Wooden Platform Older Than Stonehenge Discovered Beneath Scottish Crannog

The University of Southampton announced on Tuesday that a large wooden platform dated to more than 5,000 years ago was found hidden beneath a man-made stone island in a Scottish loch. The artificial island, known as a crannog, is located in Loch Bhorgastail on the Isle of Lewis.

The platform predates Stonehenge. The study, conducted over several years, revealed a layered timber construction below the stone capping of the island. Hundreds of Neolithic pottery shards were found floating in the water nearby. The finds indicate the platform was first built during the Neolithic period.

Archaeologist Dr. Stephanie Blankshein of the University of Southampton said crannogs are small artificial islands typically thousands of years old. Hundreds exist in the lochs of Scotland and many remain unexplored or undiscovered. The resources and labour required to construct them suggest complex communities and the great significance of these sites.

The analysis found that the crannog started out as a circular wooden platform measuring around 23 meters across and topped with brushwood. During the Middle Bronze Age, about 2,000 years later, a second layer of brushwood and stone was added. A third layer was added some 1,000 years later during the Iron Age.

An ancient stone causeway leading from the loch’s shore to the crannog has also been found submerged in the waters. Large quantities of pottery, often still containing food residue, and worked stone found on and around the islands suggest their use for communal activities such as cooking or feasting.

Researchers used stereophotogrammetry, a technique that calculates the 3D shape and position of objects by analyzing differences between photographs taken from different viewpoints. This allowed them to study the crannog as a single continuous structure both above and below the waterline.

The approach had not been possible using only a land or underwater survey. Professor Fraser Sturt, director of the Southampton Marine and Maritime Institute, noted that fine sediments, choppy conditions, floating vegetation and distorted or reflected light all hinder shallow water imaging.

Photogrammetry is very effective in deep water but runs into problems at depths of less than a metre. To address this, researchers used two small waterproof cameras with low light performance and a wide field of view. A diver manoeuvred the cameras through the water, matching the pace and position of a drone launched above.

By combining stereophotogrammetry, drone technology and innovative post-processing of the data, the team produced an accessible approach that is portable and cost effective. The fieldwork using the technique in shallow water was recently published in the journal Advances in Archaeological Practice.