Mackenzie River great depths to bedrock. A characteristic feature of the delta is its numerous pingos, or hills of earth-covered-ice – some 1,400 of them. The Peel River, carrying much of the runoff from the northern Yukon, joins in the delta at a point northeast of Fort McPherson. Below there, the Mackenzie diverges into several large channels with the largest heading north-northeast, emptying into the Beaufort Sea west of Tuktoyaktuk. At , the Mackenzie River drainage basin encompasses nearly 20 percent of Canada. About , or 54 percent of the basin, lies above Great Slave Lake. Permafrost underlies about three-quarters of the
Lake Huron as two 'lobes of the same lake'). Aggregated, Lake Huron-Michigan, at , "is technically the world's largest freshwater lake." When counted separately, Lake Superior is larger than Huron and higher. Lake Superior drains into the St. Marys River which then flows southward into Lake Huron. The water then flows south to the St. Clair River, at Port Huron, Michigan and Sarnia, Ontario. The Great Lakes Waterway continues thence to Lake St. Clair; the Detroit River and Detroit, Michigan; into Lake Erie and thence – via Lake Ontario and the St. Lawrence River – to the Atlantic Ocean. Like the other