During the Fraser (Late Wisconsin) Glaciation, the Cordilleran ice sheet advanced southward from source areas in British Columbia and terminated in the United States between the Pacific Ocean and the Continental Divide. The ice sheet extended farthest along major south-trending valleys and lowlands that traverse the international boundary; it formed several composite lobes segregated by highlands and mountain ranges. Each lobe dammed sizable lakes that drained generally southward or westward along ice margins and across divides. -- Waitt and Thorson, 1983 |