Jökull - 01.12.1952, Blaðsíða 7

Á síðustu árum hefur aukizt mjög áhugi
jöklafræðinga á lagskiptingu í jöklum, eftir að
amerískir og enskir jöklafræðingar (G. Gibson,
J. L. Day og W. V. Lewis) höfðu sýnt fram á, að
sumir botn- og daljöklar skríði fram eftir bjúg-
mynduðum skriðflötum (rotational movement).
Raunar er slík hverfihreyfing í jöklum Islend-
ingum kunn frá fornu fari, svo sem sjá má af
kaflanum um Island i Danasögu Saxós. Ymis-
legt hefur verið deilt um það, hvers uppruna
lagskiptingin í jöklunum sé, og skal ekki farið
nánar út í það, en víst má telja, hvað sem öðru
líður, að lögin í jökli þeim í Reykjafjöllum, sem
hér hefur verið lýst, séu árslög, mynduð af ár-
legum fyrningum á hjarnsvæði jökulsins.
SUMMARY:
BEDDED BANDS IN A GLACIER
IN REYKJAFJÖLL
The author describes a very regular banding
observed in a glacier in Reykjafjöll, NW of
Torfajökull in Southern Iceland. At the time
of observation, Sept. 6th, 1952, the glacier was
quite deprived of its snowcover from the previ-
ous winter but as it was only vieiued from
a distance no exact data about the number and
thickness of the bands can be given. It mœy
however be regarded as certain, that the black
layer which separates the upper part of the
glacier from the lower part, was formed by an
ashfall from the volcano Katla in 1918. Above
that layer more than 20 bands were discernible
and nearly fourty beneath that layer. From this
it can be concluded with a fair degree of
certainty that the bands of this glacier are
annual „bedded bands“ formed by the yearly
surplus of accumulation in its firn area. The
approximate average thickness of the layers
beneath the ash layer is ab. 1 m. The oldest
layers date back to ab. 1880.
In this connection it may be mentioned that
the oldest ■ mentioning of a „rotational move-
ment“ in glaciers dates back to the mediœval
times. Its is found in a description of the Ice-
landic glaciers, surely based on the experience
Jökull í Reykjafjöllum séður frá Hrafntinnu-
skeri.
A glacier in Reykjafjöll viewed from Hrafn-
tinnusker. (Above the black layer the banding
has been made somewhat more distinct on the
photo with a pencil.)
Photo S. Þórarinsson, 6-IX, 1952.
of Icelanders who lived in the neighbourhood
of the southern outlets of Vatnajökull, and in-
cluded in Saxo Grammaticus: Gesta Danorum,
which was written ab. 1200 A. D.
Sigurdur Thorarinsson.
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