The Rocky Mountain Trench, also known as the Valley of a Thousand Peaks or simply the Trench, is a large
valley
A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams ove ...
on the western side of the northern part of
North America's Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...
. The Trench is both visually and
cartographically a striking
physiographic
Physical geography (also known as physiography) is one of the three main branches of geography. Physical geography is the branch of natural science which deals with the processes and patterns in the natural environment such as the atmosphere ...
feature extending approximately from
Flathead Lake
Flathead Lake ( fla, člq̓etkʷ, label= Salish, kut, yawuʔnik̓ ʔa·kuq̓nuk) is a large natural lake in northwest Montana.
The lake is a remnant of the ancient, massive glacial dammed lake, Lake Missoula of the era of the last interglacia ...
,
Montana
Montana () is a state in the Mountain West division of the Western United States. It is bordered by Idaho to the west, North Dakota and South Dakota to the east, Wyoming to the south, and the Canadian provinces of Alberta, British Columb ...
, to the
Liard River, just south of the
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...
–
Yukon
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
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
Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps.
Topography is a field of geoscience and planetary sc ...
has been carved into
U-shaped glacial valleys, it is primarily a byproduct of
geologic faulting. The Trench separates the
Rocky Mountains
The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico ...
on its east from the
Columbia Mountains
The Columbia Mountains are a group of mountain ranges along the upper Columbia River in British Columbia, Montana, Idaho and Washington. The mountain range covers 135,952 km² (52,491 sq mi). The range is bounded by the Rocky Mountain T ...
and the
Cassiar Mountains
The Cassiar Mountains (french: Chaîne des Cassiars) are the most northerly group of the Northern Interior Mountains in the Canadian province of British Columbia and also extend slightly into the southernmost Yukon Territory. They lie north and ...
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
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...
. 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 basin
A drainage basin is an area of land where all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
s: the
Columbia
Columbia may refer to:
* Columbia (personification), the historical female national personification of the United States, and a poetic name for America
Places North America Natural features
* Columbia Plateau, a geologic and geographic region i ...
,
Fraser,
Peace
Peace is a concept of societal friendship and harmony in the absence of hostility and violence. In a social sense, peace is commonly used to mean a lack of conflict (such as war) and freedom from fear of violence between individuals or groups. ...
and
Liard
The Liard River of the North American boreal forest flows through Yukon, British Columbia and the Northwest Territories, Canada. Rising in the Saint Cyr Range of the Pelly Mountains in southeastern Yukon, it flows southeast through British ...
. Two reservoirs of the
Columbia River Treaty fill much of its length today -
Lake Koocanusa
Lake Koocanusa () is a reservoir in British Columbia ( Canada) and Montana ( United States) formed by the damming of the Kootenai River by the Libby Dam in 1972. The Dam was formally dedicated by President Gerald Ford on August 24, 1975.
T ...
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 Columbia River ( Upper Chinook: ' or '; Sahaptin: ''Nch’i-Wàna'' or ''Nchi wana''; Sinixt dialect'' '') is the largest river in the Pacific Northwest region of North America. The river rises in the Rocky Mountains of British Columbia ...
, the
Canoe River
The Canoe River is a river in southeastern Massachusetts. It is longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed April 1, 2011 and part of the Taunton River Watershed.
The Canoe Ri ...
, the
Flathead River, the
Fraser River
The Fraser River is the longest river within British Columbia, Canada, rising at Fraser Pass near Blackrock Mountain in the Rocky Mountains and flowing for , into the Strait of Georgia just south of the City of Vancouver. The river's annual ...
,
the Parsnip River, the
Finlay River, the
Fox River, and the
Kechika River
The Kechika River is a tributary of the Liard River, about long, in northern British Columbia, Canada. The Kechika flows generally northwest through the northernmost section of the Rocky Mountain Trench before turning east to join the Liard, a ...
. 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
Kinbasket Lake (or Kinbasket Reservoir) is a reservoir on the Columbia River in southeast British Columbia, north of the city of Revelstoke and the town of Golden. The reservoir was created by the construction of the Mica Dam. The lake include ...
