These are glacial erratics.
— okay, _technically_ they’re _not_ ‘erratics’ because an erratic has to be of a type of rock _different_ from the rock it is deposited on - hence: erratic - but I don’t know what else to call them and ‘glacial boulder-thingies’ doesn’t sound as impressive. Back to the story… —
You can see them pretty much everywhere in the Burren but they seem to be more common in the northwest. If you hike up to Black Head from Fanore you’ll pass through areas with dozens of huge boulders, scattered like marbles from some game between giants.
We don’t have to go that far. We have our own erratics right here in our backyard. The big one pictured here is on the hillside north of the Perfumery. There’s another big one between the road and the turlough to the south. Where do they come from? Well, not so long ago (in geological time, barely an eye blink) this part of Ireland would’ve been covered in ice. The last ice age (Last Glacial Period or LGP) lasted from 115,000 years ago up until about 11,700 years ago. The extent of the ice cover would have varied during this period and it would have retreated out of Ireland maybe around 16,000 years ago.
As these glaciers expanded over the landscape they would have ground off the surface of the bedrock underneath them and trapped huge amounts of stones, boulders, gravel, etc. within the ice. As the ice retreated and melted, the boulders were left behind. And this is why you see these huge, rounded rocks dotting the landscape.
When you come across one, stop. Maybe sit on it. And imagine 20,000 years ago when where you are sitting now would have been covered in a layer of ice maybe 500 or a 1000 metres deep. It would have been _at least_ at thick as the highest mountains in the Burren, but _on top_ of them again. The sea level would have been 120m lower and you would have been able to walk to the Aran Islands and far beyond. When the ice retreated it left a landscape scraped clean, utterly barren, and yet within a few thousand years there were trees, grasses, animals and even people here.
That’s one of the many things I like about the Burren, the constant reminders of how small we are and how short and insignificant all of our worries are. In the grand scheme of things…