Seahenge Scanning Completed

By Jon Pratty | 09 January 2002

Left: Seahenge in 1999. (c) Mark Brennand, Norfolk Archaeological Unit/English Heritage.

Just before Christmas 2001, English Heritage released images taken from 3d laser scans of the Bronze Age timber circle known as Seahenge: it now seems the gamble to dig up the ritual site may be paying off.

Inspecting the timbers at microscopic level, using an almost forensic approach, wetland archaeology experts at Flag Fen Archaeology Centre near Peterborough have found the earliest marks made by metal tools yet found in this country. The use of metal-edged tools on the wood comes just 100 years after it is thought Bronze was first smelted and sharpened in Britain.

Right: 4000 year old axe marks can clearly be seen in this oak timber from Seahenge. (c) English Heritage/PA picselect.

At least 38 different axes were used to shape the timbers and it is now thought the construction was a community affair - organised, directed and almost certainly religious in nature.

Further scrutiny of the wood showed which timbers were cut from the same tree and the order in which the posts were set into the ground. First the central stump was erected, then a back panel and an entrance opposite were set out, followed by marker timbers in an arc. Spaces between the markers were then filled in with more timber.

The timbers were split into semi-circular logs, the bark-covered side showing outwards. According to wetland archaeology expert Maisie Taylor, when originally built, the posts may have been around four metres high.

The posts would have hidden the oak in the centre, the whole thing looking like one giant tree stump. The enormous central stump was lowered into the ground using honeysuckle ropes threaded through holes. Incredibly, these survive.

Left: Laser scan of post showing how the scans can be moved and manipulated in three dimensions. (C) English Heritage/PA Picselect.

Structures like these were crucially important to early Britons. "The worship of ancestors and the belief in the next world was what gave people stature and authority in the real world," said Francis Pryor, Director of Archaeology at Flag Fen, near Peterborough.

Right: Base of an oak post showing more toolmarks. (c) English Heritage/PA Picselect.

So the location of the wood ring, on remote boggy land, with an upturned oak in the centre perhaps supporting a sacrificial offering, was significant.

"This shore was, and is, a bleak place, a nevermore, neither the underworld nor on the edge of nowhere," said Pryor. "It's often foggy. There's the constant noise of the sea. An eery place, full of atmosphere. People would have come to worship at the site from quite a wide area. Perhaps 30 or 40 miles or more. And the journey would have been just as much part of the ritual as the final destination."

"Although it is called Seahenge it isn't a true henge. It was never at sea and it wasn't a henge," said Pryor.

Left: Alistair Carty of Archaeoptics scanning the timbers at Flag Fen. (C) English Heritage/PA Picselect.

Earlier in 2001 English Heritage decided to contract Glasgow company Archaeoptics to scan the timbers using a new lightweight portable 3d laser scanner. It was the first time such technology had been used in archaeology.

Now 3d animations, high-resolution images and flypasts have been created. These allow precise measurements of the fresh-looking axe marks in the oak posts. These are first generation impressions from the originals. The resulting 3d images can even be used to generate precise replicas using a rapid prototyping machine.

"In my opinion, in 20 years time archaeologists will regard laser scanning as a tool as vital to the profession as radio carbon dating has become," said Pryor. "I watched it while we were filming Time Team recently. They scanned a skull and it was over in minutes. It would have been a couple of days work, before. As the technology comes down in price we'll be using it for all manner of everyday tasks on digs - recording finds of pottery etc."

"It frightens some archaeologists, but we'll all be using it. It's a quick, efficient and accurate technique."

Right: Francis Pryor, Director of Archaeology at Flag Fen near Peterborough.

As a result of the painstaking investigation and scanning at Flag Fen the significance of the timbers has been established and English Heritage have agreed on a five-year £40,000 programme to preserve and display the circle. Then a decision will be made about how and where to publicly display the timbers.

Chemical preservation may now obscure the delicate tool marks on the structure, but thanks to the laser scans, the secrets of Seahenge should soon be available for all to see on the net.

"The scans allow us to preserve the unique fingerprints, the axe marks, left by the early Bronze Age people who built the structure," said David Miles, Chief Archaeologist at English Heritage. "They allow us to preserve the timbers and yet people will be able to see them very widely. The research has to be there for everyone to access."

Click on the Northcoastal website to find out what's happening to the Seahenge site at a local level in Norfolk.

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