Understanding how and where magmas rises in the volcanic edifices of La Réunion is of importance for many topics, including volcanic hazard assessment and geothermal energy. The LGSR team has been devoted to this work for decades.
Our work shows that magma rises toward Piton de La Fournaise through complex, inclined pathways that are influenced by the fabric of the oceanic crust under La Réunion.
Magma ascent at Piton des Neiges has been also influenced by this crustal fabric.
Featured publication : Michon, L., Ferrazzini, V., Di Muro, A., Villeneuve, N., & Famin, V. (2015). Rift zones and magma plumbing system of Piton de la Fournaise volcano: How do they differ from Hawaii and Etna? Journal of Volcanology and Geothermal Research, 303, 112–129. doi.org/10.1016/j.jvolgeores.2015.07.031
Gravitational deformation (known as spreading) is concurrent to volcano growth during the lifetime of a volcanic edifice. Spreading may occur during eruption or in inter-eruptive periods, and may lead to rare bu catastrophic mass wasting events, such as for Mount St Helens in 1980.
Our team has devoted a large attention to the deformation of basaltic volcanoes in relationship with their eruptive or intrusive activity. Field work on an eroded volcano (Piton des Neiges) showed that sill intrusion is the most common mode of magma injection in an edifice. Sill intrusion may be explained by recurrent stress permutation in a volcanic edifice. Numerical simulation of sill intrusion suggests sills are able to generate lateral flank deformation. These simulations lead us to search for evidence of co-intrusive flank displacement during sill intrusion, which was found in 2016. Applying these results to Piton de la Fournaise, it is likely that the large flank sliding that occurred during the April 2007 eruption was due to a sill intrusion in the eastern flank of the edifice.
Featured publications :
Chaput, M., Famin, V., & Michon, L. (2014). Deformation of basaltic shield volcanoes under cointrusive stress permutations. Journal of Geophysical Research: Solid Earth, 119(1), 274–301.
Berthod, C., Famin, V., Bascou, J., Michon, L., Ildefonse, B., & Monié, P. (2016). Evidence of sheared sills related to flank destabilization in a basaltic volcano. Tectonophysics, 674, 195–209. http://doi.org/http://dx.doi.org/10.1016/j.tecto.2016.02.017
Cayol, V., Catry, T., Michon, L., Chaput, M., Famin, V., Bodart, O., … Romagnoli, C. (2014). Sheared sheet intrusions as mechanism for lateral flank displacement on basaltic volcanoes: Applications to Réunion Island volcanoes. Journal of Geophysical Research B: Solid Earth, 119(10), 7607–7635.
Froger, J. L., Famin, V., Cayol, V., Augier, A., Michon, L., & Lénat, J. F. (2015). Time-dependent displacements during and after the April 2007 eruption of Piton de la Fournaise, revealed by interferometric data. Journal of Volcanology and Geothermal Research, 296, 55–68.
Famin, V., & Michon, L. (2010). Volcano destabilization by magma injections in a detachment. Geology, 38(3), 219–222.
Understanding the origin of flank activity on basaltic island volcanoes is pivotal to better assess the potential occurrence of volcanic eruptions in the inhabited areas of the edifice.
Our work on the magma paths at Piton de la Fournaise shows that the volcanic activity mostly occurs along preferential intrusion paths, whose origin is related either to the reactivation of crustal structures (Michon et al., 2007; 2015; Boudoire et al., 2017) or to the deformation of the edifice triggered by successive magma intrusions (Michon et al., 2015).
Featured publications :
Michon, L., F. Saint-Ange, P. Bachèlery, N. Villeneuve, and T. Staudacher (2007), Role of the structural inheritance of the oceanic lithosphere in the magmato-tectonic evolution of Piton de la Fournaise volcano (La Réunion Island), J. Geophys. Res., 112, B04205, doi:10.1029/2006JB004598.
Michon, L., Ferrazzini, V., Di Muro, A., Villeneuve, N., Famin, V. (2015). Rift zones and magma plumbing system of Piton de la Fournaise: how do they differ from Hawaii and Etna? J. Volcanol. Geotherm. Res., 303, 112-129.
Boudoire, G., Liuzzo, M., Di Muro, A., Ferrazzini, V., Michon, L., Grassa, F., Derrien, A., Villeneuve, N., Bourdeu, A., Brunet, C., Giudice, G., Gurrieri, S. (2017). Investigating the deepest part of a volcano plumbing system: Evidence for an active magma path below the western flank of Piton de la Fournaise (La Réunion Island), J. Volcanol. Geotherm. Res., 341, 193-207.