Jökull - 01.12.1984, Blaðsíða 61

Fig. 4. The photo
shows a branch of
the Lakagígar 1783
A. D. and Eldgjá
934 A. D. lavas,
south of Eldmessu-
tangi. The Lakagígar
lava stopped here
(foreground), while
the Eldgjá lava pro-
ceeded further (seen
grassgrown and with
pseudocraters).
Mynd 4. Myndin
sýnir Skaftárelda-
hraunið frá 1783 og
Eldgjárhraunið frá
934 sunnan Eld-
messutanga.
In 1983 it will be 200 years since the Lakagígar
eruption took place and one may speculate if
such an event is likely to happen in the near
future! There is at least one similar event on
Iceland, which can be identified in the Greenland
Ice Sheet — the Eldgjá eruption around 934
A.D., so it is not a very frequent phenomenon.
The Eldgjá eruption took place close to the
region of the Lakagígar eruption and I remember
my own fascination, when a few years ago I saw
these two lava streams; the one on top of the
other, both visible at certain places, where the
Lakagígar lava had stopped its advance, while the
Eldgjá íava had run further. The lavas are today
moss- or grassgrown and one can almost tell the
difference in eruption dates by the character of
their green “blankets”.
The Eldgjá eruption
In Fig. 4 outliers of the Lakagígar and Eldgjá
lavas are seen; the photo shows a location south
of Eldmessutangi, where part of the Lakagígar
lava flow stopped; at this branch the older Eldgjá
flow did proceed further. A characteristic feature
in the not overrun Eldgjá lava is its almost
“Etruscan tomb-like”, pseudocraters (seen as
grass-grown mounds on the photo).
Recent evidence, (Larsen 1979), indicates, that
the Eldgjá eruption took place after Landnam,
but not later than 950 (Thorarinsson personal
communication, 1977).
The finding of the Eldgjá signal in the Green-
land Ice Sheet originated in a kind of “ping-
-pong” letters between me and Thorarinsson,
where some misunderstandings, preliminary
results and new findings resulted in the final
dating of the Eldgjá eruption to 934 ± 2 years by
means of the Créte acidity record. It is an episode
in my working with ice cores, which I remember
with great affection.
There are several interesting features about the
Eldgjá fallout on the ice sheet, which differ from
the Lakagígar event. First of all the Eldgjá acid
deposition took place over 3 years, Fig 5, and
shows a maximum fallout in the winter of 934—
935. The Créte record is the most ideal of the
existing records; also with respect to dating. It is
not unusual, that stratospheric fallout is high in
the winter time, this was e.g. the case for the
Tambora fallout (Hammer et al. 1980), but in the
case of Eldgjá it points to a rather violent and
JÖKULL 34. ÁR 59