New work at Loch Bhorgastail in Scotland has changed what archaeologists thought they knew about a small artificial island.
The site lies just off Isle of Lewis and is one of many crannogs scattered across Scotland. At first glance, it appears to be little more than a low mound of stone. Excavations, however, has revealed a far more complex structure beneath the surface.
Teams from the University of Southampton, working with the University of Reading, began excavations in 2021. Pieces of wood had been seen before, but they were thought to be minor supports.
As the trench deepened, a clearer picture emerged. The stone layer sits on a structured base of timber and brushwood. The wood is not just reinforcement; it forms the island’s main body.
Dating work places the earliest phase between 3500 and 3300 BC. That puts it earlier than Stonehenge construction. Similar dates have been recorded at other sites in the region.
Finds from the water around the island add to that timeline. Divers recovered large amounts of Neolithic pottery, suggesting repeated visits or activity over a long period.
The structure did not remain unchanged. Evidence points to later building phases. In the Middle Bronze Age, new layers of brushwood and stone were added. Activity continued into the Iron Age. A stone causeway, now submerged, links the island to the shore.
To map the site, researchers used stereophotogrammetry. The method combines overlapping photographs to create a 3D model. It is widely used underwater but can be difficult in shallow conditions.
At Loch Bhorgastail, visibility is affected by sediment, plant matter and surface light. To deal with that, the team adjusted their approach. Two waterproof cameras were fixed at a set distance apart and moved through the water by a diver. This setup improved image overlap and reduced gaps in the data.
The result is a detailed model showing the island above and below the waterline as a single structure.
Professor Fraser Sturt of the Southampton Marine and Maritime Institute said shallow water has long been a problem for this type of imaging. The revised method helped produce more reliable results.
Crannogs are common in Scotland, but their purpose is still not fully understood. Building one would have required time, materials and labour. That points to organised communities and some level of planning.
The findings from Loch Bhorgastail add to a growing view that these sites were more complex than simple dwellings.
Details of the work have been published in the journal Advances in Archaeological Practice.
Header Image Credit : University of Southampton
Sources : Journal Advances in Archaeological Practice
