crag and tail

roche moutonee



The family of drumlinoid landforms



Drumlinoid glacial landforms

Definition: the family of streamlined landforms characteristic of large areas of the beds of  former glaciers and ice sheets.

Drumlinoid glacial landforms

Geomorphologists recognise many types of streamlined glacier bedforms - such as the classic roches moutonnées, crag and tails and drumlins - but these distinctive features are part of a continuum of forms. The term drumlinoid is sometimes used to refer to this continuum. It is useful to think in these terms because drumlins made entirely of glacial till may occur alongside others with a rock core and yet within the same area may be found crag and tails carved almost exclusively from bedrock.

This continuum of drumlinoid forms reflects complex interactions between rock type and structure and glacier flow operating over a range of timescales.

Geological controls include rock resistance to glacial erosion and rock structures, like fracture patterns, that affect the size and shape of landforms of glacial erosion.

Glaciological controls include the ice thickness and flow rates that link to thresholds between glacial erosion and deposition.

Chronological controls relate to timescales for formation, with the possibility of inheritance of form or sediment from earlier glacial phases and that earlier erosional forms are buried by deposition as ice thins.

Many drumlinoid landforms are therefore difficult to characterise or to map.