Dawn. The first rays of sun break through the thick mist that has settled over the bay. The black rocks stand out in the fog like pillars, monuments to an age that has long ago been forgotten. This is the Giant’s Causeway. In the morning light, it’s easy to see why it’s a UNESCO World Heritage Site, referred to in any guidebook as one of the natural wonders of the world. Located in the northern tip of Northern Ireland, the Causeway is composed of tens of thousands of rock columns, linking to form a structure almost like a cobblestone highway, which runs across the beach and into the sea. The tops of the columns form regular geometric shapes – most with 5, 6, or 7 sides. Almost a million visitors a year travel to the remote Antrim Coast to experience this display of geology at its finest. But the Causeway is more than just a marvel for hungry eyes and cameras; it tells a story – a story that begins some 60 million years ago.
A quick trip back in time takes us to a landscape much different than today. The Atlantic Ocean had begun to spread, and volcanoes were formed at its edges. Northern Ireland was just one of these volcanic coastlines. Eruption after eruption coated the ground with a sea of hot lava; as the lava from each eruption was exposed to the air, it cooled and hardened into basalt – the black rock that makes up the columns we see today. As it cooled, it contracted and cracked. The top layer of lava, exposed directly to the air, cooled fastest and cracked the most, leaving behind little more than a jumble of rocky debris. The lava below cooled more slowly, forming vertical cracks that divided the rock into regular geometric columns. Many eruptions occurred during this period, forming multiple layers of columns, more than 100 metres thick. At one time, the columns would have been hidden from view by layers of younger material, deposited in the millions of years that came afterwards. However, over the years, waves, rain, wind and glaciers have worn away those layers, exposing the pillars we see today. But the Causeway is just as vulnerable to these same processes. Its present form is only a small remnant of the structure created 60 million years ago; in another few million years, the Causeway will have completely eroded away.
The Irish have their own version of events, one steeped in centuries of folklore and Guinness. As the story goes, once upon a time, the Irish giant Finn MacCool decides to challenge the Scottish giant Benandonner. While Finn could easily have crossed the sea to Scotland, he hates getting his feet wet, and so he decides to build a bridge. Crossing over the causeway, he glimpses Benandonner in the distance. Terrified by his size, Finn runs back to Ireland, where he asks his wife, Una, to hide him. Without delay, Una dresses her husband as an infant and lays him down in a cradle. Shortly thereafter, Benandonner crosses the causeway looking for Finn and comes upon his house. Una tells Benandonner that Finn is out but will return shortly, if he would like to wait. But upon seeing the size of the ‘baby’, the Scottish giant panics, imagining how large Finn himself must be. He retreats across the sea, shattering the causeway behind him. To this day, identical columns can be found on the Scottish isle of Staffa, across the sea.
Alan Shapiro is a Master’s student at Columbia University and an alumni of the University of Alberta’s earth sciences program.
Creative Commons photograph courtesy of Sean McEntee on Flickr.