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.
By Geologist Christer Hoel, M.Sc.
Read more: Rock Avalanches in the Fjords
Two farms were run in this remote area until year 1958. Then they were abandoned, but are still kept as a cultural heritage.
The discovery of the crack
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 is around 500 meters.
The fracture has been widening with up to 4 cm each year, and is still widening. Since the 1990s permanent electronic measuring by means of extension stays has been done, with some intermissions, in order to measure the widening out of the fracture.
Monitoring the crack
From 2004/2005 a considerable number of more measurement methods have been utilized to give a continuous surveillance of this area.
The area which is moving reaches from 150 to 900 meters above the fjord. Drilling has revealed that there has been movement down to 62 meters under the surface.
It has been estimated that possibly 54 million m3 of rock is about to slide into the fjord. Scientists have stated that this one day will happen; it is just a matter of time.
However, it cannot be predicted exactly when it will happen. This will create tsunamis of sizes never ever experienced in historic time in Norway.
Former rock avalanches, shortly after the last ice age
However, geological surveys in Sunnylvsfjorden has revealed that gigantic rock avalanches have entered this fjord some distance to the north of Åkerneset shortly after the last ice age.
The fjord is 150-200 meters shallower where this has happened than in adjacent areas. What we can expect also seems to have happened before in this area.
Different scenarios in case of a future Rock Avalanche
In case of a rock avalanche containing 54 million m3 of rock material, there will be a wave some 100 meters high on the opposite side of the fjord. The tsunami which reaches Hellesylt will produce a wave as large as 85 meters high, whereas in Geiranger the similar will give a wave with height 70 meters.
A possible alternative with a rock avalanche containing 18 million m3 of rock material, will create a wave which will be 35 meters high in Hellesylt and in Geiranger 30 meters.
The scenario with the largest amount of rock material falling into the fjord will furthermore create a tsunami which will produce a wave 14 meters high in Tafjord, not far from the wave height experienced at the same place in 1934.
Waves several meters high will also hit a large number of other settlements in the Sunnmøre district, and will be noticeable even in Ålesund.
The consequences of this rock avalanche and the following tsunamis will be without parallel.
As in Loen and Tafjord, a rock avalanche on Åkerneset will warn itself. It is, however, important to interpret the signals correctly and be able to handle the situation accordingly.
In order to handle the situation in case of this kind of scenario, the authorities have made detailed plans for quick evacuation of the population and other measures.
Trailer from the Movie “Bølgen” about Åkerneset
This article is written by Geologist Christer Hoel, M.Sc. – Linkedin
- Blikra, L.H.; Longva, O.; Harbitz, C. & Løvholt, F. : Quantification of rock-avalanche and tsunami hazard in Storfjorden, Western Norway. Norwegian Journal of Geology, 2005.
- Blikra, L.H.; Anda, E.; Høst, J. & Longva, O. : Åknes/Tafjord-prosjektet. Sannsynlighet og risiko knyttet til fjellskred og flodbølger fra Åknes og Hegguraksla. Rapport 2006.039 .
- Fantefilm: Trailer from the movie Bølgen.
- https://www.nve.no/naturfare/overvaking-og-varsling/fjellskredovervaaking/kontinuerlig-overvaakede-fjellpartier/aaknes/ (Photo: Åge Kjølås/NVE)
- Norges Geotekniske Institutt 2011: Åknes/Tafjord-project. Numerical simulations of tsunamis from potential and historical rock slides in Storfjorden; Hazard zoning and comparison with 3D laboratory experiments. Rapport.