Who doesn’t marvel at those wonderful travel pictures of the fiords of Norway? Waterfalls, quaint houses perched on green slopes, snowy glaciers far above and likely, a cruise ship sailing far below.
One hesitates to sully this image with negative mentions, but steep-sided fiords do present a real and present danger in the form of rockfalls and rockfall-generated waves. “Fiord tsunami” I call the latter, however some find this liguistic mixture ludicrous as ‘lutefisk sushi’.
Terms aside, rockfalls and rockfall waves are serious business -- many dozens have occurred in historical time. The latest fiord tsunami happened in 1934 just outside of the town of Tafjord. Waves rose up to 62 meters elevation there and 41 persons perished.
The greatest rockfall threat looming today lies on Akerneset Mountain, flanking Sunnylvsfjorden 23 km west of Tafjord. There, a set of ominous cracks gape 900 meters above sea level. The cracks are thought to bound a sliver of mountain maybe 60 million cubic meters in volume that, like others did before, will surely fall into the fiord someday.
My computer simulations in the movie above predict that a fiord tsunami 100 m high would be sourced from a Akerneset rockfall. Not good news for Hellesylt and Geiranger, two pretty towns nestled just four and eleven minutes away by tsunami. The truly scary part of the story is that the crack widths are expanding by 3-20 cm/year.
As you might expect, scientists now closely monitor the landslide region with a battery of instruments. Their hope is that a pre-failure increase in the rate of crack expansion could provide prior warning of an impeding slide perhaps days in advance.
The notion of “Furious Fiords” has not escaped the attention of big-budget moviemakers as fodder for a docudrama/disaster flick. Recently a Norwegian film company released the movie titled “Bolgen” (Norwegian for “Wave”) staring this very same fiord tsunami. Take a look at the teaser…
Steven N. Ward Santa Cruz
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John Rundle is a Distinguished Professor of Physics and Geology at UC Davis and the Executive Director of the APEC Collaboration for Earthquake Simulations. He chaired the Board of Advisors for the Southern California Earthquake Center from 1994 to 1996. Read John's blog.