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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities
 

Lead Supervisor:  Marie Edmonds, Earth Sciences  

Co-Supervisor:  Donald Dingwell, Ludwig-Maximilians-Universitat (LMU), Munich and Yan Lavallee, Liverpool University

Importance of the area of research concerned: 
Water-rich magmas crystallize extensively during ascent, undergoing rapid and large changes in rheological properties driven by water degassing and consequent crystallisation. The outgassing flux of magmatic volatiles such as water, carbon dioxide, sulphur dioxide and other species, may be fundamentally controlled by the permeability of the magma during ascent and eruption. Volcanoes such as Soufriere Hills (Montserrat), Santiaguito and Fuego (Guatemala) and Colima (Mexico) undergo transitions in activity between lava dome building and vulcanian explosive activity, driven by changes in magma ascent and outgassing rate. Time series of gas flux from such systems shows variability that is related to changes in magma ascent rate and permeability, but the relationship between these are poorly understood. Measurement of volcanic gas fluxes is one of the fundamental ways in which we monitor volcanoes. A better understanding of the controls on the gas fluxes will lead to enhanced eruption forecasting and will feed into developing better measurement strategies.
Project summary : 
Magma permeability changes during ascent of magma up the conduit, due to degassing, decompression-induced crystallisation and shear deformation. The ability of volcanic gases to escape from volcanic systems, and hence eruption style, is to a first order controlled by magma permeability. To study this process, it is necessary to conduct experiments, preserving the textures by quenching. In this project we will conduct experiments on a range of arc and rift magmas with different melt compositions and water contents erupted from volcanoes which have well-characterised time series of sulphur dioxide outgassing fluxes measured using automated spectrometer networks. We will utilise the experimental results to understand the variability in the gas fluxes and develop a forecasting framework that will allow the degassing regime to be interpreted in terms of magma decompression (and flux) rate.
What will the student do?: 
The student will collate volcanic gas, erupted magma flux and seismicity time series from a range of target volcanoes, to include Mount St Helens, Santiaguito and Soufriere Hills volcanoes. Samples of the lava erupted from each volcano will be acquired, heated and ‘regassed’ by equilibrating the silicate melt with water at a range of pressures. The samples will then be used to conduct a range of decompression experiments under a range of different conditions of decompression rate, temperature and fO2. Quenched experimental products will be characterised using QEMSCAN, EPMA and their Darcian permeability measured in the laboratory. The results of the experiments will be used to interpret long time series of gas data, making use of numerical modeling approaches, and a forecasting tool will be developed.
References: 
Edmonds M, Oppenheimer C, Pyle DM, Herd RA, Thompson G. SO2 emissions from Soufrière Hills Volcano and their relationship to conduit permeability, hydrothermal interaction and degassing regime. Journal of Volcanology and Geothermal Research. 2003 May 15;124(1-2):23-43.
Lavallée Y, Benson PM, Heap MJ, Hess KU, Flaws A, Schillinger B, Meredith PG, Dingwell DB. Reconstructing magma failure and the degassing network of dome-building eruptions. Geology. 2013 Apr 1;41(4):515-8.
Mueller S, Melnik O, Spieler O, Scheu B, Dingwell DB. Permeability and degassing of dome lavas undergoing rapid decompression: an experimental determination. Bulletin of Volcanology. 2005 Jul 1;67(6):526-38.
Applying
You can find out about applying for this project on the Department of Earth Sciences page.