Greinar (Vísindafélag Íslendinga) - 01.01.1977, Side 18

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It is a reasonable assumption, which also turns out to be
in agreement with facts, that the air circulation had the same
main character during the Older as the Younger Dryas. In
particular, we seem to be allowed to postulate a similar wind
system in Iceland during both these periods, the same as is
now prevailing. (Cf. also Chapter 10 and (26)). This would
mean a similar position of the ice divide from Vatnajökull to
Mýrdalsjökull (and it seems equally likely that the striae,
indicating the ice divide, in Fig. 1, are of Younger or Older
Dryas age), but a lower temperature in the Older Dryas would
produce a higher glacier wall here and a more pronounced
precipitation shadow north of it. The northern rand moraines
might be expected rather close to Younger Dryas moraines.
Both might possibly still be detected in spite of the existence
of the Ódáðahraun lavas.
Considering glaciations in Iceland more generally, we see
that from the northeastern corner of Vatnajökull there ex-
tends a chain of mountains and mountain ridges due north to
the Melrakkaslétta lowland. Heights of 800 m to 1000 m are
common in the southern part of the chain, and here the east
component of the prevailing southeast wind and precipitation
was astride the chain. The latter was nowhere in any shadow
behind the Vatnajökull, but it would itself cast a shadow on
the lower terrain on its west side. The chain as a whole would
be glaciated, and an inspection of the map in scale 1:100,000
indicates very clearly the sidewards gullies which indicate the
erosion by glacial waters. The use of these gullies, gives a
clear demarcation of the extension of the glacier towards both
sides of the mountain chain, Fig. 2. A still better information
and verification is gained from aerial photographs. Tongues of
narrower glacier extended east and west, and it was almost
certainly (subject to closer field test) such a tongue which crept
upon the eastern margin of the huge lava field from the great
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Fig. 3. As part of Fig. 2, we infer a local glacier from Leirhafnarfjöll to ex-
plain the fact that a glacier overran marine molluscs at Röndin close to
Kópasker in Older Dryas time (3).