Archaeologists discovered why Stonehenge’s sandstone boulders have lasted for millennia

The solar units behind Stonehenge simply after the winter solstice.
  • A brand new research gives perception into why Stonehenge has remained unchanged because it was constructed 5,000 years in the past.
  • Sarsens, the large boulders that make up a part of Stonehenge, include interlocking quartz crystals.
  • These crystals – a few of that are 1 to 1.6 billion years outdated – make the rock very sturdy.
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A lot of Stonehenge has remained virtually unchanged since Stone Age builders erected its large sandstone boulders, or sarsens, 5,000 years in the past on England’s Salisbury Plain.

A brand new research reveals how the monument has stood the take a look at of time so efficiently: The quartz crystals that make up the sarsens kind an interlocking construction that makes the boulders almost indestructible.

“Now we have got a good suggestion why these things’s nonetheless standing there,” David Nash, a professor of bodily geography on the College of Brighton who co-authored the research, stated. “The stone is extremely sturdy – it is actually immune to erosion and weathering.”

The research additionally revealed that a few of Stonehenge’s sarsens include grains of rock which can be between 1 billion and 1.6 billion years outdated.

Unlocking the sarsens’ chemical secrets and techniques

Drilling work at Stonehenge in 1958, throughout which cores of sarsen stone had been extracted from Stone 58.

The brand new analysis was born out of an act of repatriation.

In 1958, a workforce was repairing a cracked chunk of sandstone, and a driller named Robert Phillips took a 91-centimetre-long piece of Stonehenge. He finally introduced the relic to his dwelling in Florida within the US, however after 60 years, the Phillips household repatriated it to Historic England, a charity that preserves Stonehenge.

The rock’s return provided Nash’s workforce a chance to analyze the monument’s geological origins. Stonehenge is protected by legislation, so it is not possible to extract new samples for research.

The researchers analysed Phillips’ pattern, together with one other present in a close-by museum, to take a look at the sarsens’ inside construction. They zapped the rock with X-rays, checked out it beneath microscopes, and CT-scanned it.

“This small pattern might be probably the most analysed piece of stone apart from moon rock!” Nash stated in a press launch.

His workforce found that the pattern comprises tiny grains of quartz that match collectively like a puzzle. These grains had been cemented collectively by different quartz items that crystallised – “creating this extremely sturdy interlocking matrix of crystals that make up the rock,” Nash stated.

A microscope picture of the pattern from Stonehenge’s Stone 58 reveals a tightly interlocking mosaic of quartz crystals. The outlines of quartz sand grains are indicated by arrows.

That interlocked construction might assist clarify why Stonehenge has persevered for millennia.

The analysis additionally revealed that the sarsens are composed of sediment deposited through the Mesozoic period, between 252 million and 66 million years in the past, when dinosaurs walked the Earth.

The piece Phillips took got here from a sarsen referred to as Stone 58 – a boulder sticking 21 toes out of the bottom, and weighing about 24 tons. Stonehenge initially had 80 such sarsens in square-shaped archways, however solely 52 stay. In keeping with Nash, 50 of these 52 share the identical chemical make-up, so it is doubtless the findings from Stone 58 apply to the remaining.

“No person’s checked out a sarsen in such element earlier than, it is a good little illustration of Stonehenge’s historical past,” he stated.

David Nash from the College of Brighton analyzes a sarsen core from Stone 58 at Stonehenge.

The sarsens doubtless got here from close by woods

Neolithic individuals erected Stonehenge in two waves of development 5,000 and 4,500 years in the past. The monument consists of two concentric circles of sarsens, with smaller bluestones arrange between these arcs.

Archaeologists traced the bluestones to a website referred to as Waun Mawn in Wales, 225 kilometres away. Some proof suggests the bluestone circle was constructed there first, then moved to its last resting place centuries later. When Stone Age farmers migrated east throughout the island, they introduced the bluestones, weighing 2 to 4 tons, with them.

However the sarsens’ origin remained a thriller till final 12 months, when Nash helped uncover that the sandstone boulders got here from an space 24 kilometres away from the monument referred to as West Woods.

A big sarsen stone at West Woods, the realm the place most Stonehenge sarsens got here from.

Nash thinks Stonehenge’s builders doubtless used some kind of curler, or dragged the sarsens on a slippery floor like frosty floor.

“There is not any proof they used animals to do it, however we do not know,” he stated.

Stonehenge’s builders ‘picked the precise stuff’

Concepts about what Stonehenge was used for run the gamut from a celestial calendar to a sacred graveyard. The monument’s foremost entrance aligns with dawn on the summer time solstice.

“Put merely, Stonehenge was the ceremonial centre of southern England,” Matt Leivers, an archaeologist with Wessex Archaeology in England, beforehand informed Insider.

Contained in the sarsen circle at Stonehenge.

Nash stated he is not certain whether or not Stonehenge’s builders knew “they picked the precise stuff to construct a monument that is going to final a very long time.”

However had they picked a unique sort of native materials, just like the chalk rock that makes up England’s White Cliffs of Dover, Stonehenge would not have remained standing this lengthy.

Any menace to the monument’s longevity now, it appears, would come from native bunnies.

“The one factor that would occur with Stonehenge is doubtlessly rabbits may burrow beneath the stones and undermine them from under, making them fall over onto their sides,” Nash stated.

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