Jökull - 01.12.1982, Síða 36

Fig. 4. Maps and profiles of
esker E5 in 1966, 1968, 1977
(Pennington 1978).
Mynd 4. Kort og snið af malar-
ásnum E5 árin 1966, 1968, 1977.
Ridge Crest Profiles
vided by Howarth and Price (1969), Derbyshire (1974)
and Boulton (1977). The concentration of the pro-
glacial drainage into three major rivers, Stemma,
Jökulsá and Fjallsá, concommitent with the expans-
ion of the four proglacial lakes: Stemmulón, Jökuls-
árlón, Breidárlón and Fjallsárlón, has been the
fundamental reason for the preservation of extens-
ive areas of glacial and íluvioglacial deposition in-
side the ”1890” moraine. Between 1890 and 1937
the altitude of the ice margin infront of Máva-
byggdarönd actually decreased by some 10 metres
in a series ofsteps (Price 1969, Fig. 10). After rising
again by some 20 m it fell in the early 1960s by
another 20 m so that the surfaces of the proglacial
lakes along the ice margin in 1965 were at the
following altitudes above sea level: Fjallsárlón 12.5
m, Breidárlón 27.5 m, lakes east of Mávabyggda-
rönd 19.5 m, Jökulsárlón 5.5 m, Stemmulón 8.5 m.
All of the meltwater drainage west of Mávabyggda-
rönd was directed towards Breidárlón which in turn
drained to the Fjallsárlón. East of Mávabyggda-
rönd meltwater drainage was captured immediate-
ly at the ice front by a series of lakes parallel to the
ice margin and which drained either to Jökulsárlón
or Stemmulón. All four of the major lake basins are
deep and descend below sea level (Howarth and Price
1969): Fjallsárlón 58 m (46 below sea level), Breid-
árlón 84 m (57 m below sea level), North Stemmu-
lón 36 m (28 m below sea level, and Jökulsárlón
(Derbyshire 1974), 104 m (98 mbelow sea level). The
origins of these lake basins are not fully understood,
but they have had a profound effect on the develop-
ment of landforms, drainage patterns and rates of
ice marginal retreat. Although this paperis primari-
ly concerned with recording past changes in the
drainage system it is interesting to speculate what
may happen if the front of Breidamerkurjökull cont-
inues to retreat. The surface of Breidárlón now
32 JÖKULL 32. ÁR