Jökull - 01.12.1982, Blaðsíða 37

Fig. 5. Aerial photograph
(1965) of esker E5.
Mynd 5. Loftmynd af malarásnum
E5 árið 1965.
stands some 20 m above Jökulsárlón. A series of
lakes and river channels extends westwards from
Jökulsárlón to within about 500 m of the eastern
shore of Breidárlón. If, with continued glacier re-
treat an eastward drainage from Breidárlón should
develop it could result in a rapid lowering of the
Breidárlón by some 20 m with a potentially cata-
strophic flood into the Jökulsárlón and out through
the Jökulsá to the ocean. Unfortunately the 1980
photography does not cover the Breidárlón (Fig. 1),
but it does indicate a considerable increase in the
area of the [ökulsárlón and north Stemmulón since
1965.
COASTAL CHANGES
Welch and Howarth (1968), have described the
changes which have taken place in the coastline at
the mouth of the Fjallsá, Jökulsá, and Stemma be-
tween 1904 and 1965. Further changes have taken
place between 1965 and 1980 (Fig. 1). The mouthof
the Stemma has migrated south-westwards by app-
roximately 4.5 km leading to a silting up of the
lagoon which existed from 1904 to 1965 (Welch and
Howarth 1968, Fig. 14). The spit at the mouth ofthe
Jökulsá also extended westwards by approximately
200 m. The eastward extension of the spit at the
mouth of the Stemma has ceased and the river
channel has broken through the proximal end ofthe
spit and the beginnings of a westward growing spit
can be detected. fVelch and Howarth (1968, p. 94)
concluded that for the period 1904 - 1965, “Mea-
surements of the coastal features indicate a general
drift ofdeposits and a lengtheningofspits from west
to east at average rates of nearly 40 m per year in the
west and 60 m per year in the east”. They also state
that coastal retrcat at thejökulsá has averaged 10 m
per year between 1904 and 1965. Although detailed
JÖKULL 32. ÁR 33