Giant's Causeway

The Giant's Causeway and Causeway Coast were inscribed on the World Heritage List in 1986, in the first batch of British nominations, and constitute one of the United Kingdom's five natural properties. They lie on the north coast of County Antrim, in Northern Ireland.

The site is made up of some forty thousand basalt columns, most of them hexagonal, wedged against one another like a pavement running down into the sea. They formed during the Palaeogene, some sixty million years ago, when the opening of the North Atlantic caused massive eruptions of fluid lava: as it cooled, the flow contracted and fractured along a regular pattern that produces vertical prisms. It is one of the most spectacular and best-exposed examples of columnar jointing in the world, and its study in the eighteenth and nineteenth centuries was decisive in the debate between Neptunists and Plutonists over the origin of rocks.

Irish legend attributes the formation to the giant Fionn mac Cumhaill, who is said to have built a causeway to cross to Scotland, where similar formations on the island of Staffa complete the story. The cliffs of the coast hold seabird colonies and a cliff flora of interest, with rare species on the inaccessible ledges.