drumlin Smooth, streamlined, oval-shaped land-form, one end of which is blunt and the other tapered. Drumlins may occur singly, but more commonly they are found within a large group, called a ‘drumlin field’ or ‘drumlin swarm’. Usually they are composed of boulder clay, but occasionally they are made of solid rock (hence ‘rock drumlin’). They are believed to be formed beneath the outer zone of an expanding ice sheet, during a major advance: they result from the selective deposition of material that is then streamlined by the moving ice. The long axis of a drumlin lies parallel to the direction of the advance.

drumlin A smooth, streamlined, oval-shaped land-form, one end of which is blunt and the other tapered. Drumlins may occur singly, but more commonly they are found within a large group, called a ‘drumlin field’ or ‘drumlin swarm’. Usually they are composed of till or boulder clay, but occasionally they are composed largely of solid rock (hence ‘rock drumlin’). They are believed to be formed beneath the outer zone of an expanding ice sheet, during a major advance: they result from the selective deposition of material that is then streamlined by the moving ice. The long axis of a drumlin lies parallel to the direction of the advance.

drum·lin / ˈdrəmlin/ • n. Geol. a low oval mound or small hill, typically one of a group, consisting of compacted boulder clay molded by past glacial action.