Ireland can be subdivided into a series of physical regions. (Before reading about the physical regions in Ireland, we recommend you read our brief description of the effects of the glaciation which largely formed these regions):

• the north-west Caledonian province
• the Antrim plateau
• the Drumlin belt
• the western Caledonian province
• the Mourne uplands
• the central plain
• the southern hill and vale province
• the south-eastern Caledonian province
• the Munster ridge and valley province

The Effects of Glaciation

Beneath it all, Ireland is made up of very old rock. In the Caledonian and Armorican phases of mountain building, much of north-western Europe was folded into mountains of a Himalayan scale. Millions of years of Ice Ages and denudation have reduced these mountains to mere shadows of their former selves. The remnants of this vast mountain chain are to be found in Ireland, Scotland and Scandanavia. In Ireland today, 75% of the land is below 150 metres (492 feet) and the highest peak is only 1,041 metres (3414 feet) high (Carrantuohill, county Kerry).

Most of the regions of Ireland were formed by glaciation in the last Ice Age of 20,000 to 10,000 years ago. This map may help you to picture what is being described. If you are interested in the Ice Age, there is a separate account of the Ice Age in the History section.

In lowland areas the main effect was the deposition of sheets of drift material. This material, which later became fertile agricultural land, was laid down unevenly, sometimes consisting of gravels and sometimes of clays. The shape that this material was left in varies across the province. Around Dublin, it was shaped into a gently undulating form which is good for agriculture. In the central lowlands the drift material has been shaped by the melting ice in a more irregular, hummocky manner. The drainage is typically confused and many lakes were formed in the hollows. Many of these lakes later turned into the peat bogs that characterise the region today. Where water flowed beneath the retreating ice itself, it formed long, sinewey 'eskers', which can still be seen in the Shannon basin.

To the north of the central plain, where the ice melted last, the scraping ice has moulded the landscape into tens of thousands of tightly-packed hillocks called 'drumlins'. These drumlins, which extend from Donegal Bay in the west to to Strangford Lough in the east, are not good agriculturally, and has tended to produce a natural barrier to settlement throughout Irish history.

The upland areas were stripped bare of soil by the ice, this being one of the sources of the drift material that was smeared across the lowlands. Where ice formed in mountain-side valleys, great curved basins called 'corries' have been scooped out leaving sharp escarpments where the corries meet. These are particularly noticeable in MacGillicuddy's Reeks in county Kerry.

The North-Western Caledonian Province

This region, covering counties Donegal and Tyrone, is underlaid by ancient pre-Cambrian rocks which have been folded into mountains. The Sperrin Mountains and the Donegal Mountains are made up of hard, quartzitic peaks which were rounded, but not destroyed, by the ice. The Ice Age stripped the whole region of soil, and today even the valleys have a lack of soil. The region is thus agriculturally poor, with settlement being limited to the coasts and the upland areas generally being left to small lakes and bogs. The coasline is typified by sharp and steep cliffs. Between the Sperrins and Donegal lies the Foyle basin which leads to the sea at Lough Foyle. The Foyle is made up of numerous rivers (for example, the Derg, the Mourne, the Strule) which wind their way through Tyrone to the sea.

The Antrim Plateau

The Antrim plateau in north-western Ireland is an extensive sheet of basalt which rises to over 360 metres (1180 feet). It was formed by a huge horizontal outpouring of lava in the Tertiary period. Much of this has since been eroded, but enough of the Plateau remains to be a spectacular area. The hard rock has proved resistant to weathering and the north and eastern cliffs fall almost directly into the sea. The Antrim Coast Road, built on the skree slopes between the cliffs and the sea, is a spectacular drive. Inland, nine east-to-west Glens (valleys) are cut into the Plateau. Agriculture is possible in these sheltered Glens, but the top of the Plateau remains largely uninhabited. In the west, the plateau descends beneath Lough Neagh, which is the largest freshwater lake in the British Isles. There are no steep cliffs on the west side of the Plateau; rather they slowly merge with the glacial plain of the River Bann.

