard to the built-up areas and available maps. This is integrated in a conceptual multi-hazards and complex natural systems for the two cities. It demonstrates the highly complex situation at risk and how people were resilient before "modernity". This leads us to develop a plan dedicated to the communication of sustainable solutions, to make solutions possible

Evaluation Of An Open-Source Collaborative WebGIS Prototype In Risk Management With Students

Over the past decades, advancements in web services and web-based geospatial technologies have led to increasing delivery, access and analysis of rich spatial information over the web. With the use of open access data and open-source technology, it has become possible to make better, transparent and informed decisions for policy and decision makers. Under the framework of the European Marie Curie CHANGES project, a prototype web-based collaborative decision support platform was developed for the evaluation and selection of risk management strategies, mainly targeting flood and landslide hazards. The design of the conceptual framework was based on the initial feedback and observations obtained from field visits and stakeholder meetings of the case study areas of the project. A three-tier client-server architecture backed up by Boundless (OpenGeo) was applied with its client side development environment for rapid prototyping. The developed prototype was tested with university students to obtain feedback on the conceptual and technical aspects of the platform as well as to analyze how the application of interactive tools in the exercise could assist students in studying and understanding risk management. During the exercise, different roles (authorities, technicians, community) were assigned to each group of students for identification and selection of risk mitigation measures in the study area: Cucco village located in MalborghettoValbruna commune of North- Eastern Italy. Data were collected by means of written feedback forms on specific aspects of the platform and the exercise. A subsequent analysis of the feedback reveals that students with previous experience in GIS (Geographical Information Systems) responded positively and showed interests in performing exercises with such kinds of interactive tools for learning, compared to the ones with fewer or no GIS experience. These results also show that the prototype is useful and supportive as a decision support tool in risk management while userfriendliness, interactivity and practical aspects of the platform could be further improved

The neglected role of karst features in rock mass characterization and stability assessment

Stability analyses in karst settings, whether to assess the equilibrium conditions of natural slopes or to design engineering interventions, coexist with a significant uncertainty related to difficulties in modelling karst features. As a matter of fact, most of the rock mass classification systems do not directly take into account the presence of karst structures such as voids, conduits or caves, which can strongly influence the mechanical behaviour and the water flow in rock masses. In the last decades, the identification and characterization of discontinuity systems for rock mass characterization, aimed at stability analyses, have been intensively investigated by means of remote sensing techniques. However, semi-automatic or automatic methods for the extraction of discontinuities from point clouds are not easily applicable in karst because surface and subsurface features produce irregular surfaces, which are difficult to classify even using the most-advanced algorithms. This occurs even more heavily in the case of soft rocks, such as calcarenites. In this study, a demonstration of the influence of karst features in rock mass characterization and slope stability assessment is presented. First, the results of the Discontinuity Set Extractor (DSE) software used on an appropriate case study show that the irregular surfaces produced by carbonate dissolution, further enhanced by weathering, caused an incorrect classification of the discontinuity sets. Second, a high-resolution Digital Outcrop Model (DOM) was used to generate a very fine mesh (average element size = 35 cm, to take into account the large-scale karst structures) and to carry out 3-D numerical stability analyses by means of Finite Element Method, using a continuum-based approach. Although in the current conditions the examined slope is stable, the results illustrate that the maximum shear strain is localized in correspondence of the karst features (e.g. caves and voids) and at the sea level. By applying the Shear Strength Reduction method, it was found out that weathering processes can cause the same structures to be under yield and lead to localized failures. In addition, the key role that the discontinuities (extracted using an ad-hoc procedure) play on the rock mass mechanical behaviour was investigated using a 2-D FEM, based on a discontinuum approach. The results, which are in agreement with field observations, point out that karst processes, which features are characterized by the highest values in pervasiveness and aperture of the discontinuity systems and tend to reduce the rock bridges over time, need to be implemented in the rock mass classification systems and in numerical modelling techniques to avoid incorrect results

Use of LIDAR in landslide investigations: a review

This paper presents a short history of the appraisal of laser scanner technologies in geosciences used for imaging relief by high-resolution digital elevation models (HRDEMs) or 3D models. A general overview of light detection and ranging (LIDAR) techniques applied to landslides is given, followed by a review of different applications of LIDAR for landslide, rockfall and debris-flow. These applications are classified as: (1) Detection and characterization of mass movements; (2) Hazard assessment and susceptibility mapping; (3) Modelling; (4) Monitoring. This review emphasizes how LIDAR-derived HRDEMs can be used to investigate any type of landslides. It is clear that such HRDEMs are not yet a common tool for landslides investigations, but this technique has opened new domains of applications that still have to be develope

Introduction to vertical geology thematic issue

AbstractThis paper is an introduction to the special issue of the first Vertical Geology Conference—VGC-14 which was held at the University of Lausanne in February 2014. The context of the meeting and its goal is presented and a definition and short introduction to the theme of Vertical Geology is given. Finally, the paper introduces all articles contained within this special issue

The Goli d’Aget Member: Early Permian volcanoclastic and volcanic rocks within the Briançonnais Grand St-Bernard Nappe (Valais, Switzerland)

The well-preserved sedimentary structures of the Goli d’Aget Member (Early Permian) allow to distinguish four successive environments of deposition: 1) An alluvial plain with important channeling and evidence of volcanic activity; 2) A shallow lacustrine environment with a low water level, deposition of massive carbonates and an increasing contribution of volcanic materials; 3) A fluviatile plain with the deposition of volcanic tuffs; 4) A deltaic to lacustrine environment occasionally covered by pyroclastic flows. An ignimbritic rhyolite from the upper part of the Goli d’Aget Member has an age of 267-282 Ma (U-Pb on zircon). Major and trace elements, as well as zircon typology point to a calc-alkaline and volcanic-arc affinity for that high-silica rhyolite. The Goli d’Aget Member may be the best-preserved unit among the Permian units from the Swiss Penninic Western Alps. This series provides an important point of comparison with other local Permian units (Dent de Nendaz and Cleuson Members) and with similar series in the Western Alps including the Melogno porphyroids in the Ligurian Alps and the Rochachille Series near Briançon (France)