Irish legend (at least this version of it) tells of a giant, Finn MacCool, who builds a causeway of stone columns across the ocean to the Scottish island Staffa, in order to be with the woman he loved. Considering the sheer beauty of the location in Northern Ireland this legend is based on, it is no surprise the story is also full of extraordinary romanticism. Giant’s Causeway is one of the most popular tourist sites in Northern Ireland and – in my own opinion – does not fail to take one’s breath away.
Since learning about the basalt flows that characterize the features of the Causeway in a Geology class several years ago, I have been dying to return to Ireland and see the Causeway for myself. Writing about it and sharing it will, for now, suffice until my Ireland itch returns.
Similar hexagonal columns are also found in Scotland, as well as other parts of the world, helping to explain the “path” across the ocean Finn constructed. As I said, these geometric pillars are common, as are basalt flows (a lava flow rich in heavy minerals and metals like iron, calcium, and magnesium, and only 50 percent silica, making it less viscous than more silica and gas-rich lava flows). About 60 million years ago, during the Paleogene period, intense volcanic activity sent forth an extensive basalt flow over a chalk bed. As it cooled, fissures and cracks began to form in the rock, creating pillars. More lava flows covered this basalt bed, but because its mineral composition was slightly different, no fissures formed. It wasn’t until the Ice Age that frozen sea water eroded the topmost layer of basalt, down to the middle layer of basalt columns, helping to form the Causeway.
Today, there are roughly 37,000-40,000 of these basalt pillars and basalt features. Many of the pillars are hexagonal, but other range in four, five, six, even ten sides, and also vary in height depending on the speed at which the rock cooled. The faster a lava flow cools, the smaller the pillar; the longer the flow takes to cool, the bigger the pillar. This is true with all lava flows, especially those rich in silica and other minerals: it means that lava flow is going to form huge crystals of quartz, obsidian, garnet, et cetera. In other words, big, beautiful rocks.
The world is a breathtaking place if you simply know where to look. For me, if the rocks and books are old, chances are I’ve already fallen in love. The amazing thing about Ireland (but why pick just one? I could give you hundreds) is the richness in culture and history, and you see it especially in the land and landscape. Every spot has a legend, a history, a people. I spent two weeks on the island and by the time I left my head was heavy with folklore and history.
Hopefully you can see Giant’s Causeway is no exception: it’s beautiful, unusual, and attached to a deeply-rooted story. Around the time I was learning about Giant’s Causeway a friend from the English program told me about his own trip there some years before that, making the Geology nerd in me furiously jealous.
Trust me, once you’ve seen it, you’ll get it.
Adventure on, my fair readers, and hopefully you can fall in love with every old and strange rock as I have.
Volcanism 