Jökull - 01.12.1985, Blaðsíða 25

were encountered. These have not been used in the
ordinary M5 calculations, but are indicated by dashed
lines, and with such M5 values as would result from their
inclusions shown as open circles.
The measurement at point 0 was made on a striated
rock surface outcropping through the snow (18/7 1983)
in the innermost part of the cirque, at an altitude of
about 350 m. The lowest point (no. 8), within the area
of fresh surfaces which were clearly covered by ice
during the Little Ice Age, lies at about 200 m above
present sea level. Point no. 9 is at the same altitude. No.
10 is a calibration sample from the much older Late
Weichselian glacial hummocky terrain further downval-
ley (Fig. 7). Its M5 consists of the largest thalli found
between 85 m and present sea level.
The rather stepwise decrease in thalli diameter
between points 6 and 5 and points 3 and 2 together with
the short distances between these moraines probably
indicate temporary standstills of the glacier front at
moraines 5 and 2, or at least a decreased rate of
recession. The reason that the M5 for point no. 8 is
smaller than for point no. 7 is probably that the former
surface is situated below and in front of a rather steep
slope (Fig. 7), a typical snow-drift site. Therefore the
ridge at point no. 7 was freed from ice or long lasting
snow cover, preventing lichen colonization, before the
point no. 8 area. The steep decrease in lichen diameter
Fig. 13. Northern Hornstrandir with
(1) the Little Ice Age extent of ice in
cirques definitely glaciated at that
time, and (2) such cirques which were
probably glaciated then. Of the figur-
es (3) the upper set shows altitudes of
cirque floors, the lower set the alti-
tude to which the Little Ice Age glaci-
ers descended. The arrows (4) indi-
cate which cirques today retain small
glacier 13. mynd. Jöklun á Litlu lsöld
á norðurhluta Hornstranda. Tákn: (1)
stœrð hvilftarjökla sem örugglega
gengu fram, (2) stærð hvilftarjökla
sem sennilega gengu fram, (3) „telj-
ari“: Hœð hvilftarbotns yfir sjávar-
máli „nefnari“: Hœð jökuljaðars yfir
sjávarmáli á Litlu Isöld, (4) smájöklar
í hvilftum í dag.
from point no. 9 to points no. 8 and 7, and the fact that
M5 at point no. 9 is also larger than that in the calibra-
tion area, suggests that point no. 9 is indeed situated
just outside the area reached by the Little Ice Age
glacier.
The maximum thalli diameter on the Little Ice Age
moraines at Fannarlág is roughly 60 mm (M5: 57.6 mm).
Moraines from about 1895 in front of Breidamerkur-
jökull in southern Iceland have maximum thalli dia-
meters between 50 and 54 mm and M5’s around 45 mm
(Gordon and Sharp 1983). Moraines of similar age from
Sólheimajökull, also on the south coast, have maximum
diameters of about 50 mm (Jaksch 1975), and on the
1887 moraines at Skálafellsjökull in the southeast, the
maximum thalli diameter is close to 80 mm (Gordon
and Sharp 1983). Depending on the method of calcula-
tion (using maximum thalli or M5’s) this gives annual
growth rates between 0.5 and 0.9 mm/yr. The harsher
climate on Hornstrandir can be supposed to suppress
lichen growth compared with southern Iceland (e.g.
Beschel 1961, Webber and Andrews 1973), as is also
indicated by the low growth rate in central North Ice-
land (about 0.5 mm/yr; Caseldine 1983). A 0.5 mm/yr
growth rate would date the outermost Little Ice Age
moraines in Fannarlág to about 1860, and a lower
growth rate would give them an even older age.
There are no data in the scattered references to the
JÖKULL 35. ÁR 23