Stonehenge<\/a>. But what of the other, smaller monoliths known as bluestones?<\/p>\nAfrica and Ireland continued to be suggested as possible sources. One theory posited that they had arrived with ancient Greek tin traders, used as ballast in their ships. Perhaps they came from Brittany or Finland; British sources mooted included Dartmoor and Edinburgh. Then, in 1921, geologist Herbert Thomas established that Stonehenge\u2019s bluestones had been quarried from the Preseli Hills in Pembrokeshire. But how did they get to Stonehenge? Were they transported by Neolithic people, or could they have been carried east by glaciers?<\/p>\n
Thomas had no doubt that humans were responsible, and most experts since have agreed. However, the glacier theory lingers, supported less by solid geological evidence than by disbelief that anyone would have travelled so far \u2013 150 miles in a straight line \u2013 to source these megaliths some 5,000 years ago when they were quarried.<\/p>\n
Over the past few years, new lab technologies have enabled geologists Richard Bevins and Rob Ixer to confirm that Pembrokeshire was indeed the main source of the bluestones. They have identified two outcrops in the Preseli Hills \u2013 Craig Rhos-y-felin and Carn Goedog \u2013 that were the sites of megalithic quarries for two specific types of bluestone known at Stonehenge.<\/p>\n
Yet not all of Stonehenge\u2019s bluestones were sourced from Pembrokeshire. Bevins and Ixer believe that the Altar Stone, a unique greenish sandstone megalith lying flat near the centre of Stonehenge, came from elsewhere. Their research suggests that it\u2019s probably from eastern Wales or the Marches, though they haven\u2019t ruled out another, more distant source.<\/p>\n Stonehenge glossary<\/h4>\nSarsens | Stonehenge\u2019s largest stones<\/h6>\n They weighed between 4 and 40 tonnes and were quarried on the Marlborough Downs, 15\u201320 miles north of the site<\/p>\n
Bluestones<\/h6>\n These smaller stones weighed between 1 and 4 tonnes and are believed to have been transported to Stonehenge from the Preseli Hills in west Wales<\/p>\n
Megalith<\/h6>\n A large standing stone<\/p>\n
Trilithon<\/h6>\n A free-standing structure consisting of two upright stones and a third across the top (which is known as the Lintel) Dressing The act of sculpting the individual stones into a desired shape using smaller boulders of hard sarsen<\/p>\n
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Stone cold certainty<\/h3>\n But what of Stonehenge\u2019s sarsens? These were, it seems, collected around 2,500 BC \u2013 five centuries later than the bluestones. Sarsen is almost pure silica, making examples from one location all but identical\u00a0to another \u2013 so defeating traditional geological attempts to use variations within the stones to help identify sources. Now, though, science has again come to the rescue, thanks to the work of David Nash of Brighton University and a technology called portable X-ray fluorescence (pXRF).<\/p>\n
Nash\u2019s team analysed the surfaces of the sarsens at Stonehenge, firing radiation from a gadget the size of a hair dryer. By studying X-rays reflected back, they created a geological \u201cfingerprint\u201d that showed all the stones to be very similar to each other.<\/p>\n
Conservation work undertaken at Stonehenge in 1958 involved drilling a slender stone core from one of the sarsens. (Image by ATY WHITAKER\u2013HISTORIC ENGLAND\u2013UNIVERSITY OF READING)<\/span><\/figcaption><\/div>\n Analysis of the core, returned to England in 2018, enabled David Nash\u2019s team to pinpoint the source of that sarsen. (Image by DAVID NASH\u2013UNIVERSITY OF BRIGHTON\/JULIET BRAIN)<\/span><\/figcaption><\/div>\nA further breakthrough arrived when\u00a0a metre-long rod, or core, of sarsen unexpectedly turned up in Florida. This core was originally drilled from a Stonehenge trilithon during conservation work back in 1958; Robert Phillips, who\u2019d been on the job, had taken it with him when he moved to the United States. In 2018, Phillips offered it back to English Heritage \u2013 and Nash and his team stepped in. Now they could compare a Stonehenge megalith with sarsen boulders they had sampled across southern England, crushing up the rock and applying sophisticated geochemical analyses.<\/p>\n
The only match for the megalith\u00a0was in West Woods, on the edge of the Marlborough Downs. So this is the source of the Florida core \u2013 and, by implication, all the other Stonehenge sarsens, which pXRF had shown to be so alike.
2<\/span> How were the stones transported to their current site?<\/h3>\n<\/div> Sea and river voyages have been proposed \u2013 but human-powered overland treks seem most likely<\/strong><\/p>\nMoving stones weighing up to 4 tonnes from the hills of west Wales to the plains of southern England would be a mighty undertaking even in the 21st century. That our Neolithic ancestors achieved the feat seems mind-blowing.<\/p>\n
Yet achieve it they did. Herbert Thomas suggested that the bluestones had been hauled along an overland route of 170\u2013180 miles, passing north of Gloucester to avoid the Severn estuary \u2013 the crossing, he thought, would have been too dangerous.<\/p>\n
However, many archaeologists disagreed, favouring the theory that the stones had been transported by water. They argued that the Altar Stone had been quarried at Milford Haven, a natural harbour a day\u2019s walk south of the Preseli Hills, and that this would have been the departure point for transport by sea.<\/p>\n
The\u00a0voyage might have hugged the coast to the Bristol Channel, then taken one of two routes: following English rivers to Stonehenge, sledging the short land sections; or continuing south-west along the coast, around Land\u2019s End, east to Christchurch harbour and then up the river Avon.<\/p>\n
The scale of this transport operation must have been unmatched in Europe at the time <\/blockquote> <\/div> <\/div> <\/div>\n<\/div> On the face of it, transporting the sarsens would have been far easier. They had to travel only 15\u201320 miles south overland from the Marlborough Downs. But sarsens are far bigger than bluestones, weighing in at between 4 and 40 tonnes compared with the 1\u20134-tonne bluestones. What\u2019s more, the sarsens were artificially shaped, and some of that carving would have been carried out on site, so they would have been heavier when they were transported.<\/p>\n
Many archaeologists have envisioned men with ropes pulling stones across rolling logs.\u00a0This idea has featured in TV programmes and numerous experiments, and is enshrined today in a full-scale model at Stonehenge. Yet research carried out by Barney Harris, an archaeologist at University College London, has cast doubt on this theory. Experiments, along with observations of people moving megaliths in Indonesia, demonstrate that rollers are uncontrollable; stationary sleepers or fixed tracks would be required.<\/p>\n
Due to the stones\u2019 vast size and irregular shapes, a sledge would have been essential. The biggest loads would have weighed more than 45 tonnes, which could be pulled only along a fixed trackway. The scale of this operation, particularly the volume of timber required, must have been unmatched in Eu- rope at the time.<\/p>\n
It\u2019s easier to envisage the transport of the smaller bluestones, dragged on sledges over sleepers or perhaps even carried with poles or wooden frames; such methods have been recorded in north-east India.<\/p>\n
Listen: Mike Pitts answers listener questions on Britain\u2019s most famous prehistoric monument, Stonehenge, on this episode of the HistoryExtra<\/em> podcast.<\/strong><\/p>\nYou can also listen to this\u00a0ad-free version<\/a><\/strong><\/p>\n
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