Washboard moraine

A washboard moraine, also known as minor, DeGeer or annual moraine, is a geomorphic feature caused by glaciers. As the glacier melts it leaves behind an accumulation of rock debris. Annual glacial advances and recessions cause parallel ridges to form a few meters apart. Because the accumulation of debris is annual, the moraines do not get very large and stand only a few meters high. The name "washboard moraine" refers to the fact that, from the air, it resembles a washboard. Washboard moraines can be seen in many places such as South Dakota, Maine, and Iceland.

Referenceshttp://maine.gov/doc/nrimc/mgs/explore/surficial/facts/jan00.htmEasterbrook, Don J. Surface Processes and Landforms. Prentice Hall. 1999