Publications
Evidences of Plug Pressurization Enhancing Magma Fragmentation During the September 2016 Basaltic Eruption at Piton de la Fournaise (La Réunion Island, France)
During the September 2016 eruption of Piton de la Fournaise volcano on Réunion Island, a sudden shift from typical effusive activity to explosive ash and bomb emission occurred. This transition was linked to the pressurization of a degassed, cooled magma plug beneath a secondary vent (Vent B), which enhanced magma fragmentation. The study integrated geophysical data with textural and petrological analyses, revealing that the explosive phase involved denser, crystal-rich tephra (sideromelane and tachylite) alongside more gas-permeable, vesicular fragments (golden pumice and fluidal scoria). Permeability measurements and chemical analyses suggested that the sideromelane and tachylite components originated from subsurface crystallization of the initial magma types. This finding highlights the potential danger posed by such transitions in volcanic activity, particularly for tourist areas accustomed to 'gentle' eruptions.
The 2007 caldera collapse of Piton de la Fournaise volcano: Source process from very-long-period seismic signals
In April 2007, Piton de la Fournaise volcano on Réunion Island experienced its largest caldera collapse in at least 300 years, characterized by a series of 48 subsidence increments with seismic signals equivalent to magnitudes Mw 4.4 to 5.4. Analysis of these very-long-period (VLP) seismic events revealed a piston-like mechanism driven by the contraction of the magma reservoir and the collapse of the overlying rock column. The study found that the collapse dynamics were primarily controlled by rapid magma withdrawal, likely from a bubbly state, leading to an acceleration in subsidence increments—a pattern similar to the 2018 Kīlauea collapse. This suggests that such events are linked to progressive weakening of the volcanic edifice and increasing rates of magma extraction.
Control of source fertility on the eruptive activity of Piton de la Fournaise volcano, La Réunion
Research on Piton de la Fournaise volcano, Réunion Island, reveals that its eruptive activity is directly linked to the fertility of its mantle source. The study demonstrates that decadal-scale eruptive sequences are initiated by melt extraction from fertile, incompatible element-enriched veins within the plume source, while reactive flow of enriched melts increases mantle porosity, promoting further melt extraction. This dual control mechanism led to a fourfold increase in magma supply between 1998 and 2014, offering insights into similar surges at other hotspot volcanoes like Kilauea, Hawaii. The findings highlight the critical role of lithological heterogeneities in mantle plumes in regulating short-term eruptive activity.
On the Link Between External Forcings and Slope Instabilities in the Piton de la Fournaise Summit Crater, Reunion Island
Renewed volcanic activity at Piton de la Fournaise, Reunion Island, significantly increases the frequency and volume of rockfalls in its summit crater. A study analyzing 10,477 rockfalls between 2014 and 2016 found that preeruptive seismicity is the primary trigger for large-volume collapses, often with a delay of one to several days. While rain alone does not cause particularly large rockfalls, its combined action with seismic vibrations likely accelerates crack growth in fractured crater edges, leading to larger collapses. The research also observed that the locations of the largest rockfalls migrate toward future magma extrusion sites before eruptions. The study used a combination of seismic records and photogrammetric data to validate rockfall locations and volumes.
Uncovering the hidden signature of a magmatic recharge at Piton de la Fournaise volcano using small earthquakes
A ring-shaped zone of weakness beneath Piton de la Fournaise volcano, revealed through advanced seismic analysis, suggests preexisting structural vulnerabilities that influence eruptive behavior. Using a template matching method, researchers detected thousands of small earthquakes in 2014 and 2015, uncovering persistent seismicity patterns linked to magma recharge. Notably, deep earthquake migration in 2015 preceded a shallow seismic swarm, indicating the formation of a hydraulic connection between deep magma sources and a near-sea-level reservoir—likely missed in past observations due to detection limitations. This study highlights how subtle seismic signals can decode volcanic processes, offering insights into the hidden dynamics shaping eruptions at UNESCO-listed Réunion Island's volcanic landscapes.
Improved detection of preeruptive seismic velocity drops at the Piton de La Fournaise volcano
Researchers have identified a previously undetected preeruptive seismic velocity drop of 0.15% associated with the June 21, 2014 eruption at Piton de La Fournaise volcano on Réunion Island. This discovery was made possible by correcting seismic velocity data for pore pressure changes caused by rainfall, which had previously obscured the signal. The study used a transfer function to model the relationship between fluid pressure and seismic velocity variations, allowing for the isolation of true preeruptive signals during a period of low eruptive activity (2011–2013). This advancement improves the potential for more reliable volcanic eruption prediction by mitigating interference from environmental factors.
