Aline Peltier

Institut de Physique du Globe de Paris · Observatoire Volcanologique du Piton de la Fournaise

In this study, the geomorphological evolution of an inner flank of the Dolomieu at Piton de La Fournaise/La Réunion was investigated with the help of terrestrial laser scanning (TLS) data, terrestrial photogrammetric images, and historical webcam photographs. While TLS data and the terrestrial images were recorded during three field surveys, the st...

Eruptions in basaltic volcanoes are often preceded by increasing seismicity and surface deformation, which progressively damage and weaken the volcanic edifice. We show how damage and crack interaction produce the inverse Omori‐Utsu law for earthquakes during pre‐eruptive periods. Rock mass continuity, representing damage, is shown to decrease expo...

Volcano observatories (VOs) around the world are required to maintain surveillance of their volcanoes and inform civil protection and aviation authorities about impending eruptions. They often work through consolidated procedures to respond to volcanic crises in a timely manner and provide a service to the community aimed at reducing the potential...

Forecasting eruptions is a fundamental goal of volcanology. However, difficulties in identifying eruptive precursors, fragmented approaches and lack of resources make eruption forecasting difficult to achieve. In this Review, we explore the first-order scientific approaches that are essential to progress towards forecasting the time and location of...

Taking prompt and effective actions to mitigate risks associated with an effusive eruption greatly depends on the monitoring of lava flow emplacement. Here we report on the monitoring of the lava flow emplaced during the 19 September to 05 October 2022 eruption at Piton de la Fournaise (La Réunion) that involves an unprecedentedly large data set ac...

Quantifying the effect of external forcings like seismicity or rain on slope destabilization is a long-standing and challenging issue. To investigate the respective roles of these forcings, we analyze an unprecedented 10-year long catalog of rockfalls occurring in the crater of the Piton de la Fournaise volcano (La Reunion Island), using statistica...

Changes in magma properties and transport geometry can have a direct impact on volcanic activity. However, such variations can be difficult to track during eruptions. We report previously undetected very-long-period (VLP) signals at Piton de la Fournaise that can be used to probe changes in magma transport. Source analysis of VLP events during the...

Volcano Observatories (VOs) around the world are required to maintain surveillance of their volcanoes and inform civil protection and aviation authorities about impending eruptions. They often work through consolidated procedures to respond to volcanic crises in a timely manner and provide a service to the community aimed at reducing the potential...

Near‐real time analysis of magnetization can provide important information for the imaging of volcano systems and their spatiotemporal evolution. This study focuses on the contribution of volcano‐magnetic signals from reiterations of ground magnetic measurements to investigate the evolution of active structures at the Piton de la Fournaise volcano...

In May 2018, the Mayotte island, located in the Indian Ocean, was affected by an unprecedented seismic crisis, followed by anomalous on-land surface displacements in July 2018. Cumulatively from July 1, 2018 to December 31, 2021, the horizontal displacements were approximately 21 to 25 cm eastward, and subsidence was approximately 10 to 19 cm. The...

The “Fani Maoré” eruption off the coasts of Mayotte has been intensively monitored by applying methods similar to those used for subaerial eruptions. Repeated high-resolution bathymetric surveys and dredging, coupled with petrological analyses of time-constrained samples, allowed tracking the evolution of magma over the whole submarine eruptive seq...

Effective and rapid effusive crisis response is necessary to mitigate the risks associated with lava flows that could threaten or inundate inhabited or visited areas. At Piton de la Fournaise (La Réunion, France), well-established protocols between Observatoire Volcanologique du Piton de la Fournaise - Institut de Physique du Globe de Paris (OVPF-I...

Since 1979, Piton de la Fournaise (La Réunion) has erupted on average two times per year, with 95 % of these eruptions occurring within an uninhabited caldera. However, lava flows have occasionally impacted populated regions on the island, as in 1977 and 1986. Since 2014, an integrated satellite data–driven multinational response to effusive crises...

