Jökull - 01.12.1983, Blaðsíða 89

The Quaternary Alpine Glaciation
and marine Erosion in Iceland
GUTTORMUR SIGBJARNARSON
National Energy Authority, Grensásvegur 9, 108 Reykjavík, Iceland
ABSTR.4CT
Geomorphological studies of the coastal areas of South-
eastern and Eastern Iceland show the main topographical
landforms eroded by alpine glaciation and marine abrasion.
Those areas of lceland which show predominantly alpine
landscape are presented on a map as well as the largest ones
of the coastal cliffs. Attention is drawn to the difference in
the development of the strandflat and coastal scenery in the
northem and southern parts of Iceland. This evaluation
leads to that conclusion that the thickness of the Pleistocene
glaciers has been much less in the Southeastem Iceland than
in the North and that there have always been some ice-free
areas during the glacials.
INTRODUCTION
The paper presented here is intended as a small
contribution to the Quatemary geomorphology of
Iceland. It is not a complete account, nor does it
reach any defmite scientific conclusions, but rather
considers and discusses two important aspects i. e.
the importance of alpine glaciers and of marine
erosion in the formation of the landscape. The work
is particularly based on observations on the coast-
lines and coastal areas of southeastern and eastern
Iceland from Fljótsdalshérað to Eyjafjöll, although
other areas are of course considered. In the light of
these observations it is attempted to build up a
picture of the thickness and extent of glaciers in
previous glacial periods in this area, and indeed for
the country as a whole, although it is as yet imper-
fect.
GEOMORPHOLOGY OF ICELAND
IN QUATERNARY TIME
Few earth scientists will doubt that many of the
more important features in the Icelandic landscape
bear witness to Quaternary glaciation, such as
fjords, valleys, corries and serrated edges (arétes).
Many authors have discussed or pointed at these in
their work. Mention can be made of Thorvaldur
Thoroddsen (1905-06, 1908-1911), Helgi Pjetursson
(1905, 1906, 1908), Trausti Einarsson (1959, 1961,
1962, 1972. 1977), Gudmundur Kjartansson (1943,
1955, 1961, 1962, 1966), Sigurdur Thórarinsson (1937,
1951, 1956, 1960), Thorleifur Einarsson (1961, 1968,
1969, 1976), Kristján Semundsson (1979),and Thórdís
Olafsdóttir (1975) as well as various other papers by
these authors not mentioned here. In addition a
large number of other earth scientists both from
Iceland and abroad have mentioned these features,
it being sufficient to refer here to Arthur Holmes
(1965), Ame Noe-Nygárd(1962), Gunnar Hoppe(1968)
and Hubertus Preusser (1976). Nodiscussion will here
be made on the theories of individual authors or
their separate topics but refererence is made to their
work where relevant.
There are different opinions amongst these aut-
hors as regards the possible thickness and extent of
glaciers during glacial periods and whether certain
areas have been ice-free and even vegetated
throughout the Quatemary Era. In the last few
decades the opinion has become rapidly popular
that Iceland has been covered by a very thick ice
sheet, even 2000-3000 m, in previous glaciations
and that it has calved off the edge ofthe continental
shelf at depths ofat least 200 m or more so that the
country was completely covered by ice. This view is
very similar to that held for the ice sheets of Scand-
inavia and Canada. According to this view the
formation of the Icelandic landscape and its contin-
ental shclf should be foremost due to erosion by a
thick ice sheet with an ice centre and main divide
somewhere in the central highlands.
In my opinion many geomorphological and glac-
iological arguments are decidedly against this
theory. In the discussion that follows I shall tr>' to
JÖKULL 33. ÁR 87