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Mackenzie,river, c.1,120 mi (1,800 km) long, issuing from Great Slave Lake, Northwest Territories, Canada, and flowing generally NW to the Arctic Ocean through a great delta. Between Great Slave Lake and Lake Athabasca it is known as the Slave River. At Lake Athabasca, the Finlay-Peace river system and the Athabasca River join the Mackenzie. The Finlay-Peace-Mackenzie system (c.2,600 mi/4,180 km long) is the second longest continuous stream in North America. The Liard River is the largest tributary flowing directly into the Mackenzie. The river is navigable from the Arctic Ocean to Great Slave Lake between June and October. Between Great Slave Lake and Lake Athabasca there are rapids (14 mi/23 km) that must be portaged; above the rapids are more than 400 mi (644 km) of navigable waters. The Liard River affords transportation between Fort Nelson, British Columbia, and the Arctic; the Athabasca-Mackenzie system is followed by a major shipping route between Edmonton, Alta., and the Arctic. Numerous lakes in the Mackenzie basin act as reservoirs and natural flood controls. The basin, flanked by the Rocky Mts. and the Canadian Shield, is the northern portion of the Great Plains of North America; arctic air masses follow the valley south into the interior of the continent. Much of the Mackenzie valley is heavily forested and, where climate permits, its deep soil is well suited to agriculture. Numerous trading posts were established along the Mackenzie in the early part of the 19th cent. and fur trapping is still an important activity there; the chief trading posts are Fort Simpson, Fort Providence, and Aklavik. The region was the domain of fur traders until the 1930s when vast oil fields and other mineral resources were discovered; Norman Wells is the chief oil-producing town. In the early 1970s large natural gas fields were discovered in the Mackenzie delta region. A plan to construct the Mackenzie Valley Pipeline from the Arctic Ocean to Alberta, which would have been the greatest construction project ever undertaken, was shelved in 1977 after a federal royal commission concluded that, though feasible, the project involved serious legal, political, and environmental problems. Peter Pond was possibly the first European to enter (1777) the Mackenzie drainage area, but Sir Alexander Mackenzie, the 19th-century Canadian explorer, was the first to descend (1789) the river to the Arctic Ocean.
an open bay of the Beaufort Sea, located along the northern coasts of Canada, between Cape Kaye and the delta of the Mackenzie River. Length, about 70 km; depth, 5-10 m; depth at Cape Kaye, more than 20 m. Ice forms in September and begins to thaw in early June.
a system of mountain ranges in northwestern Canada, part of the eastern belt of the Cordilleras. The mountains are bounded by the Peel River in the north and the South Nahanni in the south. Length, approximately 700 km; elevation, to 2,469 m (the Mackenzie Mountains proper reach an altitude of 2,164 m). The ranges are composed primarily of sedimentary rocks, and there are traces of ancient glaciation. Many tributaries of the Mackenzie River rise on the slopes. Vegetation is represented by taiga, consisting for the most part of spruce forests, open woodlands (to elevations of 1,200-1,500 m), and mountain tundra.
a river in northwestern Canada. It issues from the Great Slave Lake and empties into the Arctic Ocean (Beaufort Sea), forming a delta with an area of about 12,000 sq km.
The Mackenzie River proper is about 1,600 km long; together with the Peace River (from the source of the Finlay River) the length is 4,250 km. The basin area, including the systems of the Slave, Peace, and Athabasca rivers, which all belong to the basin of Great Slave Lake, is 1,804,000 sq km. The Mackenzie’s principal tributaries are the Liard, Arctic Red, and Peel on the left and the Great Bear River on the right. The valley of the Mackenzie is filled with strata of alluvial and aqueoglacial deposits, is very swampy, and is covered with spruce forest. The river is fed by snow and rain; its high-water period occurs during the spring and summer. The average discharge is 14,000 cu m per sec. The river freezes over in September or October, and the ice breaks up in May; in its lower course the ice breaks up in early June. The length of the navigable waterways of the entire Mackenzie River system, from Waterways on the Athabasca River to the port of Tuktoyaktuk on the Arctic Ocean, totals 2,200 km. The largest population centers are Aklavik, Inuvik, Norman Wells (a center of the petroleum industry), Fort Norman, and Fort Providence. The river was discovered and first traveled by A. Mackenzie in 1789.