Monitoring ground surface deformation is an essential component of volcano monitoring, along with other techniques, such as seismology, geochemistry and geology. This chapter presents the different sources at the origin of the deformation observed in a volcanic context, followed by a review of the various techniques used for measuring such deformat...

Despite significant advancements in understanding crustal melt transport, determining the shallow magmatic architecture at any given volcanic system remains a significant challenge with geophysical methods alone. In this study, we present a new conceptual model combining previously studied models for geomechanical magma reservoirs and dyke-shaped c...

Identifying the causes of flank destabilization of active volcanic edifices is key to prevent catastrophic events. The persistent seismicity recorded below the eastern flank of Piton de la Fournaise shield volcano (Réunion Island), both in between and during eruptive events, may give indications on the mechanical stability of this edifice. Whether...

Volcanic activity can induce flank failure, sometimes generating large earthquakes and tsunamis. However, the failure structures have never been fully characterized and the failure mechanism is still debated. Magmatic activity is a possible trigger, either through fault slip, which might be induced by dyke intrusions, or through sill intrusions, wh...

Formalised elicitation of expert judgements has been used to help tackle several problematic societal issues, including volcanic crises and pandemic threats. We present an expert elicitation exercise for Piton de la Fournaise volcano, La Réunion island, held remotely in April 2021. This involved 28 experts from nine countries who considered a hypot...

In this study, we demonstrate the strong potential of combining Unmanned Aerial Vehicle (UAV)-based thermal infrared (IR) and magnetic measurements to image the thermal state of volcanic edifices, as well as the distribution of active volcano-tectonic features at depth. Since magnetization is strongly dependent on temperature and alteration, therma...

In this study, we demonstrate the strong potential of combining Unmanned Aerial Vehicle (UAV)-based thermal infrared (IR) and magnetic measurements to image the thermal state of volcanic edifices, as well as the distribution of active volcano-tectonic features at depth. Since magnetization is strongly dependent on temperature and alteration, therma...

L’impact des catastrophes naturelles est devenu une préoccupation forte de nos sociétés modernes. Parmi celles-ci, les éruptions volcaniques sont redoutées pour leurs effets dévastateurs locaux, régionaux ou globaux. Depuis le début du XXe siècle une expertise scientifique s’est progressivement développée visant à évaluer les aléas de l’activité vo...

Deep-sea submarine eruptions are the least known type of volcanic activity, due to the difficulty of detecting, monitoring, and sampling them. Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (Indian Ocean) has extruded at least 6.5 km3 of magma to date, making it the largest monito...

Volcanic eruptions shape Earth’s surface and provide a window into deep Earth processes. How the primary asthenospheric melts form, pond and ascend through the lithosphere is, however, still poorly understood. Since 10 May 2018, magmatic activity has occurred offshore eastern Mayotte (North Mozambique channel), associated with large surface displac...

Since 2018, the submarine east flank of Mayotte Island (Comoros archipelago) is the site of a major eruption located at 3.5 km depth bsl on a WNW-ESE volcanic ridge. Samples brought by oceanographic cruises carried out to monitor this seismo-volcanic crisis indicate that this volcanic ridge is built by a bimodal sodic alkaline magmatic series that...

The brutal onset of seismicity offshore Mayotte island North of the Mozambique Channel, Indian Ocean, that occurred in May 2018 caught the population, authorities, and scientific community off guard. Around 20 potentially felt earthquakes were recorded in the first 5 days, up to magnitude Mw 5.9. The scientific community had little pre-existing kno...

Piton de la Fournaise, situated on La Réunion island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the volcanological observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ∼ 250 histo...

In four study areas within different lithological settings and rockfall activity, lidar data were applied for a morphometric analysis of block sizes, block shapes and talus cone characteristics. This information was used to investigate the dependencies between block size, block shape and lithology on the one hand and runout distances on the other h...

