Approximately 380 mya, Ireland had moved to a position just south of the equator (Fig. 1.12(b)). Sandstone was laid down at this time, as Ireland experienced a desert climate.
z z equator
Approximately 300 mya, sea levels had risen and Ireland lay under a warm, calm sea close to the equator. Limestone was formed over thousands of years at this location as the bones and shells of fish and other sea creatures accumulated on the sea floor.
30° S 60° S zz Fig. 1.12(b) Ireland approximately 380 mya.
About 250 mya, Ireland had moved to a location 20° north of the equator. The Armorican fold mountain range was formed in Munster (e.g. Macgillicuddy’s Reeks and Caha Mountains) when the Eurasian and African plates collided. As the greatest force came from the south, these folds have an east to west directional trend. Sandstone was brought above sea level during this folding period while the Munster ridge and valley landscape was also formed.
zz 60° N
Approximately 65 mya, Ireland experienced the impact of sea-floor spreading. The Eurasian and North American plates separated with water rushing in to create the Atlantic Ocean. As the plates moved apart, lava poured out of fissures created on the earth’s crust in the north-east of the country. The lava cooled quickly on the earth’s surface creating the Antrim–Derry Plateau and the distinctive six-sided columns of basalt at the Giant’s Causeway (Fig. 1.13).
30° N DID YOU KNOW? equator Ireland is currently moving north at a rate of approximately 4 cm per year. Fig. 1.12(c) Present-day location of Ireland. Giant‘s Causeway
Clogherhead, Co. Louth
Fig. 1.13 Features of the landscape formed by tectonic activity in Ireland.
