On Saturday, September 6th, a huge cloud of grey dust barreled down the side of the Fer-à-Cheval cirque in Sixt-Fer-à-Cheval of France‘s Haute-Savoie. Initial reports claimed at least 12,000 cubic meters of rock collapsed in the incident. However, according to France’s Ici, the actual number could be quite a bit higher.
Ce samedi en fin de matinée en Haute-Savoie 12000m3 de roche en quelques minutes…Cirque du fer à cheval à Sixt pic.twitter.com/EbpceKS3pu
— Seb de la Montagne (@seb74mieussy) September 6, 2025
Landslide in France’s Haute-Savoie
Ici reports that French geomorphologist and CNRS researcher attached to the EDYTEM Laboratory Ludovic Ravanel believes the landslide was certainly above 12,000 cubic meters of rock. His report puts the number closer to 20, 30, or potentially up to 40,000 cubic meters. The Fer-à-Cheval cirque is not new to landslides, but one of that magnitude is rather exceptional.
While no hiking trails were damaged or affected by the landslide, the mayor of Sixt-Fer-à-Cheval has prohibited access to the Fond de la Combe as a safety precaution. The Mountain Terrain Restoration services must make a conclusion before the area can be reopened. According Ludovic Ravanel, the mountain is likely still quite unstable but further landslides of such significance are unlikely.
At this point officials aren’t sure exactly what caused the landslide. While permafrost thawing and causing cracks is often the culprit, this slide occurred outside of the permafrost area. Meteorological data will have to be analyzed to help understand whether the alternation of heatwaves and rain is the cause. It’s also possible that the rock had just gotten unstable over the years.
8 firefighters were dispatched to the scene following the slide to search for potential victims, but no mountain climbers were found around the popular route. The municipality was on alert for potential disappearances in the area following the slide. Markers were installed to divert hikers from the path near the rockfall zone on September 8th.
