Återgångsmorän

Återgångsmorän is a geomorphological term used in glaciology to describe a type of moraine formed during pauses or brief re-advances in the retreat of a glacier. The term combines the Swedish åter (back, again) with gång (movement or advance) and morän (moraine), and is employed to distinguish a ridge deposited at specific moments when the glacier terminus paused its retreat.

Formation and characteristics come into play when a retreating glacier stabilizes or temporarily thickens, allowing debris accumulated at the ice front to be deposited as a discrete ridge behind the preceding terminus. Multiple återgångsmoräns can occur along a valley if the glacier repeatedly paused during retreat. They are typically composed of unsorted glacial till and may range from small humps to elongated ridges aligned roughly parallel to the former ice front. Erosion and burial by subsequent deposits can alter their appearance, and they may be partially overlain by newer sediments or reworked by meltwater processes.

Significance in glaciology lies in their potential to record intermittent pauses in glacier retreat, offering a proxy for short-term climate fluctuations and dynamic responses of glaciers to global or regional changes. Relative dating is commonly used, often supplemented by stratigraphic relationships with other moraines and, when possible, radiometric or surface-exposure dating.

See also: Moraines, Recessional moraines, Glacial geology.

Note: Återgångsmorän is used in some Swedish-language sources to describe this specific moraine type and may not be universally applied in all geologic literatures.