ROCK AVALANCHES AND OTHER MASS MOVEMENTS IN WESTERN NORWEGIAN FJORD AREAS
By Geologist Christer Hoel, M.Sc.
The fjord areas of Western Norway are well known for their many rock avalanches and other mass movements which have happened fairly regularly since the last Ice Age. In the following articles, a number of them are presented.
In the inner of the Nordfjord region in the northern part of the Sogn and Fjordane County the settlement Loen is situated, a small settlement by the fjord. In 1905 a large rock avalanche in the southern part of the near-by idyllic Lake Lovatnet created waves killing 61 people. In 1936 a much larger avalanche created even bigger waves which caused the death of 74 people.
Tafjord is a small settlement in the inner of Tafjorden, one of the fjord parts in the inner areas of the Sunnmøre district. On the 7. of April 1934 a large rock avalanche took place by the fjord on its northeastern side, creating tsunamis which caused the death of 23 people in Tafjord and 17 people in Fjørå, another small settlement, longer out by the fjord.
In the inner parts of the Hardangerfjord, at the outlet of the Osafjorden tributary fjord, on the Bagnsnes side, a large part of the fjord side has once fallen out. This has even given basis for a legend. But is there any truth in the legend? One thing is clear: With tremendous force has the block which fell out penetrated the fjord bottom.
At 10 o´clock in the evening on January 8th in 1731, a large part of the mountain today known as Skafjell fell into the fjord on the opposite side of Stranda. A small farm situated on a headland nearby was struck by the rock avalanche and disappeared. The avalanche created waves up to 30 meters high, which flowed some 100 meters inwards land in Stranda, destroying all boat houses except for two, and all boats laying by land.
Something was happening up there in the mountain area to the west of the Tjelle settlement. Farming people at Tjelle, certainly also on Trollmyr and Rød, knew that above the wooded hillside just west of Tjelle, there had been changes in the landscape. This does not seem to have been talked about in the settlements, but the people who walked in the mountains to Tjellasetra, could not fail to notice a crack which clearly every year became wider and deeper. They did not interpret this feature, nor the fact that during the last autumn and spring there were increasingly frequent rockfalls in the mountain Tjellafjellet.
Åkerneset is a steep and mountainous part of the western fjord side of the fjord Sunnylvsfjorden in the inner part of the Sunnmøre district, situated in the middle between the settlements Stranda and Hellesylt. Two farms were run in this remote area until 1958. Then they were abandoned, but are still kept as a cultural heritage.
In 1983 a person who once had his childhood on one of the farms in the area re-discovered what the population for generations had called “The Crack”. It used to be a long but narrow fracture in the rock along the mountain side. Now it was a couple of meters wide. The length was around 500 meters. The fracture has been widening with up to four centimetres each year, and is still widening.
Most of the roads along the fjords in Western Norway are all year around the scene for mass movement of different sorts and sizes. This may include rock falls, rockslides, landslides, debris flows, mud flows, snow avalanches and rock avalanches.
Some of the roads are particularly well-known for their high level of mass movements exposed over them. In order to try to control potential rockslides, landslides etc. the Norwegian Public Roads Administration make efforts to secure the sides of hills and mountains.