Following an intense seismic crisis in May 2018, a large submarine effusive eruption offshore the island of Mayotte (SW Indian Ocean) has extruded at least 6.4 km 3 of magma, making it the largest witnessed submarine eruption as well as the largest effusive eruption since Iceland's 1783 Laki eruption. We present a detailed petrological and geochemi...

The Comoros volcanic archipelago is related to a complex E-W zone of immature right-lateral wrenching of the lithosphere in the context of the Lwandle and Somalian plate boundaries. A major volcano-tectonic crisis began in May 2018 offshore Mayotte, the easternmost island of the archipelago, resulting in the construction of a large submarine volcan...

Piton de la Fournaise, situated on La Réunion Island (France), is one of the most active hot spot basaltic shield volcanoes worldwide, experiencing at least two eruptions per year since the establishment of the observatory in 1979. Eruptions are typically fissure-fed and form extensive lava flow fields. About 95 % of some ~250 historical events (si...

In March 2020, the coronavirus disease 2019 outbreak was declared a pandemic by the World Health Organization and became a global health crisis. Authorities worldwide implemented lockdowns to restrict travel and social exchanges in a global effort to counter the pandemic. In France, and in French overseas departments, the lockdown was effective fro...

In high mountain regions, rockfalls are common processes, which transport different volumes of material and therefore endanger populated areas and infrastructure facilities. In four study areas within different lithological settings, LiDAR (light detection and ranging) data were acquired for a morphometric analysis of block sizes, block shapes and...

In the frame of the research project IOGA⁴MET, a new ground-based GNSS network is being deployed in the Southwest Indian Ocean (SWIO) since November 2017. This new network opens up for new research opportunities in geodesics and atmospheric sciences in this area regularly exposed to natural hazards, and significantly expands the International GNSS...

Identification of internal structures in an active volcano is mandatory to quantify the physical processes preceding eruptions. We propose a fully unsupervised Bayesian inversion method that uses the point compound dislocation model as a complex source of deformation, to dynamically identify the substructures activated during magma migration. We ap...

We apply three different methods based on the analysis of the multicomponent seismic data to detect seismovolcanic tremors and other seismovolcanic signals, to propose an approach to classify them, and to locate their sources. We use continuous seismograms recorded during 1 year by 21 stations at the Piton de la Fournaise volcano (La Réunion, Franc...

We produced new multi-temporal Digital Elevation Models (DEMs) of the April 2007 summit collapse at Piton de la Fournaise from previously unused aerial photographs. This dataset revealed the precise temporal evolution of collapsed volume and caldera morphological changes. Four days after the onset of an eruption at an unusually low elevation, the s...

Volcanic tremor is key to our understanding of active magmatic systems, but due to its complexity, there is still a debate concerning its origins and how it can be used to characterize eruptive dynamics. In this study we leverage machine learning techniques using 6 years of continuous seismic data from the Piton de la Fournaise volcano (La Réunion...

Volcanic activity is always accompanied by the transfer of heat from the Earth’s crust to the atmosphere. This heat can be measured from space and its measurement is a very useful tool for detecting volcanic activity on a global scale. MIROVA (Middle Infrared Observation of Volcanic Activity) is an automatic volcano hot spot detection system, based...

Monitoring temporal changes of volcanic interiors is important to understand magma, fluid pressurization and transport leading to eruptions. Noise-based passive seismic monitoring using coda wave interferometry is a powerful tool to detect and monitor very slight changes in the mechanical properties of volcanic edifices. However, the complexity of...

Present-day volcano imaging and monitoring relies primarily on ground surface and satellite remote sensing observations. The overall understanding of the volcanic edifice and its dynamics is thus limited by surface investigation, spatial resolution and penetration depth of the ground methods, but also by human and material resources, and harsh envi...

Understanding the thermo-rheological regime and physical character of lava while it is flowing is crucial if we are to adequately model lava flow emplacement dynamics. We present measurements from simultaneous sampling and thermal imaging across the full width of an active channel at Piton de la Fournaise (La Réunion, France). Our data set involves...

