Copyright Geological Survey of Ireland 2006.
Copyright Geological Survey of Ireland 2006.
The word ‘karst’ comes from the Karst region of Slovenia – a rocky limestone area with underground drainage and little or no sign of surface water. Here the dissolution of the limestone and dolomite rocks has created extensive cave systems that facilitate underground drainage. Dry valleys, swallow holes and enclosed depressions (dolines) are features of karstic areas.
Although Ireland has a geology that features extensive tracts of limestone, karstic topography is evident in only a few areas such as the Burren, the Gort lowland to the east, near Cong in Co. Galway (shores of Lough Mask) and in south-west Fermanagh. This is because an extensive cover of glacial drift materials overlies the limestone in most areas. Drainage is developed on the drift, reducing the impact of solution through the limestone.
Karstic topography was more extensive in the warmer, sub-tropical, conditions that prevailed in Ireland for many milions of years before the Ice Age. Although much of the evidence for Ireland 's karstic past was stripped away by the great ice sheets, rock borings and quarrying activities sometimes expose sections. At a few localities, parts of the land surface may represent features of fossil karst: tor-like blocks of limestone at Fenit, Co. Kerry, have been interpreted as comparable to the pinnacle karst of modern China and Indonesia, while some steep-sided limestone hills, such as the Rock of Dunamase, Co. Laois, and possibly Knocknarea, near Sligo town, have been identified as comparable to the 'hums' of tropical karst areas.