Jökull - 01.12.1953, Blaðsíða 39

ANCHORED STONE POLYGONS AT LOW LEVELS WITHIN
THE ICELAND BASALT REGIONS
In a preliminary paper of a compilatory
nature I arrived at the following main clas-
sification of Iceland in respect of polygons:
„Low level coastal areas and valley bottoms:
All polygons shallow („floating"), with
gravel margins, usual dimeters 20—80 cm.
Well assorted throughout. Gradually merg-
ing into
Inland plateaux at 400—800 m levels:
Polygons usually relatively shallow and
assorted, with gravel margins. Usual dia-
meters 60—200 cm, tending to incraese
with altitude.
The basalt plateaux at about 600—1000 m
levels:
Polygons usually deep („anchored") and
assorted, with block margins. Usual dia-
Swedish-Icelandic Investigations 1936—37—38.
Geografiska Annaler, Stockholm 1937—1940.
1943.
Lewis, W. V., in Discussion on the origin of
glacial drift. The Journal of Glaciology, Vol.
I. London 1950.
Thorarinsson, Sigurdur, Uber anomale Glet-
scherschwankungen. Geologiska Föreningens
i Stockholm Förhandlingar. 1938.
Thoroddsen, Th., Island, Grundriss der Geo-
graphie und Geologie. Pet. Mitt. Erg. Heft
152/53. Gotha 1905-06.
Todtmann, E. M., Im Gletscherriickzugsgebiet
des Vatnajökull auf Island, 1951. Neues Jb.
Geol. Palaontol. Stuttgart 1952.
ÁGRIP: Dr. E. M. Todtmann, jarðfrœöingur
frá Hamborg hefur oft liomið hingað til lands
til jöklarannsókna. Síðastliðið sumar dvaldi hún
10 daga við Eyjabakkajökul. I ofanritaðri grein
lýsir hún svœðinu framan við jökulinn og rekur
lengdarbreytingar hans, frá því er hann gekli
fram árið 1890. Styðst hún við flugmyndir og við
athuganir Sigurðar Þórarinssonar, sem dvaldist á
þessum slóðum sumarið 1935. Jökullinn geklt
nokltuð fram árið 1931 og sömuleiðis 1938, en
heildarlega hefur jökullinn hörfað til baka um
1300 m síðan 1890.
meters 2—10 m.“ (Notes on Patterned
Ground in Iceland. Geografiska Annaler
1951, p. 147).
Since I compiled this paper I have paid more
attention to patterned ground during my travels
in Iceland without, however, having had oppor-
tunity to study these interesting phenomena
systematically. To the above-mentioned classi-
fication I should now like to add the following
remarks:
During my travels in the tertiary basalt re-
gions in N and E Iceland the two last summers
I have found anchored polygons with block
margins even on low level coastal areas and
valley bottoms. Three examples may be
mentioned:
1. On a rather plain area SW of Skógafjall
in Hrútafjörður, N Iceland (8 km W of
Ivjörseyri) in ab. 250 m height I ob-
served rather regular anchored polygons
with block margins. The diameter of the
polygons was 2 á 3 m, and the diam. of the
blocks in the margins 10—35 cm. This
type of polygons seems to be common on
the ridges between Hrútafjörður and Gils-
fjörður, and may probably be found at
lower levels than 250 m.
2. In Búlandsdalur, S of Búlandstindur, E.
Iceland, I found on the valley bottom in
ab. 150 m height stone polygons of the
same type and size as in Hrútafjörður. This
was the only type of polygons observed in
that valley.
3. N of the mouth of Búlandsdalur the river
Búlandsá has formed very nice gravel ter-
races in ab. 50 and ab. 22 m height respect-
ively. On these terraces are found small
floating gravel polygons and rings 30—50
cm in diam. The same type of floating
polygons, with diameter varying between
30 and 80 cm, is common on gravel plains
near the farm Teigarhorn in ab. 20 m
height, but in that height one can also
find rather irregular, anchored stone poly-
gons, and one can find both types of
polygons on the same place such as shown
37