Thompson Plateau

Last updated
Thompson Plateau

Thompson Plateau, near the Dominion Radio Astrophysical Observatory.jpg

Thompson Plateau, near the Dominion Radio Astrophysical Observatory

South BC-NW USA-relief ThompsonPlateau.png

Location map of the Thompson Plateau; dotted line is boundary of the Bonaparte Plateau.
Coordinates 50°15′00″N120°30′00″W / 50.25000°N 120.50000°W / 50.25000; -120.50000 Coordinates: 50°15′00″N120°30′00″W / 50.25000°N 120.50000°W / 50.25000; -120.50000 [1]
Age Mesozoic

The Thompson Plateau, also known as the Okanagan-Thompson Plateau, forms the southern portion of the Interior Plateau of British Columbia, Canada, lying to the west of Okanagan Lake, south of the Thompson River and to the east of (although never adjoining it) the Fraser River. At its most southern point the plateau is squeezed by the mountainous terrain of the Cascade Range abutting closer to the Okanagan Valley. Its southwestern edge abuts the Canadian Cascades portion of that extensive range, more or less following the line of the Similkameen River, its tributary the Tulameen River, and a series of passes from the area of Tulameen, British Columbia to the confluence of the Thompson River with the Nicoamen River, a few miles east of Lytton, British Columbia, which is in the Fraser Canyon. Its northeastern edge runs approximately from the city of Vernon, British Columbia through the valley of Monte Creek to the junction of the same name just east of the city of Kamloops. Northeast of that line is the Shuswap Highland. [1]

Interior Plateau

The Interior Plateau comprises a large region of the Interior of British Columbia, and lies between the Cariboo and Monashee Mountains on the east, and the Hazelton Mountains, Coast Mountains and Cascade Range on the west. The continuation of the plateau into the United States is known there as the Columbia Plateau.

British Columbia Province of Canada

British Columbia is the westernmost province of Canada, located between the Pacific Ocean and the Rocky Mountains. With an estimated population of 5.016 million as of 2018, it is Canada's third-most populous province.

Canada Country in North America

Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering 9.98 million square kilometres, making it the world's second-largest country by total area. Canada's southern border with the United States is the world's longest bi-national land border. Its capital is Ottawa, and its three largest metropolitan areas are Toronto, Montreal, and Vancouver. As a whole, Canada is sparsely populated, the majority of its land area being dominated by forest and tundra. Consequently, its population is highly urbanized, with over 80 percent of its inhabitants concentrated in large and medium-sized cities, many near the southern border. Canada's climate varies widely across its vast area, ranging from arctic weather in the north, to hot summers in the southern regions, with four distinct seasons.


Some definitions[ which? ] include the Bonaparte Plateau to the north, which lies in the angle of the Thompson and Bonaparte Rivers, and south of the uppermost reaches of that river and a small tributary of the North Thompson, Lemieux Creek.

The Bonaparte Plateau, in British Columbia, Canada, is a subarea of the larger Cariboo Plateau which extends to the Quesnel River and lies between the Cariboo Mountains on the east and the Fraser River on the west. The Cariboo Plateau is a subarea of the Interior Plateau, aka the Fraser Plateau.

The Bonaparte River is a tributary of the Thompson River, joining it at the community of Ashcroft, British Columbia. The river is about 150 kilometres (93 mi) long, including the 17 kilometres (11 mi) length of Bonaparte Lake. Rising on the Silwhoiakun Plateau to the northwest of Kamloops, the Bonaparte River flows west and south to join the Thompson River.

The dominant landscape of the Thompson Plateau is a high, almost plains-like rangeland fairly heavily forested with subalpine forest and tamarack swamp where there exists a significant cattle ranching industry, but plunging steeply to the valleys of the Thompson and Okanagan on its outer perimeter which feature more semi-arid landscapes that include rattlesnakes, a ground-creeping variety of prickly pear cactus, sagebrush, and tumbleweed, in addition to fruit growing operations that often rely on irrigation. In its core is the broad and open rangeland of the Nicola Valley, at the focus of which is the town of Merritt, British Columbia. Towards its southern edges, the plateau is fairly mountainous and includes the ski area at Apex (west of Penticton), as well as the small but rugged Kruger Range which runs south from there to the confluence of the Similkameen and Okanagan Rivers.

<i>Crotalus oreganus</i> species of reptile

Crotalus oreganus is a venomous pit viper species found in North America in the western United States, parts of British Columbia, and northwestern Mexico. Seven subspecies are currently recognized, including the nominate subspecies described here.


