Brodgar excavation ends, but the secrets of the stone circle are becoming clearer

Brodgar excavation ends, but the secrets of the ring becoming clearer. (Sigurd Towrie)

The month-long excavation at the Ring of Brodgar came to an end this week.

With the northernmost ditch exposed for less than 24 hours, work to backfill both ditch trenches at the Ring of Brodgar was completed today, Friday, August 1. It’s now a case of waiting for the results of post-excavation tests to see whether the unanswered questions surrounding the monument can be answered once and for all.

But although it was primarily a sample-gathering exercise, the four-week excavation has revealed much about the construction of the iconic monument. And if the 800-or-so visitors at the open day on Sunday are anything to go by, the excavation caught the attention of many.

The reason for the dig was simple. There is very little known about the Ring of Brodgar – much, such as its age, is pure assumption, based on other sites.

So what do we know?

The monument comprises a circular ditch and internal stone circle. The ditch is approximately 123 metres in diameter, with two opposed causeway entrances in the north-west and south-east. The stone circle has a diameter of approximately 103 metres.

And that’s about it.

Picture Sigurd Towrie

Taking measurements in Trench A. (Sigurd Towrie)

An attempt to date the site in 1973, by Professor Lord Colin Renfrew, failed — primarily due to the limitations of available dating techniques.

So this summer, a team of archaeologists set out to try to retrieve datable material and examine archaeological and palaeo-environmental samples, with the aim of resolving this.

At the head of the project were Dr Jane Downes, of the Orkney Research Centre for Archaeology (ORCA) and Dr Colin Richards, of the University of Manchester.

The 1973 trenches were re-opened and extended — and the rock-cut ditch was visible for the first time in decades.

Trench C, to the south of the circle, lay in the shadow of the South Knowe, while Trench A traversed a section of the ditch to the north. Back in 1973, Trench A had to be abandoned due to waterlogging, but this year the excavators were more fortunate.

The ditch in Trench A measured 3.5 metres deep and, at 7.5 metres, was much wider than the ditch section uncovered in Trench C.

Commenting on the experience, Dr Colin Richards said: “It’s been a very nice thing to do — to actually get down and resolve this. A lot of the work was about taking new samples and using new techniques, but as Gordon Childe said, when working at the nearby passage grave of Maeshowe, it is a privilege to be undertaking fieldwork within the great Ring of Brodgar.

Picture Sigurd Towrie

The Ring of Brodgar (Sigurd Towrie)

“It’s incredible to see the work that went into digging out the ditch. These people were doing something on a scale that had never ever been attempted before. You see the excavated sections today and you can imagine what it was like back then. It would have been absolutely amazing.”

The bottom of the ditch in Trench A, nearest the current road, was reached on Monday morning.

“In all honesty, it looked absolutely spectacular,” said Dr Richards. “It certainly took us a lot of time and energy simply removing its soft silts and fill. Completely rock-cut, the ditch in this sector is deep, very broad and flat-bottomed. Working at its base makes you realise just how impressive this monument must have appeared when it was first excavated back in the third millennium BC. Similarly, you appreciate the sheer scale of labour that was involved in cutting through the rock to form the ditch, let alone in quarrying and moving the stones forming the circle.”

Not long into the dig, it became apparent that the ditch had not been dug out in one continuous process.

Dr Richards explained: “When we look at the excavated area, the ditch bulges outwards and appears to contract in the adjacent, unexcavated, area. To me, this suggests that, rather than being originally dug as a single entity, the ditch was probably dug in segments.

“The beautifully-round, regular circle that appears to surround the monument today is due to the subsequent peat growth, which makes it look like a smooth circle.”

“It’s difficult to know how long it took to dig,” he said. “Perhaps it was a gradual process? Perhaps over many years and involving different groups of people? Were the people who brought in the stones responsible for digging their own segment of the ditch? If that’s the case, it could have taken several hundred years to build.”

The idea that one “elite” individual, or group, was responsible for the construction of the ring can be discounted, Dr Richards believes.

“There’s long been this idea that a chief said, ‘do this’,” he said. “It was nothing like that at all.”

Instead, Dr Richards’s theory is that it wasn’t the completed stone circle that was significant, but rather the physical act of constructing it. The prestige of erecting a fine megalith, he suggests, may have been the driving force behind the development of the monuments.

A previous geological examination of the Ring of Brodgar megaliths confirmed that the stones had been brought from different sources and quarries across Orkney. These quarries, and the different type of stone obtained from them, may, therefore, represent the different people, or communities, involved in the construction of the stone circle.

This construction, he suggests, may have seen competition between villages and communities of the time.

“My suggestion is that these communities were quite fiercely competitive. The ring, rather than being this ‘harmonious temple structure’, that was a joint-effort between different communities, was maybe the site of some really quite competitive behaviour, with the various groups attempting to outdo the other with visible shows of prestige and power. Labour, and the deployment of labour, was a visible mark of prestige.”

This scenario, said Dr Richards, would see the construction of the ring taking generations — it would have grown slowly as the megaliths were brought in.

Because he feels the act of building the monument, in particular erecting the individual stones, that was the ritually significant element, he suggests the “completed” stone circle had no particular function. This, he proposes, may explain why there remains a distinct lack of evidence that Brodgar was ever used for anything.

