Mon. Nov 28th, 2022
These quarries provided the stones that built Stonehenge

Excavations at two ancient quarries in west Wales suggest how ancient people likely extracted some of the stones that now stand at Stonehenge.

The 42 stones in question are relatively some of the smaller pieces at Stonehenge: they still weigh two to four tons each. They’re called the bluestones and they came all the way from west Wales. Chemical analysis has even linked some of them to two specific quarries on the northern slopes of the Preseli Hills.

One of these, an offshoot called Carn Goedog, seems to have supplied most of the blue-gray, white-spotted dolerite in Stonehenge. And another rock in the valley below, Craig Rhos-y-felin, provided most of the rhyolite. Archaeologist Michael Parker Pearson of University College London and his colleagues have spent the past eight years excavating the ancient quarries, and that work has provided new information about Stonehenge’s origins.

A bit like string cheese

Both steep rocks are the fossilized remains of a long-past volcanic eruption. The lava burst as it cooled and hardened, like mud in a dry lake bottom, and those fissures extended far into the deposit, so the cooled lava ended up in a cluster of vertical pillars. (The Giant’s Causeway in Ireland is another well-known example of that process.)

That geological coincidence made the work of the quarries much easier than in Egypt. There, around the same time, workers were chiseling blocks out of solid rock. In Wales, the quarry workers had to keep only a column at the joints from the neighbors (it’s hard not to imagine having to peel a very large piece of string cheese, to be honest).

Pearson and his colleagues found some evidence of how they did it, thanks in part to the nearly universal human tendency to drop things and forget to pick them up again. The old quarry workers left mudbrick wedges and stone hammers, which they would have driven into the cracks between the pillars, gently prying them apart. The wedges were precision tools for delicate work; mudstone is significantly softer than the rhyolite and dolerite columns, and Pearson says that made a difference.

“A technical colleague has suggested that hitting a hard wedge could have caused stress fractures, causing the thin pillars to burst,” he said in a statement to the press. “Using a soft wedge means that if something were to break, it would be the wedge and not the pillar.”

Once they removed a pillar from the formation, the workers would have carefully lowered it onto a platform of stone and earth placed at the base of the rock. In both locations, the man-made platforms are about one meter (3.28 feet) above the ground. Pearson and his colleagues say old quarry workers would have used them as loading docks, where they would have lowered the newly quarried columns onto wooden sleds for transport.

Dating the quarries

In the soft ground of a toboggan run off Craig Rhos-y-felin, Pearson and his colleagues found a seemingly harmless object that would prove to be a vital clue: a small piece of charcoal. Another lump of charcoal popped up on Carn Goedog’s platform. The archaeologists have radioactively dated both pieces, dating to around 3,000 BC. were found to have fallen. That matches radiocarbon dates from the cremated remains of people once buried under the blue stones, which range from 3,180 BCE to 2,380 BCE. The timing suggests that whoever dropped the charcoal may have had a hand in mining the stone for the distant stone circle.

Apparently, people buried their dead (after cremation) for several centuries at Stonehenge, in the circle of pits now called the Aubrey Holes. But the upright arrangement of vertical and horizontal sandstone slabs that most people recognize today (called sarsen stones) were not built until about 500 years after the blue stones. The shape of Stonehenge (and perhaps its purpose) has changed several times over the centuries, and archaeologists are still trying to piece together the details of the story and the stories of the people who built it and gathered in its circles. to add.

Exploring the Welsh Connection

An enduring mystery of the megalithic monument is why people hauled nearly 290 km (180 miles) of four-ton stones from West Wales to southern England to build it. “Every other Neolithic monument in Europe was built from megaliths no more than 10 miles away,” Pearson says.

Last year, a team of archaeologists examined the cremated remains of people buried at Stonehenge. The archaeologists found that the proportions of the various isotopes of the element strontium in at least 10 of the cremated bodies matched the hills of western Wales, not the chalk plains of southern England. That suggested the prehistoric dead spent the last decade of their lives nearly 180 miles from Stonehenge, but perhaps not far from the freestone quarries at all (though it’s also possible they came from Scotland, Ireland, or continental Europe). Some of them may have even been brought to their final resting place in leather pouches after death and cremation. And the authors of that study say they could have gone on a journey with the bluestones.

But archaeologists are still unsure what connected these distant sites.

“We’re now looking into what was so special about the Preseli Hills 5,000 years ago and whether there were any significant stone circles built here before the blue stones were moved to Stonehenge,” Pearson said. He has previously suggested that the bluestones could have been part of a local landmark in Wales prior to their journey to Stonehenge, although he’s not yet sure what prompted the move.

Antiquity, 2019. DOI: 10.15184/aqy.2018.111

By akfire1

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