Geology of Ireland longest known free-hanging stalactites. Geology of Ireland The geology of Ireland consists of the study of the rock formations in Ireland. The island contains rocks from every age from Proterozoic to Holocene and a large variety of different rock types is represented. The basalt columns of the Giant's Causeway together with geologically significant sections of the adjacent coast have been declared a World Heritage Site. The geological detail follows the major events in Ireland's past based on the geological timescale. The oldest known Irish rock is about 1.7 billion years old and is found on Inishtrahull Island off the north
Crag Cave Crag Cave Crag Cave is a cave in Ireland, located just outside Castleisland, County Kerry. Formed in elevated limestone rock, the system extends to of surveyed passage, on two levels. It is the 7th-longest cave system in the Republic of Ireland, and the 10th-longest in the whole of Ireland. While the Geological Survey of Ireland in 1859 acknowledged the presence of "caves worn by water, some of which can be traversed for some distance," positive efforts at exploration were not made until 1981, when the upper part of the cave was explored to a sump, named the "Green Lake". When