It is hard to picture the scenes as the great ice sheet reduced and wasted away. In some places the pre-glacial drainage channels were either blocked or much altered. As the ice melted, lakes formed within the ice sheet and also between the ice front and nearby hills. These lakes were frequently short-lived. Their waters escaped either as the ice receded further or as a result of the water pressure being released as a powerful torrent gouging out new channels or perhaps greatly enlarging older channels.

Meltwater channels can be   found in many parts of Ireland , for example on both the eastern and western flanks of the Wicklow mountains. In Co. Cork the Pass of Keimaneigh cuts through the Shehy mountains. A massive channel north of Galbally, Co. Limerick, was cut through a ridge by the meltwaters of ice to the north.