The Drumlin Belt

The Drumlin Belt consists of tens of thousands of tightly-packed hillocks, called Drumlins, in a wide belt extending from county Down to Donegal Bay. They are poor agriculturally, and the hollows between them tend to become water-logged (although the lower rainfall in the east means that this is more of a problem in the west). People who come from the Drumlin regions tend to be used to being only able to see to the next hill and tend to own small farms. The shapes of Drumlins are best seen where they were flooded by the sea. One of the best places to see this is the west coast of Strangford Lough (county Down), which is a Drumlin lowland that has been flooded by sea level rises and now contains dozens of small, rounded islands.

The Western Caledonian Province

The Western Caledonian Province is a continuation of the Caledonian North-West; that is hard, rounded, quartzitic peaks underlaid by pre-Cambrian rocks. Where this hard rock meets the Atlantic Ocean, it has created spectacular sheer cliffs and fjord-like inlets. Almost all the soil was scraped away in the ice age, and the region now consists of barren rock, bog and small lakes. There is almost no human settlement in the interior. Some of the most spectacular areas are the Twelve Pins of Galway and Croagh Patrick in county Mayo. The region has been split from the Caledonian North-West by the carboniferous rocks of Donegal Bay which have been eroded more effectively by the sea.

The Mourne Uplands

The Mourne Mountains of counties Down, Armagh and Louth (which actually consist of the Mournes, the Carlingford peninsula, Slieve Gullion and Slieve Croob) are an isolated area of igneous peaks which were strongly glaciated. This has produced sharp, scoured domes with corries and steep slopes that sweep down to the Irish Sea. The peaks command panoramic views across the lowlands. This beautiful area has been the inspiration for poets down the ages.

The Central Plain

The Central Plain is a large, low-lying region dominated by the Shannon basin underlaid by limestone rocks and covered in glacial drift. In the east, where the drift is around 60m (197 feet) thick, the plain gently undulates, but this becomes thinner and more chaotic in the west forcing rivers to braid into many channels and myriads of small lakes and bogs. Occasionally, the drift is so thin that the original limestone land surface emerges producing the characteristic limestone features. The best example is the Burren in county Clare. Some regard the Drumlin belt and the southern hill-and-vale province as extensions of the Central Plain.

The Southern Hill and Vale Province

The Southern Hill and Vale Province is really an extension of the Central Plain. Here, the lowland relief has been interrupted by the remnants of ancient shale plateaux. Where these have been eroded, there are spectacular flat-topped mountains with steep skree slopes, often capped by wind-swept bogs. In some areas, deep layers of slate and shale have been folded up through the limestone surface to emerge as mountain ranges. These mountains rise without warning from the plains, for example Slieve Bloom and the Galtee mountains.

The South-Eastern Caledonian Province

The south-eastern Caledonian Province consists of a granite mass which forms one of the largest continuous mountain regions in Ireland. Originally formed beneath Ordovician strata, the top layer has now been completely eroded away (except around the edges). On top, the mass which includes the Wicklow Mountains contains blanket bog which is suitable for extensive sheep-rearing but is sparsely populated. The edges of the region contain steep, jagged slopes and is home to Powerscourt Falls, Ireland's tallest waterfall (106m, 350 feet). In county Wexford, this granite block continues beneath the plain, emerging occasionally as quartzitic hills.

The Munster Ridge and Valley Province

In Munster differential erosion has produced parallel ridges of sandstone mountains with fertile limestone floors between. In Kerry and Cork, glaciation has accenuated this topography. Good examples of the ridge and valley province are the Knockmealdown and Comeragh mountains. Where the valleys of west Kerry and Cork have been flooded by the rising sea, deep rias with mountainous peninsulas have been formed. Rivers are forced to flow eastwards or westwards along these valleys. The points where they breach the ridges turn the rivers suddenly south, a characteristic feature of this region of Ireland.