Chevalier L., Collombet M., Pinel Virginie. (2017). Temporal evolution of magma flow and degassing conditions during dome growth, insights from 2D numerical modeling [+ Corrigendum paru dans J. Volcanol. and Geothermal Res., 2017, vol. 341, pp. 371-373]. Journal of Volcanology and Geothermal Research, 333, p. 116-133 [+ Corrigendum 2017, vol. 341, pp. 371-373]. ISSN 0377-0273.
Titre du document
Temporal evolution of magma flow and degassing conditions during dome growth, insights from 2D numerical modeling [+ Corrigendum paru dans J. Volcanol. and Geothermal Res., 2017, vol. 341, pp. 371-373]
Journal of Volcanology and Geothermal Research, 2017,
333, p. 116-133 [+ Corrigendum 2017, vol. 341, pp. 371-373] ISSN 0377-0273
Understanding magma degassing evolution during an eruption is essential to improving forecasting of effusive/explosive regime transitions at andesitic volcanoes. Lava domes frequently form during effusive phases, inducing a pressure increase both within the conduit and within the surrounding rocks. To quantify the influence of dome height on magma flow and degassing, we couple magma and gas flow in a 2D numerical model. The deformation induced by magma flow evolution is also quantified. From realistic initial magma flow conditions in effusive regime (Collombet, 2009), we apply increasing pressure at the conduit top as the dome grows. Since volatile solubility increases with pressure, dome growth is then associated with an increase in magma dissolved water content at a given depth, which corresponds with a decrease in magma porosity and permeability. Magma flow evolution is associated with ground deflation of a few rad in the near field. However this signal is not detectable as it is hidden by dome subsidence (a few mrad). A Darcy flow model is used to study the impact of pressure and permeability conditions on gas flow in the conduit and surrounding rock. We show that dome permeability has almost no influence on magma degassing. However, increasing pressure in the surrounding rock, due to dome loading, as well as decreasing magma permeability in the conduit limit permeable gas loss at the conduit walls, thus causing gas pressurization in the upper conduit by a few tens of MPa. Decreasing magma permeability and increasing gas pressure increase the likelihood of magma explosivity and hazard in the case of a rapid decompression due to dome collapse.
Plan de classement
Sciences fondamentales / Techniques d'analyse et de recherche [020]
;
Géophysique interne [066]
