Ireland is an island in Northwestern Europe, in the north Atlantic Ocean. It is the third-largest island in Europe, and the 20th-largest in the world. The island measures about north-south, and east-west, with a total area of . It lies about , near the western edge of the European continental shelf, part of the Eurasian Plate. Ireland is separated from the island of Great Britain by the Irish Sea to the east, and from mainland Europe by the Celtic Sea to the south. It is bounded to the north by the North Channel and to the south by St George's Channel. Ireland is the second-largest landmass in the British Isles, after Great Britain and before Lewis and Harris.
Its main geographical features include low central plains surrounded by coastal mountains. The highest peak is Carrauntoohil (), which is above sea level. The western coastline is rugged, with many islands, peninsulas, headlands and bays, while the southern and northern coasts have a smaller number of substantial sea inlets, such as Lough Foyle and Cork Harbour; no part of the land is more than around from the sea. The island is almost bisected by the River Shannon, which at with a estuary is the longest river in Ireland and flows south from County Cavan in the province of Ulster to form the boundary between Connacht and Leinster, and later Munster, and meet the Atlantic just south and west of Limerick. Lough Neagh is the largest of several sizeable lakes along Ireland's rivers.
The island has a temperate oceanic climate, mild and humid, and is warmer than other landmasses at the same latitude thanks to the winds on the Atlantic Ocean, ocean currents, and circulations. The island is one of the least forested areas in Europe, though forestation is expanding, but has a strong agricultural sector. It has a limited range of mineral resources, and has only had two major gas finds, and none in the oil sector. Hydroelectric energy is used, and wind farms are growing; neither solar nor tidal energy is much exploited.
Politically, the island consists of the Republic of Ireland, with jurisdiction over about five-sixths of the island, and Northern Ireland, a constituent part of the United Kingdom, with jurisdiction over the remaining sixth. The island has traditionally been divided into four provinces, each of which is divided into counties. Of the 32 counties in total, 26 are in the Republic of Ireland, with the remaining 6 in Northern Ireland.
Geological development
The geology of Ireland is diverse. Different regions contain rocks belonging to different geological periods, dating back almost 2 billion years. The oldest known Irish rock is about 1.7 billion years old and is found on Inishtrahull Island off the north coast of Inishowen and on the mainland at Annagh Head on the Mullet Peninsula. The newer formations are the drumlins and glacial valleys as a result of the last ice age, and the sinkholes and cave formations in the limestone regions of Clare.
Ireland's geological history includes a wide range of elements, from volcanism and tropical seas to the last glacial period. Ireland was formed in two distinct parts, which slowly joined, uniting about 440 million years ago. As a result of tectonics and the effect of ice, the sea level has risen and fallen. In every area of the country, the rocks which formed can be seen as a result. Finally, the impact of the glaciers shaped the landscape seen today. The variation between the two areas, along with the differences between volcanic areas and shallow seas, led to a range of soils. There are extensive bogs and free-draining brown earths. The mountains are granite, sandstone, limestone with karst areas, and basalt formations. (Subscription required) Retrieved on 10 November 2007
Most of Ireland was probably above sea level during the last 60 million years. As such its landscapes have been shaped by erosion and weathering on land. Protracted erosion also means most of the Paleogene and Neogene sediments have been eroded away or, as known in a few cases, buried by Quaternary deposits. Before the Quaternary glaciations affected Ireland the landscape had developed thick weathered regolith on the uplands and karst in the lowlands. There has been some controversy regarding the origin of the planation surfaces found in Ireland. While some have argued for an origin in marine planation, others regard these surfaces as peneplains formed by weathering and fluvial erosion. Not only is their origin disputed but also their actual extent and the relative role of sea-level change and tectonics in their shaping. Most river systems in Ireland formed in the Cenozoic before the Quaternary glaciations. Rivers follow for most of their course structural features of the geology of Ireland. Marine erosion since the Miocene may have made Ireland's western coast retreat more than 100 km. Pre-Quaternary relief was more dramatic than today's glacier-smoothened landscapes.
Physical geography Mountain ranges
Ireland consists of a mostly flat low-lying area in what are known as the Midlands. It is ringed by mountain ranges such as—beginning in County Cork and working clockwise—the Boggeragh Mountains, Derrynasaggart Mountains, Caha Mountains, MacGillycuddy's Reeks, Slieve Mish Mountains, Mullaghareirk Mountains, the Twelve Bens/Maumturks group, Nephinbeg Mountains, Ox Mountains, Bluestack Mountains, Derryveagh Mountains, Sperrin Mountains, the Mournes, Wicklow Mountains, Blackstairs Mountains, Comeragh Mountains and Knockmealdown Mountains. Some mountain ranges are further inland in the south of Ireland, such as the Galtee Mountains (the highest inland range), Silvermine and Slieve Bloom Mountains. There is an area of raised land near the northeastern coast, the Antrim Plateau, which contains the Glens of Antrim; this area is sometimes called the Mountains of Antrim. The highest peak Carrauntoohil, at high, is in the MacGillycuddy's Reeks, a range of glacier-carved sandstone mountains. Only three peaks on the island are over and another 457 exceed . There are a number of walking trails in the mountains, with the longest being that through the Wicklow Mountains. In the Mourne Mountains, with multiple walking trails, a wall was built between the 13 major peaks, the Mourne Wall.
