Archaeologia Islandica - 01.01.2004, Page 64

John M. Steinberg
project developed and implemented a
protocol of surface survey, coring, auger-
ing, remote sensing (conductivity and
resistivity), and test trenches to identify
and explore archaeological remains with-
out any surface sign (Steinberg and
Bolender in press). The successful iden-
tification of anomalies associated with
archaeological sites depends on the pre-
served remains having distinguishing
characteristics. The main component of
turf, and an important attribute that dis-
tinguishes the walls from the surrounding
soil, is turfs high organic content
(Crowther 2002). Therefore, an under-
standing of the post-depositional behav-
ior of turf might be important for the
identification of biases in site identifica-
tion using remote sensing.
Turf is primarily composed of
Sphagnum (the peat mosses). Sphagnum
is the only genus in the class
Sphagnopsida but it consists of more
than 300 species. Sphagnum has two
special properties: through selective ion
absorption, the pH in the center of a tuft
of peat moss is often lower (pH=4.4) than
surrounding soil and water (pH=6.0) and,
due to a unique and unusual arrangement
of two different kinds of cells in the
leaves, it is highly absorptive. Therefore,
areas inhabited by Sphagnum are
extremely acidic. This prevents the dead
Sphagnum and other organic material
from decaying, creating peat deposits or
bogs. Turf comes from the upper layers
of partially compressed peat that has
been cut and dried. When dry, the turf is
light and has a consistency similar to
cork, which, along with its good insula-
tion properties, make it an excellent
building material.
Once a turf house is abandoned, the
strips and blocks of turf erode and fall in
various directions, usually leaving only
the bottom of the wall intact, but sur-
rounded by a substantial area of turf fall.
It is likely that in the coastal and fjord
areas of Skagafjörður, turf structures
abandoned during the Viking Age would
have been buried rapidly, preventing
their destruction by the wind and weath-
er. Soil deposition studies (Guðbergsson
1975, 1994) indicate that most of the 30
to 90 cm of aeolian soil that has accumu-
lated in lowland Skagafjörður over the
last 1100 years from eroding highland
areas (e.g., Dugmore and Buckland
1991), was deposited during the first 250
years of settlement (ffom 874-1100 AD,
see also Thorarinsson 1961).
However, good conditions for preser-
vation of turf structures do not necessari-
ly imply that the identification of the
early sites with substantial turf architec-
ture is unbiased. Once buried, the small
air pockets in turf that make up most of
its volume, are compressed, substantially
reducing the volume. Turf does contain
inorganic matter, most of it deposited in
bogs by the wind, (Johannesson 1960),
caused by highland erosion (Lág 1955).
The lower the inorganic content, the bet-
ter the turf for house building (Gestsson
1982). Increased inorganic material in
the turf blocks would have made them
heavier; reduced their ability to insulate;
and may have decreased their resistance
to wind and weather. The combination of
the reduction in turf volume and the dep-
osition of substantial aeolian soils means
that well-preserved compressed turf
62