Jökull - 01.12.1967, Blaðsíða 31

Fig. 3: A schematic block-diagram of Hagafells-
jökull Eystri showing the maximum extent of
the glacier in the last century.
Fig. 4: The sante area as on Fig. 3 in the year
1965. The glacier has almost disappeared and
the position of lake Hagavatn is entirely chang-
ed.
Hámnrks útbreiðsla Hagafellsjökuls eystri á s.l. Sama svæðið og sýnt er á 3. mynd, árið 1965.
öld. Nú er jökullinn nærri pvi horfinn og Hagavatn
hefur flutzt á nýjan stað.
cols in the Brekknafjöll Range and downhill
into the Jarlhettur Valley (Fig 2). During the
maximum extent of the glaciers in the last
century these SE moving glacier lobes were
larger in extent and niore numerous farther to
the SW in the Brekknafjöll Range, and nearly
filled the Jarlhettur Valley with ice (Fig. 3).
Hagafellsjökull Eystri is situated far from in-
habitated areas. No detailed historical records
of its position are available until after the
“jökulhlaup” (glacier burst) of 1929, wliich ori-
ginated from the Hagavatn basin. Altogether,
five “jökulhlaups” have been reported from
Hagafellsjökull Eystri in historical times, in
1708, 1884, 1902, 1929 and 1939. The two latest
ones had the greatest volumes. All these “jökul-
hlaups” must inclicate some changes in the re-
gime of the glacier. Thorarinsson (1966) con-
cludes frorn tephrochronological studies that
Hagafellsjökull Eystri reached its maximum
extent “either in the middle of the 18th century
or — just as likely — in the “Hochstands” of
the 19th century”, but before that time the
knowledge of the positions of the ice margin is
very sparse. A student group from the Uni-
versity of Durham made some investigations of
the sediment sequence in the former Flagavatn
lake bed. They found, by means of known
tephra layers, that the present outlet from the
lake had not been blocked by the glacier until
about two or three decades before 1693 (Green
1952), which is in good accordance with Thor-
arinsson’s studies (Thorarinsson 1949 and 1966).
According to information from persons who
know this area well (Ólafsson 1929) no major
change of the glacier margin of Hagafellsjökull
Eystri took place during the period from the
late 19th century to 1920, but after that the
glacier snout began to retreat very rapidly, and
in 1966 it was about 3.8 km to the NE from
the frontal moraine ridges in the Hagavatn
basin (Fig. 4).
The frontal moraine ridges from the maxirn-
um extent of Hagafellsjökull Eystri in the last
century are very conspicuous and their position
is drawn on Fig. 1. They are only lacking where
the rivers have eroded them away in the Jarl-
hettur Valley below Nýifoss and Leynifoss and
JÖKULL 17. ÁR 265