The 5-metre-long altar stone lies principally buried on the centre of Stonehenge
Laurence Berger/Getty Pictures
Researchers investigating the origins of Stonehenge’s enigmatic altar stone say it’s doable that the 6-tonne rock was carried southwards from Scotland by a glacier – however this speculation depends on an unlikely sequence of occasions, making it extra probably that people transported it.
The 5-metre-long monolith, which is partially buried and overlain by two different stones, has been in its current location, on the centre of Stonehenge’s ring of labored boulders, for round 4500 years.
In 2024, researchers together with Anthony Clarke at Curtin College in Perth, Australia, decided that the altar stone got here from north-east Scotland, based mostly on the chemistry of the rock.
“The altar stone is a sandstone – you may think about grains of sand on the seashore which were squished collectively,” says Clarke. “We are able to get an age and the chemical composition for every of these grains and construct up a fingerprint, which we are able to then forensically examine to different rocks all through the UK and Eire.”
The altar stone’s chemical fingerprint matched outcrops within the Orcadian basin, a geological function that overlays elements of north-east Scotland. This meant the stone will need to have been transported 750 kilometres southwards to Stonehenge, in southern England.
Clarke and his colleagues initially thought it was most definitely that the stone had been transported by boat. However additionally they questioned whether or not it may have been moved by glaciers over the past glacial interval, probably decreasing the gap people would have needed to carry it.
Within the new examine, Clarke and his colleagues used geological evaluation and ice stream modelling to reconstruct historical glacial actions.
They discovered that the majority ice flows from north-east Scotland went to the north, however some did head south and would have dumped their cargo of rock at Dogger Financial institution. Over the past glacial interval, Dogger Financial institution was a part of a land bridge connecting Britain with mainland Europe, nevertheless it now lies beneath the North Sea, off England’s east coast.
If a glacier had transported the altar stone to Dogger Financial institution, it could have shortened the gap people would have wanted to maneuver the stone by a number of hundred kilometres.
However Dogger Financial institution was inundated round 8000 years in the past, and the development of Stonehenge didn’t begin till round 5000 years in the past. This implies it requires an “more and more elaborate set of circumstances” to envisage how glaciation may have moved the altar stone, says Clarke.
Among the different stones that make up Stonehenge, weighing 25 to 30 tonnes, had been transported tens of kilometres by people. Which means with sufficient time, they’d have had the expertise and the desire to maneuver the altar stone even additional, says Clarke.
“These people who erected Stonehenge weren’t in any rush. This might have been very similar to the pyramids, a multi-year endeavour, so it doesn’t must occur on our trendy timescales of months,” he says.
The researchers hope that extra sampling will allow them to pinpoint the precise outcrop or quarry the place the altar stone got here from. However we’re unlikely to ever know why these folks felt compelled to undertake such an enormous process, says Clarke.
“Why will we choose marble from Italy for our kitchens?” he asks. “Why will we choose sure gems to put on round our necks? People have at all times had a fascination with discovering the suitable rock and, for no matter cause, they wanted sandstone from north-east Scotland for his or her monument in England.”
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