2015 Knowe of Swandro Excavation
Excavations at Swandro in 2015 saw a continuation of the work on the terraced beach with the further examination of the eroded Iron Age buildings investigated in the previous year. Structure 3, a Pictish building at the top of the series of eroded terraces, continued to be excavated with further signs of metalworking debris consisting of slag, furnace lining and crucible fragments being found. These infilling deposits were sampled and have high potential for botanical remains in the light fraction recovered from flotation. It now appears that the construction of the main Norse house excavated by Sigrid Kaland (1993) destroyed the eastern part of this structure, though the infill deposits may be earlier than this. To the W there seems to be a short passage leading out of the structure, with two possible steps. Further definition of other structural remains took place all along the upper terrace.
Excavation in 2015 continued to define the partially eroded structures on the beach and the excavation of the Pictish building (within the extension started in 2014). The passage to the chambered cairn was identified and the upper fill contained evidence of Viking Age activity with the finding of a coin of EANRED (King of Northumbria in the first half of the ninth century AD). Gareth Williams (in discussion of this find and within a Northern Isles context) was happy to see this as being a Viking Age deposition. The upper part of the beach containing the eroded buildings was recorded with both photogrammetry and 3D laser scanning.
The Neolithic chambered cairn on the western boundary of the Iron Age site was uncovered to assess the tidal damage to the remains. This area was originally uncovered in 2012 and the structure of the cairn determined before being carefully recovered. However, observations last year suggested that the large boulders had again shifted and that the outer of the casement walls was eroding. Excavation of the overlying beach and removal of the membrane laid down in 2012 showed an alarming amount of attrition to the monument. The stones forming the seaward part of the outer casement had been rounded by the sea and much of the retained material had been washed out. The other casement walls also seem to be tipping seawards. This summer saw a lot of rainfall and a spring developed at the foot of the cairn draining towards the sea which may be hastening the erosion. The monument was fully scanned using a 3D scanner by Dr A Wilson (University of Bradford), and aerial photos were taken (using a drone) by Lindsey Kemp and Robert Friel.
The excavated remains of the Iron Age settlement and Neolithic Chambered Cairn at Swandro in 2015. The photograph was taken by Robert Friel using a drone and shows the Iron Age settlement (left) and the chambered cairn (right). Note the erosion of the seaward side of the cairn.
The storm beach area containing the chambered cairn, which had been recorded in 2012, was re-examined in 2015 to identify and record the effect and damage caused by the sea since the site had been carefully covered and re-packed with beach cobbles.The passage entranceway on the E side of the tomb was located this season; two parallel wall faces lead through the cairn wall and are continued by a further wall which butts the outer casement walls of the cairn. It seems likely that this passage originally continued to the E but whether it was destroyed by Iron Age activity or continues in fragmentary form under the Iron Age structures which surround this side of the cairn is not yet known. This passageway has been deliberately filled with rubble and fine earth; a fragment of copper alloy and bone fragments, human and animal, were found in the top of the fill, but no further excavation took place on these deposits. Further investigation is needed to elucidate this relationship.
The tomb revetment demonstrated that heightened wave activity over the intervening winters had shifted deposits and revealed one of the lower revetment stones before clearance. Once uncovered, this area was cleaned and recorded using digital imaging and 3 dimensional scanning. It is worth noting that the cairn has suffered greatly from the effects of erosion in the intervening years, with much of the lower (seaward) circuit of the outer casement wall and the packing contained by it having been removed by the sea. Several of the large blocks from this lower revetment have been torn out and have completely disappeared. The water level at high tide regularly comes to this outer part of the tomb. The large stones that remain were angular when recorded in 2012 and now show significant smoothing by the action of the sea and movement of smaller beach material.
The surviving structural remains of the Iron Age settlement and on the right the casement walling of the chambered cairn after the beach overburden had been removed in 2015.
Observations on the erosion
The terracing of the structures and associated deposits that survive on the beach is due to the unique combination of factors affecting the erosion and as such presents a rare opportunity to examine and sample such an extensive site and understand the erosion processes acting upon it.
The erosion is rapid; midden deposits found during an examination of the beach at low tide in 2011 have been completely destroyed by the sea. The sea is actively destroying the eastern part of the site under the earthwork remains of the Norse houses; stonework still survives but most of the sediments and midden deposits have been washed away and the front stones of the remaining features show battering and wear. The main part of the site survives in the shadow of the eroded remains of the chambered cairn and it is noticeable that midden deposits survive in this area. This earlier monument appears to be suffering badly from the sea on the beach itself. This is evidenced clearly by the Chambered Cairn when the results of the 2012 season are compared with those from the 2015 season. The assessment of the erosion and effective monitoring demonstrates the importance of developing recording methodology. The re-scanning of the monument using a 3D laser scanner before re-packing, has provided an important record enabling the monument to be visualised from different perspectives and dated to a point in time. The outer packing of the cairn’s casement walls was found to have suffered significant erosion since it was first recorded in 2012. A section in a trench 1.0m wide through the casement retaining wall and packing in order to investigate the structure of the cairn demonstrated that the packing had been badly eroded or replaced by washed in beach material.
On the beach to the east of the eroding Chambered Cairn, there are walls and features which appear to pre-date the Iron Age sequence and possibly represent an entrance passage to the tomb. These too are under threat; much of the lower terrace material has been destroyed and the remaining deposits are threatened. These middens are of vital importance as they contain an irreplaceable cultural and economic biography of the site.