Jökull - 01.12.1985, Blaðsíða 24

Fig. 12. Detail from section 3 at Haelavík (Fig. 7 and
10), showing the very sharp lower contact betveen the
Haelavík tephra and the lacustrine/fluvial silt. 12.
mynd. Hér sést hve skörp neðri mörk Hœlavíkur-gjósk-
unnar eru við árlvatnasetið í sniði 3 í Hælavík.
identify any active glaciers at such low elevations. He
estimated the altitude of the „snow line“ on eastern
Drangajökull to 400 m. This can be compared with the
more recent estimate of 700—800 m for the equilibrium
line altitude (ELA) there (Th. Einarsson 1968). Old
local names for cirques on Hornstrandir suggest at least
perennial firns, or glaciers (e.g. Jökladalir: Glacier val-
leys, Fannarlág: Site of snow fields). John (1977b)
found that most of the cirque glaciers in the uplands of
northern Vestfirdir have prominent moraines. He sug-
gested that these moraines often mark the maximum
advance of the Little Ice Age glaciers, but where multi-
ple moraine sequences occur, some may date from an
earlier Neoglacial advance.
The present study
Most of the cirques on Hornstrandir, some of which
have floors as low as 150 m above present sea level,
show no sign of having been glaciated since the end of
the Weichselian. The moraines in front of them are well
weathered, the vegetation cover within them is more or
less complete, and peat formation has often taken place
in their basins.
However, there are a few exceptions. In Hlöduvík,
Haelavík and Hornvík there are 7 cirques which show
clear signs of having been glaciated recently. The cir-
ques inside Hornvík, Haelavík and Hlöduvík (shown
without question marks in Fig. 13) have one to several
fresh looking moraines in front of them. The areas
behind these moraines also look very fresh and the
vegetation cover there is sparse. This is not an effect of
altitude, as extensive vegetation cover often occurs at
higher altitudes near the cirques, and at similar exposi-
tions.
Inside Hlöduvík and Haelavík the floors of these
cirques lie around 300—350 m above sea level, but they
lie as high as 500 m inside Hornvík (Fig. 13). The
Hornvík cirques are surrounded by the highest moun-
tains on Hornstrandir, which probably causes some
precipitation shadow. This is also suggested by our
conclusions, that during the Little Ice Age the glaciers
in the more exposed cirques in Hlöduvík and Haelavík
reached 150 m below the altitude of their floors (Fig.
13), whereas those inside Hornvík only reached some 50
m below their floors. Thus during the Little Ice Age (for
dating, see below) the ELA in the cirques was down at,
or somewhat below, 300-350 m in the Haelavík/Hlödu-
vík area, but not much below 500 m at Hornvík. This
can be compared with Thoroddsen’s (1906, 1911)
approximation of 400 m for the eastern part of Dranga-
jökull.
The total glaciated area on northern and western
Hornstrandir during the Little Ice Age was 8-10 km2.
Lichenometry of the Fannarlág cirque.
A reconnaissance scudy of lichen growth was carried
out on fresh moraines and other surfaces which were
covered by the Little Ice Age glacier in the Fannarlág
cirque, at the head of the valley inside Haelavík. Today
there is no glacier in this cirque (Figs. 7 and 14). Lichens
used were of Rhizocarpon alpicola and Rhizocarpon
geographicum agg. type, and thalli of the different
species are used together in the calculations. Thalli
diameters were measured using the diameter of the
largest inscribed circle (Lock et al. 1979, p. 8). Dist-
ances between moraines and other surfaces on which
thalli were studied were measured by counting steps
during walking.
Innes (1982) showed that R. alpicola and R. geo-
graphicum agg. have somewhat different growth rates,
but in a preliminary study like ours that difference
should not matter too much. Gordon and Sharp (1983),
in a study on southern Iceland, found that for R.
geographicum agg. the growth rate since the late 19th
century was approximately linear, and Caseldine (1983)
came to the same conclusion as regards central North
Iceland.
Our results are presented in Fig. 15, where the mean
values for the five largest thalli (M5) on each surface
(numbered as in Fig. 7) are shown together with the size
interval covered by them. In two cases (points 5 and 7)
single unexpectedly large and perhaps coalescent thalli
22 JÖKULL 35. ÁR