Geology of Ireland 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 coast of Ulster. Outcrops
Spannagel Cave do not support the formation of caves. The only exceptions are pockets of rock capable of karstification such as limestone, dolomite, gypsum and other carbonates. These pockets are generally of quite low thickness, and only allow small caves to be formed. The creation of caves also requires water solubility. The Spannagel Cave has arisen in a large vein of Jurassic calcite marble of the Hochstegen Formation, a marble with over 90% total carbonate content, that runs through the slate mantle of the "Western Tauern window". The formation of this extensive cave as a result of geological corrosion (and mixing corrosion)