Ireland’s Physical Environment
Fado, fado, Ireland's geologic roots began with the formation of Western Europe. The island of Ireland today is a direct result of the earth-building forces that created Eurasia over two billion years ago. Over time, layers of sediment accumulated on the floor of ancient geologic seas, creating limestone. A mixture of this limestone and lava settling on the ocean floor formed the island of Ireland. At the same time these earth-building forces constructed the island, the forces of erosion have worked to wear it down.
Ireland is not one homogeneous physical area, but rather a complex land. It has experienced mountain building through faults and folds, uplifts, and magma flows. All the landscapes resulting from earth building are subject to erosion by the forces of ice, water, and wind. Streams and waves erode materials from one place and deposit them in another. Ice Age glacial flows bulldozed and scoured the surface as they expanded and dumped debris as they retreated.
Today, Ireland is a land of plains and highlands. The plains are in the center of the island, and the hills are in the coastal zones. The best way to envision the physical geography of Ireland is to think of it as resembling a cereal bowl. Ireland has a low, broad interior, the bottom of the bowl, and is surrounded by highlands, the rim of the bowl.
The broad interior is called the central lowlands. It contains extensive glacial debris, peat bogs, rivers, lakes, and coastal shores. It is Ireland's most productive agricultural zone. Dublin, the capital and largest city in Ireland, is located where the central lowlands region reaches the east coast.
On the rim of this lowland are hills, low mountains, and steep sea cliffs. These highland areas are more difficult to navigate. They include small villages and towns and typically less productive soils.
Overall, processes of physical geography in Ireland have resulted in a small island connected to the geologic history of Western Europe. At the end of the Ice Age (Pleistocene Period) over 10,000 years ago, the glaciers receded from Europe, depositing sediment, called glacial drift, and forming lakes, rivers, and fjords.While there are few fjords (such as the Killary fjord between counties Mayo and Galway in Ireland), many of the lakes and rivers of the central lowlands were formed at the end of the Ice Age.
The mountains of northwest Ireland, while covered with glacial drift, are actually part of a mountain range that stretches from Scandinavia to Scotland and Ireland. This mountain chain is the eroded remnants of the ancient Caledonian mountains, covered in places by the Atlantic Ocean and Irish Sea. In Ireland, the mountains extend through the island's northwest. Along the coast, their rocky cliffs are still subject to the scouring forces of erosion.
The mountains and highlands of southern Ireland are remnants of the Armorican mountains that once extended from Ireland eastward to central Europe. The Armorican highland landscape varies in Ireland from west to east. In the west, in County Kerry and the western part of County Cork, the landscape contains high sandstone mountains, numerous peninsulas, and flooded lowlands and inlets. The Macgillycuddy Reeks Range in this region contains Carrauntuohil, which at 3,414 feet (1,041 meters) is the highest mountain in all of Ireland.
The Armorican mountains in eastern Cork and Waterford counties are composed of sandstone, limestone, and shale. Through water erosion, ridges and valleys have formed parallel to each other, extending from west to east. The ridges are comprised of resistant sandstone rock.Water eroded the limestone and shale, creating the valleys. As a result, the ridges are hill-like, and streams occupy the lower valleys. The streams in this area have developed a definite trellis drainage pattern. The trellis pattern forms when stream erosion forms water gaps by cutting through less resistant rock in the ridges. As a result, rivers of the region drain from west to east and suddenly make almost 90-degree turns to the south flowing through narrow water gaps. This is true of the rivers Bandon, Lee, Bride, Blackwater, and Suir.Where the rivers enter the sea, they form excellent harbors.
The central lowlands region begins along the Atlantic Coast between the mouth of the River Shannon on the south and Galway Bay on the north. It extends eastward across the island to occupy area between Dublin and Dundalk. In the north, the central lowlands begin at Laugh Foyle and extend southward to Tipperary and Tralee. The lowlands range in elevation from sea level to 400 feet (122 meters). While the central lowlands indeed reach sea level in several places along Ireland's shores, most points of the lowlands region range from 200 feet (61 meters) to 400 feet (122 meters).
Understanding glacial erosion processes is crucial to understanding the physical geography of Ireland.With glaciation, the land was bulldozed as the ice moved forward. Later, the glaciers dumped debris as they melted and retreated, resulting in uneven terrain. The terrain of the central lowlands is generally covered by layers of drift materials (rocks, gravels, and clays) in varying thickness.
The northern part of the central lowlands is covered by thousands of glacial hills, called drumlins, and lowlands or hollows. Drumlins are easy to recognize since they resemble the upside down (inverted) bowl of a teaspoon with a steep rounded side and a more gentle tapering side. Hollows are the lowlands between the hills. Drumlins extend offshore along the northwest coast, where they form islands that can be easily recognized by their inverted spoon shape.
