Archaeologists working in Scotland have uncovered new details about a 5,000-year-old artificial island hidden beneath the waters of Loch Bhorgastail on the Isle of Lewis. What looks today like a small stone island was once a carefully built timber platform dating back to the Neolithic period, making the site older than Stonehenge.
The research team from the University of Southampton, working with colleagues from the University of Reading, studied the crannog, a type of small human-made island found in Scottish lochs. Crannogs were long linked mostly to the Iron Age and later periods, but growing evidence shows some began much earlier, between 3800 and 3300 BCE.
Excavations and underwater surveys revealed that the Loch Bhorgastail crannog started as a circular wooden platform about 23 meters, or 75 feet, wide. Builders placed layers of timber and brushwood to create the base. Around 2,000 years later, during the Middle Bronze Age, people added more brushwood and covered parts of the structure with stone. Another building phase followed in the Iron Age roughly 1,000 years later.
Researchers also identified a submerged stone causeway linking the island to the shore, showing the site was once easier to access before water levels changed.
The waters around the island contained hundreds of fragments of Neolithic pottery, including pieces from jars and bowls. Some vessels still held traces of food residue. Archaeologists think these finds point to repeated communal activity, likely involving cooking, food preparation, and gatherings. The amount of labor needed to construct such islands suggests organized communities with enough planning and manpower to build in a lake environment.
Studying sites like this has always been difficult because traditional archaeological methods work well either on land or in deeper water, but not in the narrow zone between them. This shallow area, often less than one meter deep, creates what researchers call a “white ribbon” of missing data, where neither terrestrial survey tools nor marine geophysical equipment performs well.
To solve this problem, the team developed a new workflow using stereophotogrammetry in shallow water. Photogrammetry creates detailed 3D digital models by combining many overlapping photographs. In this case, archaeologists used two waterproof cameras mounted a fixed distance apart on a frame. A diver moved the system through the water while carefully controlling position with centimeter-level accuracy.
The method also combined underwater imagery with drone surveys taken above the site. Ground control points, artificial scale bars, and RTK-GNSS positioning data helped merge land and underwater records into one continuous 3D model.
This produced high-resolution digital models, elevation maps, and orthomosaics covering both the visible stone island and the submerged archaeological remains. Researchers said the system reached accuracy levels comparable to drone surveys on land, while remaining portable and relatively low cost.
Shallow-water imaging usually faces several problems. Fine sediment clouds the water, vegetation blocks visibility, and reflected sunlight distorts images. These issues have made archaeological recording in extreme shallows frustrating for years. The new workflow reduced many of these obstacles and created a repeatable method for future fieldwork.
Beyond Loch Bhorgastail, the technique offers archaeologists a practical way to document the difficult boundary between land and water, an area where evidence of ancient settlements, ritual sites, and coastal activity often survives.
The work not only adds another early Neolithic crannog to Scotland’s growing list, but also gives archaeologists a better tool for studying sites once hidden in this overlooked zone. With hundreds of crannogs still unexplored across Scotland, the method could help reveal more early human activity preserved beneath shallow waters.
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