Flute (glacial)

A glacial flute is a landform created by the movement of a glacier around a boulder. They are long ridges on the ground parallel to the movement. Examples can be found in many places including Iceland, Alaska and Canada.

Illustration of a specimen of glacial fluting from the Great Lakes region

As glaciers move along the surface of the earth, rocks are slowly mixed in with the ice. Rocks may reach the bottom of the glacier and begin to scrape along the earth. Eventually boulder sized rocks become lodged in the ground. Once the boulder is in place, the glacier flows around it. As a result, a cavity is formed on the down slope side of the boulder. This cavity is then filled with sediments such as till and outwash. Similar cavities can also be formed as the glacier moves over bedrock outcrops or bed irregularities which also may form flutes.

These mounds are usually only a couple of metres high but hundreds of metres long. They are named flutes as their long and narrow shape resembles the musical instrument.

References

• Easterbrook, D. J. (1999) Surface processes and landforms. (Second Ed). Prentice Hall, Upper Saddle River, New Jersey. ISBN 978-0-13-860958-0.