Upper Summit Lake (British Columbia) River, Great Slave Lake and the Mackenzie River into the Beaufort Sea portion of the Arctic Ocean. Upper Summit Lake (British Columbia) Upper Summit Lake is a lake in Regional District of Fraser-Fort George, in the Central Interior of British Columbia, Canada, about north of the city of Prince George and south of the community of Bear Lake. It lies just west of Highway 97 (John Hart Highway). Upper Summit Lake is about long and wide, and lies at an elevation of . There are no inflows, and an unnamed creek flows from the southern tip of the lake to
Mackenzie River Lakes are remnants. Today's Mackenzie River is very young in geologic terms – its channel formed over a period of no more than several thousand years as the ice sheet retreated. Prior to the ice ages, only the Peel River tributary flowed through what is now the Mackenzie Delta into the Arctic Ocean. The other tributaries of the Mackenzie combined into the "Bell River" which flowed east into Hudson Bay. During glaciation the weight of the ice sheet depressed northern Canada's terrain to such an extent that when the ice retreated, the Mackenzie system was captured to lower elevations in