Jökull - 01.01.2010, Page 191

The retreat of Breiðamerkurjökull at Skálabjörg, SE Iceland
760
47 0
720
680
6
06
640
0
70
N
300 m
stream
LIA moraine ridge
alluvial fan
talus
small-scale sorted stripes
large-scale sorted stripes
solifluction lobes and tongues
permanent snow patch
erosional escarpment
episodic stream
Esjufjoll hut
..
peat / meadow (Tjaldmyri)
Ccontour lines
Figure 6. Map of periglacial
forms in the southern part of
Skálabjörg. – Landmótunarkort
af sunnanverðum Skálabjörgum.
dily increases down-slope which may be an effect of
enhanced glacial erosion in recent times. Below the
highest moraine ridge on the eastern slope, five irreg-
ular and sublty visible lateral moraine ridges or other
accumulation horizons inherited from longer glacial
still-stands can be distinguished (Figures 2H and 7).
The ridges lie at 681 m, 670 m, 655 m, 636 m and
610 m a.s.l. The southwestern slope has seven similar
glacial landforms at 695 m, 685 m, 683 m, 654 m, 650
m, 635 m and 630 m (Figures 2G and 7).
Clasts from the highest moraine ridge are better
rounded in comparison with those found just behind
it, on an older surface (Table 4). This clearly shows
the young, glacial origin of the ridge. The surface of
the study area above the highest moraine ridge appar-
ently lacks glacial sediments. Only two glacially abra-
ded boulders were found on the eastern slope of the
nunatak, 46 and 64 m behind the moraine ridge and
about 7 and 10 m higher respectively. They were
found near the top end of the eastern research profile
shown on Figure 5. The boulders seem to have slid
down the talus slope since they sit on scree. A black
sand interpreted as volcanic ash overlies regolith on
undulating surface on the majority of the study area
above the highest moraine ridge. Two local hills, ris-
ing about 40 m above the oldest moraine ridge, exhi-
bit slight ice-moulding: asymmetry typical for roches
moutonnées and bedrock surfaces glacially abraded in
places. We infer that the whole southern part of Skála-
björg must have been glaciated a long time before the
LIA, but the exact timing of surface exposure is not
known (Gudmundson, 1997).
Contemporary deglaciation is also manifested by
the rapid disappearance of a small glacier filling the
Fossadalur valley between Vesturbjörg and Skála-
björg (Figures 1, 2D and 4). A large terminal arcua-
te moraine produced by this glacier (flowing south-
wards) is clearly visible on the aerial photograph
JÖKULL No. 60 191