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The Burren: Karst of Ireland - the Burren

The main features and places of the Burren
The main features and places of the Burren (David Drew)
Click on the Map above for a larger version

The Burren plateau of north-west Co. Clare is the finest example of a karstic terrain in Ireland, with a full assemblage of the curious landforms and subterranean drainage systems that characterise such limestone terrains. The Burren is famous internationally, not just because of its beautiful limestone landscapes but also because of the remarkable flora of the region and its rich archaeological heritage. The term "Burren" is derived from the Gaelic for "stony place".

The Burren is bounded to the west and north by the Atlantic Ocean and the southern shores of Galway Bay, respectively. The southern boundary, an east to west line from Corofin, to Kilfenora, to Lisdoonvarna, to the coast at Doolin, is where the limestone passes beneath younger rocks composed of shale and sandstone. To the east of the plateau lie the Gort-Kinvarra lowlands.

A doline on the summit of Aillwee Hill
A large enclosed basin (doline) on the summit of Aillwee Hill near Ballyvaughan
(David Drew)

The Burren is 360 km2 in extent and forms a plateau gently tilted to the south, at 200-300 m above sea level in the north and 100 m in the south, bounded by steep scarps on all but the southern flank. The highest point is the shale-capped Slieve Elva at 345 m above sea level.

To the west of the Burren, the Aran Islands are an extension of the main plateau in many respects, and for long periods during the recent geological past were almost certainly linked to the Burren by dry land.

North flank of the Burren
Bare rock is widespread on the hills of the north flank of the Burren overlooking Galway Bay.
Glacial ice moving across the Burren from the north has smoothed the seaward facing slopes.
(David Drew)

To a greater degree than in any other karst region (and perhaps any region) of Ireland, the rocks that form the skeleton of the area is bare rock or rocky pasture. Accordingly, differences in the character or structure of the limestone are often manifested in particular landforms or other features of the landscape. For example, the northern hills of the Burren overlooking Galway Bay rise in tiers of cliffs and terraces where horizontal lines of weakness in the rock have been exploited by erosive waters and the loosened rock subsequently scraped away by glaciers. Below these terraces, massive, unfractured limestones form smooth slopes whilst above the terrace3d zones the limestones have crumbled more readily and allowed a thin soil cover to develop. These are the upland pastures of the Burren, long used to graze cattle during the winter months. Thin bands of clay or other non-soluble rocks force water, seeping down through the fissured limestone, to emerge at the surface to form many small springs - the main source of water for stock on the otherwise waterless upland. In the south-eastern Burren, the rocks have been folded and fractured by earth movements and each distortion of the strata is faithfully reflected in the landscape, for example in eccentrically shaped hills such as Mullaghmore and Slieve Rua.

Springs and Wells
Springs and wells supply almost all the water used on the Burren. Killeany spring near Lisdoonvarna is used to supply water over a wide area. The tourist centre of Ballyvaughan utilises water from springs on the mountains nearby and from a bored well just outside the town. Corofin, another important tourist centre, uses water from Lough Inchiquin, which is fed largely by spring waters from the Burren plateau.

All of these supplies are vulnerable to contamination from any pollutants that are allowed to enter the underground waters of the Burren.

The landscape of the Burren, especially the central and eastern parts, seems a stony chaos to the casual observer. Only at the junction of the limestone and the impermeable shale rocks, around Slieve Elva for example, are there valleys containing streams. Where these streams cross from the shale to the limestone they disappear underground at swallow holes, the waters flowing through cave systems before emerging from springs such as those at Killeany and St. Brendan's Well near Lisdoonvarna. Away from the non-limestone rocks, the landscape is pitted with fragments of gorges and with innumerable hollows or enclosed basins termed dolines. Some of these basins are a few metres in depth and width, but others, for example the enclosed depression at Carron, are several square kilometres in extent and tens of metres deep.

Another remarkable feature of the Burren is the large expanses of bare limestone called limestone pavements. The vertical fissures (joints) in the rock have been opened by acidic rain water (grikes), thus compartmentalising the rock surface into blocks or clints, each a few square metres in extent. Limestone pavements are a legacy of the ice age that ended some 15,000 years ago in this part of Ireland. The ice scraped away the surface debris of soil, stones and the topmost layer of solutionally weakened rock, to leave a massive, uneroded rock surface when the ice melted. Extensive limestone pavements are common in high Alpine limestone areas of Europe and elsewhere where ice persisted until very recently.

Bare rock of the Burren overlooking Galway Bay
Bare rock on the hills of the north flank of the Burren
(David Drew)

Human Impact on the Burren
The barren appearance of the Burren may be due, in part at least, to past human actions. Evidence from soils lodged in cracks in the rocks and from ancient preserved pollen suggest that in prehistoric times the Burren may have been wooded, with more fertile and more widespread soils than now. The cutting down of the forests by early settlers may have allowed the soils to be eroded away - an occurrence known to have taken place in many of the world's karst regions.

The Burren contains the greatest number of explored caves of any karst region of Ireland, most of them narrow, twisting canyon-like passages carrying a stream and located in the west of the area close to Lisdoonvarna.

Aillwee Cave near Ballyvaughan, containing vast, dry caverns, is one of Ireland's oldest caves and must have formed when the landscape of the Burren was very different from that of the present day. 

Exploring the cave of Pol an Ionain at Ballynalackan, involves a low, stony crawl in water. However, at the end of the crawl, the explorer enters a large chamber where, hanging from the roof is a huge stalactite, 6.7 m long and reputedly the longest known in the world.

Although other karst areas in Ireland have impressive archaeological remains, the passage graves on the Bricklieve Mountains for example, the evidence for human occupancy of the Burren for the past six millennia or more is striking. Stone has of necessity been the building material and hence structures have been preserved long after they were built.

In addition to the famous wedge-tombs and ring forts, the surface of the plateau is covered by networks of field walls, hut circles and other more obscure features all of which testify to the attraction humans have had to what seems a bare and inhospitable region, largely devoid of soil and water.

From The Karst of Ireland: Limestone Landscapes, Caves and Groundwater Drainage Systems.
Karst Working Group 2000, Geological Survey of Ireland.
ISBN 1899702415

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