Landslide

A landslide is when very large quantities of rock (boulders, debris and/or rubble) fall into the valley at high speed.

One cause of landslides may be the lack of counterpressure from ice after a glacier has melted.
Another cause may be thawing permafrost.

On April 18 and May 9, 1991, a total of around 30 million m3 of rock fell into the valley near Randa. No people were injured. However, considerable damage was caused to the infrastructure (railroads, buildings and roads).