outwash plain

An outwash plain is the extensive stretch of sediment carried by a meltwater stream away from a glacier’s tip, hundreds of miles in reach. Outwash plains are composed of gravel, sand, and clay (clay, being the lightest, is borne the farthest), with a topography from nearly level to hilly, and moderate to negligible in its rise and fall. A pitted outwash plain occurs when ice blocks separate from a glacier’s tip and are borne along with the outwash, ending up partly buried. When they melt, the surface around them collapses, and the outwash plain’s otherwise smooth surface is now pitted, the pits often water-filled. These are commonly called kettle lakes. Examples of pitted outwash plains can be found in Vilas County, Wisconsin, and near Lansford, North Dakota.

Larry Woiwode