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
Callao Cave and a height of . The cathedral-like room has been turned into a chapel by the local people. A rock formation serves as the altar of the chapel lit by a stream of light coming from a rooftop opening. The conditions inside the caves have caused the formation of stalactites and stalagmites, more so in the deeper chambers. Several spectacular speleothems or formations are found inside the cave like flowstones, glittering dripstones, cave curtains, crystal helictites, columns, etc. Callao Cave is classified by the Department of Environment and Natural Resources as a Class II cave. This describes caves with areas