, 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
Columbia may refer to:
* Columbia (personification), the historical female national personification of the United States, and a poetic name for America
Places North America Natural features
* Columbia Plateau, a geologic and geographic region i ...
, 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
The Interior Mountains or Northern Interior Mountains are the semi-official names for an expansive collection of mountain ranges that comprises much of the northern half of the Canadian province of British Columbia and a large area of southern Y ...
) and the Southern Trench (between the
Continental Ranges
The Continental Ranges is a major grouping of mountain ranges in the Rocky Mountains located in eastern British Columbia and western Alberta. It is a physiographic designation for use by geologists and is not used by the general public; it is no ...
and
Columbia Mountains
The Columbia Mountains are a group of mountain ranges along the upper Columbia River in British Columbia, Montana, Idaho and Washington. The mountain range covers 135,952 km² (52,491 sq mi). The range is bounded by the Rocky Mountain T ...
), separated by the northeastern portion of the
Interior Plateau west of the
Hart Ranges
The Hart Ranges are a major subrange of the Canadian Rockies located in northeastern British Columbia and western Alberta. The mountains constitute the southernmost portion of the Northern Rocky Mountains.
The Hart Ranges were named in honour o ...
. The Copley Range of the
Arctic Pacific Lakes Provincial Park forms the
drainage divide
A drainage divide, water divide, ridgeline, watershed, water parting or height of land is elevated terrain that separates neighboring drainage basins. On rugged land, the divide lies along topographical ridges, and may be in the form of a singl ...
between the northerly
Parsnip-
Finlay-
Peace
Peace is a concept of societal friendship and harmony in the absence of hostility and violence. In a social sense, peace is commonly used to mean a lack of conflict (such as war) and freedom from fear of violence between individuals or groups. ...
system into the
Arctic Ocean
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...
(via the
Mackenzie River) and the southwesterly
McGregor-
Fraser system into the
Pacific Ocean
The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the conti ...
. The northern end of the Columbia Mountains at ~54°N near
Prince George,
British Columbia
British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, for ...
, 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 fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectoni ...
ing, while the southern part of the Trench was created by
normal fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
s. 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.
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
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
into
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...
. 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.
Geology
Right-lateral
strike-slip
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
movement of the
Tintina Fault The Tintina Fault is a large right-lateral strike-slip fault in western North America, extending from northwestern British Columbia, Canada to the centre of the U.S. state of Alaska. It represents the Yukon continuum between the Rocky Mountain Tre ...
on the Tintina-Northern Rocky Mountain Trench may have begun during the middle
Jurassic
The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
. The fastest rates of slip probably occurred during two pulses in the middle
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
and early
Cenozoic
The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...
, respectively, with the latter probably occurring during the
Eocene
The Eocene ( ) Epoch is a geological epoch that lasted from about 56 to 33.9 million years ago (mya). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''ēṓs'', ...
. Between to over of total right-lateral movement has occurred, of which of offset has occurred since the mid-
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
. The result is that terrains to the west of the fault system have moved toward the north. In the context of
plate tectonics
Plate tectonics (from the la, label= Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of larg ...
, 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 San Andreas Fault is a continental transform fault that extends roughly through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal) ...
, the extension of the
Basin and Range Province
The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternating ...
, 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
Yukon (; ; formerly called Yukon Territory and also referred to as the Yukon) is the smallest and westernmost of Canada's three territories. It also is the second-least populated province or territory in Canada, with a population of 43,964 as ...
, the
U.S. state of
Alaska
Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U ...
and along the
British Columbia Coast
, settlement_type = Region of British Columbia
, image_skyline =
, nickname = "The Coast"
, subdivision_type = Country
, subdivision_name = Canada
, subdivision_type1 = Province
, subdivision_name1 = British ...
.
History and accessibility
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 is essentially without roads, excepting a few
cat trails for fire, outfitters, or logging. It is due to several turns of fate, and strategic administrative decisions since 1824, 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, 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
Route 97, or Highway 97, may refer to:
Australia
- Olympic Dam Highway, South Australia
Canada
* British Columbia Highway 97
** British Columbia Highway 97A
** British Columbia Highway 97B
** British Columbia Highway 97C
** British Columbia ...
bridge on the
Parsnip River has routes on both sides of
Williston Lake
Williston Lake is a reservoir created by the W. A. C. Bennett Dam and is located in the Northern Interior of British Columbia, Canada.
