300 million years in the making

You’ll be fascinated to learn that the rocks that make up the Cliffs of Moher were formed over 300 million years ago during the Upper Carboniferous period. You’ll experience this as visible bands of Namurian sandstone, siltstone and shale.

How Were the Cliffs Formed?

About 320 million years ago, during the Upper Carboniferous period, the area of the Cliffs of Moher was much warmer and situated at the mouth of a larger river. Heavy rainfall created great floods that washed sand and mud into rivers flowing to the sea. The sand, silt and mud were dumped at the mouth of the great delta and over time, the sediments became compacted into solid rock which we now know as the Cliffs.

Individual rock layers vary from centimetres to metres. Each layer is a representation of a specific event in the life of the ancient delta as it migrated into the sea.

Today the Cliffs are undergoing coastal erosion as waves crash against the foot of the Cliffs causing sections of the upper cliff face to collapse.

View Bedrock Map of North Clare and the Burren

Find out more about the Geology of the Cliffs


Looking out from the top of the cliffs you’ll see many coastal landforms: Sea Stacks, Sea Stumps and caves that have been formed as a result of erosion.

You can’t miss the great sea stack – Branaunmore, standing 67 metres high. Once part of the Cliffs, it was separated by erosion.

The Cliffs of Moher lets you see a rare example of a sedimentary basin – rock formation that is normally only visible under the sea.

There are different types of trace fossils in the Cliffs of Moher flagstones which are the feeding trails and burrows of unidentified marine creatures.

These patterns of the rocks have led to a demand for Liscannor flagstone and in the 19th century a strong quarry industry grew in the area. You can see this stone in the paving of the Cliffs of Moher visitor centre and on the pathways and viewing platform.

Look out for the sea arch at Hag’s Head – just below the Napoleonic signal tower – as well as many smaller sea arches which are visible from sea level.

One of the Cliff’s sea caves featured in the movie ‘Harry Potter and the Half Blood Prince’.

The Burren

Just North of the Cliffs you will find the Burren – a dramatically beautiful Karst landscape with its own geological and natural story to tell. Together, The Cliffs of Moher and the Burren form the Burren & Cliffs of Moher UNESCO Global Geopark.

Be part of this living landscape

The Burren and Cliffs of Moher Geopark was awarded membership of the UNESCO-supported Global Geoparks Network in 2011. Not only does the region have the geological importance that is required of a Geopark, it also has the all-important network of organisations that oversee tourism in the area as well as coordinated education and conservation efforts.

In March 2016 the Burren and Cliffs of Moher Geopark was recognised as a global leader in sustainable destination development. The Geopark was named winner of the Destination Leadership award by the National Geographic in their prestigious international awards programme, the World Legacy Awards.  This followed designation in 2015 as the European Destination of Excellence for Tourism & Gastronomy.  These are only two of the many international and national awards won by the Geopark and its partner tourism businesses.

Over 530 square kilometers in size, the Burren and Cliffs of Moher region offer diversity that is second to none and is a living landscape comprising people, place, learning and livelihood.  Whether you choose a farmer-guided walk on Mullaghmore, feast on delicious local food or stay in a family-run bed and breakfast – you are doing your bit to support the sustainable development of this important area.

Deborah Evers & Neil Hawes of the Burren Food Trail

One of Ireland’s most famous sights, the Cliffs of Moher are entirely vertical and the cliff edge is abrupt. On a clear day the views are tremendous, with the Aran Islands etched on the waters of Galway Bay. From the cliff edge you can just hear the booming far below as the waves crash and gnaw at the soft shale and sandstone.

With a due-west exposure, sunset is the best time to visit.

Lonely Planet