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News from Rupert Soskin: stone pillar is blueschist
I don't know whether Rupert Soskin posts here any more (if he does come on to discuss this I will delete this entry). I've just read this on the Facebook "Standing with Stones" page and, having not long since visited Bryn Celli Ddu, found it Very Interesting indeed.
Below is Rupert's FB post:
"Hi folks, Rupert here.
I thought it important to share this as many of you have expressed an interest. I was contacted last night on Twitter by Ffion Reynolds who had been to Bryn Celli Ddu with a geologist who identified the 'tree' pillar as blueschist - i.e rock, not fossil.
Now, the interesting thing about blueschist is that it is a metamorphic rock which only forms in extremely particular circumstances, best explained by this quote from the United States Geological Survey's website:
For many years geologists have been able to relate individual facies to the pressure and temperature conditions of metamorphism.
But they had no satisfactory explanation for the geologic processes that form metamorphic rocks, that is, until the theory of plate tectonics emerged.
One good example is this relatively rare metamorphic rock called "blue schist."
Experimental work had shown that the minerals in blue schist form only under very unusual metamorphic conditions.
These conditions are a pressure range equivalent to a depth of 15 to 30 kilometers in the crust and a very cool temperature, only 200 to 400 degrees centigrade.
That's the approximate cooking temperature of a kitchen oven or toaster.
At a depth of 15 to 30 kilometers, however, the temperature is normally about twice as hot, 500 to 750 degrees centigrade.
So the only way that rocks can be metamorphosed to blue schist facies , is to be quickly shoved down to those extreme depths and then rapidly brought back up before the rocks have time to heat up completely.
And that's exactly what happens where two tectonic plates are colliding in a subduction zone.
In fact, blue schist bearing rocks normally occur in long linear zones that mark ancient plate subduction boundaries.
One of the principal reasons I clung to the fossil theory was the cylindrical tree-trunk shape which had clearly not been cut, despite all previous descriptions of it being 'carefully worked'.
The formation of blueschist could allow a seam of cooling rock to literally roll up between the tectonic plates rather like a piece of seaside rock.
This leaves us with two, rather lovely points:
One: The builders of Bryn Celli Ddu would know no difference, it was still a magical stone tree.
And Two: Metamorphic rock does not form in conveniently sized pieces. There must be more."
Posted by tjj
30th June 2015ce
Sun-disc from the dawn of history goes on display in Wiltshire for summer solstice
Stonehenge sun-disc from the dawn of history goes on display in Wiltshire for summer solstice
Wiltshire Museum will exhibit a gold 'Stonehenge sun-disc', which may have been worn on clothing or a head-dress
Marking this year’s summer solstice an early Bronze Age sun-disc, one of the earliest metal objects found in Britain, has gone on display for the first time at Wiltshire Museum.
Archaeologists believe the disc was forged in about 2,400 BC, soon after the great sarsen stones were put up at Stonehenge. It is thought it was worn on clothing to represent the sun.
The sun-disc, one of only six such finds, was discovered in a burial mound at Monkton Farleigh, just 20 miles from Stonehenge.
It was found during excavations by Guy Underwood in 1947 along with a pottery beaker, flint arrowheads and fragments of the skeleton of an aWe have the best Bronze Age collections in Britain and we are delighted to be able to display this incredibly rare sun-disk through the generosity of the donors,” said David Dawson, Museum Director.
Preserved by Dr Denis Whitehead since its discovery, the sun-disc was seen by the museum's archaeologists the first time was when he brought it to the opening of the Prehistory Galleries in 2013.
It joins and unparallelled collection of Bronze Age treasures at the Museum dating to the time of Stonehenge and worn by people who worshiped inside the stone circle. Chief among them are the famous golden Bush Barrow treasures found in the Normanton Down Barrows less than a mile from Stonehenge.
The sun-disc is a thin embossed sheet of gold with a cross at the centre, surrounded by a circle. Between the lines of both the cross and the circle are fine dots which glint in sunlight.
Pierced by two holes, it is thought the disc, which is the size of a two pence piece and not much thicker than aluminium cooking foil, could have been sewn to a piece of clothing or a head-dress.
Until recently it had been presumed that early Bronze Age gold may have come from Ireland, but thanks to new scientific techniques developed at Southampton University evidence suggests the gold may have originated from Cornwall.
Presented to the museum in memory of Dr Whitehead, it has now been cleaned by the Wiltshire Council Conservation Service and placed on display in time for this year’s mid-summer solstice.
Posted by moss
19th June 2015ce
Edited 21st June 2015ce
Exploring ancient life in the Vale of Pewsey
The Vale of Pewsey is not only rich in Neolithic archaeology. It is home to a variety of other fascinating historical monuments from various periods in history, including Roman settlements, a deserted medieval village and post-medieval water meadows. A suite of other investigations along the River Avon will explore the vital role of the Vale's environment throughout history.
Dr Leary continued: "One of the many wonderful opportunities this excavation presents is to reveal the secret of the Vale itself. Communities throughout time settled and thrived there - a key aim of the dig is to further our understanding of how the use of the landscape evolved - from prehistory to history."
