A substantial rockfall on the north face of Zugspitze, Germany’s highest mountain, raised a visible dust cloud early last week. Researchers estimate that about 13,800 cubic metres of rock fell in total. The main collapse was accompanied by numerous smaller falls before and after it, and material is still crumbling away.
Johannes Leinauer, a slope-movement expert at the Technical University of Munich, expects smaller falls—from a few cubic metres to tens of thousands—to increase. He said it is not possible to predict in general whether or when a much larger collapse might occur. Rockfalls on the scale of last week’s event happen on Zugspitze every few years.
The collapse began across an area about 100 by 40 metres, at roughly 2,800 metres above sea level on an 80-degree slope. Researchers expect warm permafrost in this section. Permanently frozen ground helps bind mountain rock; as it thaws, slopes can become less stable.
In a nearby research tunnel at the same elevation, temperatures measured 15 metres inside the rock have risen from −1.2°C to −0.7°C since 2007. Heat takes about three months to penetrate the rock, so researchers expect the strongest warming inside the mountain in the coming months. They plan to place a laser scanner about four kilometres away to track movement on the north face. Leinauer said major collapses are usually preceded by visible loosening and smaller rockfalls.