Bright and early, we set off for the tippy-top north coast of Ireland, to a geologic anomaly known as the Giant’s Causeway. We passed through many small towns, none of which looked any different than those in the southern portion. The Gaelic language isn’t used on signs, as it was in the south, but its absence wasn’t apparent until our guide pointed that out.
The roads are as narrow and twisting as everywhere else, and I was grateful for the skill of our driver. Mile after mile, we passed through sleepy little fishing villages as we wound our way north.
According to legend, a giant in Ireland and a giant in Scotland were going to do battle, and a large causeway (in this case, a basalt bridge) was built so they could meet. But after the giants had spied on each other, and the Scottish one, tricked into thinking the Irish Giant was much bigger and likely to defeat him, destroyed the causeway, leaving basalt columns, like stepping stones, on each shore.
Geologically speaking, around 50 to 60 million years ago, the area was subject to intense volcanic activity, when highly fluid molten basalt intruded through chalk beds to form an extensive lava 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 pillar-like 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, many of which with names like “organ” and “harp” and “camel’s hump.”