Aline Peltier

Research Teaching Media-releases

Research

The main goal of my research is the study of fluid circulations (magma, hydrothermal fluids) in volcanic area from geophysic data.

My research focuses on three topics :

(1) follow up and modelling of magma storages and transfers from ground deformation data ;

(2) follow up and characterization of hydrothermal circulations in volcanic area from geophysical data ;

(3) study of the interplay between hydrothermal systems and volcano activity.

These studies were carried out on volcanoes with a magmatic and/or hydrothermal active system (Piton de la Fournaise, Kilauea, Yasur, Stromboli, Etna, Vesuvius, Karthala, Taupo, White Island, Soufrière of Guadeloupe).

(1) Insights into magma plumbing system.

- At Taupo (New Zealand), our results, discriminating what parts of the deformation are due to the regional setting, the hydrothermal and magma circulations and the seismic activity allow us to characterize the main sources (seismic, hydrothermal and magmatic ones) beneath the lake (Peltier et al., 2009).

(A) Location of the cross section for the plot (B), (B) Cumulative height change (in mm) along a west-east cross-section in the northern part of the lake recorded between 1986 and 1996. (C) Comparison between vertical displacements (coloured circles) recorded by levelling data (relative to BP) and horizontal displacements (arrows) recorded by GPS (relative to B4LG) between February 2005 and February 2007.After Peltier et al. (2009).

Predicted ground vertical displacements for an uniform extension rate of 10 mm yr− 1, for a non-uniform extension rate of 5 mm yr− 1 to the south and 10 mm yr− 1 to the north, and for non-uniform extension rate including the effect of a weak caldera. And comparison with the interpolated levelling data observed between 1984 and 1996. After Peltier et al. (2009).

- At Piton de La Fournaise (La Réunion), the combined analysis of ground deformation and geochemical data allows us to constrain the shape of the plumbing system of Piton de La Fournaise and the chronology of its re-filling (Peltier et al., 2005, 2007, 2008, 2009, 2010; Smittarello et al., 2019). One of the major results of this work is to have highlighted evolutions in the eruptive regime and behavior of the volcano over the past 40 years (Peltier et al., 2009, 2010, 2016, 2018; Brenguier and al., 2012; Roult et al., 2012) but also on a historical scale (Peltier et al., 2012) in connection with refilling and destabilization of the magam feeding system.

Left: North-south cross section through Piton de La Fournaise with pre-eruptive GPS displacements recorded before the August 2004, February 2005, October 2005, November 2005, December 2005 and July 2006 eruptions. Coloured circles correspond to hypocenters of the pre-eruptive seismic swarms associated with the listed inflation periods (Valérie Ferrazzini-OVPF, personal communication). Dotted circle represents the location of the modelled magma reservoir after Peltier et al. (2008) (Gauss Laborde Réunion coordinates, meters). After Peltier et al. (2009).
Right: Examples of horizontal displacements (from GPS) caused by dyke injections associated with (a) proximal eruptions (examples with the August and September 2003 eruptions) and (b) distal eruptions (examples with the February and December 2005 eruptions). Dotted white circles represent the source areas for the dykes leading to (a) proximal and (b) distal eruptions. After Peltier et al. (2009).

Schematic model of the shallow magmatic system of Piton de La Fournaise. Dykes feeding the summit and proximal eruptions started at the top of the shallow reservoir, whereas the dykes feeding the distal eruptions started at the base and eastern part of the magma reservoir.

East-west cross section through Piton de La Fournaise showing the location of earthquakes and magma storage at depth. Location of the March 1998 pre-eruptive seismic swarm (stars) after Battaglia et al. (2005). After Peltier et al. (2009).

- Basaltic volcanoes, like Etna (Italy), Hawaiian volcanoes (USA) and Piton de la Fournaise (La Réunion Island, France), are amongst the largest volcanic edifices on Earth. On these huge active volcanoes, the continuous action of magmatic pressure leads to large deformation areas that ultimately control the volcano structure and topography with more or less mobile flanks, which
respond to long-lasting stress field conditions (gravitational stress, magmatic processes and/or regional tectonics...). Large-scale deformation and flank instabilities of volcanoes represent a significant hazard because they can lead to major edifice destabilizations and large landslides. In this context our works, led in the framework of the ANR SlideVOLC project, aim to better understand these catastrophic events. Our capability of predicting such catastrophic events relies on both our understanding of the complex link between the stress field, the volcanic and hydrothermal processes, and our ability to interpret the monitored signals as precursors. (ANR SlideVOLC project; Poland, Peltier et al., 2017).

Flank displacements determined from GNSS at (A) Kilauea, (B) Piton de la Fournaise, (C) Etna.
After Peltier et al. (2015) et Poland, Peltier et al. (2017).

- At Piton de La Fournaise (La Réunion), we studied the effect of rock rheology and strength on the dynamics of volcanic processes, exploring elasto-plasticity (Got et al., 2013; Peltier et al., 2015). With this new approach, eruptive cycles, rifting, motion of the seaward flank, ground displacements and magma-edifice interaction are well understood in terms of stress/strain cycles and edifice strength. We showed that modelling incremental surface deformation data allows constraining edifice rheology (Got et al., 2013; Carrier et al., 2015).

Example of deformation cycle at Piton de la Fournaise. After Got et al. (2013).

(2) Identification and characterization of hydrothermal systems.

The joined analysis of self potential data, ERT profils, thermal and CO2 anomalies allows us to better constrain the extension of the hydrothermal systems of the following volcanoes: Stromboli (Finizola et al., 2010; Revil et al., 2011), Piton de La Fournaise (Barde Cabusson et al., 2012; Dumont et al., 2019), Karthala, Yasur (Peltier et al., 2012) and La Soufrière de Guadeloupe (Brothelande et al., 2014). In volcanic area, hydrothermal fluid circualtions are controlled by pre-existing structures (caldera boundaries, fractures, ...) and the regional/local tectonic setting.

(a) Temperature (◦ C), self-potential (in mV), soil CO2 concentration (in ppm) measurements and DC resistivity tomogram from RES2DINV (in ohm m) along the profile Ginostra-Forgia Vecchia. Vertical scaling factor for the resistivity inverted section 1.7. RMS error 15 per cent at iteration 5 using a Gauss–Newton algorithm. Note the asymmetry in both the self-potential profile and resistivity tomogram between the SW and E sections. Note that the positive self-potential anomalies are associated with CO2 degassing structures (Revil et al., 2011).

(b) Comparison between the temperature measurements (performed at a depth of 30 cm), the self-potential measurements, the soil CO2 flux data, the ground penetrating radar data and the electrical resistivity tomography along a W–E profile in Stromboli (Finizola et al., 2010).

(A) Temperature map of the Yasur cone and associated structures superimposed on a digital elevation model. (B) Aerial photo of Yasur (courtesy of Clémentine Bacri and Adrien Normier, ORA association). “OYs”, “Ys” and “Yk” stand for Old Yasur, Yasur and Yenkahe, respectively. “AA”, “F”, and “HS” stand for Argilized Area, Fault and Hidden Structure, respectively.After Peltier et al. (2012).

(3) Interplay between hydrothermal systems and volcano activity.

From a combined analysis of geophysical, seismological, and structural data, we explore the possible rule of the hydrothermal system on the volcano's activity (seismic activity, ground deformation, eruption triggering, destabilizations), with the examples of White Island (New Zealand, Peltier et al., 2009) and Piton de La Fournaise (La Réunion, Lénat et al., 2012; Chaput et al., 2019).