Jökull - 01.12.1985, Page 15

Fig. 4. Air-photo showing the high-
lands inside southern Adalvík, with
Stadarvatn (S) and Thverdalur (T)
indicated. Note: (1) The very even
surfaces of the highest plateaux, situ-
ated around 400 m, covered by mat-
ure block fields and showing no sign
of glacial erosion or deposition, (2)
the nivation hollows and cirques in
various stages of development found
along the plateau edges, (3) the glaci-
ally sculptured terrain surrounding
the high plateaux and, here, reaching
up to approximately 300 m. Photo
published with permission of the Geo-
detic Survey of Iceland. 4. mynd. Há-
lendið innaf sunnanverðri Aðalvík.
Staðarvatn: S, Þverdalur: T. Takið eft-
ir (1) jöfnu yfirborði hásléttunnar, án
ummerkja eftir jökla, (2) hvilftum og
skálum afýmsu tagi með jaðri háslétt-
unnar, (3) jökulrofnu umhverfi há-
sléttunnar. Hér nær jökulrof um 300
m yfir sjó.
assumed that the only part of western and northern
Hornstrandir which could have been affected by that
outlet glacier and its tributaries would be the Adalvík
area. Some ice may have flowed into that area from
Jökulfirdir, through the slightly less than 300 m high
passes to the east. If the Adalvík glaciers are given a
minimum gradient of 25 m/km (empirically derived
from Iateral channels in North Iceland by Norddahl
1983) the glacier terminus outside Adalvík will have
fallen some 6—10 km off the outermost capes (Fig. 5).
That is still 10-25 km inside the present 100 m depth
curve on the shelf. The same gradient has been used for
reconstructing the outer limits of the glaciers coming
out of Fljótavík, Fllöduvík, Haelavík and Hornvík.
These could hardly have been affected by the ísafjardar-
djúp glacier, but were built up by coalescing cirque
glaciers, so they probably did not reach as far out as the
Adalvík glacier. Thus their positions marked in Fig. 5
would seem to be maximum assumptions. Fig. 5 shows a
maximum concept as there are no indications that the
íce-surface reached all the way up to the plateau edges.
But the often steep, if not vertical mountainsides are
usually far from optimal for the preservation of lateral
features.
The high plateaux and the steeper mountains
reaching above the surface of actively eroding glaciers
are indicated in Fig. 5. However, to a large extent these
plateaux were probably covered by thin inactive and/or
cold based ice-fields. This is indicated by the existence
there even today of perennial snow fields or small firns
(Fig. 3).
The general ELA during the maximum glaciation
probably was below 150 m above present sea level, as all
cirques along the outer coast with their floors around
that altitude were glaciated. The unknown stand of sea
level in relation to land at that time does, however,
complicate the question of the relative altitude of the
ELA.
Thus, at the time of maximum glaciation ice-free
areas on what is dry land today could have existed as (1)
steep nunataks south of Hlöduvík, Haelavík and Horn-
vík, (2) narrow rims between plateau edges and the ice
fields up there and (3) ice-free slopes between outlet
glaciers and the plateau edges. These habitats could no
doubt have supported some vegetation. If ice-free
marginal areas of the shelf were dry land, vegetation
probably persisted there too.
JÖKULL 35. ÁR 13