Archaeologia Islandica - 01.01.2010, Page 23

ON FARM MOUNDS
the turf walls from above and will wash
away small quantities of soil which in
tum makes the construction unstable and
can cause it to cmmble in places and thus
require frequent repairs with the addition
of more material. Water freezing in the
walls will cause them to crack with the
same results whereas wind may steadily
erode material from turf walls requiring
repairs but possibly not the same degree
of build-up of material on site. Whereas
degradation of turf walls due to rain and
frost rarely removes any material from
the site - these factors simply move
material from the walls to build up on the
floor or flat ground around the structure -
wind erosion may do so and it is possible
that in extreme conditions this may check
the build-up of farm-mounds.
The rate of wind erosion depends on
the qualities of the turf. Turfs cut in dry
soil with high mineral content and coarse
grains will erode more easily than turfs
cut in bogs with a high density of roots
and/or finer, more cohesive silts. The rate
also relates to the degree of precipitation
as well as the stability of the climate. The
rapid freeze-thaw cycles typical of win-
tertime in North Atlantic coastal regions
will increase the rate of frost damage;
whereas the more stable cold winters of
regions like North Iceland and the
Greenlandic settlements will largely can-
cel out this factor.
There is an old rule of thumb in
Iceland which says that in the South turf
buildings needed to be rebuilt every 60
years whereas in the North they could last
for 100 years or more. It is likely that this
refers to the need to replace the roof and
timber frame but that turf walls needed as
a rule more frequent repairs.1 The differ-
ence between North and South is no
doubt related to the difference in climate.
The South has much greater precipitation
than the North and - like the Faroes and
Atlantic Norway - has relatively mild
winters which means that frost rarely
lasts for a long time but freezing can
occur many times throughout the winter.
There is no research to support this
adage, but it is possibly not a coincidence
that all the farm-mounds so far excavated
in Iceland are in the South and that in the
North there are examples of low farm-
mounds like at Hofstaðir and limited
accumulation like at Laufás (see below).
It is therefore arguable that climatic con-
ditions are a major factor in the build-up
of farm-mounds, and that the wet and rel-
atively mild sub-arctic conditions associ-
ated with the Gulf Stream may play a
significant part in their accumulation.
In contrast soil quality, drainage and
organic chemistry are much more
localised variables which can at most
explain why farm-mounds form in some
locations and not in others. It is however
1 Eggert Ólafsson claims that an Icelandic turf-house can last upto 100 years if it is properly built, which, in the mid-18(l1
century, he found to be rare - Ferðabók I, 15 - whereas in the context of praising the buildings of North Iceland he says that
well-built walls could last more than 50 years - Ferðabók II, 52. Bruun 1928, 128 reports that in the North a turf-wall can
last for 20 years without any repairs but 12-14 years in the South. Nilsson 1943, 293 also says that without repairs a turf wall
can stand for 20 years, but that with repairs a turf-building in the North would normally last for 50 years, and upto 100 years
if it was well built. Houses in the South he reckons would only last half as long. Guðmundur Hannesson 1943, 62 also refers
to 100 years as the maximum age of well built walls in the North. Gísli Gestsson 1982, 168 says that a well built stone-wall
could last for as long as 60-100 years, suggesting that turf walls would last considerably shorter.
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