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The Rocky Mountain Trench, also known as The Valley of a Thousand Peaks or simply the Trench, is a large valley in the northern part of the Rocky Mountains. It is both visually and cartographically a striking physiographic feature extending approximately from Flathead Lake, Montana, to the Liard River, just south of the British Columbia-Yukon border near Watson Lake, Yukon. The trench bottom is 3-to-16 km (2–10 miles) wide and ranges from 600–to-900 metres (2,000–3,000 feet) above sea level. The general orientation of the Trench is an almost uniform 150/330 degree geographic north vector which has also become convenient for north/south aviators. Although some of its topography has been carved into glacial valleys, it is primarily a by-product of faulting. The Trench separates the Rocky Mountains on its east from the Columbia Mountains and the Cassiar Mountains on its west. It also skirts part of the McGregor Plateau area of the Nechako Plateau sub-area of the Interior Plateau of British Columbia. It is up to 25 km wide, if measured peak-to-peak, and varies in valley relief, but is clearly visible from the air, satellite/remote sensing and is commonly discernible to those ascending any of the mountains or ridges lining it. It is drained by four major river basins: the Columbia, Fraser, Peace and Liard. Two reservoirs of the Columbia River Treaty fill much of its length today - Lake Koocanusa and Lake Kinbasket. A further British Columbia power initiative created Lake Williston. Rivers that follow the Trench, at least in part, are the Kootenay River, the Columbia River, Canoe River, the Flathead River, Fraser River, Parsnip River, Finlay River, Fox River, and the Kechika River. The North Fork of the Flathead River, flowing into Flathead Lake with the other branches of the Flathead River, is part of the Columbia River system. The Kechika is part of the Liard River system, and the Fox, Parsnip and Finlay Rivers and part of the Peace River system. The Canoe River is a short tributary of the Columbia system, draining into Kinbasket Lake, a reservoir on the Columbia River. The Kootenai River, however, does not fully follow the Trench but exits Canada southwest via Lake Koocanusa reservoir to the Libby Dam. The Kootenay (Canadian spelling) River is a tributary of the Columbia, joining the Columbia at Castlegar, BC after a meander through the USA as the Kootenai River (US spelling). For convenience the Rocky Mountain Trench may be divided into two sections - being the Northern Rocky Mountain Trench and Southern Rocky Mountain Trench. The dividing point reflects the separation of north and easterly flows to the Arctic Ocean versus south and westerly flows to the Pacific Ocean. A break in the valley system at ~54°N near Prince George, British Columbia may be used for this purpose. The northern portion of the Trench is dominated by strike-slip faulting while the southern part of the Trench was created by normal faults. Despite differences in timing and faulting styles of the northern and southern portions, they were aligned with each other because faulting for both was controlled by a pre-existing, west-facing, deep basement ramp with over 10 km of vertical offset. ==Northern Rocky Mountain Trench== The Northern Rocky Mountain Trench is closely aligned with the Tintina Trench near the British Columbia-Yukon border at 60 degrees north latitude, and the two trenches could arguably be classified as one and the same - or 'extensions' of each other. The Tintina Trench extends further north-westward through the Yukon into Alaska. The visible expression of the two trenches is lost where they plunge under the boreal forests of the Liard Plain proximate to the small communities of Watson Lake, Yukon and Lower Post, BC. The highest point in the northern Trench is Sifton Pass at an elevation of about 1010 metres near the bend of Scarcity Creek. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rocky Mountain Trench」の詳細全文を読む スポンサード リンク
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