Long‐term mass transfer at Piton de la Fournaise volcano evidenced by strain distribution derived from GNSS network
Piton de la Fournaise, a basaltic volcano on Reunion Island, exhibits long-term mass transfer from its summit to the eastern flank, contributing to the formation of the Grandes Pentes relief. This process is evidenced by strain distribution analysis derived from a dense GNSS network installed since 2007. The study reveals that during summit deflation (2011-2014), the upper eastern flank extended eastward while the lower flank contracted, steepening the topographic slope. This deformation regime indicates progressive loading of the lower flank by the upper one, suggesting a potential instability. The research also highlights how volcanic 'pulsation'—alternating inflation and deflation—enhances rock fracturing, reduces stiffness, and increases permeability, providing insights into the volcano's structural dynamics.
Automated identification, location, and volume estimation of rockfalls at Piton de la Fournaise volcano
Researchers developed automated methods to identify, locate, and estimate the volume of rockfalls at Piton de la Fournaise Volcano using seismic signals. These methods achieved a 92% success rate in discriminating rockfall events from other seismic activity and accurately located observed rockfalls within 100 meters. By analyzing seismic energy, the study estimated volumes for 12,422 rockfalls occurring between April 2007 and May 2011, identifying the most hazardous areas of the volcano's summit. The approach combined fuzzy set theory for event discrimination, kurtosis-based signal picking, and surface-wave propagation modeling to enhance hazard assessment.
Timing of a large volcanic flank movement at Piton de la Fournaise Volcano using noise-based seismic monitoring and ground deformation measurements
A significant volcanic flank movement at Piton de la Fournaise (PdF) Volcano, La Réunion Island, was detected using noise-based seismic monitoring and ground deformation measurements. The study revealed that a large velocity reduction in seismic signals began just days before the major 2007 April 2 eruption, coinciding with widespread flank movement triggered by magma injection. This finding underscores the potential of combining seismic velocity changes with geodetic observations to monitor hazardous slope instabilities, providing critical insights for volcanic hazard assessment.
Large scale modeling of the transport, chemical transformation and mass budget of the sulfur emitted during the April 2007 eruption of Piton de la Fournaise
During the April 2007 eruption of Piton de la Fournaise, one of the largest eruptions recorded on Réunion Island in the last century, a total of 230 kilotons of sulfur dioxide (SO₂) were emitted, with 60 kilotons transforming into sulfuric acid (H₂SO₄). Using satellite observations and mesoscale chemical modeling (MesoNH-C), researchers estimated that 27 kilotons of SO₂ and 21 kilotons of H₂SO₄ were deposited at the surface through dry deposition. The study also reconstructed the temporal evolution of SO₂ emissions, identifying a peak degassing rate of 1800 kg/s on April 6. This top-down approach provides valuable data for local studies and enhances understanding of volcanic sulfur cycling in atmospheric models.
Satellite-based evidence for a large hydrothermal system at Piton de la Fournaise volcano (Reunion Island)
A large hydrothermal system beneath Piton de la Fournaise volcano, Reunion Island, has been identified through satellite-based evidence. During the April 2007 eruption, sulfur dioxide (SO₂) emissions from the Dolomieu crater's collapse phase were significantly higher than those explained by lava effusion alone, suggesting the sudden release of SO₂ from a previously hidden hydrothermal system. This discovery provides new insights into the magmatic source evolution and its potential role in eruptive behavior at this active volcano.
Evolution of magma conduits during the 1998–2000 eruptions of Piton de la Fournaise volcano, Réunion Island
A groundbreaking study reveals that the 1998–2000 eruptions of Piton de la Fournaise volcano on Réunion Island were driven by lateral dikes rooted at shallow depths, typically less than 1000 meters. These dikes, which account for 17% of the emitted lava volume, highlight the significant role of exogenous growth in volcanic edifice construction. The research used interferometric synthetic aperture radar (InSAR) data combined with 3-D boundary element models and Monte Carlo inversion to analyze coeruptive displacements, providing unprecedented insights into magma conduit evolution. Additionally, the study found that dikes initially propagate vertically from a deep source before being injected laterally at shallow depths, consistent with neutral buoyancy levels in the edifice.
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