Jökull - 01.11.1998, Side 3

JÖKULL
lceland journal of Earth Sciences
46. Ár 1998 No. 46
Jöklarannsóknafélag íslands • Jarðfræðafélag íslands
The cover photo
The cover photo of this issue of Jökull shows the
so-called Jökulborgir in the Langjökull ice cap, west-
em Iceland. Jökulborgir are a sequence of bumps in
the surface of the ice cap that are formed when the ice
flows over sharp peaks in the bottom topography,
aligned along a volcanic fissure. There are five bumps
aligned in the same direction as the Jarlhettur peaks
which are further to the south, outside of the margin of
the ice cap.
A further description of Jökulborgir can be found
in the 1980 Yearbook of the Iceland Tourist Associat-
ion. There is a shallow trough in the glacier landscape
downstream of each of the Jökulborgir bumps and the
ice flows uphill against the slope of the ice surface for
some distance in each of the troughs. The bumps are
heavily crevassed due to extending ice flow near the
surface but there is little crevassing in the troughs
where the flow is compressing near the surface.
This feature in the glacier landscape is relatively
steady from year to year and the glacier therefore
flows in similar way in this area as a shallow brook
flowing over rocks.
Similar bumps and troughs can be seen on several
other ice caps and glaciers in Iceland, but Jökulborgir
Three-dimensional linear Newtonian flow over a sharp bedrock peak.
- Þrfvítt flæöi línulegs “Newtonsks” efnis yfir skarpan tind í botnlandslagi.
JOKULL, No. 46, 1998
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