Manioc : Portail | resultats 361 - 380 pour la recherche: éruption

« Le désastre de la Martinique ; M. Mouttet ; Réveil de l'activité volcanique dans l'Amérique centrale », Sur terre et sur mer, supplément mensuel au Journal des voyages n° 292

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Le Gavroche. Journal satirique hebdomadaire. Numéro spécial consacré aux événements de la Martinique. Paris, n° 18

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Martinique. Saint Pierre. Après la catastrophe du 8 Mai 1902. Les ruines du lycée
Auteur(s) : Phos

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Seismic anisotropy in the asthenosphere beneath the Eifel region
Auteur(s) : Walker, K. Bokelmann, Goetz Klemperer, S. Bock, G.
Auteurs secondaires : Institute of Geophysics and Planetary Physics [San Diego] (IGPP) ; University of California [San Diego] (UC San Diego) Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Department of Geophysics, Stanford University ; Université du Québec GeoForschungsZentrum - Helmholtz-Zentrum Potsdam (GFZ) Joachim R. R. Ritter; Ulrich R. Christensen

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Saint-Pierre de la Martinique. La plage. La montagne Pelée se trouve au fond du sujet
Auteur(s) : L'Harmattan

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Martinique. Ruines de Saint-Pierre. La place Bertin. La montagne Pelée et le cône
Auteur(s) : Leboullanger

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Vue générale des ruines de Saint-Pierre
Auteur(s) : Russon

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Martinique. Ruines de St-Pierre après la catastrophe de 1902 et laMontagne Pelée en pleine éruption
Auteur(s) : Russon

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Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
The morphogenetic evolution of the Lesser Caucasus has been strongly influenced by Plio-Quaternary volcanic and tectonic events and Pleistocene glaciations. Fluvio-lacustrine environments, indicated by diatomaceous deposits, prevailed in the Syunik region of southern Armenia during the Pliocene and Pleistocene. The Pleistocene diatomaceous deposits studied contain leaf impressions and pollen, allowing local palaeoclimatic reconstructions. The chronology of morphogenetic events has been determined by 17 radiometric dates (K/Ar, Ar/Ar, U/Th), palaeomagnetic investigations and is placed in a spatial context by a detailed geomorphological map and a 24-km geological transect of the Vorotan valley, the main area studied. Before 1.21 Ma, tectonic movements (antecedents of the lower part of the Vorotan valley) generated extensive lake formations with diatomaceous deposits. From 993 ka, volcanic eruptions produced lava flows that covered the fluvio-lacustrine accumulations. During Marine Isotopic Stages 12, 6 and 4, glaciers and fluvio-glacial deposits were probably present overall the principal uplands and valleys of southern Armenia. At 53.68 ka (MIS 3), 12.6 ka, 10.78 ka and 4.14 ka (MIS 1), the development of travertines on some slopes and in some valleys highlights temperate and humid climatic phases. Palaeobotanical studies of leaf and pollen floras show that the vegetation changed several times from forested to steppic phases in response to the climate oscillations of the Lower Pleistocene. This work proposes a first morphogenic and palaeoclimatic reconstruction from the lower Pleistocene to the Postglacial period, when the first settlements of the population in the Lesser Caucasus were influenced by tectono-volcanic events, lake level changes and glacialeinterglacial oscillations forced by the obliquity orbital parameter (41 ky cycles).
ISSN: 1040-6182

hal-00481939
https://hal.archives-ouvertes.fr/hal-00481939
DOI : 10.1016/j.quaint.2010.02.008

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Magnetic interactions at the origin of abnormal magnetic fabrics in lava flows: a case study from Kerguelen flood basalts
Auteur(s) : FANJAT, Gregory Camps, Pierre Shcherbakov, Valera BAROU, Fabrice Sougrati, Moulay Tahar Perrin, Mireille
Auteurs secondaires : Manteau et Interfaces ; Géosciences Montpellier ; Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) - Université des Antilles et de la Guyane (UAG) - Institut national des sciences de l'Univers (INSU - CNRS) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Laboratoire de météorologie physique (LaMP) ; Centre National de la Recherche Scientifique (CNRS) - Institut national des sciences de l'Univers (INSU - CNRS) - Université Blaise Pascal - Clermont-Ferrand 2 (UBP) Institut Universitaire de Technologie de Montluçon (IUT) ; Ministère de l'Éducation nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.) Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier (ICGM ICMMM) ; Université Montpellier 1 (UM1) - Université Montpellier 2 - Sciences et Techniques (UM2) - Ecole Nationale Supérieure de Chimie de Montpellier (ENSCM) - Université de Montpellier (UM) - Centre National de la Recherche Scientifique (CNRS) Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (FEMTO-ST) ; Université de Technologie de Belfort-Montbeliard (UTBM) - Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM) - Centre National de la Recherche Scientifique (CNRS) - Université de Franche-Comté (UFC) Recherches en Psychopathologie, nouveaux symptômes et lien social (EA 4050) ; Université de Rennes 2 (UR2) - Université Catholique de l'Ouest - Université de Brest (UBO) - Université de Poitiers

Éditeur(s) : HAL CCSD Oxford University Press (OUP)
Résumé : International audience
Anisotropy of low-field magnetic susceptibility (AMS) of basaltic lava flows can give some clues about post-emplacement tilting occurring in volcanic sequences. Such a study has been carried out on a sequence of 19 successive lava flows from Kerguelen Archipelago. Surprisingly, two different patterns were observed. The first one - herein called normal fabric - is consistent with the lava-flow direction inferred from geological observations, whereas the second one observed for about 70 per cent of the analysed samples - herein called abnormal fabric - appears to be unrelated to the shear history of the lava flows during their emplacements. These abnormal fabrics are not strictly inverse fabric but seem to have a more complex origin. The unusual nature of these abnormal fabrics has been confirmed by lattice preferred orientation of plagioclases obtained from high-resolution electron backscattered diffraction measurements. The aim of this study is to propose a physical interpretation of these fabrics. A first step in our understanding was to clearly identify the nature and the magnetic properties of the Fe-Ti oxides assemblage. Thus, we present a comprehensive rock magnetic analysis relying on low- and high-temperature thermomagnetic curves (K-T), crossover diagrams, first-order reversal curves, ore-microscopy, Mössbauer measurements and electron backscattered images. We found that in the present case the abnormal fabrics are probably linked to a mixture of prevailing single domain (SD) strongly interacting grains population and a subsidiary multidomain grains population. SD grains are identified as small magnetite crystallized within the interstitial glass in globular aggregates along the silicate framework. Then a question arises: to what extent such SD interacting grains in globular aggregates can affect the magnetic susceptibility and its anisotropy? To answer this question, we developed a physical model in which the total energy density of an SD grain with an uniaxial anisotropy is minimized. In this model, the distribution function of the direction of the magnetic interaction field is comprised between two boundary states. It is either isotropic, which formally corresponds to the thermal demagnetized state, or it is ordered, which formally corresponds to the Alternative Field demagnetized state. We show that in both cases the degree of anisotropy decreases as the interaction field increases. Thus, we conclude that the abnormal fabric encountered in this study can be simply explained by strong magnetostatic interactions that would explain the large scattering of AMS often observed in basaltic lava flows.
ISSN: 0956-540X

hal-00716449
https://hal.archives-ouvertes.fr/hal-00716449
https://hal.archives-ouvertes.fr/hal-00716449/document
https://hal.archives-ouvertes.fr/hal-00716449/file/gji-S-12-HAL.pdf
DOI : 10.1111/J.1365-246X.2012.05421.X

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