Jökull - 01.12.1978, Page 28

The Miklafell moraine
The easternmost evidence of this end
moraine is found to the south of Laugafell
(Fig. 1), as a narrow ridge, only 1 — 2 m high,
made of very coarse till with boulders. The
ridge strikes east-west. South of Laugafells-
hnjúkur the ridge turns southwest and can be
traced up to Miklafell at the northeastern
corner of Hofsjökull. In some places the end
moraine appears not as a ridge but as a belt of
large boulders (Fig. 9). Southwards the ridge
becomes broader and higher, reaching 10 m
height at its end about 1 km north of Mikla-
fell, where the present glacial rivers from
Hofsjökull have cut it off (Fig. 10). The
southernmost 1 km of the end moraine consists
mostly of black pumice with some basaltic
boulders. The pumice fragments are up to 5
cm in diameter and fragments of volcanic
bombs were found too. This indicates that the
eruption occurred not far away.
In the north side of Miklafell an ice-contact
slope in a lateral moraine consists entirely of
this black pumice. The gradient of the ice-
contact slope is 1:25 (2.3°) and it can be traced
over a distance of 1 km. At its southern end the
moraine has been washed away by the rivers
draining from Hofsjökull. In the north the
ice-contact slope ends opposite the end
moraine.
The areal extent of the black pumice is
small. Inside the end moraine the pumice was
noticed in a few places, and outside only
nearest to the ridge where it bears clear
evidence of being water transported. A pos-
sible source of the pumice are low hyaloclastic
ridges of subglacial origin, about 2—4 km to
the south of the end moraine (Fig. 10). How-
0 1 1 I 2 km 1
1 ■ 3n
4 EE3 5 ÍH 6 4^
7 J 8
Fig. 10. The southernmost part of the
Miklafelbmoraine and the ice-contact slope
on the mountain side. Explanations: 1. The
Miklafell end moraine. 2. The Hofsjökull end
moraine from 1890. 3. Fluvioglacial
sediments. 4. Black pumice. 5. Hyaloclastite.
6. Ice-contact slope. 7. Drainage channel in
loose sediments. 8. Glacier.
Mynd 10. Syðsti hluti Miklafellsgarðsins og jað-
arhjallinn í framhaldi hans. Skyringar: 1. Mikla-
fellsgarðurinn. 2. Jökulgarður frá mestu framrás
Hofsjökuls um 1890. 3. Jökulárset. 4. Svartur vikur.
5. Móberg. 6. Jaðarhjalli. 7. Þurr farvegur grafinn í
set. 8.Jókull.
26 JÖKULL 28. ÁR