Postdoctoral Positions at The Laboratoire Magmas et Volcans
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The Laboratoire Magmas et Volcans (University Blaise Pascal, Clermont-Ferrand, France) invites applications for 2 postdoctoral research positions funded by the Regional Council of Auvergne for a duration of 18 months. Candidates should send a message of interest and all other relevant material to the contact persons mentioned below. Information regarding administrative issues should be requested to Olivier Roche (o.roche@xxxxxxxxxxxxxxxxxxxxxxx).
Contracts must start before 1st March 2014. Please see deadlines for application below.
Project n°1
Project title: Modelling the three-phase viscosity of basaltic-andesitic magmas.
Supervising scientists: T. Menand, A. Harris and L. Gurioli.
Project objectives: (i) Modelling the three-phase viscosity of basaltic-andesitic magmas as a function of their composition, and their content in both volatiles and microlites. (ii) Testing whether a causal link exists between higher volatile and/or microlite contents and a higher explosive behaviour for basaltic-andesitic magmas.
Project context and description: This is part of a larger project on the explosive behaviour of basaltic-andesitic volcanoes. Although most basaltic or basaltic-andesitic magmas erupt effusively, some behave more explosively. Possible causes include higher contents in exsolved volatiles and\or microlites. Testing this hypothesis, however, requires knowledge of the rheology of these magmas, and especially their viscosity, which controls their ascent velocity as well as their explosive behaviour. Most viscosity models deal with two phases, and account for either the presence of crystals or bubbles in the silicate melts. The first aim of the project is to combine these models into a new model that accounts for the three-phases, following that initially presented by Harris and Allen (2008) for lavas and Gurioli et al. (2013) for magmas resident in the conduit. This new model will then include volatile and microlite contents, and textures of selected basaltic-andesitic magmas that erupted explosively, as well as a fluid viscosity relation tailored to the composition. Testing calculated three-phase viscosities against textural data measured on ejected tephras, pyroclasts and bombs should enable us to ascertain whether a causal link exists between higher volatile and/or microlite contents and higher explosive behaviour for basaltic-andesitic magmas.
Candidate profile: The applicants should have strong numerate skills, and a strong background in earth sciences would be appreciated.
Contact person: T. Menand (t.menand@xxxxxxx)
Deadline for application: 1st November 2013.
Project n°2
Project title: Deciphering the cause of strongly explosive basaltic-andesitic eruptions through textural analyses of associated tephra deposits.
Supervising scientists: J.-L. Le Pennec, L. Gurioli, O. Roche.
Project objectives: (i) Deciphering the cause of strong basaltic-andesitic explosive eruptions (ii) Characterizing tephra deposits (structure, grainsize, clasts texture and componentry) to discriminate the contributions of deep vs. shallow processes in driving the strong explosivity of selected basaltic-andesitic eruptions.
Project context and description: This is part of a larger project on the explosive behaviour of basaltic-andesitic volcanoes. Although most basaltic or basaltic-andesitic magmas erupt effusively, some behave more explosively, and widespread Plinian fallout and pyroclastic density current deposits of basaltic-andesitic compositions have been documented e.g. in intra-plate, divergent and subduction settings. The postdoctoral research project consists in investigating both structural (e.g. grainsize) and textural (e.g. componentry, shape, vesicularity, permeability) properties of pyroclastic products resulting from strongly explosive basaltic-andesitic eruptions. This project requires developing sampling and laboratory protocols to obtain routine high-resolution measurements of the structure and the texture of pyroclastic clasts, notably through selecting appropriate grainsize fractions to perform the analyses. Available devices for tephra studies include sieve columns, a permeameter, a morpho-grainsizer (Malvern G3S), water and gas pycnometers, and a SEM. The measurements and results require ample data processing (e.g. with FOAMS software) and statistical treatments (filtering, discriminant and multivariate statistical analyses) to identify key parameters that yield relevant information on the origin of the strong explosivity of some basaltic-andesitic eruptions. Applications to selected pyroclastic deposits in Chile and the Chaîne des Puy basaltic field are targeted.
Candidate profile: The applicants should have strong background in volcanology, notably in the study of explosive volcanic eruptions, and should be familiar with tephra studies and possibly with statistical techniques.
Contact persons: Please contact both Jean-Luc Le Pennec (jeanluc.lepennec@xxxxxx) and Lucia Gurioli (L.Gurioli@xxxxxxxxxxxxxxxxxxxxxxx).
Deadline for application: 1st December 2013.
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