Канаданың таулы аңғары: Роки тауларының ойысы

Long valley in British Columbia

The Rocky Mountain Trench, also known as the Valley of a Thousand Peaks or simply the Trench, is a large valley on the western side of the northern part of North America's Rocky Mountains. The Trench 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 wide and is above sea level. The general orientation of the Trench is an almost straight 150/330° geographic north vector and has become convenient as a visual guide for aviators heading north or south. Although some of its topography has been carved into U shaped glacial valleys, it is primarily a byproduct of geologic 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 wide, if measured peak to peak, and varies in valley relief, but is clearly visible by air and satellite/remote sensing and is easily discernible to those ascending any of the mountains or ridges lining it. The Trench 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, the Canoe River, the Flathead River, the Fraser River, the Parsnip River, the Finlay River, the 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 are 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 River (Canadian spelling) is a tributary of the Columbia, joining the Columbia at Castlegar, BC after a meander through the United States as the Kootenai River (US spelling). For convenience the Rocky Mountain Trench may be divided into two sections, the Northern Trench (between the Muskwa Ranges and Interior Mountains) and the Southern Trench (between the Continental Ranges and Columbia Mountains), separated by the northeastern portion of the Interior Plateau west of the Hart Ranges. The Copley Range of the Arctic Pacific Lakes Provincial Park forms the drainage divide between the northerly Parsnip Finlay Peace system into the Arctic Ocean (via the Mackenzie River) and the southwesterly McGregor Fraser system into the Pacific Ocean. The northern end of the Columbia Mountains at ~54°N near Prince George, British Columbia, where the Fraser River leaves the Trench to enter the Interior Plateau, 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 of vertical offset.

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 near the bend of Scarcity Creek.

Right lateral strike slip movement of the Tintina Fault on the Tintina Northern Rocky Mountain Trench may have begun during the middle Jurassic. The fastest rates of slip probably occurred during two pulses in the middle Cretaceous and early Cenozoic, respectively, with the latter probably occurring during the Eocene. Between to over of total right lateral movement has occurred, of which of offset has occurred since the mid Cretaceous. The result is that terrains to the west of the fault system have moved toward the north. In the context of plate tectonics, strike slip movement of the Tintina Fault on the Tintina Northern Rocky Mountain Trench is also related to strike slip movement along the San Andreas Fault, the extension of the Basin and Range Province, and other extensional or strike slip fault systems in western North America. The Tintina Fault is one of the two major fault zones paralleling the Northern Cordilleran Volcanic Province, the other being the Denali Fault in the Yukon, the U. S. state of Alaska and along the British Columbia Coast.

The Southern Rocky Mountain Trench was created mainly by Cenozoic aged extension (normal faulting). What little strike slip movement that is found in the southern trench is not considered significant. The extensional faulting was nonetheless substantial, having extended as deep as The southern trench also differs from the northern trench in that it is more sinuous and is asymmetrical in cross section (perpendicular to its length). The western side of the Southern Rocky Mountain Trench is more subdued and irregular than the east side. During late Paleozoic to Mesozoic time, rapid sediment deposition and subsidence to the west transitioned in the area of the modern Rocky Mountain Trench into a stable continental shelf in the east. The Nevadan Orogeny destroyed the western wedge of sedimentary rocks during Jurassic to middle Cretaceous time, thrusting them up into metamorphic fold belts. Currently, strata on either side of the Southern Rocky Mountain Trench consist mainly of Precambrian and Paleozoic metasedimentary and sedimentary rocks. Within the trench are unconsolidated Cenozoic sandstones and conglomerates. The aforementioned basement ramp along which orogeny related thrust faulting and subsequent strike slip and normal faulting occurred is probably associated with the ancient continental shelf of Paleozoic and Mesozoic time.

The large valley and tributaries have always offered an economy based on ranching and logging. This has been supplemented by fortuitous locations of several mines often in side valleys and producing lead, zinc, coal and gypsum. The Canadian Pacific Railway (CPR) also constructed a spur line which extends northward up the southern Trench between Cranbrook and Golden. This serves to interconnect the southerly rail route of the Crowsnest Pass to the CPR mainline through Rogers Pass. Today it carries Crowsnest coal to Tsawwassen for export. A southerly rail link through Yahk enables freight shipments into Idaho and the Western US. Tourism has become an active force in the economy. The Southern Trench is also known for a number of ski resorts in the trench or in the nearby tributary valleys. These destinations include Fairmont, Panorama, Kimberley, Purden, Kicking Horse and the original Bugaboo heli ski lodge. Numerous other ski touring and back country lodges are also found here. The summer sports of golf, boating, fishing, and hiking round out the appeal to a growing weekend and permanent recreational population. Hunting, fishing, off roading, and camping will continue to be attractive pastimes. These include guided activities and individual pursuit of the area. The generous mix of low elevation, good climate, fine scenery, diverse recreation and resort accommodation has fostered a vacation based real estate industry for communities and rural areas surrounding Cranbrook, Windermere, Invermere, Radium, and Golden. There are many other local unincorporated communities and post offices.