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A drumlin (Gaelic druim the crest of a hill) is an elongated whale-shaped hill formed by glacial action. Its long axis is parallel with the movement of the ice, with the blunter end facing into the glacial movement. Drumlins may be more than 150 ft (45 m) high and more than 1/2 mi (.8 km) long, and are often in drumlin fields of similarly shaped, sized and oriented hills. Drumlins usually have layers indicating that the material was repeatedly added to a core, which may be of rock or glacial till. All over the world, drumlins appear to be of the same age.

There are many theories as to the exact mode of origin and plenty of controversy among geologists interested in geomorphology. Some consider them a direct formation of the ice, while a theory proposed since the 1980s by John Shaw and others postulates creation by a catastrophic flooding release of highly pressurized water flowing underneath the glacial ice. Either way, they are thought to be a waveform (similar to ripples of sand at the bottom of a stream). It is also poorly understood why drumlins form in some glaciated areas and not in others.

Drumlins are common in New York, the lower Connecticut River valley, Minnesota, Wisconsin, Canada, Poland and Northern Ireland. They are regarded as a creation of the last Wisconsonian Ice ageFor the animated movie, see Ice Age (movie . For the band, see Ice Age (band . An ice age is a period of long-term downturn in the temperature of Earth's climate, resulting in an expansion of the polar ice caps and mountain glaciers (" glaciation"). Glaci.

A similar formation, with a more resilient (generally volcanic) core, is a CragUniversity of Stirling. The Wallace Monument stands on the crag at the right, and the long tail slopes down leftward A crag (sometimes spelled cragg, or in Scotland craig) is a rocky hill or mountain, generally isolated from other high ground. Crags are f.

1 See also

• SedimentSediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. Sedimentation is the deposition by settling of a suspended ma
• geologyGeology (from Greek γ&eta ge "the earth") and λογος logos "word", "reason")) is the science and study of the Earth, its composition, structure, physical properties, history, and the processes that shape it. Geolog

2 External links

• Douglas E. Cox, "Drumlins and subglacial meltwater floods"
• Douglas E. Cox, "The role of vortices in drumlin formation" Introductions to the current dialogue.