Caves normally occur in limestone rocks because they are soluble in slightly acid water. Although water in limestone areas normally travels down through cracks and joints in the limestone, which gradually dissolve into bigger spaces, we only call them caves when they are big enough for humans to enter.
Pothole is another name for a cave, but usually indicates a vertical shaft, rather than a near horizontal passage.
Cave formations such as stalactites, stalagmites, columns, helictites, gour pools and curtains occur when water, saturated in dissolved limestone, drips into free airspace within a cave and gives off carbon dioxide and precipitates calcium carbonate (also called calcite - the same material as the rock itself).
To find out more about caving in Ireland contact the Speleological Union of Ireland: www.caving.ie
Links to showcaves in Ireland:
Aillwee Cave, Co. Clare :
Crag Cave, Co. Kerry :
Dunmore Cave, Co. Kilkenny : www.heritageireland.ie/en/HistoricSites/East/DunmoreCaveKilkenny/
Mitchelstown Cave, Co. Tipperary :
Marble Arch Caves, Co. Fermanagh :
Calcite formations in Dunmore Cave, Co. Kilkenny
Photo: Terence P. Dunne