Geography
The lake fills the basin of the upper Peace River, backing into the Rocky Mountain Trench which i ...
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.
The
Kaska Dena
The Kaska or Kaska Dena are a First Nations people of the Athabaskan-speaking ethnolinguistic group living mainly in northern British Columbia and the southeastern Yukon in Canada. The Kaska language, originally spoken by the Kaska, is an Atha ...
culture of Fort Ware and
Lower Post
Lower Post is an aboriginal community in northern British Columbia, Canada, located on Highway 97, the Alaska Highway, approximately 15 miles (23 kilometres) southeast of Watson Lake, Yukon. Its historical mile designation is Mile 620. It is lo ...
refer to their ancestral use of the natural route as The Trail of The Ancient Ones. They also call it the Davie Trail honoring David Braconnier, the founding chief of the community at Ware (Fort Ware - originally called Kwadacha which the HBC named Whitewater Post)
1797 - John Finlay records the forks of the Finlay and Parsnip Rivers and ventures part way up each river. The Finlay River later comes to bear his name.
1823 to 1825 -
Samuel Black was sent by the HBC north through Finlay Forks to The Fox River (Kwadacha) and returned later that season. He narrowly missed being the first white person to go all the way up the Northern Trench to the Liard River but chose not to listen to his guide - heading north westward seeking the source of the
Finlay River instead. He travels far enough NW to discover the headwaters of another Trench tributary - The Turnagain River. Natives there find a marker left by Black and report it to historic Fort Halkett on the Liard River
1831 - John Macleod of the HBC records the mouth of the Kechika River emptying out of the northern end of the Trench into the Liard near the BC-Yukon border.
1872 - Capt. William F. Butler ascends part of the Finlay River and records both the Fox River and Fox Lake to the north (Ft. Ware / Kwadacha was not yet established.)
1897 to 1898 – The Canadian government sends a police patrol under Inspector Moodie to map a possible supply route from the Peace River to the Yukon - specifically Dawson City. The patrol, assumed to have perished, eventually arrived at
Fort Selkirk
Fort Selkirk is a former trading post on the Yukon River at the confluence of the Pelly River in Canada's Yukon. For many years it was home to the Selkirk First Nation (Northern Tutchone).
History
Archaeological evidence shows that the site h ...
. They proved the viability of the route and produced a surviving map of it. (Yukon Archives)
1898 – McGregor's book ''The Klondike Rush Though Edmonton'' summarizes various sources (papers) saying up to 45 parties were reported along the route from Fox River to Sylvestre's Landing. There was also a reported drive of cattle on this route (echoed in Moodie's reports and in Kaska oral history.)
1906 – A North West Mounted Police patrol under field supervision of Inspector Constantine began the construction of the
Police Trail westward from Hudson Hope and then northward up the Northern Trench from HBC's post at Fort Graham.
1907 - British Columbia Premier R. McBride intervened and asked Canada to direct the police resources to connect with the more westerly Telegraph Trail route. Under protest, the NWMP field team did so. That trail was soon abandoned due to its non-viable character. The political route departure from Fort Graham westward added 400 rugged snowy kilometres to the total distance without going any favorable ground or measurable distance closer to the north. The Davie Trail is noted to be excellent for wintering horse due to low snow accumulations.
1912 - British Columbia Magazine - prospector Bower reports Sifton Pass as the most eventual and most practicable for a railway form the Fraser River to the Yukon.
1914 - Premier McBride advocates a railway on Insp. Moodie's route according to B. Kenelly in a pamphlet 'The British Columbia Peace. Fort St John' 1936.
1926 - Whitewater Post is established by HBC. Whitewater is the translation of Kwadacha, a nearby river.
1930 to 1931 - British Columbia Department of Public Works investigates a road route over Sifton Pass.
