Jökull - 01.12.1970, Blaðsíða 33

duction utilised in this paper a time difference
of six years is not too significant.
Between 1904 and 1931 (Fig. 3) the Jökulsá
gradually became incised in the proglacial de-
posits but how rapidly this took place is not
known. Todtmann (1960) only states that in
1931 the ice front in the area of the present
Jökulsárlón was generally 20—30 m from the
moraine ridges, but where the Jökulsá flowed
out it was much closer. Between 1904 and 1908
most of the drainage east of the Jökulsá fol-
lowed channels cut through the three outermost
moraines. These channels (e.g. 6, 8, 10, 11, 12
and 20) ranged from 3 to 30 m in width. By
1908 a series of lakes between the moraine
ridges permitted the development of a drainage
system parallel to the ice front, the main com-
ponents of which were channel 20 and the
upper part of channel 8. This sequence of
channels being first of all cut through moraine
ridges and then being diverted parallel to and
on the proximal side of the ridges is clearly
demonstrated by channels 7, 14, 21 and 24. By
1908 the number of channels carrying water
frorn the ice front east of the Jökulsá to beyond
the moraine system had been reduced to 6 (20,
6, 5, 15 and the Stemma). By 1931 this number
had been reduced to one as streams 13, 7, 21
and 24 all flowed into the river Stemma.
Stream 7 drained a small proglacial lake.
West of the Jökulsá, as the ice moved back
from its 1904 position, a few channels develop-
ed between the moraine ridges and therefore
run parallel to the ice front, e.g. 40 and 42.
By 1937 (Fig. 4) there were only four drainage
routes through the 1890 moraine west of the
Jökulsá; channel 51 parallel to the Fjallsjökull
ice front; channel 49 draining the forerunner
of the Breidárlón; channel 45 which was a
direct proglacial stream at right angles to the
ice front and channel 43 which hacl four feeder
streams issuing directly from tlie ice front.
It should be noted that up until 1937 no
large proglacial lakes had developed, although
the first stages in the development of the
Breidárlón and the Stemmulón can be detected.1
1931(37)—1945
Undoubtedly the most important develop
ments during this period were the occupation
of topographic lows by four large proglacial
1) Stemmarlón on the figures should read
Stemmulón.
JÖKULL 20. ÁR 31