Built from stones weighing between 2 and 25 tonnes, the structure of Stonehenge demonstrates a scale of construction hard to imagine before the invention of the wheel. The mystery deepens when you consider that the stones are not from the local bedrock. So why these stones, and how did they get there?

Recent work I carried out with geochemist Anthony Clarke from the University of Curtin, Australia, might have an answer to these two questions for the most far travelled stone of Stonehenge – the Altar Stone.

The Altar Stone was sourced from 700km away in north east Scotland, from a region of bedrock geology known as the Orcadian Basin that was once a lake called Lake Ocradie. The sandstone of the Altar Stone was formed from these lake sediments. Now, new work by our international team has looked to test the possibility it was transported by glaciers.

It is the largest and heaviest of the so-called bluestones (Stonehenge’s travelled rocks), weighing 6 tonnes and measuring 4 metres long. The bluestones were the first stones of Stonehenge predating the larger stones which form the arches by 2,000 years.

We know the north of the UK was covered by ice until approximately 15,000 years ago at the end of the last ice age. This ice was so thick and persistent that it flowed like a slow moving river, picking up and carrying rock and debris with it. The team looked to........

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