Jökull - 01.12.1982, Blaðsíða 5

The Extent of the last Inland Ice Sheet of Iceland
GUNNAR HOPPE
Department of Physical Geography, University of Stockholm,
S-10691 Stockholm, Sweden
ABSTRACT
Evidence of glaciation in the peripheral areas of Iceland-
summarized in Fig. 8 - makes it clear that the whole
coastland once was covered by an inland ice sheel. Traces of
glacial activity on many highpoints close to the present coast
demonstrate that the ice sheet must have had a considerable
thickness and that it invaded vast areas of the shelf. It must
be considered rather probable, however, that high peaks and
ridges, especially close to the shelf slope might have remained
above the surface of the ice sheet. - The rather wellpreserved
glacial features and a rapid land upheaval suggest a late
IVeichselian time of the glaciation.
INTRODUCTION
The extent of the diflerent inland ice sheets of the
last glacial epoch has been the subject of innumer-
able papers and heated debate throughout this
century. A main element in the discussion has been
the possibility that ice-free areas, or refugia where
plants and animals could have survived glaciation,
existed in a number of regions. Arguments for re-
fugia have mainly been concerned with peculiarities
in thc distribution of biota, but certain geological
and geomorphological features, such as pinnacle-
like mountain peaks (regarded as former nunataks),
deep weathering of rocks, and the absence of glacial
markings have been cited as evidence also. Object-
ions against the refugium theory are based on other
interpretations of the distribution of both biota and
weathering phenomena, but mainly on observat-
íons of typical glacial features, such as erratics,
roches moutonnées and striae, within the area of
„refugia”.
Thorvaldur Thoroddsen, the eminent founder of
this century’s earth sciences in lceland, believed
that Iceland was almost completely covered by ice,
with the exception of smalf mountain peaks and
ridges close to the ice margin (1906); it should be
added that Thoroddsen believed that Iceland had
been glaciated only once. Under the influence ofthe
Scandinavian discussion arguments for ice-free re-
fugia on Iceland were put forward by several scient-
ists, beginning with the Swedish entomologist Carl
Lindroth (1931) and Thoroddsen’ssuccessoras lead-
ing Icelandic earth scientist Sigurdur Thorarinsson,
who demonstrated the nunatak-like appearance of
mountains in different parts of Iceland (1937).
A short survey of early papers on supposed Ice-
landic refugia was given in Hoppe (1968). The gen-
eral opinion in the first part of the 1960’s, when the
situation was reviewed at a symposium in Reykjavík
about „North Atlantic biota and their history”
(Löve and Löve 1963), seems to have been that con-
siderable areas of Iceland and the surrounding
shallow shelf were ice-free during the last glaciation.
My own interest in refugia problems, gradually
widening to the problems of the extension of the
inland ice sheets in northwestern and arctic Europe,
was wakened by Carl Lindroth, my biology teacher
when a young student. As far as Iceland is concern-
ed it has been stimulated by countless discussions
with Sigurdur Thorarinsson, often during travels in
Iceland and beginning with a most memorable ex-
cursion in 1948, led by Sigurdur and initiated by
Hans VV:son Ahlmann.
My fíeld work in Iceland on the problem of ice-
sheet extent has been undertaken, for nearly 20
years, in connection with visits for other reasons,
and the time for research always has been rather
restricted. Field studies, mainly searching for evid-
ence of glaciation, have been concentrated near the
coast especially to localities where refugia have
been proposed. It is thus natural that early on I
became interested in Grímsey, as the outermost
island oflceland.
It is certainly a deficiency that time has not per-
mitted a deeper consideration of the dating quest-
ion. A basic assumption has been that glacial mark-
JÖKULL 32. ÁR 3