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.

Durand, V., Mangeney, A., Haas, F., Jia, X., Bonilla, F., Peltier, A., Hibert, C., Ferrazzini, V., Kowalski, P., Lauret, F., Brunet, C., Satriano, C., Wegner, K., Delorme, A., & Villeneuve, N. (2018). On the Link Between External Forcings and Slope Instabilities in the Piton de la Fournaise Summit Crater, Reunion Island. Journal of Geophysical Research: Earth Surface, 123(10), 2422–2442. Portico. https://doi.org/10.1029/2017jf004507