 Both the US and Canada consider Turtle Mountain to be a sibling ecodistrict with the Pembina Escarpment, as both countries place both areas within the same larger ecoregions.Some US sources use the term "Manitoba Escarpment" for the Canadian portion of the Pembina Escarpment, but in Canada, the term Manitoba Escarpment refers to a separate geographical region along the Saskatchewan-Manitoba border.The Pembina Escarpment is separated from the Manitoba Escarpment by the Assiniboine and Souris River valleys, which were covered by Lake Souris at the time of Lake Agassiz when both escarpments were formed.