Coins left by visitors damaging UK World Heritage Site

Visitors to the Giant's Causeway have been urged to stop wedging coins into the gaps between the famous stones as they are damaging the site.

Coins squeezed into the gaps in the basalt columns of the tourist attraction in north Antrim eventually rust and expand, putting pressure on the surrounding rock, staining it and causing it to crumble, the National Trust said. Scores of coins left in the cracks are being removed by the trust, an operation it estimates will cost more than £30,000.

Dr Cliff Henry, from the National Trust, said visitors "really love and cherish the Giant's Causeway, and many form deep personal connections to this special landscape". Made up of more than 40,000 columns, it was designated Northern Ireland's first Unesco World Heritage Site in 1986.

Dr Henry said some "may want to leave a token of their visit, but the coins are causing damage and we are urging people to stop the practice and to leave no trace so this natural wonder remains special for future generations". Coins wedged into the joints and cracks in the rock are harming the 173-acre (700,000 square metre) area's basalt both aesthetically and physically, the British Geological Survey found.

Dr Henry said it's study showed "coins are rusting, and expanding to three times their original thickness, which puts huge pressure on the surrounding rock, causing it to crumble". In addition, there are "unsightly streaks of copper, nickel and iron oxides [that] are also staining the stones where the coins are corroding".

Local conditions, including sea spray and the mixture of metals in the coins, speed up expansion and corrosion. Specialists in stone conservation, sponsored by the National Trust and Causeway Coast and Glens Heritage Trust, have started removing as many coins as possible without causing further damage from 10 test locations.

They hope to go on to remove all the remaining coins, and have appealed to visitors not to leave any more. Read more on Sky News:New footage of parade collisionRecord fine for water firmDominic Cummings on Tory leader Mr Henry said they hope "if visitors see fewer coins in the stones and hear appeals to stop the damaging practice the problem can be solved".

While geologists will say the Giant's Causeway was created by an outpouring of Basalt lava 60 million years ago around the time the North Atlantic was opening up, legend has it that it was formed by an Irish giant named Finn McCool who wanted to cross the Irish Sea to Scotland..