Large transversal moraine ridges (Ribbed type)

A Ribbed moraine is a type of hummocky moraine, characterized by irregular ridges that are more or less oriented at right angles to the ice flow direction. Ribbed moraines are mainly older than the latest stage of deglaciation. They are often composed of basal till or lodgement till, and are subglacially deposited, probably in the same zones as the drumlins. Ribbed moraine ridges occur in the Valsörarna, Mickelsörarna and Köklot areas.

Ribbed moraines, Valsörarna

Drumlins and Ribbed moraines were formed 11 000-10 000 years ago about 200-700 km behind the ice marging. At the time, huge ice lobs filled the Bothnian Bay area and the ice flow was roughly south-southeast as shown by stratification and drumlin orientations.

Ribbed moraines