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Alternatively, drumlins may be residual, with the landforms resulting from erosion of material between the landforms. The dilatancy of glacial till was invoked as a major factor in drumlin formation. [14] In other cases, drumlin fields include drumlins made up entirely of hard bedrock (e.g. granite or well-lithified limestone). [15]
Drumlins may be composed of stratified or unstratified till ranging in size from sand to boulders. The non-uniformity of drumlin composition is representative of the diverse origin of the sediments. [38] Banding or layering of till may occur in drumlins as till accumulates on the drumlin formation in successive layers. [38]
The Withrow Moraine and Jameson Lake Drumlin Field National Natural Landmark is located on the Waterville Plateau, which lies in the northwest corner of the Columbia River Plateau. The plateau is formed on top of the Columbia River Basalt Group a large igneous province that lies across parts of the states of Washington , Oregon , and Idaho in ...
Kames are sometimes compared to drumlins, but their formation is distinctively different. A drumlin is not originally shaped by meltwater, but by the ice itself and has a quite regular shape. It occurs in fine-grained material, such as clay or shale, not in sands and gravels. And drumlins usually have concentric layers of material, as the ice ...
A geological formation consisting of symmetrical anticlines that intersect each other at their respective apices. drill core A drill specifically designed to remove a cylinder of material, much like a hole saw. drumlin An elongated, whale-shaped hill formed by glacial action. dunite
Drumlins and ribbed moraines are also landforms left behind by retreating glaciers. Many depositional landforms result from sediment deposited or reshaped by meltwater and are referred to as fluvioglacial landforms. Fluvioglacial deposits differ from glacial till in that they were deposited by means of water, rather than the glacial itself, and ...
Drumlins are found in groups called drumlin fields or drumlin camps. One of these fields is found east of Rochester, New York; it is estimated to contain about 10,000 drumlins. Although the process that forms drumlins is not fully understood, their shape implies that they are products of the plastic deformation zone of ancient glaciers.
The Peterborough drumlin field is a large physiographic feature to the north of the Oak Ridges Moraine. It has a northeast to southwest orientation, and is cut by a network of deep valleys with wide, flat floors. The valleys are steep-sided, and have a branching pattern.