Ireland is sometimes known as the "Emerald Isle" because of its green landscape.
Rivers and lakes
Waterbodies accounted for around 2% of the land area of Ireland. In the Republic of Ireland there are over of rivers and streams, more than of lake and over of reservoirs; these are not evenly distributed—over 30% of the watercourse length is found in Counties Cork, Donegal and Mayo, while Counties Mayo and Galway hold over 40% of the total lake area. Almost all of the reservoir area lies in just two counties, Wicklow (2/3) and Cork (1/3). In Northern Ireland, Lough Neagh is by far the leading source of water.
The River Shannon, at in length, is the longest river in Ireland and Britain. With a drainage area of , the Shannon River Basin covers one-fifth of the island. The Shannon crosses 11 counties and divides the west of Ireland from the south and east. The river develops into three large lakes along its course, Lough Allen, Lough Ree, and Lough Derg. The River Shannon enters the Atlantic Ocean at Limerick city along the Shannon Estuary.
Other major rivers include the River Liffey and its leading tributary, the River Dodder, and the nearby Tolka River, River Slaney, the Three Sisters (the Rivers Nore, Suir and Barrow), River Lee, River Erne, Foyle River, River Bann, River Lagan, and River Boyne. There are also multiple River Blackwaters, the most significant being the Munster Blackwater. The river with the greatest output volume is the Shannon but the second-greatest volume is in the short but powerful River Corrib.
Lough Neagh, in Ulster, is the largest lake in Ireland and Britain with an area of . The largest lake in the Republic of Ireland is Lough Corrib . Other large lakes, besides the three major Shannon examples, include the two linked lakes known as Lough Erne, Lough Mask and Lough Corrib, and Lough Conn.
Inlets
In County Donegal, Lough Swilly separates the western side of the Inishowen peninsula from the wider county. Lough Foyle on the other side, is one of Ireland's larger inlets, situated between County Donegal and County Londonderry. Clockwise round the coast is Belfast Lough, between County Antrim and County Down. Also in County Down is Strangford Lough, actually an inlet partially separating the Ards peninsula from the mainland. Further south, Carlingford Lough is situated between Down and County Louth.
Dublin Bay is the next sizeable inlet. The east coast of Ireland has no major inlets until Wexford Harbour at the mouth of the River Slaney. On the south coast, Waterford Harbour is situated at the mouth of the River Suir, into which the other two of the Three Sisters (the Rivers Nore and Barrow) flow. The next major inlet is Cork Harbour, at the mouth of the River Lee, in which Great Island is situated.
Dunmanus Bay, Kenmare estuary and Dingle Bay are all inlets between the peninsulas of western County Cork and County Kerry. North of these is the Shannon Estuary. Between north County Clare and County Galway is Galway Bay. Clew Bay is located on the coast of County Mayo, south of Achill Island, while Broadhaven Bay, Blacksod Bay and Sruth Fada Conn bays are situated in northwest Connacht, in North Mayo. Killala Bay is on the northeast coast of Mayo. Donegal Bay is a major inlet between County Donegal and County Sligo.
A recent global remote sensing analysis suggested that there were of tidal flats in Ireland, making it the 43rd-ranked country in terms of tidal flat area.
Headlands Malin Head is the most northerly point in Ireland, while Mizen Head is one of the most southern points, hence the term "from Malin to Mizen" (or the reverse) is used for anything applying to the island of Ireland as a whole. Carnsore Point is another extreme point of Ireland, being its southeasternmost point. Hook Head and the Old Head of Kinsale are two of many headlands along the south coast. Loop Head is the headland at which County Clare comes to a point on the west coast of Ireland, with the Atlantic on the north, and the Shannon estuary to the south. Hag's Head is another headland further up Clare's north/western coastline, with the Cliffs of Moher along the coastline north of the point.
Islands and peninsulas
Achill Island, off the west coast, is the largest of Ireland's offshore islands. Achill is inhabited, and is permanently connected to the mainland by a bridge. Some of the next largest islands are the Aran Islands, off the coast of southern Connacht, host to an Irish-speaking community, or Gaeltacht. Valentia Island off the Iveragh peninsula is also one of Ireland's larger islands, and is relatively settled, as well as being connected by a bridge at its southeastern end. Omey Island, off the coast of Connemara, is a tidal island.
Some of the best-known peninsulas in Ireland are in Counties Cork and Kerry: the Dingle peninsula, the Iveragh peninsula and the Beara peninsula. Other promontories outside the southwest include the Fanad (Fannet Head), Mullet Peninsula, the Old Head of Kinsale, Hook Head, Howth Head and the Cooley Peninsula. The Inishowen peninsula in County Donegal includes Ireland's most northerly point, Malin Head, and several towns, including Buncrana on Lough Swilly, Carndonagh and Moville on Lough Foyle.
Ireland's most northerly undisputed land feature is Inishtrahull island, off Malin Head. Rockall Island lies farther north but its status is disputed, being claimed by the United Kingdom, Republic of Ireland, Denmark (on behalf of the Faroe Islands) and Iceland. The most southerly point is the Fastnet Rock.
The Hebrides off Scotland and Anglesey off Wales were grouped with Ireland ("Hibernia") by the Greco-Roman geographer Ptolemy..
Forests