1934 -
Charles Bedaux, a noted international workplace management consultant (time and motion studies) leads and finances the
Bedaux Expedition - formally known as the Bedaux Canadian Subarctic Expedition. While his advance scouts arrive at McDame Post near Good Hope Lake, the leader and entourage abandon their mission at Driftpile Creek due to fatigue, lack of horse feed, and impending winter. The controversial adventure is the subject of a 1995 Bedaux film biography titled
Champagne Safari.
1942 - February a final decision was reached regarding the A, B, and C routes for a northern Highway. It will connect the
North West Staging Route airfields and bypass the Northern Trench for the joint Canada-Alaska Highway
Alcan Highway, alternately
Alaska Highway. The three routes had been the subject of considerable economic competition between governments and communities since the Klondike Gold Rush. The A route was a Stikine option similar to Highway 37 of today. The B route favors the Trench option. The C route following the airfields east of the Rocky Mountains and then crossing to the west near the Liard River is the chosen route.
1942 - March 28 the American government initiates a highly secret survey. It was undertaken for the purpose of assessing a military railway link up the Northern Rocky Mountain Trench. It was completed on Sept 28. Nov 15 US General Somervell declines to proceed with a military railway. Canada's Major Charles presents drawings for the Northern Trench portion of a railway from Ware to Lower Post of , $112,000,000 cost, with 17,000 personnel over 400 days. Of the 1217 total miles of proposed railway to Alaska, 530 are on Canadian soil and lie within the Northern Rocky Mountain Trench or the Tintina Trench.
1949 - US Congress Public Law 391 authorises a location survey for a railway from Prince George to Fairbanks. Prince George Board of Trade advocates the Trench route - the B route.
1950 - October, Canadian Transport Minister Lionel Chevrier advocates the 1942 route in a secret document to Federal Cabinet. A budget of $750,000,000 is presented.
1953 - Whitewater Post or Kwadacha of the HBC closes. Today the Kaska Dena Community of Fort Ware (Ware) remains as a full-time settlement.
1957 - Swedish industrial savant
Axel Wenner-Gren advocates resource mega-developments for the Peace River area. Among his proposals he envisions a monorail up the Northern Trench. Some area proposals came to partial fruition but the monorail did not.
1960 to 1967 - The Government of BC declines the Northern Trench as their strategic railway choice, favoring instead a route to the west similar to the telegraph route. Part of the reason is that the
Lower Finlay and
Parsnip River portions of the Northern Trench would be flooded by the damming of the Peace River. Reservoir land acquisition commences. Their selected westerly rail route - the Dease Lake Extension along the A Route - has been, in part, abandoned, and in lesser part been reopened to Takla Siding for logging use.
1964 - US Congress tables the
NAWAPA
The North American Water and Power Alliance (NAWPA or NAWAPA, also referred to as NAWAPTA from proposed governing body the North American Water and Power Treaty Authority) was a proposed continental water management scheme conceived in the 1950s b ...
proposal by Parsons Engineering Group - would see flooding of the portions of the Trench as part of a continental-scale water diversion.
1971 - Sir
Ranulph Fiennes descends the Trench from Kechika mouth - mostly on foot, partly solo as part of his circum-polar expeditio
For this and other feats he is later recorded by Guinness Book of Records as the World's 'Greatest Living Explorer.'
1981 - 'Skook' Davidson; long time outfitter proposes a 'federal' national park in the Northern Trench.
1998 - After several years of round table discussions The British Columbia Government takes first legislative steps to establish a 'provincial'
Muskwa-Kechika Management Area
The Muskwa-Kechika Management Area (M-K or M-KMA) is a provincially run tract of land in the far north of British Columbia. It has an advisory board that advises the government on land-use decisions. Established by provincial government legislat ...
br>
It covers an area considerably larger than the floor of the Trench and its immediate tributaries.
1999 - Karsten Heuer completes the final section of the Y2Y hike (Yellowstone to Yukon) at Lower Pos
2000 - Extension of the
Muskwa-Kechika Management Area
The Muskwa-Kechika Management Area (M-K or M-KMA) is a provincially run tract of land in the far north of British Columbia. It has an advisory board that advises the government on land-use decisions. Established by provincial government legislat ...
into the Northern Trench. Much of the Northern Rocky Mountain Trench's furthest reach is within this British Columbia Protected Area. Significant exposure is given to the M-KMA in the November 2008 National Geographic Magazine as a follow-up to their partial funding of a recent expedition to Gataga Pass
In 2009 context the Northern Trench could have, and might yet, become the preferred route for the 120-year-old concept of a
Canada Alaska Railwaybr>
concept. Discussions among feasibility experts still do not seem to favor the B Route despite it being lower, more direct, fewer major river crossings and considerably less snow.
