Continued research may help people living in other parts of Norway should or when the next tsunami strikes.
Destructive tsunamis can hit fjords and lakes as well as along Norway's coastline. One of the most infamous occurred in Møre og Romsdal county’s Tafjord in 1934. A giant rockslide starting 700 metres up the mountain splashed into the fjord giving people just seconds before they were engulfed by the ensuing tsunami. Over forty people died.
Tafjord was not the most horrifying inland tsunami in Norway. Another rockslide generated a 40-meter high wave in Lovatnet in Sogn og Fjordane county in 1905, killing more than sixty. The same lake suffered again in 1936 when 74 people lost their lives to a tsunami with almost no warning.
Norway has some 200,000 lakes. Can anything be done about the danger? How do we know where to start?
One of us (Bård) came up with a suggestion together with colleagues at the Norwegian Geotechnical Institute. Tsunamis can only occur where the slopes allow large rockslides to reach the lakes. That reduced the number of potentially threatened lakes to 12,000.
It is still a daunting number, so we then analysed the position of all potential rockslides around each lake. The more potential rockslides, and the steeper the slope, the more dangerous the lake.
The 100 most dangerous locations are mainly in Vestlandet (western) and Nord-Norge (northern). The combination of steep slopes, deep water, and shoreline settlements create the risk of a tsunami disaster.
More work is needed, however. The analysis so far includes only the height and steepness of the slopes. Geology and knowledge of past rockslides are not included.
These are important factors for determining the real tsunami threat in any given area. Gathering this information requires exhaustive fieldwork. We are better able to focus our efforts with our list of prioritised lakes.
The next step is warning systems. A rockfall plunging into the fjord in Hellesylt and Geiranger, Møre og Romsdal county, could create an 85 metre high tsunami. Nearby municipalities have established a monitoring facility and routines for alerting the public at elevated threat levels.
Banning lakeside living is not a solution. Neither is ignoring the threat. Just be aware and prepared!
Bård Romstad is a Research Fellow at CICERO. Dr. Ilan Kelman is a Senior Research Fellow at CICERO.
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