5th Swiss Geoscience Meeting, Geneva 2007
Rock falls in Loen, western Norway, in 1905 and 1936 and the
devastating waves they generated in Lake Lovatnet
Atle Nesje
Department of Earth Science, University of Bergen, Allégaten 41, N-5007 Bergen, Norway
January 15th 1905 and September 13th 1936 two of the most devastating natural
hazards in modern times occurred in Norway. The rock falls in 1905 and 1936 triggered
large waves along the shores of Lake Lovatnet. In 1905 and 1936 there were 61 and 74
casualties, respectively, altogether 135. In total, seven rock falls occurred from the
vertical cliff Ramnefjellet in Loen during the period 1905-1950 (Table 1).
The 1905 rock fall
15 January 1905, between 23.00 and 24.00 PM, two loud bangs were heard from
Ramnefjellet. A volume of 50,000 m3 of rock fell down from an altitude of about 500 m
and put on move about 300,000 m3 of till and talus material at the base of the slope. It
has been estimated that 870.000 tons of material moved into the lake. The rock fall
generated large waves with a maximum height of 40.5 m above the lake level in
Lovatnet (52 m a.s.l.).
The 1936 rock fall
The September 13 rock fall in 1936 occurred at 04.30 AM. One million m 3 of rock fell
down and into the lake. The rock fall generated waves with a maximum height of 74.2 m
above the lake level.
Table 1. Rock falls from Ramnefjellet in Loen, western Norway in the period 1905-1950.
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Date
Volume rock Volume till/
Fallout
Maximum
No. of
3
3
(m )
talus (m )
(m a.s.l.) wave height (m)
casualties
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15.01.1905
50,000
300,000
500
40.5
61
20.09.1905 ca. 15,000
ca. 50,000
400
>15
0
13.09.1936 1 million
800
74.2
74
21.09.1936 ca. 100,000
800
ca. 40
0
06.10.1936
?
800
?
0
11.11.1936 >1 million
800
>74
0
22.06.1950 ca. 1 million
800
ca. 15
0____