Here's the written version of the presentation I gave today. I wrote this last night to get my thoughts in order, but didn't actually read it.


Introduction

Using geophysics and soil sampling to locate probable positions of buried structures, we can determine precise places to cut test trenches in order to gather more accurate data regarding their sizes and dates. After we dig a trench, we scrape its side walls with trowels in order to achieve a clear picture of structural components, such as turf walls, in cross-section. Once we have a clean trench side, we study it and draw it.

Given Iceland’s ubiquitous tephra layers, the structures that we find usually contain turfs with identifiable inclusions that provide dating information. In addition to gathering simple dates, we try to explain the structure’s current condition by studying the profile. For example, if we find the H1 tephra (a bright white layer deposited in 1104 by Mount Hekla) in a turf, then we know that the structure incorporating it went up after that date. If we find the H1 tephra in bits and pieces, then we can determine that people used small turfs to build that portion of the wall, whereas if we find long deposits of H1 in turf, then we can conclude that they used a long stringer in the wall.

Besides the white H1 tephra, we search our profiles for a dark grey tephra laid down in 1300, and a dark grey/blue one deposited in 1766. At the bottom of most of our trenches we find H3, a yellowish brown tephra dating to 2800 BP. A thin black/green tephra from about 871, known as the Landnam tephra, could also appear. In addition to tephra layers, we often find deposits of trash, known as midden, that have deteriorated into layers of grey/yellow/black/orange/brown/pink and include specks of charcoal and bone.

Hof

At Hof we initially opened two five-meter by half-meter trenches to clarify resitivity anomalies lying down hill from two large, still-visible structures on the hill above. In one of these hand-dug trenches, we discovered a concentration of burned soil and found a substantial deposit of natural stones in the other.

We then extended both trenches up into and across the visible structures in an attempt to determine whether and how much any turf used in their construction slumped down the hillside. Additionally, we also expected to find material suitable for dating the structures within or beneath their turf or stone components.

In the less visible, presumably older structure, we located bits of H1 tephra amongst its stones, but found the same tephra nowhere else. We take this to indicate abandonment of this structure before 1104, which allowed tephra to settle in gaps in its deteriorating wall. In the upper structure, we found H1 within turfs clearly showing a date of construction post 1104. A number of large stones within the main structure may indicate that a second structure lies over the first one.

Later, we opened a third trench in the lower area to check another anomoly and found a midden close to the surface. Within it we found recent porcelin and numerous animals bones, all of which may have come from the larger, more recent structure above. We have no proof of association at this point, but the third trench has a few spots of H1 in its south wall.

Reynistadur

Using a backhoe, we placed a number of five-meter trenches in two areas at this farm: a lower area to the west of the farm’s driveway, and a higher area to the east. In the lower area, four of our trenches encountered evidence of cultural material, and in the upper area three trenches came down on structures.

The lower area’s trenches found two different areas, with one pair of trenches clipping edges of turf walls containing H1 layers, indicating construction after 1104. The other pair of trenches brought to light a more complicated situation. One of these trenches revealed turf with H1 in places, again indicating use after 1104.

Our last lower trench, however, showed us not only extensive H1 deposits, but also a deposit of stones with remains of wood posts amongst them. We did not find a turf wall in this trench. In order to clarify the extent of the structure and gain a better understanding of it, we extended this trench another five meters by hand. This work brought to light one of the structure’s walls as well as evidence that someone had laid turf with H1 layers in it to level the middle area.

Our three trenches in the upper area differed a great deal. In one we found H1 in situ, except where we also found a stone-based turf wall with no tephra in it or on the other side of it at the same level. We believe, then, that we have a structure predating 1104, with the tephra layer falling outside while it stood. Later, based on additional H1 inclusions we found in turfs near the top of the wall and to either side of it, we believe that the structure here underwent repairs. Additionally, another wall with H1 tephra appears to the west, perhaps indicating the building of a new structure or an addition to the main one.

Our second upper trench cut through the steepest part of a hillside, and again showed the H1 in situ and in turfs. The turfs themselves appeared in two distinct layers, one rather packed and the other relatively loose in composition. We take this to indicate that the walls here underwent different phases of construction, one on top of the other, probably after the first had already slumped down the hillside to some extent. We found the H1 tephra in situ below the lower turfs as well as included within them, indicating that the original wall went up after that date. A few stones in the lower turf at the short west end of the trench also seem to indicate that the wall had a foundation there that the trench did not cut across. The upper section of turf wall contained inclusions of the 1300 or 1766 tephra.

Our third trench in the upper area cut through a wall of substantial stones overlaid with turf. These turfs contained tephra from the 1766 eruption indicating a relatively late date for the structure’s construction and use. One end of this trench revealed an area that may have been a hearth or work area, as evidenced by burned soil and pieces of slag found nearby, and the fact that it seems to be located above a hard packed floor area containing some bones. The stone wall defining the used area clearly lies within an area dug out from sterile H3/H4 tephra layers.

Getagerdi

We also opened a number of five-meter trenches at this farm, using a backhoe, and extended two of them by hand to a length of ten meters. Despite a number of resistivity anomalies, none of our trenches revealed any evidence of any type of structure. Further on-site work revealed that variations in H3 tephra or gravel deposits may have caused some of the anomalies.

Holar

At Holar we opened several one-meter by five-meter trenches and one one-meter by ten-meter trench. In two we found only gravel causing anomalies, perhaps because of modern land-levelling activities. In a couple of other trenches we found some cultural layers, but not much of particular interest. In our long trench we found numerous substantial stone walls covered and filled with turfs. These walls represent either a series of buildings or a complex site, or both. With only one meter or less of them exposed we cannot be sure of their relationships. Another trench turned up a deep midden and large stone with very clayey turf above. This turf includes H1 so the structure here postdates 1104.

Glumbaer

We have not yet studied all of our trenches at Glumbaer, however one does cut through a pit or ditch. This pit or ditch cuts through an in-situ H1 layer as well as though H3/H4 layers further below. Some midden material, such as bone and ash, as well as organic layers and non-tephritic turfs accumulated in this low area before the 1766 eruption overlaid them with a deposit of dark grey/blue tephra. At some point after 1766, further turfs that include 1766 tephra slumped into the pit or ditch as a wall to the north deteriorated. Alternatively, the turfs above the in-situ 1766 deposit may result from someone laying down turfs to flatten the area for agriculture.

Conclusions

At Hof we have structures and other activity dating from before 1104 to recent times. At Reynistadir we have long-term activitiy as well, from before 1104 to at least 1766. Getagerdi did not provide any material for dating, so we have no information about it at this time. Holar contains numerous structures in a complex, long-lasting environment. Glumbaer, at least in one small area, so far shows evidence for late development, but this may change as we examine additional trenches.

Various tephra layers within and around structures allow us to define their sizes and roughly estimate their dates of construction. Through careful study and discussion of trench profiles, we can often determine a sequence of events not visible from the ground surface or even from geophysics and soil sampling.