Determining how the Stonehenge was built is one of archeology’s great mysteries. It’s difficult enough to build a piece of Ikea furniture in 2019; how was it possible that prehistoric Europeans transported giant pillars hundreds of miles to their final resting place in Salisbury Plain? There’s a popular origin theory involving Neolithic ships, but in a study released Tuesday in Antiquity, researchers undermine it by going straight to Stonehenge’s source — the ancient quarries that housed the stones.
For the past decade, archeologists and geologists have worked together to figure out exactly where Stonehenge’s stones come from. The ancient structure consists of an outer ring of sandstone blocks, together with an inner ring and horseshoe of volcanic bluestone blocks. The outer blocks, while huge, don’t pose too much of a conundrum: Sandstone is relatively common in England, and these were quarried only 30 miles away from the structure. The bluestones, however, are more perplexing. In 2011, researchers matched the bluestones of Stonehenge with geological sources in west Wales, over 100 miles away. Since then, scientists have been trying to figure out the exact locations of those west Wales quarries.
Now, a team from University College London reports they’ve found two of them. One, called Carn Goedog, is 180 miles away from Stonehenge on the north slope of the Preseli hills. The other, called Craig Rhos-y-felin, is in the valley below. The team estimates at least five of Stonehenge’s bluestones came from Carn Goedog, and Craig Rhos-y-felin contains rhyolite, another type of igneous rock found at the monument.
“What’s really exciting about these discoveries is that they take us a step closer to unlocking Stonehenge’s greatest mystery — why its stone came from so far away,” team leader and University College London professor Mike Parker, Ph.D. explained Tuesday. “Every other Neolithic monument in Europe was built of megaliths brought from not more than 10 miles away.”
At Carn Goedog, Parker and his team found wedge-shaped stone tools as well as an artificial platform at the base of the outcrop of stones. Importantly, in the soft sediment of a hollowed-out track track at Craig Rhos-y-felin, they also found pieces of charcoal dating to around 3,000 B.C., which coincides with the initial building of Stonehenge.
The geologists involved in the study determined that the bluestone outcrops at Carn Goedog are natural, vertical pillas and — with the use of the stone tools — it was very possible that ancient Europeans broke them free from the rock face by hitting the vertical joints between each pillar. The pillars were then eased down onto a platform that the team says “acted as a loading bay for lowering them onto wooden sledges before dragging them away.”
The location of these quarries supports the idea that the stones were transported by land to the actual Stonehenge site. Previously, some historian theorized that the stones were brought by sea.
“Some people think that the bluestones were taken southwards to Milford Haven and placed on rafts or slung between boats and then paddled up the Bristol Channel and along the Bristol Avon towards Salisbury Plain,” co-author and Bournemouth University professor Kate Welham, Ph.D. explains. “But these quarries are on the north side of the Preseli hills so that the megaliths could have simply gone overland all the way to Salisbury Plain.”
What the team wants to determine now is why the Preseli Hills were so important 5,000 years ago. It’s possible that there could be more stone circles there — ancient structures erected before the bluestones ever traveled to Stonehenge. If these other stone circles are found, however, their purpose will most likely be a mystery as well.
Geologists and archaeologists have long known that the bluestones of Stonehenge came from the Preseli Hills of west Wales, 230km away, but only recently have some of their exact geological sources been identified. Two of these quarries—Carn Goedog and Craig Rhos-y-felin—have now been excavated to reveal evidence of megalith quarrying around 3000 BC—the same period as the first stage of the construction of Stonehenge. The authors present evidence for the extraction of the stone pillars and consider how they were transported, including the possibility that they were erected in a temporary monument close to the quarries, before completing their journey to Stonehenge.