Volcanic tremor is key to our understanding of active magmatic systems but, due to its complexity, there is still a debate concerning its origins and how it can be used to characterize eruptive dynamics. In this study we leverage machine learning (ML) techniques using 6 years of continuous seismic data from the Piton de la Fournaise volcano (La Réu...

Volcanic tremor is key to our understanding of active magmatic systems but, due to its complexity, there is still a debate concerning its origins and how it can be used to characterize eruptive dynamics. In this study we leverage machine learning (ML) techniques using 6 years of continuous seismic data from the Piton de la Fournaise volcano (La R\'...

The added value of combining InSAR and GNSS data, characterized by good spatial coverage and high temporal resolution, respectively, is evaluated based on a specific event: the propagation of the magma intrusion leading to the 26 May 2016 eruption at Piton de la Fournaise volcano (Reunion Island, France). Surface displacement is a non linear functi...

The Dolomieu caldera collapse (April 2007) was one of the most outstanding events of recent decades at Piton de la Fournaisevolcano. Forecasting such a destructive event is difficult but since then, the development of tools and monitoring networks has improved our knowledge of the dynamics of volcano instability. However, the precise location of vo...

Supplementary information to the paper

Early detection of the onset of a caldera collapse can provide crucial information to understand their formation and thus to minimize risks for the nearby population and visitors. Here, we analyse the 2007 caldera collapse of piton de la Fournaise on La Réunion Island recorded by a broadband seismic station. We show that this instrument recorded ul...

Structures developing above long‐term growing shallow‐level magma reservoirs, such as resurgent domes, may contain information on the reservoir itself. To understand the formation of such tectonic features, we have investigated the deformation process around a shallow pressurized magma reservoir embedded in a damaging elastic volcanic edifice. Our...

Magma propagation is an unsteady process controlled by magma‐crust interaction. To provide information on its dynamics, we invert complementary ground deformation data spanning the 8 hr preceding the 26 May 2016 eruption at Piton de la Fournaise (PdF) volcano (La Réunion, France). Data are inverted using 3‐D boundary element models combined with a...

Satellite-based surveillance of volcanic hot spots and plumes can be coupled with modeling to allow ensemble-based approaches to crisis response. We complete benchmark tests on an effusive crisis response protocol aimed at delivering product for use in tracking lava flows. The response involves integration of four models: MIROVA for discharge rate...

Volcanic eruptions are foundational events shaping the Earth's surface and providing a window into deep Earth processes and composition. Most eruptions occur on established volcanoes, exploiting longstanding magma reservoirs and pathways. Those creating new volcanoes are rare and usually too small or too remote to be well monitored, particularly in...

Piton de la Fournaise is one of the world's most active and visited volcanoes. Its summit crater (Cratère Dolomieu), the main tourist attraction, underwent a major caldera collapse in 2007 and its rim is not yet stabilized. In order to assess the caldera rim instability risk for visitors, we followed its structural evolution from 2007 to 2015. Usin...

In recent decades, soil CO2 flux measurements have been often used in both volcanic and seismically active areas to investigate the interconnections between temporal and spatial anomalies in degassing and telluric activities. In this study, we focus on a narrow degassing area of the Piton de la Fournaise volcano, that has been chosen for its proxim...

We have analysed the impact of different forcings, such as rain and seismicity, on slope instabilites on an active volcano. For this, we compiled a catalog of the locations and volumes of rockfalls in the Piton de la Fournaise crater using seismic records. We validated it by comparing the locations and volumes to those deduced from photogrammetric...

Anticipating eruptions early enough to give warning to authorities is one of the main goals in volcanology. However, identifying and providing unequivocal identification on volcano reawakening remain challenging issues, mostly when unrests are sudden or undetectable. At the Piton de la Fournaise volcano, a clear increase in both the seismicity and...