The sandstone you see in cross-section here was laid down between 313 and 326 million years ago, in the Carboniferous. The cliffs preserve a record of a river delta dumping sand, silt, and clay into a deep marine basin - some of the finest deltaic geology exposed anywhere in the world, two hundred meters of vertical history compressed into legible layers. Each band of darker shale or paler sandstone is a single depositional event: a flood, a storm, a year of slow accumulation that the next year's deposit sealed in place.

Geologists come here to read it like a book. Trace fossils run through the rock - scolicia tracks of feeding invertebrates, burrow casts of creatures whose names are now untraceable. Ripple marks survive on the upper surfaces of certain beds, the last memory of a current that flowed when nothing on land had yet evolved into a flower. The cliffs are still being unmade. Wave action undercuts the base, blocks of rock peel away under their own weight, and the cliffline retreats inland a centimeter or two each century. Branaunmore - a 67-meter sea stack at the foot of the cliffs below O'Brien's Tower - was once part of the mainland.

Atlantic puffins nest here in the thousands, with their orange-striped beaks and clumsy stutter-step takeoffs, raising chicks in burrows on the small Goat Island and on isolated cliff terraces unreachable by anything but wings. Choughs - the cliff-dwelling crows with red beaks and red legs - work the air currents. Razorbills, guillemots, kittiwakes, fulmars: the cliffs are an Important Bird Area, designated by BirdLife International, and the spring breeding season turns the rock-face white with seabirds.

The water beneath holds its own theater. Grey seals haul out on rocks at the base. Common and bottlenose dolphins ride the currents. Minke whales pass through in summer. Basking sharks - the world's second-largest fish, twelve-meter filter feeders that look terrifying and eat plankton - cruise the coast from late spring. Occasionally a sunfish surfaces, that strange flat circle of a creature whose evolutionary path nobody quite understands. On the cliff tops, feral Bilberry goats graze the rough grasses, descendants of escaped domestic stock. The Irish hare bounds among the limestone scattered above the cliff edge.

Just off the cliffs, where a reef rises just enough to disrupt the swell driving in from three thousand miles of open Atlantic, a wave breaks that surfers spent decades trying to reach. They named it Aileens - more properly Aill na Searrach, the cliff of the foals - and on the rare days when the swell, wind, and tide line up it produces ten-meter walls of water. The wave features in the 2008 documentary Waveriders, and it has put Ireland on the global big-wave map.

The cliffs themselves have appeared in more places than most natural wonders. The Princess Bride in 1987 used them as the Cliffs of Insanity. Harry Potter and the Half-Blood Prince in 2009 filmed Dumbledore and Harry searching a sea cave at their base. Maroon 5 filmed the video for Runaway here. Westlife filmed My Love. In 1999, Dusty Springfield's brother Tom scattered most of her ashes from the cliff top. There is an Irish fiddle tune called The Cliffs of Moher that traditional musicians have played for at least a century.

By the 1990s Clare County Council faced a problem most tourism authorities would envy: too many visitors. Almost a million people a year were arriving at a site with no real infrastructure, walking right to the unprotected cliff edge to take photographs. The Council planned a visitor centre that would handle the crowds without disfiguring the cliffline. Built into a hillside on the approach to the cliffs, partially underground, with geothermal heating, solar panels, and grey-water recycling - the 32-million-euro Cliffs of Moher Visitor Experience opened in February 2007 after seventeen years of planning. The interpretive exhibition won an award from the Association of Heritage Interpretation. The judges called the whole facility "one of the best the judges had ever seen."

Numbers kept climbing - 1.4 million in 2016, 1.5 million in 2017, 1.6 million in 2018, around 1.1 million in 2022 of whom 41 percent arrived from the United States. The official Cliff Walk runs 14 kilometers from Hag's Head to Doolin, with an unofficial path closer to the edge that has produced too many injuries and deaths over the years. In February 2025, after repeated rockfalls and fatal accidents, the council closed the unofficial coastal trail entirely. As of September 2025 it remained closed. The cliffs are still there, of course. The cliffs are always there. The question is how to let humans visit without unmaking either them or us.