Greinar (Vísindafélag Íslendinga) - 01.01.1977, Blaðsíða 56

54
We think Fig. 7 to be as good an approximation as existing
data now allow.
The Settlement of Iceland is put at 874 A.D. which falls into
a time of warm and still a little ameliorating climate. The vol-
canism was very faint and declining during the first centuries,
as we shall now discuss in more detail.
The volcanic activity in the Snæfellsnes zone only just
reaches the historic time (Eldborg in Hnappadalssýsla), as
we can probably take the account in Landnámabók as good
evidence (40).
The Median zone did better. A lava flow of probably about
1150 A.D. partly covered a farm, the ruins of which are other-
wise clear. In the Eastern zone, even Hekla was inactive.
But by about 1100 the first slight cooling set in, and we
get immediately the first historic eruption of Hekla in 1104
or 1106, according to different annals. The whitish acid pumice
from this eruption covered the ruins of all farms in the dis-
trict Þjórsárdalur, most of which may have been deserted about
50 years earlier (41); (42). Hekla and Katla now become peri-
odic volcanoes, and the same applies to Grímsvötn. Annal re-
ports on unidentified eruptions on the western part of the
Reykjanes peninsula from 1150 to the middle of the 14th cen-
tury may also correspond to the deterioration of climate, with
lowering of temperature to a provisory minimum around 1300
A.D. (In an unpublished study I came to the conclusion that
the tale of a lava flow in year 1000, when it was decided on
Þingvellir to accept Christianity as the official religion, was
geologically questionable.1)
After a milder period between about 1400 and 1500 A.D., a
new cooling set in very slowly but leading to the lowest hist-
1) I asked the expert University Librarian Dr. Björn Sigfússon in which
sources the tale was found. His answer was: “the only source is Kristni-
saga (History of Christianity in Iceland), which is known to be historically
unreliable”. In the present connection we cannot use this dating of the
lava. A date after 1100 is more acceptable; and the history was only
written two centuries later, we should keep in mind.