Mass flows, turbidity currents and other hydrodynamic consequences of small and moderate earthquakes in the Sea of Marmara

Earthquake-induced submarine slope destabilization is known to cause mass wasting and turbidity currents, but the hydrodynamic processes associated with these events remain poorly understood. Instrumental records are rare, and this notably limits our ability to interpret marine paleoseismological sedimentary records. An instrumented frame comprising a pressure recorder and a Doppler recording current meter deployed at the seafloor in the Sea of Marmara Central Basin recorded the consequences of a Mw 5.8 earthquake occurring on 26 September 2019 and of a Mw 4.7 foreshock 2 d before. The smaller event caused sediment resuspension and weak current (&lt;4 cm s−1) in the water column. The larger event triggered a complex response involving a debris flow and turbidity currents with variable velocities and orientations, which may have resulted from multiple slope failures. A long delay of 10 h is observed between the earthquake and the passing of the strongest turbidity current. The distance traveled by the sediment particles during the event is estimated to have extended over several kilometers, which could account for a local deposit on a sediment fan at the outlet of a canyon (where the instrument was located), but the sedimentation event did not likely cover the whole basin floor. We show that after a moderate earthquake, delayed turbidity current initiation may occur, possibly by ignition of a cloud of resuspended sediment.</p

Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this special issue (https://www.biogeosciences.net/special_issue900.html), results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among 18 articles. Here, the scientific context, project objectives, and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue

Coastal Flooding Events on the French coast of the Eastern English Channel: the Result of a Combination of Meteorological, Marine, and Morphological Factors

International audienceOn account of increasing inhabitation and development of coastal areas, the economical stakes are high for forecasting and prevention of coastal flooding risk. Because of their exposure to prevailing Westerlies, morphological, and topographic features, low coastal areas on the French coast of the eastern English Channel are particularly sensitive to this natural risk. This sensitivity, that has always characterized this study area, is becoming worrying to politicians and inhabitants. The study aim is to identify, from 1949 to 2010, the possible increase in frequency and intensity of these meteorological and marine events, and their characteristics for forecasting objectives. The chosen approach is made up of three elements: 1) An analysis of strong west wind over the last decades has been implemented from Meteo-France data of Dieppe, reliable regional meteorological station. Beyond multi-annual random fluctuations, we have noticed a decrease in frequency and intensity of strong winds traditionally involved in flooding events. 2) An analysis of past events has been carried out from many information sources to warrant the accuracy of statements and their exhaustiveness. Thanks to this database, the main results are: i) the absence of increasing trend about frequency and intensity of coastal flooding events; ii) the cartography of coastal flooding risk for each urbanized area; iii) the definition of wind and tide level thresholds (7 m/s and 8.49 m at Dieppe) above which there is flooding. 3) A characterization, on the synoptic scale, of meteorological conditions ending in flooding has been performed. In matching this piece of information with the past events inventory, we have identified: firstly the two major types of low pressure trajectories that generated overflowing, so the two main atmospheric circulations prone to flooding, and secondly the fundamental meteorological aspect of the high north-west pressure gradient (≥ 20 hPa from "Pointe du Raz" (France) to Cromer city (U.K.)) of these flooding events. Frequency of this particular pressure configuration in the English Channel does not highlight any significant trend during the last century. Beyond tide level and wind (speed, direction) thresholds, another factor explains coastal flooding events. This is the matter of atmospheric cold front during high tide, observable in 70 % of coastal flooding events in the eastern English Channel. Analysis of these coastal flooding events cannot be restricted to simple meteorological and marine conditions during overflowing by the sea. This work emphasizes the need for longer analysis period. It is important to encompass the possible beach "preparation time" (lowering of the beach profile) by meteorological and marine conditions for a few days or weeks before flooding event. This "preparation time" may be short: 48 hours of strong winds (> 8 m/s) may be sufficient to shape a beach profile prone to overflowing. Coastal flooding is the result of a combination of factors from various time and space scales, which goes over the simple combination of extreme sea-level and strong wind perpendicular to coast

Questions of religion and cultural policy in France

This article explores how questions of religion have impinged on or informed various dimensions of culture-shaping policy in France. Firstly, it considers how religious references have been orchestrated in high-level attempts to frame secular national identities, but also how such processes have assumed quasi-religious forms and functions. Secondly, it analyses the changing place of religion in French educational curricula, and recent contested endeavours to introduce it as a cultural ‘fact’ into those curricula. Thirdly, the article examines influential framings of art policies in their relation to religion. It considers the pivotal function of religious fragments and debris in Malraux’s vision of the imaginary museum, and the use by Bourdieu of sustained religious metaphors to describe the sacralizing dynamics of secular artworlds. Finally the article examines in a long-term perspective the implicit and explicit cultural policies of religious bodies themselves in their attempts to act upon prevailing cultures

Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this Special Issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among seventeen articles. Here, the scientific context, project objectives and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue

Introduction to the French GEOTRACES North Atlantic Transect (GA01): GEOVIDE cruise

The GEOVIDE cruise, a collaborative project within the framework of the international GEOTRACES programme, was conducted along the French-led section in the North Atlantic Ocean (Section GA01), between 15 May and 30 June 2014. In this Special Issue, results from GEOVIDE, including physical oceanography and trace element and isotope cyclings, are presented among seventeen articles. Here, the scientific context, project objectives and scientific strategy of GEOVIDE are provided, along with an overview of the main results from the articles published in the special issue