IFSA-Butler periodically takes us on trips, and this past weekend we went to to Belfast, North Ireland. Remarkably enough, the island of Ireland is actually two different countries. One is The Republic of Ireland, and the other is North Ireland, a part of the UK. One of the highlights of the trip was visiting the Giant’s Causeway, an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic eruption.
It is said that a giant from Ireland built the bridge of interlocking basalt columns to fight a giant in Scotland, a bridge that was later destroyed. From wikipedia:
The story goes that the Irish giant Fionn mac Cumhaill (Finn MacCool) was challenged to a fight by the Scottish giant Benandonner. Fionn accepted the challenge and built the causeway across the North Channel so that the two giants could meet. In one version of the story, Fionn defeats Benandonner. In another, Fionn hides from Benandonner when he realises that his foe is much bigger than him. Fionn’s wife, Oonagh, disguises Fionn as a baby and tucks him in a cradle. When Benandonner sees the size of the ‘baby’, he reckons that its father, Fionn, must be a giant among giants. He flees back to Scotland in fright, destroying the causeway behind him so that Fionn could not follow. Across the sea, there are identical basalt columns (a part of the same ancient lava flow) at Fingal’s Cave on the Scottish isle of Staffa, and it is possible that the story was influenced by this.
And here is the scientific reason the Giants Causeway formed (again with help from wikipedia):
Around 50 to 60 million years ago, during the Paleogene Period, Antrim was subject to intense volcanic activity, when highly fluid molten basalt intruded through chalk beds to form an extensivelava plateau. As the lava cooled, contraction occurred. Horizontal contraction fractured in a similar way to drying mud, with the cracks propagating down as the mass cooled, leaving pillarlike structures, which are also fractured horizontally into “biscuits”. In many cases the horizontal fracture has resulted in a bottom face that is convex while the upper face of the lower segment is concave, producing what are called “ball and socket” joints. The size of the columns is primarily determined by the speed at which lava from a volcanic eruption cools. The extensive fracture network produced the distinctive columns seen today.
At the causeway I didn’t actually know these facts, and mostly just had fun scrambling around the strange looking rocks and getting blasted by sea spray.