Ive had a number of questions recently about 'Radio carbon dating at Stonehenge' Here is a comprehensive anwser:
Radio carbon dating determines the age of ancient objects by means of measuring the amount of carbon-14 there is left in an object. A man called Willard F Libby pioneered it at the University of Chicago in the 50's. In 1960, he won the Nobel Prize for Chemistry. This is now the most widely used method of age estimation in the field of archaeology.
How it works
Certain chemical elements have more than one type of atom. Different atoms of the same element are called isotopes. Carbon has three main isotopes. They are carbon-12, carbon-13 and carbon-14. Carbon-12 makes up 99% of an atom, carbon-13 makes up 1% and carbon-14 - makes up 1 part per million. Carbon-14 is radioactive and it is this radioactivity which is used to measure age.
Radioactive atoms decay into stable atoms by a simple mathematical process. Half of the available atoms will change in a given period of time, known as the half-life. For instance, if 1000 atoms in the year 2000 had a half-life of ten years, then in 2010 there would be 500 left. In 2020, there would be 250 left, and in 2030 there would be 125 left.
By counting how many carbon-14 atoms in any object with carbon in it, we can work out how old the object is - or how long ago it died. So we only have to know two things, the half-life of carbon-14 and how many carbon-14 atoms the object had before it died. The half-life of carbon-14 is 5,730 years. However knowing how many carbon-14 atoms something had before it died can only be guessed at. The assumption is that the proportion of carbon-14 in any living organism is constant. It can be deduced then that today's readings would be the same as those many years ago. When a particular fossil was alive, it had the same amount of carbon-14 as the same living organism today.
The fact that carbon-14 has a half-life of 5,730 years helps archaeologists date artefacts. Dates derived from carbon samples can be carried back to about 50,000 years. Potassium or uranium isotopes which have much longer half-lives, are used to date very ancient geological events that have to be measured in millions or billions of years.
Stonehenge News and Visitor Information.
Tuesday 9 March 2010
Monday 8 March 2010
Stonehenge team wins project of the year
The team which discovered the site of a second stone circle, 500 years older than the nearby Stonehenge has won a prestigious archaeology award.
The sensational discovery of a 5000 year-old “Blue Stonehenge” was made by a team led by archaeologists from Manchester, Sheffield and Bristol Universities on the West bank of the River Avon last year.
The Stonehenge Riverside Project – as they are known - won the Research Project of the Year award at the Current Archaeology awards held at the British Museum.
The Stonehenge Riverside Project is funded by the Arts and Humanities Research Council and the Royal Archaeological Institute.
The award was given following an online vote by readers of Britain’s biggest archaeology magazine.
The new circle was 10m in diameter and was surrounded by a henge – a ditch with an external bank.
However, the stones were at some point removed, leaving behind nine uncovered holes. The team believe they were probably part of a circle of 25 standing stones.
The outer henge around the stones was built around 2,400 BC, but distinctive chisel-shaped arrowheads found in the stone circle indicate that the stones were put up as much as 500 years earlier.
When the newly discovered circle’s stones were removed by Neolithic tribes, they may, according to the team, have been dragged to Stonehenge, to be incorporated within its major rebuilding around 2500 BC.
Archaeologists know that after this date, Stonehenge consisted of about 80 Welsh stones and 83 local, sarsen stones. Some of the bluestones that once stood at the riverside probably now stand within the centre of Stonehenge.
Professor Julian Thomas, from The University of Manchester and a co-director of the Stonehenge Riverside Project, said: “We are delighted to win this award - and it’s a tribute to the team who have done such a great job.
“We are still coming to terms with this truly sensational discovery: it’s amazing the circle of bluestones were dragged from the Welsh Preseli mountains, 150 miles away around 5,000 years ago.
“It adds weight to the theory that the River Avon linked a ‘domain of the living’ – marked by timber circles and houses upstream at the Neolithic village of ‘Durrington Walls’ – with a ‘domain of the dead’ marked by Stonehenge and this new stone circle.
“The Stonehenge Riverside Project also discovered a Late Neolithic settlement outside the enormous henge at Durrington Walls, upriver from Stonehenge, and a series of contemporary timber buildings and other structures in and around Durrington which may have been ceremonial in character.”
Notes for editors
The Stonehenge Riverside Project is run by a consortium of university teams. It is directed by Prof. Mike Parker Pearson of Sheffield University, with co-directors Dr Josh Pollard (Bristol University), Prof. Julian Thomas (The University of Manchester), Dr Kate Welham (Bournemouth University) and Dr Colin Richards (The University of Manchester). The 2009 excavation was funded by the National Geographic Society, Google, the Society of Antiquaries of London, and the Society of Northern Antiquaries.
Most of the circle remains preserved for future research and the 2009 excavation has been filled back in.
Stoneheneg Stone Circle
The sensational discovery of a 5000 year-old “Blue Stonehenge” was made by a team led by archaeologists from Manchester, Sheffield and Bristol Universities on the West bank of the River Avon last year.
The Stonehenge Riverside Project – as they are known - won the Research Project of the Year award at the Current Archaeology awards held at the British Museum.
The Stonehenge Riverside Project is funded by the Arts and Humanities Research Council and the Royal Archaeological Institute.
The award was given following an online vote by readers of Britain’s biggest archaeology magazine.
The new circle was 10m in diameter and was surrounded by a henge – a ditch with an external bank.
However, the stones were at some point removed, leaving behind nine uncovered holes. The team believe they were probably part of a circle of 25 standing stones.
The outer henge around the stones was built around 2,400 BC, but distinctive chisel-shaped arrowheads found in the stone circle indicate that the stones were put up as much as 500 years earlier.
When the newly discovered circle’s stones were removed by Neolithic tribes, they may, according to the team, have been dragged to Stonehenge, to be incorporated within its major rebuilding around 2500 BC.
Archaeologists know that after this date, Stonehenge consisted of about 80 Welsh stones and 83 local, sarsen stones. Some of the bluestones that once stood at the riverside probably now stand within the centre of Stonehenge.
Professor Julian Thomas, from The University of Manchester and a co-director of the Stonehenge Riverside Project, said: “We are delighted to win this award - and it’s a tribute to the team who have done such a great job.
“We are still coming to terms with this truly sensational discovery: it’s amazing the circle of bluestones were dragged from the Welsh Preseli mountains, 150 miles away around 5,000 years ago.
“It adds weight to the theory that the River Avon linked a ‘domain of the living’ – marked by timber circles and houses upstream at the Neolithic village of ‘Durrington Walls’ – with a ‘domain of the dead’ marked by Stonehenge and this new stone circle.
“The Stonehenge Riverside Project also discovered a Late Neolithic settlement outside the enormous henge at Durrington Walls, upriver from Stonehenge, and a series of contemporary timber buildings and other structures in and around Durrington which may have been ceremonial in character.”
Notes for editors
The Stonehenge Riverside Project is run by a consortium of university teams. It is directed by Prof. Mike Parker Pearson of Sheffield University, with co-directors Dr Josh Pollard (Bristol University), Prof. Julian Thomas (The University of Manchester), Dr Kate Welham (Bournemouth University) and Dr Colin Richards (The University of Manchester). The 2009 excavation was funded by the National Geographic Society, Google, the Society of Antiquaries of London, and the Society of Northern Antiquaries.
Most of the circle remains preserved for future research and the 2009 excavation has been filled back in.
Stoneheneg Stone Circle
Friday 5 March 2010
Subscribe to:
Posts (Atom)