Southern Rocky Mountain Trench
Geology
The Southern Rocky Mountain Trench was created mainly by Cenozoic-aged extension (
normal fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
ing). 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
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
to
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...
time, rapid sediment deposition and
subsidence
Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope mov ...
to the west transitioned in the area of the modern Rocky Mountain Trench into a stable
continental shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
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
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...
and Paleozoic
metasedimentary and
sedimentary
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles ...
rocks. Within the trench are unconsolidated Cenozoic
sandstones
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks.
Most sandstone is composed of quartz or feldspar (both silicates) ...
and
conglomerates.
The aforementioned basement ramp along which
orogeny
Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An '' orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted ...
-related
thrust fault
A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks.
Thrust geometry and nomenclature
Reverse faults
A thrust fault is a type of reverse fault that has a dip of 45 degrees or less.
If ...
ing and subsequent strike-slip and normal faulting occurred is probably associated with the ancient
continental shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...
of
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon.
The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838
by combining the Greek words ''palaiós'' (, "old") and ...
and
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretace ...
time.
Geography
The southern Rocky Mountain Trench comprises approximately one half of the Trench in British Columbia and includes three regions, the
Robson Valley,
Columbia Valley and
East Kootenay (from north to south). It hosts dozens of communities and two major reservoirs -
Kinbasket Lake
Kinbasket Lake (or Kinbasket Reservoir) is a reservoir on the Columbia River in southeast British Columbia, north of the city of Revelstoke and the town of Golden. The reservoir was created by the construction of the Mica Dam. The lake include ...
, and
Lake Koocanusa
Lake Koocanusa () is a reservoir in British Columbia ( Canada) and Montana ( United States) formed by the damming of the Kootenai River by the Libby Dam in 1972. The Dam was formally dedicated by President Gerald Ford on August 24, 1975.
T ...
(an acronym of Kootenay/Canada/USA.) There are intersections with two other trench features. At the approximate midpoint of Kinbasket Lake, the now submerged Columbia River exits the Trench in an almost southerly direction toward Revelstoke and flows beyond to its point of exit from Canada south of Trail BC. West of Donald BC, the Beaver river flows in from the south - but it represents the intersection of the lesser but impressive feature called the Purcell Trench. The Purcell Trench as it proceeds southward becomes the valley of the
Duncan River and
Duncan
Duncan may refer to:
People
* Duncan (given name), various people
* Duncan (surname), various people
* Clan Duncan
* Justice Duncan (disambiguation)
Places
* Duncan Creek (disambiguation)
* Duncan River (disambiguation)
* Duncan Lake ...
and
Kootenay Lake
Kootenay Lake is a lake located in British Columbia, Canada. It is part of the Kootenay River. The lake has been raised by the Corra Linn Dam and has a dike system at the southern end, which, along with industry in the 1950s–70s, has changed ...
s.
There are four geographic segments of the Southern Rocky Mountain Trench:
#The segment of the Trench encompassing the uppermost court of the Fraser River from east of Prince George and continuing southeastward to the town of
Valemount
Valemount () is a village municipality of 1,018 people in east central British Columbia, Canada, from Kamloops, British Columbia. It is between the Rocky, Monashee, and Cariboo Mountains. It is the nearest community to the west of Jasper Natio ...
is known as the
Robson Valley, named after
Mount Robson
Mount Robson is the most prominent mountain in North America's Rocky Mountain range; it is also the highest point in the Canadian Rockies.
The mountain is located entirely within Mount Robson Provincial Park of British Columbia, and is part o ...
which overlooks its southern end. Valemount is the Westerly portal to the Yellowhead Pass.
