A protective wall has been constructed to prevent accidents and damage at the edge of the Cliffs of Moher. The wall comprises huge over-lapping vertical slabs of Liscannor flagstones, locally quarried from the same Namurian siltstone strata that appear at the top of the cliffs. Originally this wall was built during the Irish famine in the 1830s to provide work for people who were on the verge of starvation. Some people think the wall is too high and impedes the views – but I think it not only serves to protect people who might recklessly climb on the cliff edge, and to protect the plants and birds that live on the edge, but it is also a subtle evocation of the silhouette of the cliffs beyond.
Some of the flagstones are naturally decorated with patchwork patterns of encrusting lichens. I’m not too sure why some slabs have lichens and others do not. Maybe, the clean slabs are relatively recent replacements.
Liscannor flagstones are also used for paving, and form the horizontal treads of steps that lead visitors to paths along the first few hundred yards of cliffs to the north and south of the visitor centre. The flagstones, in both the barrier walls and the paths, feature strange curvilinear patterns and textures which are trace fossils (also called ichnofossils), known as Olivellites. They are thought to be the fossilised feeding trails of marine gastropod-like creatures – made in much the same way that Acteon tornatalis ploughs a furrow in soft sediments of British shores today as it hunts down its prey.
The kerb-like stones that form the risers of steps on the footpaths are made of a different rock – an earlier Carboniferous limestone from the Burren. The stone is absolutely packed with fossilised corals (colonial, tabulate, and solitary forms), large brachiopod shells, and a few smaller gastropod molluscs. The Cliffs of Moher are a great wonder but the fossils, for those who notice them, are a small marvel of their own.
Cliffs of Moher Visitor Experience, Co. Clare – Visitor guide leaflet.
Sleeman, A. G., Scanlon, R. P., Pracht, M. & Caloca, S. (2008) Landscape and Rocks of the Burren: A special Sheet in the Bedrock Geology 1:50,000 Map Series, published by Geological Survey Ireland, ISBN 189970257-1.
Hennessey, R., McNamara, M., and Hoctor, Z. (Compilers) (2010) Stone, Water and Ice – A geology trip through the Burren, The Burren Connect Project, ISBN 0-9567204-2-9.
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