First ever interior scan of Silbury Hill

Submitted by Andy B on Saturday, 25 August 2001 Page Views: 2219

Unique 3D Images Will Guide English Heritage On Vital Repairs To Prehistoric Monument

21st century AD science is coming to the rescue of Silbury Hill in Wiltshire, built between the 28th and 20th centuries BC. English Heritage is preparing to use the latest techniques to map the interior of Western Europe's biggest and most mysterious neolithic monument.

3D images will be used to plan repairs to the hill where an 18th century mineshaft has opened up, leaving a hole on the summit.

Archaeologists and scientists from English Heritage, who look after the hill, and engineers from Cementation Skanska, who are undertaking the seismic survey, started preliminary work to stabilise the hill on 8 August. The shaft has been temporarily filled with lightweight polystyrene and will be covered with a cap of chalk so that the survey, scheduled to begin on 20 August, can go ahead in safety.

The stabilising work has been designed to have minimum impact on the hill and its precious archaeology. Modern technology that would have been the envy of the ancient craftsmen has been called into play. Where they had to use wooden buckets and antler picks, Cementation Skanska can call up a lightweight winch to transport materials and a helicopter to lift the chalk to the hilltop.

English Heritage's Acting Regional Director Chris Smith said: "The survey will be a vital tool in our plan to repair Silbury Hill. It will provide a unique internal view of one of our oldest and least-understood monuments, something no-one has ever been able to attempt before. What we learn will help us secure the long-term future of the mound that our ancestors spent so much time (three million man-hours) and energy in building."

The seismic survey will allow English Heritage to look deep into the hill and plot the extent of the shaft and other tunnels and holes, dug over the last 200 years by various people, curious to discover the mound's secrets. Experts will use the survey to work out a solution to what is an old problem. Photographs from the 1920s and '30s show that the shaft has opened up at least twice before and it is thought that these collapses lie at the root of the hill's instability.

The survey technique, known as 3dT, produces three dimensional images through the ground (rather like a medical CAT scan) identifying structures and major features such as cavities and man-made excavations. The process involves the generation of seismic (sound) signals both at the surface and inside four small diameter, vertical boreholes that Cementation Skanska will drill down into the hill. The seismic data is recorded and after processing, is presented as an image on computers. The cores of the boreholes will provide valuable archaeological information on the development of Silbury Hill and the boreholes themselves will allow English Heritage to monitor the hill's stability in future.

Drilling should finish by the end of September and the results be known by late October. English Heritage will then be able to formulate a repair plan. This should ensure that Silbury Hill is secure and our understanding of it enhanced for generations to enjoy over the next few millennia.

For Health and Safety reasons the hill is closed to the public. Secure fencing has been erected and the hill is being regularly monitored.

Further details are available at
http://www.english-heritage.org.uk/news-events/heritage-briefing/silbury_eh. asp

Contributor Bio for Andy B: Megalithic Portal Founding Editor.

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