#From Valemount and Canoe Southeastward to the eastern egress of
Rogers Pass at Donald, BC just north of the town of
Golden the Trench cradles the waters of
Kinbasket Lake
Kinbasket Lake (or Kinbasket Reservoir) is a reservoir on the Columbia River in southeast British Columbia, north of the city of Revelstoke and the town of Golden. The reservoir was created by the construction of the Mica Dam. The lake include ...
the reservoir created by
Mica Dam
Mica Dam is a hydroelectric embankment dam spanning the Columbia River 135 kilometres north of Revelstoke, British Columbia, Canada. It was built as one of three Canadian projects under the terms of the 1964 Columbia River Treaty and is operat ...
; this region before the reservoir was part of the route of the interprovincial highway, once known as the
Big Bend Highway, prior to the 1960s opening of the Roger's Pass section of the
Trans-Canada
The Trans-Canada Highway ( French: ; abbreviated as the TCH or T-Can) is a transcontinental federal–provincial highway system that travels through all ten provinces of Canada, from the Pacific Ocean on the west coast to the Atlantic Ocean on ...
.
#The Trench from Golden extending SE to the headwaters of the Columbia River at
Columbia Lake is known as the
Columbia Valley. Golden is the westerly portal to the Kicking Horse Pass on Highway #1 eastbound to Alberta.
#The southernmost Canadian part of the Trench is the core of a region known as the
East Kootenay, comprising the upper of the two Canadian portions of the valley of the
Kootenay River. Here, near
Cranbrook, British Columbia
Cranbrook ( ) is a city in southeast British Columbia, Canada, located on the west side of the Kootenay River at its confluence with the St. Mary's River. It is the largest urban centre in the region known as the East Kootenay. As of 2016, Cra ...
, the Trench is much wider than to the northwest, forming more of a broad basin than the U-shaped valley which typifies most of the Trench elsewhere from Columbia Lake northwards to the Liard. This segment bifurcates near Wasa 100 km north of the US border. The off-shooting western fork contains the City of Cranbrook affords access to the nearby City of Kimberley. Elko is the westerly portal to the Crowsnest Pass on Highway 3 eastbound to Alberta.
The southward transborder extension of the Trench into Montana is the primary containment for
Lake Koocanusa
Lake Koocanusa () is a reservoir in British Columbia ( Canada) and Montana ( United States) formed by the damming of the Kootenai River by the Libby Dam in 1972. The Dam was formally dedicated by President Gerald Ford on August 24, 1975.
T ...
, a Kootenay River reservoir created by the
Libby Dam near
Libby, Montana
Libby is a city in northwestern Montana, United States and the county seat of Lincoln County. The population was 2,775 at the 2020 census.
Libby suffered from the area's contamination from nearby vermiculite mines contaminated with particularl ...
.
The Kootenai National Forest
/ref>
Culture and economy
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
Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...
, zinc
Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...
, coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
and gypsum
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywa ...
. The Canadian Pacific Railway
The Canadian Pacific Railway (french: Chemin de fer Canadien Pacifique) , also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canad ...
(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
Tsawwassen ( ) is a suburban, mostly residential community on a peninsula in the southwestern corner of the City of Delta in British Columbia, Canada. It provides the only road access to the American territory on the southern tip of the peninsul ...
for export. A southerly rail-link through Yahk
Yahk is an unincorporated hamlet in southeastern British Columbia, Canada, just north of the Canada-U.S. border. Yahk Provincial Park borders the village to the south. Yahk is located on the Moyie River.
CBC Television talk show '' The Hou ...
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 resort
A ski resort is a resort developed for skiing, snowboarding, and other winter sports. In Europe, most ski resorts are towns or villages in or adjacent to a ski area – a mountainous area with pistes (ski trails) and a ski lift system. In Nort ...
s 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
Windermere (sometimes tautologically called Windermere Lake to distinguish it from the nearby town of Windermere) is the largest natural lake in England. More than 11 miles (18 km) in length, and almost 1 mile (1.5 km) at its wides ...
, Invermere, Radium
Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rat ...
, and Golden. There are many other local unincorporated communities and post offices.
