Rissa Landslide

In 1978 near Rissa, Norway, a landslide devastated an area of 0.127 sq miles, which included 7 farms. The slide contained about 7 to 8 million cubic yards of debris - the biggest slide in Norway in this century. Of the 40 people caught in the slide area, only 1 died.

The cause of this landslide was later determined to be the failure of a quick clay (marine clay) that was triggered by the excavation and stockpiling of 900 cu yards of soil placed by the shore of Lake Botnen. The stock-piled soil was generated by excavation work from the construction of a new wing being added to an existing barn. Note the relationship between the volume of the slide (~7.5 million yards) to the volume of the excavation that triggered it (~900 yards) - a ratio of over 8,000.

The slide started at the lake shoreline and developed retrogressively landward, occurring over a period of 6 minutes. About 70-90 m of shore slid into the lake.

The AVI clips below show portions of the slide in progress as filmed from a nearby vantage point. Look at the houses in the video clips to get a sense of the size of the failure - in the second clip, you can see houses and barns being carried away by the slide.

Part 1 - note the speed with which the landslide is moving

Part 2 - note that the slide is moving over great distances even though the ground is virtually flat