EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Lava flow hazard map of Piton de la Fournaise volcano 

Oryaëlle Chevrel1, Massimiliano Favalli2, Villeneuve Nicolas3,4,5, Andrew Harris1, Alessandro Fornaciai2, Nicole Richter3,5,6, Allan Derrien3,5, Patrice Boissier3,5, Andrea Di Muro3,5, and Aline Peltier3,5
Oryaëlle Chevrel et al.
  • 1Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France (
  • 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), Via Battisti, 53, 56125 Pisa, Italy.
  • 3Université de Paris, Institut de physique du globe de Paris, CNRS, F-75005 Paris, France.
  • 4Université de La Réunion, Laboratoire Géosciences Réunion, F-97744 Saint-Denis, France.
  • 5Observatoire Volcanologique du Piton de la Fournaise, Institut de physique du globe de Paris, F-97418 La Plaine des Cafres, France.
  • 6Helmholtz Centre Potsdam, German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam, 14473, Germany

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 (since the first confidently dated eruption in 1708) have occurred inside an uninhabited horse-shoe shaped caldera (hereafter referred to as the Enclos) which is open to the ocean on its eastern side. Rarely (12 times since the 18th century), fissures have opened outside of the Enclos where housing units, population centers and infrastructure are at risk. In such a situation, lava flow hazard maps are a useful way of visualizing lava flow inundation probabilities over large areas. Here, we present a lava flow hazard map for Piton de la Fournaise volcano based on: i) vent distribution, ii) statistics of lava flow lengths, iii) lava flow recurrence times, and iv) simulations of lava flow paths across multi-temporal (i.e., regularly updated) topography using the DOWNFLOW stochastic numerical model. A map of the entire volcano highlights that the most probable (up to 12 %) location for future lava flow inundation is within the Enclos, where about 100,000 visitors are present each year. Hazard distribution changes throughout the analysis period due to the high frequency of eruptions that constantly modifies the vent opening distribution as well as the topography and the lava flow dimensional characteristics. Outside of the Enclos, probabilities reach 0.5 % along the well-defined rift zones and, although hazard occurrence in inhabited areas is deemed to be very low (<0.1 %), it may be underestimated here, as our study is only based on post-18th century records and neglects cycles of activity at the volcano. Specific hazard maps considering different event scenarios (i.e., events fed by different combinations of temporally evolving superficial and deep sources) are required to better assess affected areas in the future – especially by atypical, but potentially extremely hazardous, large volume eruptions. At such an active site, our method supports the need for regular updates of DEMs and associated lava flow hazard maps if we are to be effective in mitigating the associated risks.

How to cite: Chevrel, O., Favalli, M., Nicolas, V., Harris, A., Fornaciai, A., Richter, N., Derrien, A., Boissier, P., Di Muro, A., and Peltier, A.: Lava flow hazard map of Piton de la Fournaise volcano , EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12266,, 2021.

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