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 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.
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 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.
Caves
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