Jökull - 01.12.1953, Blaðsíða 23

Fig. 12. The lake in
Hveradalur and the ice
cauldron (6) SW of it.
View to the south.
Jökullónið í Hveradal og
ketilsigið ncesta fyrir suð-
vestan það. Séð til suðurs.
Photograph
by S. Þórarinsson,
3 July 1953.
biggest mud pool (3 on the map) I named
Kraumur. Thin layers of sulphur deposits are
found, especially on tlie valley slopes and in
the small area W of Gámur marked 2 on the
map. The thermal area continues towards SW
beneath the ice. Ab. 300 m SW of the lake
there are two powerful steam vents (6 on the
map), which have percolated the ice-cover (Figs.
12 and 13), and farther east is a large cauldron
(7) due to subglacial melting.
The valley SW of Gámur seems to be formed
as a volcanic fissure. Its steep NW slopes are
covered by lava lumps clustered together so as
to form a continuous thin lava layer. Higher
up on the slopes is a cover of scoria. The vol-
canic action forming these layers is probably of
a very recent date.
The lake in the SW end of the valley varies
much in depth and extent. When photographed
by the Royal Air Force on 12 March 1944 (Thor-
arinsson 1950, Fig. 2) the lake was at least 0.5
km in length, but when Ó. Jónsson visited the
valley on 9 July 1946 he found no lake at all
there (Jónsson 1953, p. 57). When we were there
one month later we found a small lake, but on
our last visit the lake level was at least 10 m
higher than on our visit in 1946. The lake level,
however, has never in recent years risen high
enough to find an outflow through the valley
towards NE. It must thus be drained under
the ice towards NW, but probably the water
then has to penetrate a narrow ridge of young
volcanic material.
As we do not know how far the thermal area
extends under the ice cover, we can only very
roughly estimate its size, but probably the area
Fig. 13. Inside the ice cauldron shówn on
Fig. 12.
Ncermynd af ketilsiginu á 12. mynd.
Phot. by S. Þórarinsson, 3 July 1953.