Diffuse CO<Subscript>2</Subscript> degassing at Vesuvio,Italy

At Vesuvio, a significant fraction of the rising hydrothermal–volcanic fluids is subjected to a condensation and separation process producing a CO₂–rich gas phase, mainly expulsed through soil diffuse degassing from well defined areas called diffuse degassing structures (DDS), and a liquid phase that flows towards the outer part of the volcanic cone. A large amount of thermal energy is associated with the steam condensation process and subsequent cooling of the liquid phase. The total amount of volcanic–hydrothermal CO₂ discharged through diffuse degassing has been computed through a sequential Gaussian simulation (sGs) approach based on several hundred accumulation chamber measurements and, at the time of the survey, amounted to 151 t d^–1. The steam associated with the CO₂ output, computed assuming that the original H₂O/CO₂ ratio of hydrothermal fluids is preserved in fumarolic effluents, is 553 t d^–1, and the energy produced by the steam condensation and cooling of the liquid phase is 1.47×10¹² J d^–1 (17 MW). The location of the CO₂ and temperature anomalies show that most of the gas is discharged from the inner part of the crater and suggests that crater morphology and local stratigraphy exert strong control on CO₂ degassing and subsurface steam condensation. The amounts of gas and energy released by Vesuvio are comparable to those released by other volcanic degassing areas of the world and their estimates, through periodic surveys of soil CO₂ flux, can constitute a useful tool to monitor volcanic activity.Editorial responsibility: H. Shinohara     

How natural are Alpine mountain rivers? Evidence from the Italian Alps

Historical, human‐induced channel adjustments in lowland gravel‐bed rivers have been documented in several geographical contexts worldwide. In particular, it is now widely accepted that the vast majority of European rivers are far from any natural, reference state prior to anthropic disturbances, and a ‘complete’ restoration is hardly achievable. However, few investigations have addressed changes that have occurred in mountain rivers of the Alps, and these channels are commonly reckoned quite ‘natural’ by society. This paper intends to describe how human pressure on Italian Alpine basins has been quite relevant for several centuries – in terms of land‐use variations, in‐channel structures, timber transport (splash damming) and riparian vegetation management – such that nowadays ‘reference conditions’ cannot be found even in small mountain creeks. In addition, recent natural climatic variations (e.g. the Little Ice Age) are superimposed on human disturbances, thus defying the definition of any ‘equilibrium’ morphological conditions even under ‘human‐free’ states. A summary of published as well as unpublished works on historical channel adjustments in rivers of the Italian Alps is presented in order to document the impacts deriving from human pressure at different basin scales and for different river morphologies, from steep confined streams to large unconfined rivers. General options for river management and restoration actions aiming to combine geomorphological functionality and flood hazard mitigation are discussed, in the light of the current European legislative context. Copyright © 2011 John Wiley & Sons, Ltd.     

Structural performance of automated multi-depth shuttle warehouses (AMSWs) under low-to-moderate seismic actions

Bulletin of Earthquake Engineering - Automated Multi-Depth Shuttle Warehouses (AMSWs) are compact storage systems that provide a large surface occupation and therefore maximum storage density....     

Formation of an ‘a’ā lava delta: insights from time-lapse multibeam bathymetry and direct observations during the Stromboli 2007 eruption

Five consecutive multibeam bathymetries collected before, during, and after the 2007 Stromboli eruption, combined with visual inspections, allowed us to document the morphological evolution of an ‘a’ā lava-fed delta and to reconstruct the main processes acting during its submarine emplacement. The 2007 Stromboli delta extended down to 600-m water depth and covered an area of 420?×?10³ m², with a maximum thickness of 65 m and a total estimated volume of ≈7?×?10⁶ m³, i.e., three times larger than its subaerial counterpart. The lava delta grew mainly through the emplacement of discrete lobes about 50–150 m in size. Lobes were fed from point sources along the paleoshoreline, and their subaqueous pathways seem to be mainly controlled by the submarine morphology, with flows mostly filling in depressions left by previous lobes. The main controlling factors on the lobe morphology and thickness are the effusion rates and the pre-eruption morphology, i.e., the geometry and gradients of the basal surface. Data also shows that sudden slope failure of portions of the submarine delta may occur simultaneously with accretion, implying that a significant part of the delta material can be transported to greater depths by submarine gravity flows. The present study is relevant for future monitoring and hazard assessment during the growth of active lava-fed deltas as well as for a better interpretation of ancient volcaniclastic successions inland.     

Can we tell more than we can know? The limits of bivariate drought analyses in the United States

The joint occurrence of extreme hydroclimatic events, such as simultaneous precipitation deficit and high temperature, results in the so-called compound events, and has a serious impact on risk assessment and mitigation strategies. Multivariate frequency analysis (MFA) allows a probabilistic quantitative assessment of this risk under uncertainty. Analyzing precipitation and temperature records in the contiguous United States (CONUS), and focusing on the assessment of the degree of rarity of the 2014 California drought, we highlight some critical aspects of MFA that are often overlooked and should be carefully taken into account for a correct interpretation of the results. In particular, we show that an informative exploratory data analysis (EDA) devised to check the basic hypotheses of MFA, a suitable assessment of the sampling uncertainty, and a better understanding of probabilistic concepts can help to avoid misinterpretation of univariate and multivariate return periods, and incoherent conclusions concerning the risk of compound extreme hydroclimatic events. Empirical results show that the dependence between precipitation deficit and temperature across the CONUS can be positive, negative or not significant and does not exhibit significant changes in the last three decades. Focusing on the 2014 California drought as a compound event and based on the data used, the probability of occurrence strongly depends on the selected variables and how they are combined, and is affected by large uncertainty, thus preventing definite conclusions about the actual degree of rarity of this event.     

Nouvelles données sur le Messinien de Méditerranée occidentale : les gisements à Aphanius crassicaudus (Agassiz poissons téléostéens,cyprinodontiformes) des Marches (Italie)

Résumén

La découverte, dans le Nord des Marches (Italie), de nouveaux gisements de Poissons Cyprinodontidae appartenant à l’espèce Aphanius crassicaudus (AGASSIZ), conduit à réexaminer, à la lumière des données lithostratigraphiques, la signification géodynamique des ichthyofaunes messiniennes de ce secteur de l’Apennin. Après avoir précisé la position stratigraphique et la répartition paléogéographique des gisements étudiés, les auteurs montrent que le développement des faunes à Aphanius crassicaudus (AGASSIZ) dans les eaux saumâtres du domaine continental n’implique pas la disparition corrélative du milieu marin. En effet, certains genres marins sont parfois présents à côté de cette espèce, comme c’est le cas dans le gisement de Pésaro. Les auteurs contestent en outre l’interprétation selon laquelle le fait qu’aucune ichthyofaune marine ne soit connue dans le Messinien supérieur d’Italie puisse suffire à conclure que la Méditerranée était asséchée pendant le dépôt de la « Formation à colombacci »