In 1973 Ireland became a member of the European Union. 
The heart of the country is limestone- floored lowland bounded on the south by the Armorican ridges and on the north and west by the Caledonian mountains. This lowland is open to the Irish Sea for a distance of 90 km between the Wicklow Mountains and the Carling ford peninsula, giving easy access to the country from the east. It also extends westwards to reach the Atlantic Ocean along the Shannon Estuary, in Galway Bay, in Clew Bay and again in Donegal Bay. Numerous hills break the monotony of the lowland which rises westward towards the coast in County Clare where it terminates in the cliffs of Moher, one of the finest lines of cliff scenery in Western Europe. 
Much of Ireland was covered by ice during the Pleistocene period. This ice finally melted away about twelve thousand years ago, leaving behind evidence of its former presence in most of the minor physical features of the landscape. Throughout the greater part of the lowland the bedrock is hidden by glacial deposits which, in the north central part of the country, form a broad belt of small hills (drumlins). The glacial cover also modified the early drainage pattern and in places created groundwater conditions which facilitated the growth of peat bogs. 
Caught in the recede and flow of the last Ice Ages over the last ...
The sea level dropped 130 m (426 feet) or more during the interval from around 30,000 to 15,000 years ago, when Ireland became part of continental Europe [again], and sea levels have been generally rising ever since, albeit at a much slower rate. The image to the left represents the land mass of Europe near the time of the last glacial maximum (minus the ice sheets and the ocean water). Take a close look at the "British peninsula" and the outline of Ireland and Great Britain upon it. 
In and around 20,000 years ago the area that would later reform the British Isles was mainly covered by a thick sheet of ice. This was during the last maximum expansion of the polar ice caps when sea levels were about 120 meters lower than today. To get another view of the British Isles when they were not islands, see this Pleistocene age reconstruction (circa 18000 radiocarbon years ago) of the outline of the European continent, or also see here. After about 9000 BC, the climate again warmed, the juniper spread, and the birch appeared in large numbers for the first time. Pine, elm and other forest trees also appeared, and Ireland began a long-term process of forestation. Other plants and animals crossed the land bridges as well. Red deer, wild boar, possibly bears, red squirrels, pine-martens, Wolves, foxes, stoats, and eagles and other birds of prey took up residence. Fish and game birds were soon present in abundance. 
The first definite evidence of human settlement in Ireland dates from 8000 to 7000 BC. They are known from early archaeological findings to have made an appearance in the far north in the lower Bann valley near present-day Coleraine and in the southwest in the Shannon estuary. Later they are thought to spread northeast along the coast of