DEALING WITH GEOLOGICAL HAZARDS A Coy Rock Avalanche Ingvild Haneset Nygård Ingvild Haneset Nygård is a Norwegian hydrogeologist and environmental geologist with a Masters
degree from the Norwegian University of Science and Technology. She is a former participant at the Western Michigan University Hydrogeology Field Course the summer of 2015 and is currently working at Norconsult in Norway. She is also a board member of the Norwegian chapter of the International Association of Hydrogeologists.
Has The Man fallen yet?
In the late spring of 2015 the warmth of the sun had finally returned, the snow had almost melted, and green leaves were slowly starting to bloom once more. I was on an excursion with my classmates in the western part of Norway, in Romsdalen (Map-Fig.1), with the majestic mountains towering over the bottom of the valley. I was thrilled to observe some spectacular views like Trollveggen (translation: the troll wall) and Trollstigen (translation: the troll ladder) during the ride along Romsdalen valley, but there was also an excited atmosphere in the bus, because we were about to see the unstable rock mass called Mannen (translation: The Man). The conversation in the bus went on about how dramatic the last couple of days of October 2014 had been. Those days when the whole of Norway had held its breath and all eyes, cameras, lasers, and radars were pointed towards The Man. The days when the rock mass moved 300 mm. The days when you continuously F5’ed (updated) the webpage named “Has The Man fallen yet?” (
https://www.harmannenfalt.no/ index.html) and kept up-to-date on all articles the media wrote about it. That day when families for the first time evacuated from their homes because of the red danger signal. Little did they then know that this would be only the first time of many over the years that they would have to evacuate due to the unstable rock mass,
The Man
The Man got its name from the man-shaped boulder on the top of the mountain. It rises about 1300 meters (4300 feet) above sea level and consists of dioritic to granitic gneiss and migma- tite, with a varied content of sillimanite, quartz and kyanite. Due to the deep
12 TPG •
Jul.Aug.Sep 2019
www.aipg.org
and open fractures in the upper part of the mountain, a volume of between 120,000 m3 and 180,000 m3 (i.e.350,000 to 500,000 tonnes) of massive rock is estimated to have loosened from the bed- rock. It is assumed that the loose masses will one day slide out as a huge rock avalanche to cover the bottom of the val- ley. The slide will affect settlements, the railway and the road passing through the
valley. A rock slide like that could also dam Rauma, the river that flows through the valley, which could lead to a poten- tially disastrous dam breach and fol- lowing flood.1 Because of the hazard the mountain causes, the mountain has been monitored since 2006.2 Veslemannen (translated: The Little Man) is a small part of the unstable mountain area that moves with a higher velocity than the
Fig.1: Location Map with place mentioned in text
labeled.Courtesy Google Earth.
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