Archaeologia Islandica - 01.01.2015, Blaðsíða 41

Abandoned Settlements at the Foot of Mt Hekla
according to contemporary sources many
farms in Biskupstungur and Rangárvellir
were abandoned due to the tephra fall (Is-
landske annaler, 351-52). Hekla erupted
again in 1389 and again the tephra fall
was great and caused much damage. It is
believed that this time the lava flow cov-
ered two to three farms (Islandske annaler,
351-52).
The next large eruption in Hekla was in
1510. Tephra from this eruption covered
a large part of Rangárvellir as well as the
neighbouring districts of Landsveit and
Landeyjar. Even if the quantity of tephra
from this eruption was no greater than in
many of the earlier eruptions, it seems to
have had a triggering effect marking the
beginning of the dramatic soil erosion that
was to have a significant impact on the
landscape and farms of Rangárvellir in the
following centuries (Egilsson 1856, 44-45;
Friðriksson 1988, 10).
Contemporary documents suggest that
the eruption in 1693 caused one farm in
Þjórsárdalur to be abandoned permanent-
ly and four other farms to be temporarily
abandoned; two in Landsveit and two in
Gnúpverjahreppur. This eruption is de-
scribed thoroughly in written sources so
the effects can be assessed with some ac-
curacy (Þórarinsson 1968). Eruptions in
1766 and 1845 had little effect in populated
areas because the tephra fall was mostly in
the hinterland north of the volcano where
however rangeland vegetation was affected
(Þórarinsson 1968, 84-147). The last erup-
tion in Hekla to cause significant damage
to inhabited areas was in 1947. The tephra
fall was mainly in Fljótshlíð and the north-
ern part of Rangárvellir, causing two farms
to be permanently abandoned in the latter
district (Hjartarson 1995, 164-66).
This brief overview gives an idea of the
extent of the direct influence of Hekla's
eruptions on the districts around it. The
indirect effects of the eruptions are more
difficult to assess but they seem to have had
an even greater impact on the settlement in
the form of soil erosion and other changes
of the quality of the land.
Indirect impact of Hekla: Soil erosion
Iceland is mainly made up of basaltic bed-
rock types but a tuff belt creates an arch in
the middle, stretching from the south, over
the middle of the highlands, to the north
and northeast. Ihe soil in the basaltic bed-
rock areas holds moisture better than the
sandy soil on top of the tuff and therefore
the risk of soil erosion is greater in the tuff
areas. In the research area the combination
of a tuff-based soil, volcanic activity and cli-
mate change has caused massive and wide-
spread soil erosion (Sveinsson & Campbell
1958, 255, 261). From the 13thcentury to
the 19ththe average temperature decreased
significantly (Mann et al. 2009). The effects
of this on vegetation were most severe in
the highlands of Iceland and in the settled
areas in the tuff belt, in part because of the
39