Drumlins are low hills that were formed and shaped by the flow of ice during the last Ice Age. The end facing the ice is blunter. Drumlins may occur in great swarms thereby creating what is sometimes described as ‘basket of eggs’ topography. In Ireland such swarms are evident in a great swathe of territory stretching from Sligo - Leitrim eastward through Cavan, Monaghan and Armagh into County Down . Lesser swarms are evident around Clew Bay and in south-west Clare.

The term ‘drumlin’, meaning little rise, is used worldwide. Drumlins are typically composed of glacially-deposited till or boulder clay, but may also be of solid rock which has been shaped into a drumlin form by ice movement.