Jökull - 01.01.2001, Side 84

Tómas Jóhannesson and Þorsteinn Arnalds

Figure 3. Same as Figure 2 except that a map of Iceland is not drawn as a background. The outline of country
can be clearly distinguished from the geographical distribution of avalanche accidents alone. – Sömu gögn
og í mynd 2 nema hvað kort af Íslandi er ekki í bakgrunni. Útlínur landsins má auðveldlega greina út frá
landfræðilegri dreifingu snjóflóðaslysa.
distribution of tree species cannot be used for eval-
uating avalanche hazard in Iceland. Geological ev-
idence, such as earth profiles and scattered boulders,
which are often transported by avalanches, may some-
times be used to estimate the frequency and the max-
imum historical runout distance of snow avalanches,
but studies of such evidence have only recently been
initiated.
Meteorological conditions
The most dangerous avalanche cycles in Iceland are
associated with intense lows that direct strong north
or northeasterly winds to the threatened areas in west-
ern, northern or eastern Iceland. Heavy snow fall and
accumulation of drifting snow in the starting zones
in high winds are important components that lead to
the most dangerous avalanche cycles (average wind
speeds in excess of 90 knots have been observed in
the mountains under such conditions). The snow
drift is particularly important where large plateaux
are located near steep slopes in which case snow
drift during storms can deposit huge amounts of snow
in avalanche starting zones adjacent to the plateaux.
Björnsson (1980) gives a general outline of avalanche
conditions in Iceland and includes a brief discussion
of the meteorological conditions associated with the
major avalanche cycles of this century. Jóhannes-
son and Jónsson (1996) and Ólafsson (1998) describe
weather before and during several avalanche cycles in
the Northwestern peninsula and in Neskaupstaður in
the Eastern fjords.
FATAL ACCIDENTS
A total of 193 people have been killed in snow
avalanches, slush flows and landslides in Iceland since
1901 (Jónsson et al. 1992; sources from the Icelandic
Meteorological Office; Pétursson, 1991, 1992, 1993,
84 JÖKULL No. 50