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Rocky Mountain Trench
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Rocky Mountain Trench
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 1,600 km (1,000 mi) from Flathead Lake, Montana, to the Liard River, just south of the British Columbia–Yukon border near Watson Lake, Yukon. The trench bottom is 3–16 km (1.9–9.9 mi) wide and is 600–900 m (2,000–3,000 ft) 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 25 km (16 mi) 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 10 km (33,000 ft) 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 1,010 m (3,310 ft) 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 750 km (470 mi)to over 900 km (560 mi) of total right-lateral movement has occurred, of which 450 km (280 mi) 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.
First Nations have traditionally always travelled the northern Trench. There are several post-European contact travels up the northern Trench - often of large proportion. The Trench here remains mostly wild, and the northern 300 km (190 mi) is essentially without roads, excepting a few cat trails for fire, outfitters, or logging. It is due to several turns of fate,[clarification needed] and strategic administrative decisions since 1824,[clarification needed] that the most natural land transportation corridor in northern British Columbia has been left in a wild state. On many government maps produced since 1897,[clarification needed] indications of a passable trail have been published. However, with changes in the terrain caused by beaver dams or forest fires, and despite maintenance by guide-outfitters, the trail from Fox Lake north is often hard to find, or obliterated to all but indigenous and experienced Kaska natives. It may be more commonly used as an aviation route today.
The northern trench from the Highway 97 bridge on the Parsnip River has routes on both sides of Williston Lake to Fort Ware. The route up the east side cannot be followed due to the Peace Reach of the reservoir. The road traveler will use the gravel road up the west side of the Reservoir to Ware. Beyond that point the northbound traveller will only find a narrow cat guard (a cat guard is a primitive road constructed as a fire guard by heavy equipment-usually a bulldozer-to prevent the spread of a forest fire by creating a fuel free perimeter) for a few kilometres.
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Rocky Mountain Trench
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 1,600 km (1,000 mi) from Flathead Lake, Montana, to the Liard River, just south of the British Columbia–Yukon border near Watson Lake, Yukon. The trench bottom is 3–16 km (1.9–9.9 mi) wide and is 600–900 m (2,000–3,000 ft) 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 25 km (16 mi) 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 10 km (33,000 ft) 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 1,010 m (3,310 ft) 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 750 km (470 mi)to over 900 km (560 mi) of total right-lateral movement has occurred, of which 450 km (280 mi) 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.
First Nations have traditionally always travelled the northern Trench. There are several post-European contact travels up the northern Trench - often of large proportion. The Trench here remains mostly wild, and the northern 300 km (190 mi) is essentially without roads, excepting a few cat trails for fire, outfitters, or logging. It is due to several turns of fate,[clarification needed] and strategic administrative decisions since 1824,[clarification needed] that the most natural land transportation corridor in northern British Columbia has been left in a wild state. On many government maps produced since 1897,[clarification needed] indications of a passable trail have been published. However, with changes in the terrain caused by beaver dams or forest fires, and despite maintenance by guide-outfitters, the trail from Fox Lake north is often hard to find, or obliterated to all but indigenous and experienced Kaska natives. It may be more commonly used as an aviation route today.
The northern trench from the Highway 97 bridge on the Parsnip River has routes on both sides of Williston Lake to Fort Ware. The route up the east side cannot be followed due to the Peace Reach of the reservoir. The road traveler will use the gravel road up the west side of the Reservoir to Ware. Beyond that point the northbound traveller will only find a narrow cat guard (a cat guard is a primitive road constructed as a fire guard by heavy equipment-usually a bulldozer-to prevent the spread of a forest fire by creating a fuel free perimeter) for a few kilometres.
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