Cliffs of Moher

The Cliffs of Moher run about 14 kilometers along the Atlantic coast at the southwestern edge of the Burren region in County Clare, Ireland, standing 120 meters high at Hag's Head in the south and rising to a maximum of 214 meters north of O'Brien's Tower. The cliff face exposes up to 200 meters of Namurian shale and sandstone, laid down between roughly 326 and 313 million years ago when a river delta dumped sand, silt and clay into an ancient marine basin; over time that sediment was compacted and lithified into the layered sedimentary rock now visible in the cliff, with the oldest beds exposed at the base. Ongoing wave action continues to undercut the base of the cliffs, causing sections to collapse under their own weight and producing sea caves, stacks and arches along the coastline, including the 67-meter Branaunmore sea stack, a former section of cliff separated by that same erosion. This entity documents the Cliffs of Moher specifically as a geological formation, a stratified sequence of ancient river-delta sediment now exposed as a sea cliff.