Northern Ireland’s world-famous Giant’s Causeway may have been formed in just days and not thousands of years as thought until now.
The stones attracted visitors from across the world, including the late Queen.
Explanations for their original range from the mythical – they were formed, like much of Northenr Ireland’s topography, by the giant Fionn mac Cumhaill to more prosaic explanations.
To mark Unesco’s International Geodiversity Day (6 October) curator of natural sciences at National Museums Northern Ireland Dr Mike Simms has put forward the first new possible explanation since 1940.
He considered why the extraordinary geological features are found at sea level only.
The explanation, widely accepted for decades, is that a river valley was filled with lava that ponded to a greater depth than normal.
As the thick layer of lava cooled and solidified it formed these regular columns.
Dr Simms argues that if this lava-filled hollow was a valley it would have cut through old layers of lava beneath.
He identified layers of old lava on the shore either side of the Giant’s Causeway sloping inward where older layers have not eroded away.
Dr Simms said: “An analogy I find helpful when explaining this involves cake. Eroding a river valley is rather like cutting through a layer of cake to reveal layers beneath the surface.
“In my interpretation, what we actually see are layers of older rock sloping towards the Causeway – more like a badly baked cake that has sunk in the middle.
“I believe the ground subsided as lava moved up and erupted at the surface.
“The lava filled the depression creating the conditions for the columns to form. This event likely took just a few days rather than the many thousands of years that would be needed for erosion to create a river valley.”
Dr Simms explained he first started thinking about the theory while leading a field trip to the World Heritage Site a decade ago in 2012.
“I owe a particular debt of gratitude to another geologist, a young Brazilian man who was on a field trip I was leading in 2012,” he said.
“He questioned how long it would take to erode the supposed river valley, and it was this that opened my eyes to the evidence before me.
“I had visited the Giant’s Causeway many times before, and until that moment I had just accepted the previous theory.
“It goes to show that even at world famous landmarks such as this, new discoveries can be made from a simple observation.”
The Giant’s Causeway is Northern Ireland’s only Unesco World Heritage Site and is operated by the National Trust, which has acknowledged Dr Simms’s theory.
“I had visited the Giant’s Causeway many times before, and until that moment I had just accepted the previous theory.”
Max Bryant, general manager at Giant’s Causeway and Carrick-a-Rede, said there can always be new possibilities and perspectives waiting to be discovered.
“It highlights just how marvellous, magnificent and mysterious a geological formation we have here in Northern Ireland to share with the world,” he said.
Kathryn Thomson, chief executive of National Museums NI, said she is proud to support Dr Simms’s findings.
“I think it’s wonderful he has showcased the expertise of our team and how important museums are,” she said.
“Yes, we provide spaces for people to explore and learn, but our teams also make meaningful contributions elsewhere.
“As a knowledge-based organisation, our staff are uniquely placed to present research and ideas.
“By using our vast natural science collections, for instance, we can support new discoveries and promote responsible and ethical action when it comes to our natural world.”
Dr Simms’ paper can be read here