Sagebrush is the common name of several woody and herbaceus species of plants in the genus Artemisia. The best known sagebrush is the shrub Artemisia tridentata. Sagebrushes are native to the North American west.


A tumbleweed is a structural part of the above-ground anatomy of a number of species of plants, a diaspore that, once it is mature and dry, detaches from its root or stem, and tumbles away in the wind. In most such species, the tumbleweed is in effect the entire plant apart from the root system, but in other plants, a hollow fruit or an inflorescence might serve the function. Tumbleweed species occur most commonly in steppe and arid ecosystems, where frequent wind and the open environment permit rolling without prohibitive obstruction.


The Thompson Plateau contains Nicola Athapaskan, Nlaka'pamux and Syilx settlements. The Nlaka'pamux peoples of the plateau were known as Cawa'xamux or Tcawa'xamux [2]

Nlakapamux ethnic group

The Nlaka'pamux or Nlakapamuk, also previously known as the Thompson, Thompson River Salish, Thompson Salish, Thompson River Indians or Thompson River people, and historically as the Klackarpun, Haukamaugh, Knife Indians and Couteau Indians, are an indigenous First Nations people of the Interior Salish language group in southern British Columbia. Their traditional territory includes parts of the North Cascades region of Washington.

Syilx First Nations and Native American people of the Pacific Northwest

The Okanagan people, also spelled Okanogan, are a First Nations and Native American people whose traditional territory spans the Canada–US boundary in Washington state and British Columbia in the Okanagan Country region. They call themselves the Syilx, a term now widely used. They are part of the Interior Salish ethnological and linguistic grouping. The Okanagan are closely related to the Spokan, Sinixt, Nez Perce, Pend Oreille, Secwepemc and Nlaka'pamux peoples of the same Northwest Plateau region.

Nlaka'pamux settlements include: [3]

Syilx settlements include: [3]


The rocks underlying the Thompson Plateau originated in the Pacific and were appended to the North American Plate in the Mesozoic. These rocks were pervasively intruded by magmas now forming granitic rocks. These upland surfaces are now bordered by prominent valleys over 1000 metres deep. This peneplain was overlain by thin sheets of plateau basalts formed from the Chilcotin Group lavas that flowed ten to fifteen million years ago. [4]

North American Plate Large tectonic plate including most of North America, Greenland and a bit of Siberia

The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, the Bahamas, extreme northeastern Asia, and parts of Iceland and the Azores. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust. The interior of the main continental landmass includes an extensive granitic core called a craton. Along most of the edges of this craton are fragments of crustal material called terranes, accreted to the craton by tectonic actions over a long span of time. It is thought that much of North America west of the Rocky Mountains is composed of such terranes.

The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles, a phrase introduced by the 19th century paleontologist Gideon Mantell who viewed it as dominated by diapsids such as Iguanodon, Megalosaurus, Plesiosaurus and Pterodactylus. To paleobotanists, this Era is also called the Age of Conifers.

Peneplain A low-relief plain formed by protracted erosion

In geomorphology and geology a peneplain is a low-relief plain formed by protracted erosion. This is the definition in the broadest of terms, albeit with frequency the usage of peneplain is meant to imply the representation of a near-final stage of fluvial erosion during times of extended tectonic stability. Peneplains are sometimes associated with the cycle of erosion theory of William Morris Davis, but Davis and other workers have also used the term in a purely descriptive manner without any theory or particular genesis attached.

The area was occupied by Pleistocene glaciation, and a thick mantle of glacial drift covers bedrock over a large part of it. The Pleistocene ended with a gradual stagnation and a wasting of the ice in place. As a consequence, on many slopes a series of channels was formed at successive levels as ice surfaces wasted. [5]

The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

Related Research Articles

North Cascades mountains in the U.S. and Canada

The North Cascades are a section of the Cascade Range of western North America. They span the border between the Canadian province of British Columbia and the U.S. state of Washington and are officially named in the U.S. and Canada as the Cascade Mountains. The portion in Canada is known to Americans as the Canadian Cascades, a designation that also includes the mountains above the east bank of the Fraser Canyon as far north as the town of Lytton, at the confluence of the Thompson and Fraser Rivers.

Okanagan Region of British Columbia, Canada

The Okanagan, also known as the Okanagan Valley and sometimes as the Okanagan Country, is a region in the Canadian province of British Columbia defined by the basin of Okanagan Lake and the Canadian portion of the Okanagan River. It is part of the Okanagan Country, extending into the United States as Okanogan County in north-central Washington. According to the 2016 Canadian census, the region's population is 362,258. The primary city is Kelowna.

