The Peace River Lowland, a landform region in the Alberta Plateau. The landform region is a gently rolling lowland without clearly defined outer boundaries, extending east of the Rocky Mountains on both sides of the Peace River, sloping downward to the north and east. The higher hills in the foothills east of the Rockies in northeastern British Columbia have elevations of about 1000 m and the plains west of Lake Athabasca are about 300 m above sea level. The lowland's Quaternary sediments of the former lake bottom of Glacial Lake Peace are underlain by Upper and Lower Cretaceous sedimentary rocks mainly shales of the Shaftesbury formation and sandstones of the Dunvegan and Peace River formations. The Peace River and its immediate tributaries have incised almost 200 meters into the sediments and into the Cretaceous bedrock in the western section but only about 70 meters in the east side further north around Fort Vermilion.