The basin of the River Shannon occupies the middle of the central lowlands. This is a land of limestone bedrock covered with glacial drift. The drift is thickest east of the River Shannon. It becomes quite thin on the west where streams have cut into the bedrock, resulting in valleys, lakes, and bogs. In the extreme west, the bulldozing action of glaciers resulted in an area of extensive exposed limestone bedrock pavement called the Burren. Once exposed, the limestone bedrock of the Burren experienced weathering from ice, wind, and rain. This erosion of limestone has created crevices that lead to limestone caves carved below the surface.
When a chemical process below the surface weathers limestone, geographers call the landscape karst topography. Karst topography is marked by sinkholes, deep cracks in the limestone, underground drainage, and caves. County Clare has an extensive area of karst topography. Unlike other karst areas around the globe, the ancient Irish did not use caves in the Burren as dwellings.
South of the Burren are the Cliffs of Moher. The Cliffs extend almost five miles (eight kilometers) and stand over 700 feet (214 meters) above the Atlantic Ocean. They form a massive, yet beautiful, barrier to erosional attacks by the wind and waves of the sea. These cliffs are composed of layers of three sedimentary rocks: sandstone, shale, and siltstone. Of the three layers, sandstone is the most resistant to erosion and forms the protective cap rock, slowing erosion over much of the cliffs.
Although geographically part of Northern Ireland, the island also contains a fascinating landscape known as the Antrim Basalt Plateau. This landscape is a result of repeated horizontal lava flows. The Antrim Basalt Plateau rises over 1,000 feet (305 meters) high. Over time, the plateau has eroded into a series of sheltered valleys. Lough Neagh, the largest lake in Northern Ireland, is located in the plateau. The most spectacular topography in the Antrim Basalt Plateau is the Giant's Causeway. It is an ancient zone of cliffs formed where the horizontal layer of black basalt cooled, shrunk, and resulted in the formation of almost 40,000 primarily hexagonally shaped columns that fit together as if laid in place like a mosaic.
Weather is the atmospheric conditions at a particular moment in time. Climate is weather averaged over a long period of time. Climatologists explain that one of the greatest influences on climate is the latitude of the place. Ireland is located between 51° and 55° north latitude. It is much closer to the North Pole (90° north) than it is to the equator (0°). Climatologists describe the lands between 35° and 55° as being “middle latitude.” Just knowing where Ireland is located, in the middle latitudes, and that it is an island, tells a lot about its climate. The middle latitude location, for example, indicates that the climate will be moderate, not the extreme cold of the poles, or the extreme heat of the tropics.
Islands typically have moderate temperatures because the surrounding ocean does not experience severe temperature changes. The consistent temperature of the Atlantic Ocean helps moderate Ireland's climate. So do the warm waters of the Gulf Stream and North Atlantic Drift (ocean currents). Despite being located at latitudes comparable to central Canada, Ireland's average monthly temperatures remain above freezing during the winter months.
The climate of Ireland is temperate and moist, with an average yearly temperature of 50° F (10° C). Summers are mild with average temperatures of about 60° F (16° C) during July and August. Winters are tempered and modified by the sea, resulting in an average January temperature of 41° F (5° C). Mean daily minimum temperatures average 36° F (2.5° C). Frost and snowfall are still possible, but they are generally short-lived. Frost is relatively rare in western Ireland.
While Ireland's climate is not one of extremes, it is one of rapid change. The high-pressure system over the North Atlantic Ocean consistently brings moist air onto Ireland throughout the year. In the northern hemisphere, winds circulate clockwise around the high-pressure system. Thus, westerly winds are consistently blowing moist air onto Ireland's west coast. Parts of Ireland can experience fog up to 60 days a year. This combination produces a damp, humid climate with consistent precipitation all year long.
Rainfall amounts are greatest along the entire west coast, especially in the mountains. Although monthly precipitation is fairly consistent, generally the heaviest rainfall is in the winter months and lightest is in the early summer.Average annual rainfall is 43 inches (109 centimeters). Actual rainfall, of course, varies from place to place. Dublin has one of the lowest totals, averaging 31 inches (79 centimeters) a year. The heaviest precipitation amounts are generally found in the mountains of the west where the yearly total can exceed 118 inches (300 centimeters) a year.
The fertility of soils varies, in large part because the material from which soils are formed (typically the underlying bedrock) also varies across places. This “parent” material is not the only factor in determining soil fertility. Ireland's climate makes the production of soils difficult. With few climatic extremes, it takes longer for vegetative materials to break down and for soils to develop.
