Hidden Havens: The Geology of Irish Coasts

Discover nature’s hard marvels.

Do you know your clint from your grike? Your igneous from your metamorphic rocks? If so, you’ll probably already know that the island of Ireland is a geologist’s dream. If not, what better place to discover and learn more about nature’s hard marvels?

Clare Island Cliffs, Loop Head Grooves

On the rugged, carved coast that is the Wild Atlantic Way, Mayo’s captivating Clare Island is a veritable study hotspot for geology students. The steep cliffs at Leic on the island were formed not by waves eroding the shoreline, but, astonishingly, by vertical movement of the Earth’s crust 360 million years ago. You can trace the fault line from the cliffs on the north side of the Big Hill to the sandy beach by the harbour.

The rock formations at Clare’s Loop Head Lighthouse show just how hard nature works to create her most show-stopping sights. Enormous pressure and extreme heat has carved out some of our most outlandish coastline. Striated, diagonal grooves run straight up the cliffs and bear the brunt of those endless Atlantic rollers.

Loop's captivating cliffs

Ice Age Arches

Many places in Ireland take their name from their physical geography. Fanad’s name, derived from the Irish for ‘sloping ground’, just doesn’t do it justice though. The exquisite Donegal coast near Fanad Head Lighthouse is home to some of our most iconic geological formations, including towering sea stacks and vertigo-inducing sea arches rising up out of the pounding surf. Perhaps the best example is the Great Pollet Arch.

From the sublime to the bizarre, walkers along the trail near Blackhead Lighthouse in Antrim will come upon the eye-catching ‘glacial erratics’ known locally as the Wren’s Eggs. These three ovoid boulders were deposited here over 10,000 years ago, sculptural leftovers from the last ice age. Ice is, of course, responsible for many of our most striking geological features, including the exposed bedrock flats on Benderg Beach, worn smooth by the movement of ice sheets near St John’s Point Lighthouse in County Down, Northern Ireland.

St John's Point, Co. Down

Some of the island’s exceptional geological features have been mined for more practical purposes too. The slate quarry on Valentia Island in Kerry provided slates for the British Houses of Parliament and, no doubt, a few less notable houses besides.

The island’s heritage centre explores the geological, human, natural and industrial history of the island in fascinating detail.


Whether you’re looking up – and up, and up – at seastacks and glorious arches, or dizzily peering down – and down, and down – at a sheer cliff face with birds wheeling far below, the Great Lighthouses of Ireland are prime spots for appreciating the power of nature and the formation of this simply stunning coastline.

Find out more about these lighthouses or even enjoy a unique stay in one!


Illuminating the Future at the Great Lighthouses of Ireland Gathering


Great Lighthouses of Ireland Gathering 2023: Full Schedule

Heritage & History

Step inside a Lighthouse for Heritage Week 2023