(in Gaelic Éire; in English Ireland). Northwestern Europe Island, the second largest (84,420 km²) of the British Archipelago; it faces the Atlantic Ocean to the N, W and S, while to the E the North channel, the Irish Sea and the St George channelseparate it from Great Britain. Politically it is divided into the Republic of Ireland and Northern Ireland which is part of the United Kingdom of Great Britain.
Morphologically, the island is quite simple: in the center extends a vast and almost uniform plain, raised at the edges by very ancient reliefs and of moderate height, which however do not form a compact edge but in large sections leave room for the plain to reach up to the sea. Once united to Great Britain, the island rests on a very ancient, archaeozoic and lower paleozoic (Cambrian and Silurian) base, which was affected by the two great orogeny of the paleozoic era: the Caledonian and the Hercynian. The first is responsible for the reliefs of northern and south-eastern Ireland, with the typical SW-NE trend, which can also be found in Scotland and Scandinavia, regions also included in Caledonian Europe; to the Hercynian orogeny (of which Ireland was specifically interested in the so-called Armorican corrugationon the other hand, the alignments of south-western Ireland, with roughly parallel folds arranged from W to E, which are reflected in the reliefs of Cornwall (England) and Brittany (France), must be ascribed. Gneiss and crystalline schists with powerful granite intrusions, which occurred during the corrugation phases, are widely present in the Caledonian reliefs, while the Armorican ones show a prevalence of schists, quartzites and sandstones. The central lowland is instead essentially formed by a powerful limestone stratification dating back to the Carboniferous, when much of the island was invaded by the sea. Even the Cenozoicupheavals, culminating in the Alpine orogeny, had repercussions in Ireland – probably leading to the separation of the island from Great Britain -; intense volcanic activity occurred with consequent lava outflows, of which the basalt plateau of Antrim, in north-eastern Ireland, is a striking example, which reaches the sea with the imposing columnar-shaped cliffs called Giant’s Causeway. Finally, the Pleistocene glaciation is one of the main modellers of Irish morphology; the Quaternary ices largely covered the surface of the island, leaving large morainic deposits on their retreat, especially in the central lowland, (elongated cords) and originating numerous lake mirrors. The antiquity of the relief and the incessant erosive action mean that the island lacks high peaks, culminating in MacGillycuddy’s Reeks (Mount Carrantuohill, 1041m) in the extreme and very rugged southwestern section of Ireland. Among the other main reliefs, which at no point touch 1000 m, are: to the N the Donegal mountains (Mount Errigal, 752 m), the Sperrin mountains (819 m) and the aforementioned plateau of Antrim, flanked further to the S by the Morne mountains (Mount Slieve Donard, 852 m); to the W the mountains Nephin (807 m) and Mweelrea (819 m); to the SE the imposing Wicklow massif (Lugnaquillia mountain, 926 m); finally, overhanging from the S the central basin, whose average height is around 100 m, the Silvermine (Keeper Hill, 695 m) and Slieve Bloom (Monte Arderin, 529 m) mounts. More or less extensive stretches of lowlands (e.g. the plain around Dublin, the depression of Lough Neagh, etc.) interpose themselves between the peripheral reliefs, creating a low but densely articulated coast due to glacial and river erosion. Elsewhere the coast is high and rocky, especially in correspondence with the Donegal massif and the mountains of southwestern Ireland, where digitized peninsulas extend into the Atlantic, representing the western extremities of the Armorican mountains; they were formed following a relatively recent marine transgression that invaded the lower stretch of numerous valleys, giving rise to fjords and rías.
The hydrographic network is not very developed and, due to the peripheral mountain rise, not very organic; the climatic characteristics, in particular the homogeneous distribution of the rains during the year, however, ensure a remarkable constancy of the regime. The main rivers originate from the more pronounced heights of the central lowland, where however they often wander slowly, frequently expanding into lake basins, a typical element of Irish morphology; their course, largely senile, generally undergoes a process of rejuvenation near the coast, where they often have to break through the mountains with difficulty and their slope increases significantly. The largest river in Ireland is the Shannon (368 km), which originates from the inner margins of the northern hills and, after crossing the lowland from N to S, flows into a long estuary on the west coast; the difference in level of its waters between the exit from Lough Derg and the beginning of the estuary, in Limerick, is exploited by a power station that supplies electricity to a large part of the country. From the raised rim formed by the Silvermine and Slieve Bloom mountains originate the Barrow rivers, Nore and Suir, who reunite in Waterford Harbor; together with the Blackwater, the Lee (which descend towards the E between the valleys of the mountains of Kerry) and the Slaney (which flows into Wexford Harbor, which conveys the waters of the southern and western slopes of the Wicklow mountains) constitute the major rivers of southern Ireland. The northern mountainous region is likewise furrowed by numerous rivers, which also originate from the hills at the edge of the central lowland; the main ones are the Bann and the Foyle, which flow into the North Channel, and the Erne, which after having expanded into the Upper Erne and Lower Erne lakes flows into Donegal Bay. There are many lake basins, the loughs left on the island by the Quaternary glaciation; they remember the Lough Neagh, the largest of the British archipelago (396 km²), the aforementioned Erne, the Ree and the Derg, crossed by the River Shannon, the Mask, the Corrib, the Conn, all in the Connaught region of western Ireland.
According to itypeusa, the main factors affecting the climate are the country’s insularity and the position on the direction of the Atlantic air masses which, given the fragmentation of the peripheral mountain systems, easily penetrate the interior. The entire island is therefore characterized by an oceanic, mild and rainy climate; the rains are around 800-1400 mm per year, with maximums of 3000 mm on the most exposed southwestern mountain slopes and minimums of 600-700 in the more protected eastern coastal strip. In reality, more than the excess of precipitation, their uniform distribution is remarkable (most of the territory has over 200 days of rain per year): on the other hand, the insolation is very poor, indeed the almost constantly cloudy sky is one of the Irish landscape badges, together with the mists. The average annual temperature, decreasing from W, where the influence of the Gulf Stream is active, towards E, is around 9 ºC; winters are not harsh, remaining above 0 ºC, while summers are cool, with averages of 15 ºC. Due to the high humidity and the relatively mild temperature, the island in ancient times had large wooded areas, especially broad-leaved trees; a centuries-old and irrational deforestation has now almost everywhere destroyed the ancient forest cover (at the beginning of the 21st century less than 5% of the territory). The landscape is thus dominated by heaths, bogs and pastures, thanks to which the livestock activity which is the main and traditional economic resource of the Irish has been able to develop.