Jökull - 01.11.1998, Blaðsíða 23

to the instability of the overall formation, but by com-
paring surface changes of the deposit on aerial pho-
tographs from the last decades, retreat or ice melt pat-
terns can be identified such as the kettle and kame
landscape characterising the surface of the formation
(Figure 4).
The Brækur outlet glacier is an ice-fall glacier fac-
ing north-west from the main ice cap (Figure 1).
Thoroddsen (1911) investigated the Brækur pro-
glacier zone in 1898. His observations of barometric
measurements indicate that the eastem glacier snout
was at 550 m a.s.l. Thoroddsen also mentions that the
glacier was heavily crevassed and steep (20°-30°).
Barometric measurements in 1991 showed the outer-
most ice limit to be at 690 m a.s.l. Considering the
very steep substrate of the Brækur outlet, this could
indicate a retreat of ca. 140 m up slope. In contrast to
the Klofajökull glacier, Brækur glacier shows no evi-
dence of a pre-LIA advance. Lichenometry was used
to date the outermost limit of this glacier. Some 30
samples of the Rhizocarpon geographicum species,
measured on the proximal side of the moraine, show
that the outermost limit dates from 1880±9 AD (Table
I; Figure 6). Aerial photographs, spanning the period
between 1938 to 1987, show that the glacier retreated
1 km from the maximum LIA until the early sixties
and approximately 20 m at both sides (Figure 6)
Sometime in the sixties, the glacier began a re-ad-
vance, which came to an halt in 1979. The glacier re-
mained in this position until 1987. The difference be-
tween the 1960s and the 1979-1987 position is 100 m.
The westem snout of Brækur glacier retreated 470 m
between its maximum extent and 1987, and did not
re-advance in the early sixties (Figure 6).
Z <}-----------
Glacier limit in 1979 Dead-ice hummocks
Moraine crest Flutes
w Lateral moraines______________________r------- Man. no. of moraines____________
Fig. 3. Proglacier geomorphology of the Stallurinn plateau. The outermost moraine shows the maximum extension of the
glacier, probably during the LIA. The line marked A-B is located where the maximum number of moraines occur, indicating a
retreat history.
- Landmótun jökuls á Stallinum. Ysti jökulgarðurinn sýnir líklega stöðu jökulsporðsins í lok litlu ísaldar. Línan merkt A-B sýnir
hvar hámarksfjöldi endagarða er staðsettur. Jökulgarðarnir endurspegla hötfunarsögu jökulsins.
JÖKULL, No.46, 1998
21