Search results for "Universe"

Farming intensity indirectly reduces crop yield through negative effects on agrobiodiversity and key ecological functions

2022

International audience; Farming intensity and landscape heterogeneity influence agrobiodiversity and associated ecological functions. The relative contributions of these agroecosystem components to agricultural production remain unclear because of inter-relations and weather-dependant variations. Using a structural equation modelling approach, we estimated direct and indirect contributions of farming intensity (soil management, pesticide use and fertilisation) and landscape heterogeneity (of semi-natural covers and crop mosaic) to cereal crop production, in 54 fields (mostly wheat), in two years (24 and 30 fields). Indirect effects were evaluated through agrobiodiversity (carabid and plant …

Ultra-High Energy Neutrinos at the Pierre Auger Observatory

2013

The observation of ultrahigh energy neutrinos (UHE nu s) has become a priority in experimental astroparticle physics. UHE nu s can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going nu) or in the Earth crust (Earth-skimming nu), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and …

Experimental Constraints on the Deep Magma Feeding System at StromboliVolcano, Italy

2009

International audience; New experiments have been performed on a high-K basalt (PST-9) from Stromboli volcano, Italy, to constrain the physical conditions of golden pumice magmas at their storage level and discuss their petrogenesis. Fluid-present, H2O- and CO2-bearing, near-liquidus experiments were performed at 11508C between 100 and 400MPa and under oxidizing conditions. Glasses were analyzed by Fourier transform IR spectroscopy and their H2O and CO2 concentrations compared with those in glass inclusions.Most glass inclusions cluster near the 200MPa isobar, suggesting entrapment at a depth of ~8 km. Golden pumice magmas have viscosities of 7.9 Pa s and densities of 2.48-2.57 g/cm3. Compo…

Ultra-high temperature metamorphism recorded in Fe-rich olivine-bearing migmatite from the Khondalite Belt, North China Craton

2018

International audience; We document the first occurrence of Fe‐rich olivine‐bearing migmatitic metapelite in the Khondalite Belt, North China Craton. Petrological analyses revealed two exotic assemblages of orthopyroxene+spinel+olivine and orthopyroxene+spinel+cordierite. Phase relation modelling suggests that these assemblages are diagnostic of ultra‐high temperature (UHT) metamorphism in the Fe‐rich system, with temperatures from 1,000 to 1,050°C at 0.6 GPa. U–Th–Pb SIMS analyses on zircon reveal a similar age of c. 1.92 Ga for the olivine‐bearing migmatite and an adjacent gabbronoritic intrusion that is therefore identified as the heat source for the UHT metamorphism. These results, coup…

Alteration-Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)

2021

International audience; Volcanoes are unstable structures that deform laterally and frequently experience mass wasting events. Hydrothermal alteration is often invoked as a mechanism that contributes significantly to volcano instability. We present a study that combines laboratory experiments, geophysical data, and large-scale numerical modeling to better understand the influence of alteration on volcano stability, using La Soufrière de Guadeloupe (Eastern Caribbean) as a case study. Laboratory experiments on variably altered (advanced argillic alteration) blocks show that uniaxial compressive strength, Young's modulus, and cohesion decrease as a function of increasing alteration, but that …

Étude des traces de pas de vertébrés du Permien et du Trias d'Ardèche. Enjeux et perspectives.

2022

Le département de l'Ardèche estremarquable car il offre un accès privilégié auxroches sédimentaires permiennes et triasiques danslesquelles abondent les traces de vertébrés fossiles.Une vingtaine de localités et plus de 1500empreintes de pas ont déjà été recensées le longd'une succession sédimentaire affleurant entrePrivas et Les Vans. Ce patrimoine ichnologique,reconnu internationalement, documente le passagede grands groupes de reptiles en terres ardéchoises,incluant essentiellement des représentants basauxde la lignée des crocodiles (pseudosuchiens) et de lalignée des oiseaux (dinosauriformes et dinosaures),ainsi que quelques membres de la lignée des lézards/serpents (lépidosauromorphes)…

Talant vineyards and wines: 800 years of history in Burgundy

2021

The Climats in Burgundy: issues and developments in a winegrowing landscape that has become cultural heritage

2020

Quantification de la dynamique sédimentaire en contexte anthropisé. L'érosion des versants viticoles de Côte d'Or.

2007

The wine slopes of Côte d'Or (Burgundy, France) are subject to the combined effects of runoff/erosion processes and intense cultivation practices. The purpose of this study is to characterize the erosion processes, and to quantify the sedimentary dynamics over different time scales and spatial scales. Sedimentary budgets show that the studied slopes, with grounds that are made very sensitive to the runoff phenomena by intensive mechanisation, are subject to erosion rates of several millimetres per year. Overflow triggering and its extension, which determine sediment transfer distances, are dependent on a runoff threshold. The existence of this threshold is observed through the analysis of t…

A model of degassing for Stromboli volcano

2010

International audience; A better understanding of degassing processes at open-vent basaltic volcanoes requires collection of new datasets of H2O–CO2–SO2 volcanic gas plume compositions, which acquisition has long been hampered by technical limitations. Here, we use the MultiGAS technique to provide the best-documented record of gas plume discharges from Stromboli volcano to date. We show that Stromboli's gases are dominated by H2O (48–98 mol%; mean, 80%), and by CO2 (2–50 mol%; mean, 17%) and SO2 (0.2–14 mol%; mean, 3%). The significant temporal variability in our dataset reflects the dynamic nature of degassing process during Strombolian activity; which we explore by interpreting our gas m…