Ancient Scottish crannog built on timber platform, study reveals

University of Southampton archaeologists, working with experts from the University of Reading, have discovered that a crannog (artificial island) in Loch Bhorgastail on the Isle of Lewis, Scotland, was built on a large timber platform rather than being primarily stone-based as it appears today. The discovery, made during excavation work beginning in 2021, revealed a coherent timber structure extending beneath the stone surface, which researchers say was a major surprise. The island dates to approximately 3500 to 3300 BC, making it older than Stonehenge. During underwater excavation and analysis, researchers uncovered a layered wood and brushwood construction beneath the stone surface, along with hundreds of pieces of Neolithic pottery submerged in the surrounding water. The team used a technique called stereophotogrammetry to create 3D computer imagery showing how the island looks both above and below the waterline as a single continuous structure. Their findings indicate the crannog was first established more than 5,000 years ago as a circular wooden platform about 23 metres across, topped with brushwood, with additional construction phases occurring during the Middle Bronze Age around 2,000 years later and again during the Iron Age. The archaeologists developed an innovative shallow-water photogrammetry technique to document the site, using two small waterproof cameras locked at a precise distance on a frame to compensate for disrupted data caused by fine sediments, choppy conditions, floating vegetation, and distorted light in water shallower than one metre. Principal investigator Professor Fraser Sturt noted that photogrammetry is effective in deep water but has long frustrated archaeologists in shallow conditions. While the exact purpose of these artificial islands remains unknown, Dr Stephanie Blankshein said the resources and labour required suggests complex communities capable of such feats and the great significance of these sites. The methodology has now been published in the journal Advances in Archaeological Practice.