Back in the trenches, the sheer scale of the work undertaken by the prehistoric ditch-diggers was clear. Working with tools made from stone and antler, an estimated 4,700 cubic metres (11,000 tonnes) of rock had to be quarried to create the 380 metre-circumference ditch — a momentous task previously estimated to have taken 80,000 man-hours.

“The great feat of labour employed in the digging of the ditch provides some insight into just how important this separation was to Neolithic people. From the excavation, it seems they dug a section of the ditch and then they left it. The colours of rock in the ditch in Trench A have been influenced by water logging, so the orange-brown Orkney flagstones gives way to a deep grey-blue near the base of the ditch. Strangely enough, this actually gives the appearance of water standing in the ditch bottom.

“From this evidence, it is quite clear that in the northern area, at least, standing water collected soon after the ditch was dug. This may seem strange, but it is worth remembering that the surrounding ditch was cut to enclose the area of the stone circle and in the Orcadian island world, water surrounded islands and people. Therefore, the use of water to create a division — to separate it from the rest of the world — was an appropriate strategy employing everyday imagery. They were, I believe, creating an ‘island’ — a symbolic area representing the world they lived in, and a world they knew.

“But, in terms of architecture, the circle may not have been the most significant point in the landscape. This ‘island’ has two opposed entrances — probably to enter and exit the circle. The great ring may have been built around a pre-existing pathway and passing through it may have “altered” a person’s state, a bit like entering a church and moving towards the altar. In this case, the end point of the journey may have been further along the Ness of Brodgar.”

Dr Jane Downes was delighted by the progress made during the excavation.

She said: “The excavation was really more about the retrieval of samples and the subsequent results that will come after the fieldwork is complete.

“Although the excavations 35 years ago were undertaken to obtain dating material and establish chronology, they failed due to the limitations of available dating techniques at the time. The advanced new techniques now at our disposal mean that, this time, our investigations should allow us to establish when the Ring of Brodgar was built and also help us learn a great deal more about it.

“Bob McCulloch, and his partner Mary, who came from Stirling University to sample the sections, retrieved the samples successfully, and Bob had some interesting observations about the ditch having filled in very rapidly, and perhaps being infilled deliberately — these issues will become clearer when the lab work has been done on the samples.

“Meanwhile, we’ve had David Sanderson here from the Scottish Universities Environment Research Centre (SUERC) undertaking his sampling for dating purposes. His results look promising, so we could get some good dates that will allow us to put a date on when the ditch was created.”

“We had some stunning results from the geophysics,” she added. “In fact we’ve found a lot of the ‘missing’ stone socket holes. From this, we can confirm that the circle today contains a fraction of the stones that once stood on the site.”

Survey fills in the gaps

Picture Sigurd Towrie

The south-eastern entrance to the Ring of Brodgar, with the missing megaliths replaced digitally. (Sigurd Towrie)

A survey of a section of the Ring of Brodgar’s circumference suggests there could have been more than 60 standing stones in the monument.

It has long been proposed that the ring contained 60 megaliths, although this figure has never been confirmed archaeologically.

A section of the ring’s circumference, running from the edge of Trench C, anti-clockwise past the south-eastern causeway, to Trench A, has been scanned using tomography, by excavation team members, Norma and Adrian Challands.

Adrian explained: “Whereas resistivity surveys take readings on a square grid, in plan, tomography surveys take resistance readings in section — like, for instance, a brain scan, which also employs tomography.

“We placed 40 probes, spaced at 50 centimetre intervals, and equal depths, and took readings on each probe, increasing the spacing at each of seven or eight runs. The software then produces readings in the shape of an inverted, truncated pyramid — representing a depth of two metres, or so, from the ground surface.”

Picture Sigurd Towrie

Standing at the south-eastern causeway, looking north-west. The white markers show the position of the confirmed socket holes. (Sigurd Towrie)

Picture Sigurd Towrie

The view to the north-east. Again, the white markers show the position of socket holes. (Sigurd Towrie)

Picture Sigurd Towrie

The view towards Trench C. Again, the markers represent confirmed sockets. (Sigurd Towrie)

By Monday evening, they had confirmed the locations of 19 stone sockets, spaced three metres apart. Including the surviving stones and stumps, this meant 36 stones once stood in that section —roughly half— of the stone circle. This hints that the Ring of Brodgar could have contained more than 60 stones — although the distance between stones does increase towards the north, and north-western, section of the monument.

A survey of the final section will be required to confirm the exact number on stones in the Ring of Brodgar.

Picture Sigurd Towrie

The view to the north-east - this time with computer-generated stones "restored" to the known socket holes. (Sigurd Towrie)

The excavations allowed the archaeologists the chance to examine one such socket hole. Up in the southern trench, in the shadow of the South Knowe, a stone hole in the open trench was excavated.

Although there appeared to be no stump of the megalith it housed, the large “packing” stones used to wedge the massive megalith tightly into the ground remained.

The investigation allows comparisons with other stone sockets excavated in the county — the most famous being the nearby Stone of Odin, located and excavated by Dr Richards in 1988.

The excavation was funded and supported by Historic Scotland, Orkney Islands Council, Orkney College UHI and the University of Manchester.

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