Settlements and localities
The Trench has hosted only a few communities. From north to south they are:
*Lower Post, British Columbia
Lower Post is an aboriginal community in northern British Columbia, Canada, located on Highway 97, the Alaska Highway, approximately 15 miles (23 kilometres) southeast of Watson Lake, Yukon. Its historical mile designation is Mile 620. It is loc ...
* Fort Ware (Kwadacha)
* Ingenika Point
* Mesilinka (submerged)
*Fort Grahame
A fortification is a military construction or building designed for the defense of territories in warfare, and is also used to establish rule in a region during peacetime. The term is derived from Latin ''fortis'' ("strong") and ''facer ...
(submerged)
* Mackenzie, British Columbia
* Holmes River, British Columbia
*McBride, British Columbia
McBride is a village in the Robson Valley region of British Columbia, Canada. The village is located southeast of Prince George, British Columbia, and west of Jasper, Alberta. Incorporated in 1932, McBride is located in the Robson Valley sur ...
* Tête Jaune Cache, British Columbia
*Valemount, British Columbia
Valemount () is a village municipality of 1,018 people in east central British Columbia, Canada, from Kamloops, British Columbia. It is between the Rocky, Monashee, and Cariboo Mountains. It is the nearest community to the west of Jasper Natio ...
* Boat Encampment (submerged)
* Golden, British Columbia
* Radium Hot Springs, British Columbia
* Invermere, British Columbia
* Fairmont Hot Springs, British Columbia
*Canal Flats, British Columbia
Canal Flats is a village municipality in the East Kootenay region of southeastern British Columbia. This Columbia Valley community lies between the southern end of Columbia Lake and the northwest shore of the Kootenay River. The locality, on High ...
* Kimberley, British Columbia
*Cranbrook, British Columbia
Cranbrook ( ) is a city in southeast British Columbia, Canada, located on the west side of the Kootenay River at its confluence with the St. Mary's River. It is the largest urban centre in the region known as the East Kootenay. As of 2016, Cra ...
* Eureka, Montana
* Whitefish, Montana
* Kalispell, Montana
References
{{Reflist
*Akrigg, HP & GPV, 1997, British Columbia Place Names, 3rd Edition, UBC Press
*Black, Samuel, 1780–1841.''A Voyage of Discovery from Rocky Mountain Portage on Peace River to the Source of Finlays Branch and North-Westward, 13 May to 23 June 1824'': British Columbia Archives MS-0619
*Bally, A.W., Gordy, P., and Stewart, G. 1966. Structure, seismic data, and orogenic evolution of the southern Canadian Rockies. ''Bulletin of Canadian Petroleum Geology 14'': 337–381.
*Bowes, G.E. 1963. Peace River Chronicles, ''Prescott Publishing''
*Cushman, Dan 1966. The Great North Trail ''McGraw-Hill'': 383 pp.
* Gabrielse, H. 1985. Major dextral transcurrent displacements along the Northern Rocky Mountain Trench and related lineaments in north-central British Columbia. ''Geological Society of America Bulletin 96'': 1–14.
*Gadd, Ben, Handbook of the Canadian Rockies, 2nd Edition, ''Corax Press'' 830 pp.
*Gunderson, Eric L. personal archives, 1980–2009
*Henderson, G.C. 1959. A summary of the regional structure and stratigraphy of the Rocky Mountain Trench in Holland, S.S., chairman, Symposium on the Rocky Mountain Trench. ''Canadian Mining and Metallurgical Bulletin 565'' (62): 322–327.
*Leech, G.B. 1959. The southern part of the Rocky Mountain Trench, in Holland, S.S., chairman, Symposium on the Rocky Mountain Trench. ''Canadian Mining and Metallurgical Bulletin 565'' (62): 327–333.
*van der Velden, A.J. and Cook, F.A. 1996. Structure and tectonic development of the southern Rocky Mountain Trench. ''Tectonics 15'' (3): 517–544.
*White, Bob 1983, Bannock and Beans - Memoirs of the Bedaux Expedition and Northern BC Packtrails, ''Piapot History Book Group'' and ''Gateway Publishing Co. Ltd.''
Geology of British Columbia
Geology of Montana
Geology of the Rocky Mountains
Interior of British Columbia
Landforms of British Columbia
Valleys of British Columbia