The Rolling Hills Of Burren Are Composed Of Limestone Pavements With Criss-crossing Cracks Known As Grikes, Leaving Rocks Called Clints. The Region Supports Arctic, Mediterranean And Alpine Plants Side-by-side, Due To The Unusual Environment. The Limestones, Which Date From The Visean Stage Of The Lower Carboniferous, Formed As Sediments In A Tropical Sea Approximately 350 Million Years Ago. The Strata Contain Fossil Corals, Crinoids, Sea Urchins And Ammonites. Photo