Archaeological Evaluation

Date 14 September 2018 - 18 September 2018

Event ID 1200584

Category Recording

Type Archaeological Evaluation

Permalink http://canmore.org.uk/event/1200584

HU 57797 93336 The SCAPE Trust, volunteers from Fetlar and volunteers from Archaeology Shetland carried out a programme of section cleaning, archaeological recording, sampling and survey at Sna Broch scheduled monument SM2048. Sna Broch offered an opportunity provided by coastal erosion to access extensive exposures of archaeological sediments buried beneath the ramparts and infilling ditches which form the outer works of a probable broch. Nothing survives of the broch itself.

The results will be relevant to other brochs with surviving outer works in Shetland. The project also carried out 2D survey and 3D photogrammetric survey of the monument and adjacent coastline so that historic change of the coastline could be calculated and the rate of future change estimated. This will help in the management of Sna Broch, and the methodology will be applicable to the many other significant coastal monuments around Scotland at risk from erosion.

Four existing sections created by coastal erosion across the outer rampart, inner rampart, inner ditch and remnant of central broch mound were cleaned, recorded and sampled.

The fieldwork revealed the original form of the earthworks which when first constructed had near vertical stepped profiles, faced with drystone revetment walling. The stratigraphy of the ditch sediments indicated a phased construction of the outer works, and the form of the sediments infilling the ditch, which incorporated organic rip clasts and abundant masonry, suggested a sudden slide of debris into soft waterlogged ditch fills during the monument’s demise.

A new survey of Sna Broch and landscape context has resulted in an up‐to‐date plan of the monument, a digital elevation model and orthophoto of the earthworks and a new survey of the current position of a 500m stretch of coastline.

Information from J. Hambly - The SCAPE Trust, 2020.

OASIS ID: thescape1-504537