Duncan Wilson, Historic England Chief Executive, added: "Bigger than Avebury, ten times the size of Stonehenge and half way between the Stonehenge and Avebury World Heritage Sites, comparatively little is known about this fascinating and ancient landscape. The work will help Historic England focus on identifying sites for protection and improved management, as well as adding a new dimension to our understanding of this important archaeological environment."
The Vale of Pewsey excavation also marks the start of the new University of Reading Archaeology Field School. Previously run at the world-famous Roman town site of Silchester, the Field School will see archaeology students and enthusiasts from Reading and across the globe join the excavation.
The six week dig runs from 15th June to 25th July. Visitors are welcome to see the excavation in progress every day, except Fridays, between 10:00am and 5pm. Groups must book in advance
Posted by tjj
16th June 2015ce
Prehistoric Anglesey tomb to be excavated for archaeology event
"Residents will get the chance to see the dig in action at the Neolithic Bryn Celli Ddu site during a fortnight-long event which ends with a Summer Solstice celebration.
An ancient tomb on Anglesey will be excavated this summer as part of a two-week long archeology event.
The Neolithic passage tomb of Bryn Celli Ddu is one of Wales’s best-known prehistoric monuments.
The fortnight-long event starts on June 9 and will culminate in a public open day and celebration of the Summer Solstice from June 19-22.
The excavation of the tomb will be led by the Welsh Government’s historic environment service Cadw and Manchester Metropolitan University.
It is hoped it will break new ground exploring the landscape’s ‘rock art’- a term used in archaeology to describe the human-made markings discovered in natural stone."
More at Daily Post:
Posted by thesweetcheat
8th June 2015ce
Volunteers shore up crumbling ramparts of landmark Northumberland hillfort
Volunteers from Northumberland National Park have seen the culmination of many years of work as major conservation started this week to repair the crumbling ramparts of Harehaugh Hillfort in Coquetdale.
Harehaugh Hillfort was built by Iron Age people 2,500 years ago and the essential conservation work now underway will see the hillfort finally removed from the Heritage at Risk register.
he work to save the hillfort is a direct result of more than 20 years of research, excavation and monitoring by archaeologists from Newcastle University that has been funded by Northumberland National Park Authority, Historic England and Natural England.
National Park volunteers and staff have been helping to fill 2,000 sandbags with organic topsoil to restore the profile of the badly-eroded sections of rampart.
A layer of wire mesh will be laid over and across the sandbags and buried beneath a fresh layer of soil and organic grass seed to discourage burrowing animals from returning.
The repair work will utilise 60 tonnes of organic soil and the number of hessian sandbags used equals approximately one sandbag for each year of the hillfort’s life.
continued on the following link.....
Posted by moss
7th June 2015ce
Cornwall was scene of prehistoric gold rush, says new research
David Keys in the Independent article....
New archaeological research is revealing that south-west Britain was the scene of a prehistoric gold rush.
A detailed analysis of some of Western Europe’s most beautiful gold artefacts suggests that Cornwall was a miniature Klondyke in the Early Bronze Age.
Geological estimates now indicate that up to 200 kilos of gold, worth in modern terms almost £5 million, was extracted in the Early Bronze Age from Cornwall and West Devon’s rivers – mainly between the 22nd and 17th centuries BC.
New archaeological and metallurgical research suggests that substantial amounts were exported to Ireland, with smaller quantities probably also going to France. It also suggests that the elites of Stonehenge almost certainly likewise obtained their gold from the south-west peninsula, as may the rulers of north-west Wales, who took to wearing capes made of solid gold.
Posted by moss
5th June 2015ce
National Trust spends £1m to secure precious archaeological site on Great Orme in North Wales
A chunk of the Great Orme, the imposing limestone headland on the North Wales coast which is home to Britain’s largest prehistoric mine and a herd of Kashmiri goats acquired from Queen Victoria, has been secured by the National Trust.
The £1m purchase of a large farm on the promontory overlooking the resort of Llandudno is the latest acquisition by the Trust’s 50-year-old Neptune campaign to protect special areas of coastline under threat of development.
The 140-acre Parc Farm will now be managed to promote the Orme’s status as one of Britain’s most important botanical sites as well as an area rich in archaeology, including the underground workings of the biggest Bronze Age copper mine in the UK.
The purchase means that the Trust has now secured 574 miles of coastline in England, Wales and Northern Ireland since the Neptune campaign was begun half a century ago in May 1965.
Posted by moss
26th May 2015ce
Slieve Gullion: Volunteers help repair ancient cairn
A group of volunteers has helped to repair a 5,000-year-old burial cairn on one of Northern Ireland's most significant mountains.
Around 30 of them trekked to the top of Slieve Gullion in south Armagh at the weekend to carry out the work, under the supervision of an archaeologist.
They helped to fix damage done to the huge passage grave by the weather and increasing numbers of hill walkers.
Stones had become dislodged from the top of the ancient cairn.
As a result, the entrance to the site was in danger of being blocked.
The burial chamber is lined up to illuminate with the light from the setting sun of the winter solstice on 21 December every year.
Posted by ryaner
18th May 2015ce
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