Ireland's soil compositions are complicated by the presence of glaciers during the Ice Age. The glaciers pushed and deposited soils and rocks from points north and east onto Ireland. This glacial drift covers the island at varying depths. When a glacier sits in one place and melts over time, the sediment it deposits stratifies into layers of sand, silt, clay, and gravel. Even massive boulders are deposited.
Human activities also alter soil development. The Irish removed the forests, farmed, grazed, and fertilized the land, modified drainage, and dug turf. Hundreds of years ago, the Celts were known for adding seaweed to the soil to try to increase its fertility, just as some gardeners add compost to their soil today.
Of all the ways the Irish have changed the soils, the most interesting and best known is the creation of peat bogs. There are two kinds of peat bogs: blanket bogs and raised bogs. Both kinds of bogs are composed of vegetative matter that is poorly decomposed and has accumulated over time in waterlogged soils.
Blanket peat bogs are located mainly in western Ireland, where they cover many of the rolling green hills. Blanket bogs formed, starting 6,000 years ago, because of deforestation caused by humans. Once the early farmers cleared the land of trees, soil nutrients washed away and the underlying material hardened. This made it difficult for water to be absorbed beneath the layer of hard material. As vegetation died on the hills, the remaining material would simply sit, along with water, in the waterlogged hills. This material became peat. Thousands of years later, in the 1600s, the Irish began to cut the peat, dry it, and burn it as fuel.
Extensive dome-shaped, raised bogs are found in the central lowlands. These bogs can be up to 30 feet deep and cover several square miles in area. Raised bogs were glacial lakes thousands of years ago. Over time, poorly decomposed vegetative material began to fill the lakes. The waterlogged soils lack oxygen, and without oxygen, vegetation cannot decompose easily. Because the vegetative material cannot decompose easily, the bogs have grown higher than their surroundings over time. The most extensive raised bogs are the Bogs of Allen, extending across three counties. Today, peat in the raised bogs is commercially cut and sold for fuel.
Over the eons of time, Ireland has been a land of changing climates. With climatic changes came changes in vegetation. Sometimes these climatic and vegetation changes took millions of years. On other occasions, change occurred more rapidly, as happened following the last Ice Age.
At that time, Ireland's flora (plant life) was composed primarily of tundra plants. As the climate warmed, the vegetation changed. Extensive oak forests grew to cover most of the island. In certain areas of higher elevation, the oak forests became mixed with pine and birch trees. In lower elevations, oak mixed with elm and alder. Across the island, under the canopy of trees, plants such as nuts, berries, ferns, and mosses thrived.
In discussing the environment, geographers often emphasize the native plant life. This is really not possible to do in the case of Ireland. Instead of becoming stewards of the land, the Irish completely altered the plant environment. About 6,000 years ago, they began cutting down the oak forests. This was the beginning of a destructive deforestation process that continued for several thousand years.
By 1500 A.D., good forests still remained in Ireland, but during the next two hundred years, virtually all forests were cut to provide lumber for the British to use in shipbuilding, charcoal, and barrel making. By the middle of the 1700s, the oak forests were gone, and Ireland was forced to import wood.
Today, through human action, forests cover about three percent of Ireland. The government, through the Forestry Commission, has established fast-growing coniferous plantations of spruce, pine, and fir. Other trees found in Ireland's remaining forestlands include oak, alder, ash, beech, birch, chestnut, elm, hazel, sycamore, and willow. Because it rarely freezes, even some hardy species of palm trees can be found along the south and west coasts of the island! Some of the large estates of the former British landlords contain examples of individual trees from around the world. Even gigantic, young American Redwood trees can be found in Ireland.
Flora of the mountains and highlands tends to be either blanket bogs or the moorlands of grasses, heather, and bracken ferns. Expanding thickets of gorse are also attacking these areas. Gorse is a dense, spiny, evergreen shrub with yellow flowers that crowds out other vegetation while dying at its own center. Gorse is a parasite to Ireland's plant life today, much as the kudzu vine is in the southern United States.
Ireland is also a land of beautiful flowers. Among the most fascinating are the beautiful pink flower, thrift, the large white sea champion found along the seashore, the yellow fleabane that resembles dandelions, and water lobelia, a plant whose leaves grow below lake waters and whose lilac-like flowers grow above.
In the geologic past, Ireland was once the home of woolly mammoth, tundra reindeer, spotted cave hyena, arctic fox, lemming, and migratory birds. Over time, brown bear, giant Irish deer, wolf, and wild boars replaced the mammals. The deer fell victim to carnivores and the bear and boars disappeared after the arrival of people.
