One of Stonehenge’s enduring mysteries is how its Altar Stone made the 700km (435-mile) journey from Scotland to southern England. Now, researchers think they may have part of the answer: a glacier helped transport it.
The massive six-tonne sandstone slab lies at the centre of the monument and is thought to have arrived on Salisbury Plain around 5,000 years ago. Previous studies traced the stone’s origins to northeast Scotland, but left unanswered how it covered such a vast distance.
After studying ancient ice flows, scientists at Sheffield Hallam University and Curtin University in Australia believe a glacier carried the Altar Stone from the Orcadian Basin in northeast Scotland to Dogger Bank during Britain's last ice age, between 33,000 and 11,700 years ago.
Dogger Bank, now submerged beneath the North Sea, once formed part of Doggerland – the vast prehistoric landmass that connected Britain to mainland Europe. Because the area contains no natural source of large stones, any boulders found there must have been carried in by glaciers.
Sheffield Hallam University’s Dr Remy Veness, co-lead author of the paper in the Journal of Quaternary Science, said: “We recently discovered that the origin of the Altar Stone is northeast Scotland, but how it travelled 700km to Salisbury Plain is widely debated.
“What is exciting about these findings is that they could imply that the people of Doggerland attached cultural significance to the Altar Stone long before it was incorporated into Stonehenge.
“The Altar Stone must have been significant enough [for people] to be willing to move the stone at least twice; first to save it from being submerged by rising sea levels at the end of the last ice age and then again to its final resting place on Salisbury Plains.”
Co-lead author Dr Anthony Clarke, from Curtin’s School of Earth and Planetary Sciences, said the findings suggest glaciers carried the Altar Stone as far as Doggerland, leaving Neolithic people to transport it the rest of the way to Stonehenge.
“Our modelling shows glaciers may have transported rocks part of the way during the last Ice Age – potentially as far as Dogger Bank in the North Sea – but not into southern England, meaning the stone would still have needed to be moved hundreds of kilometres by people,” said Dr Clarke.
While the study suggests glaciers carried the Altar Stone south, the researchers found no viable glacial pathway linking its Scottish source directly to Stonehenge. Instead, they believe Neolithic people transported the stone in stages, using a combination of overland, coastal and river routes.
They add that the feat of moving such a massive object over long distances points to a level of organisation and cooperation among Neolithic communities not previously fully appreciated.
“Transporting a stone of this size over such a long distance would have required planning, coordination and a deep understanding of the landscape – not to mention tremendous determination,” Dr Clarke said.
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