Giant's Causeway

Giant's Causeway


Location: County Antrim  Map

Formation: 50 to 60 million years ago


Description of Giant's Causeway

The Giant's Causeway is on the north coast of County Antrim in Northern Ireland, east of the small town of Bushmills, about 100 km from Belfast.

The Giant's Causeway has been a UNESCO World Heritage Site since 1986. It consists of about 40,000 regularly shaped basalt columns, which are about 60 million years old. About half of the columns have a hexagonal cross-section, but there are also those with four, five, seven, or eight corners. The tallest of the stone pillars are twelve meters high. The rock layer is up to 25 m thick. The Giant's Causeway runs around three miles along the cliffs and ends in the sea, from where - according to the old legend of Fionn mac Cumhaill - it reappears on the Scottish coast as Fingal's Cave. Geologists attribute the formation of the basalt dam to the cooling of hot lava. Formations of vertical basalt columns can occur when lava cools very slowly and evenly. The columnar structure is formed from stress cracks that slowly penetrate the material. These arise as a result of the cooling and shrinkage of the material and propagate perpendicularly to the cooling surface. The volcano, whose lava led to the formation of the Giant's Causeway, has now been eroded away.

In 2022, Giant's Causeway was visited by around 1,069,000 people.


Legend of Giant's Causeway

According to Irish legend, the dam was built by the giant Fionn McCumhaill (also known as Finn McCool or Finn McCumhail). It is said that one day Fionn was so insulted by his Scottish opponent Benandonner that he decided to build this dam to defeat Benandonner in a duel. He tore huge rocks from the cliffs of the coast and heaved them into the sea to build a safe route to Scotland. When he finished building, he challenged Benandonner to a fight. In order not to lose his reputation, he had no choice but to accept the challenge, and so he made his way to Ireland. Meanwhile, Fionn, tired and exhausted from working on the dam, was looking for a way to recover ahead of his clash with the Scottish giants. He then disguised himself as a baby and waited with his wife for Benandonner to arrive. When he appeared, Fionn's wife assured him that he wasn't there at the moment. At the same time she invited him for tea and promised that Fionn would come back soon. When Benandonner saw the supposed baby while waiting, he paled at the thought that the father must have been gigantic given the size of the child. He was afraid that Fionn would come to visit him. He ran back to Scotland across the causeway, destroying it behind him. This is how Fionn McCumhaill achieved his victory.




The Belfast – Londonderry railway line operated by Northern Ireland Railways connects the site at Coleraine to Portrush via the Coleraine – Portrush branch line. Local Ulsterbus links provide connections to railway stations. A 10 km (7 mile) walk from Portrush runs past Dunluce Castle; a former narrow gauge line, the Giants Causeway & Bushmills Railway was reopened for tourists in 2002.



The Giant's Causeway forms a promontory jutting out to sea; it is made up of the juxtaposition of prisms of cooled lava. The largest of these prisms reach nearly 12 meters in height. Most are hexagonal in cross section, but about 30% are pentagons and some columns have four, seven, eight or even nine or ten faces. The section of the prisms can have a flat, convex or concave surface. The set evokes an old pavement with irregular paving.



The Giant's Causeway results from the erosion by the sea of a basaltic lava flow dating back 50-60 million years (Cenozoic).

During the Paleogene (early Cenozoic), the Antrim region experienced intense geological activity linked to the opening of the North Atlantic Ocean. During these magmatic events, basaltic lavas forced a passage through the pre-existing limestone geological layers (Mesozoic). These lavas, once cooled, formed a large basaltic plateau. The Antrim plateau is in fact a trap (piling of basaltic flows), where one can distinguish three series of volcanic outpouring. The Causeway basalt belongs to the series of middle basalts.

The rapid thermal contraction of the lava as it cooled created the hexagonal columnar fracturing, perpendicular to the surface of the ground where the flow spilled out (as this surface was not strictly flat, some columns are slightly oblique). Subsequently, the sides of the prisms served as a cooling surface, and transverse, horizontal fracturing appeared. It is the latter which has been used by sea erosion to flatten the basalt columns.

The columns are made of a gray basalt, relatively rich in silica. Some of these columns have been reddened by the alteration of the rock by thermal waters (the action of which has been demonstrated in the decimetric red layers of the cliff), but also by laterization due to the tropical climate which reigned in Ireland at the very beginning of the Cenozoic era (laterization has been characterized in the decametric red layer located between the lower and middle basalts).


Fauna and flora

You can observe from the Giant's Causeway various species of seabirds (about 80), such as the petrel, the fulmar, the cormorant, the guillemot, the redshank, the oystercatcher, the puffin and even the little penguin . The banks are traversed by the wagtail and the maritime pipit. Occasionally, the eider duck lands in sheltered waters.

The National Trust for Historic Interest or Natural Beauty has compiled an inventory of rare or interesting plant species in this area. The list includes sea bream, hare's-foot clover, spring squill, coastal fescue, frog orchid, and bladder campion var. maritima.

A colony of stromatolites was reportedly found on the Giant's Causeway in October 2011.



Although known by the local population, the Giant's Causeway remained unknown to the general public until 1693, when Sir Richard Bulkeley, a member of Trinity College Dublin, presented an article on the site to the Royal Society of London.

The reputation of the site became international when in 1739, an Irish artist, Susanna Drury, made watercolors of it rewarded by the Royal Society of Dublin then distributed in the form of engravings from 1743.

In 1765, an article on the Giant's Causeway was inserted in volume 12 of Diderot and d'Alembert's encyclopedia, illustrated with Drury's engravings.

Tourists began to arrive in the 19th century, after the opening of a tram line between Portrush and the Giant's Causeway.

In the 1960s, the National Trust bought the area and developed it, destroying the old commercial developments which had distorted the site.

In 2000, a fire destroyed the site's visitor center. The new visitor center, designed by Róisín Heneghan of Heneghan Peng Architects, opened in July 2012.


In popular culture

The Giant's Causeway is the title of a novel by Pierre Benoît published in Paris by Albin Michel in 1922. The plot takes place in Ireland at the time of the revolution for independence from Great Britain.

La Chaussée was taken up again on September 18, 2015 in the opening show of the 2015 Rugby World Cup, to symbolize the spread of rugby throughout the world.

The Giant's Causeway features on the cover of Led Zeppelin's Houses of the Holy album as a fantasy setting.

The Giant's Causeway is one of the natural wonders in the Civilization VI video game.