Here, approximately 40,000 stone hexagonal stone pillars line the edge of the Antrim plateau between Causeway Head and Benbane Head, some 40 kilometres or 25 miles northeast of Londonderry on the River Foyle in Northern Ireland.
The Giant's Causeway is one of Northern Ireland's best-known tourist attractions, receiving a million visitors a year and generating half a billion pounds in tourism monies for the northern coastal region each year.
These columns tell a story of the cooling and freezing of the molten lava flows that formed them. As lava at the surface cools and freezes, it also shrinks as its molecules rearrange themselves into a solid structure. This happens much more quickly at the surface where the lava comes in contact with moist, cool air. As the basalt cools and shrinks, pressure increases in intensity and cracks begin to form. A way to dissipate this huge stress is to crack at an angle of 120 degrees, the angle that gives us a hexagon.
We see this beautifully illustrated at the Giant's Causeway in Ireland. Here, highly fluid molten basalt intruded through chalk beds which later cooled, contracted and cracked into hexagonal columns, creating a surreal visual against a dark and stormy Irish Sea. This geologic wonder was named a World Heritage Site by UNESCO in 1986 and a national nature reserve in 1987 by the Department of the Environment for Northern Ireland.
Most but not all of the Giant's Causeway and Causeway Coast World Heritage Site is owned and managed by the National Trust for Places of Historic Interest or Natural Beauty. is a charity and membership organisation for heritage conservation in England, Wales and Northern Ireland founded in 1895.