drumlins

Drumlins are elongated, hill-like landforms formed beneath or at the base of a glacier. They have a teardrop shape with a blunt, stoss end facing the direction of ice flow and a tapered lee end downstream. When viewed from above, they appear as smooth, parallel ridges with long axes that typically align with the former movement of the ice.

Drumlins are usually composed of unconsolidated sediments, such as glacial till, and they frequently occur in groups called drumlin fields. These fields are often arranged in parallel belts that reflect past ice-flow patterns. Drumlins are common in many formerly glaciated regions of North America and Europe, including parts of Ireland, Scotland, Britain, and the Great Lakes area, as well as other glaciated landscapes.

Sizes vary widely: individual drumlins range from a few hundred meters to several kilometers in length, a few hundred meters in width, and from a few to several tens of meters in height.

The exact mechanism of drumlin formation remains a topic of research and debate. Leading models emphasize subglacial processes such as lodgement and deformation of sediments beneath a moving glacier, potentially aided by basal meltwater and changing pressure conditions. It is likely that multiple processes contribute, and that the dominant mechanism can vary with local geology and ice dynamics.

Drumlins serve as valuable indicators of past ice-flow directions and glacier behavior. Their orientation helps reconstruct glacial movement during different phases of retreat and advance, and they are commonly studied alongside other glacial bedforms such as moraines and eskers.