Today, protected wild red deer are the largest animals on the island, but they are not the same species as the giant Irish deer of the past. Today, Irish wildlife includes primarily the gray seal, common seal, fox, badger, weasel, pine marten, Irish hare, rabbits, red squirrel, hedgehogs, shrew, and bats. The island also is home to turtles, frogs, toads, and one species of lizard. There are no snakes! Additionally, several hundred species of birds, both native and migratory, inhabit Ireland. They include the wren, raven, jay, callows, chough (in the cliffs of the extreme west), grebe, gannet, puffin, and whooper swan.
Fish species are numerous and have changed considerably over time. The River Shannon salmon are a popular food on the island. On aquafarms, the Irish raise salmon, turbot, prawns, and mussels. The sea around Ireland is home to pollock, mackerel, herring, sprat, blue whiting, silver smelt, gunner, cod, lobster, and crab.
The Atlantic Ocean and the Irish Sea surround Ireland, creating over 3,500 miles (5,633 kilometers) of coastline. The wave action from the ocean and the sea work to create beaches and rugged coastlines.
The River Shannon, the longest river on the island, dominates the central lowlands, flowing from County Cavan south through the center of the island. It is 211 miles (340 kilometers) long. The River Shannon widens significantly in places, forming several broad lakes, most notably Lough Derg and Lough Ree. At the city of Limerick, the river turns almost directly west, the gradient steepens, and the river begins downcutting with greater force as it drains through the Shannon Estuary. Today, the River Shannon is one of Ireland's major tourism and recreation attractions.
The second longest river on the island is the River Barrow. It flows south from the midlands toward Waterford Harbour where it is first joined by the River Nore and then the River Suir. Major lakes on the island include the Lakes of Erne, Lough Corrib, and Lough Ennell. Lough Neagh in Northern Ireland is the largest lake on the island, with a surface of over 153 square miles (396 square kilometers). Most lakes occupy basins scoured by glaciers and filled with glacial meltwater.
In addition to the rivers and lakes of Ireland, in the 1800s parliament funded the building of inland waterways, linking Dublin with the River Shannon. The Grand Canal starts in Dublin and extends westward 81 miles (131 kilometers) to Shannon Harbour. It also contains 30 miles (49 kilometers) of branch canal. A second canal, the Royal Canal, was developed by Dublin businessmen to compete with the Grand Canal. The Royal Canal begins at the River Liffey and extends 90 miles (145 kilometers) west to the River Shannon. The Irish government restored the Grand Canal, and it is upgrading the Royal Canal. These waterways provide Irish citizens and tourists with a variety of recreational activities including boating, fishing, and sightseeing.
Ireland is not a mineral-rich island. It has small amounts of several important minerals. Minerals are generally identified as one of three types: metallic, nonmetallic, and mineral fuels. Metallic minerals have a long history of importance to people. The most commonly occurring metallic minerals in Ireland are lead and zinc. The most significant deposit of these two minerals is at Navan, where mining began in 1977. Ireland is now among the European Union's leading exporters of lead and zinc.
The most abundant nonmetallic mineral in Ireland is limestone (two-thirds of the island is composed of limestone bedrock). Sand and gravel are also important nonmetallic minerals. Numerous stone quarries can be found on the island. Some date back hundreds of years and are no longer operational. Others are recent and fully operational. These materials are used primarily in construction and road building.
One important aspect of the nonmetallic mineral industries is Irish marble. Ireland's limestone bedrock provides the marble industry with access to about 40 different marble patterns and colors. The most famous of the marbles is the green Connemara marble from 600-million-year-old Precambrian deposits.
Mineral fuels are also sparsely located in Ireland. Coal deposits are rare and of minor importance. There are natural gas and oil deposits offshore, and natural gas production off the southwest coast is becoming increasingly important. The most important fuel continues to be peat from the bogs,which is used for heating fuel, fertilizer, and electrical power generation.
An early perception of Ireland is a land of forty shades of green, a country of rolling hills covered with lush green grasses, fenced off with stone and bush fences. Studying the physical geography of Ireland, shows why this perception is accurate.
Ireland's hills, mountains, and cliffs form a rim around the central lowlands of the island. In the west and the southeast, the hills are part of ancient mountain ranges that stretch into Europe. Throughout the hills in the coastal zones are the telltale signs of glaciation, from the drift-covered hills, to the drumlin islands, to glacially deposited fieldstone fencing. In the west, these hills are blanketed with peat bogs, creating multiple shades of green.
In the central lowlands, the hills are typically raised bogs, formed over thousands of years. The River Shannon dominates the landscape and history of the central lowlands.
Ireland's location on the eastern edge of the Atlantic Ocean accounts for its moderate, moist climate. The westerly winds of the middle latitudes consistently carry moist air from the Atlantic over the island, providing much fog and rain throughout the year and ensuring that the island remains forty shades of green—the “Emerald Island.”