Okanogan River river

The Okanogan River is a tributary of the Columbia River, approximately 115 mi (185 km) long, in southern British Columbia and north central Washington. It drains a scenic plateau region called the Okanagan Country east of the Cascade Range and north and west of the Columbia, and also the Okanagan region of British Columbia. The Canadian portion of the river has been channelized since the mid-1950s.

Okanogan or Okanagan refers to:

Yale-Lillooet was a provincial electoral district for the Legislative Assembly of British Columbia, Canada.

The Nicola people are a First Nations political and cultural alliance in the Nicola Country region of the Southern Interior of the Canadian province of British Columbia. They are mostly located in the Nicola River valley around the area of Merritt and are an alliance of Scw'exmx, the local branch of the Nlaka'pamux (Thompson) people, and the Spaxomin, the local branch of the Syilx or Okanagan people.

Regional District of Okanagan-Similkameen regional district in British Columbia

The Regional District of Okanagan-Similkameen (RDOS) is in southern British Columbia, adjacent to the U.S. state of Washington. It is bounded by Fraser Valley Regional District to the west, Thompson-Nicola Regional District and Regional District of Central Okanagan to the north, Regional District of Kootenay Boundary to the east, and by Okanogan County, Washington to the south. At the 2011 census the population was 80,742. The district covers a land area of 10,413.44 square kilometres (4,020.65 sq mi). The administrative offices are in the City of Penticton.

Secwepemc people in Canada

The Secwépemc, known in English as the Shuswap people, are a First Nations people residing in the Canadian province of British Columbia. Secwepemcúĺecw, their country, ranges from the eastern Chilcotin Plateau and the Cariboo Plateau southeast through the Thompson Country to Kamloops and the Shuswap Country, and spans the Selkirk Mountains and Big Bend of the Columbia River to include the northern part of the Columbia Valley region. The country's traditional territory covers approximately 145,000 square kilometres. They relied heavily on hunting, trading and fishing to support their communities. The Secwepemc are perhaps the most numerous of the Interior Salish peoples of British Columbia if based upon the numbers who speak their language.

The Jesup North Pacific Expedition (1897–1902) was a major anthropological expedition to Siberia, Alaska, and the northwest coast of Canada. The purpose of the expedition was to investigate the relationships among the peoples at each side of the Bering Strait.

Nicola, also Nkwala or N'kwala, was an important First Nations political figure in the fur trade era of the British Columbia Interior as well as into the colonial period (1858–1871). He was grand chief of the Okanagan people and chief of the Nicola Valley peoples, an alliance of Nlaka'pamux and Okanagans and the surviving Nicola Athapaskans, and also of the Kamloops Band of the Shuswap people.

Nicola River river in Canada

The Nicola River, originally French Rivière de Nicholas or Rivière de Nicolas, adapted to Nicolas River, Nicola's River in English, is one of the major tributaries of the Thompson River in the Canadian province of British Columbia, entering the latter at the town of Spences Bridge. It is named for Nicola (Hwistesmexteqen) the most famous chief of the joint community of Nlaka'pamux and Okanagan bands, founded by his father and today known as the Nicolas,, as well is its basin, which is known as the Nicola Country. It drains most of the northern Thompson Plateau, beginning near the very eastern edge of the plateau only 30 kilometres (19 mi) northwest of Kelowna, and flows from there more or less westward to feed Douglas Lake and Nicola Lake, with about 15 kilometres (9 mi) of the river's length between those two lakes. Nicola Lake at 20 kilometres (12 mi) long is the largest in the basin; the Nicola River enters at 3/4 way of its length up from its outlet, 10 kilometres (6 mi) downstream from which is Nicola Valley centre and Coquihalla Highway town of Merritt. From there the river flows 60 kilometres (37 mi) northwest to the Thompson, and is followed on that route by British Columbia Highway 8 and a spur line of the Canadian Pacific Railway.

The Scw'exmx ( Scw̓éxmx), meaning "people of the creek(s)" are a branch of the Nlaka'pamux (Thompson) people in the Nicola Country of the Canadian province of British Columbia (Scw'ex, meaning "creek", is the name of the Nicola River in the Thompson language}. Together with the neighbouring branch of the Okanagan people the Spaxomin, who live in the upper, eastern reaches of the Nicola Valley, they are generally known in English as the Nicolas. They also share governmental institutions, and their alliance dates to before the time of Chief Nicola, for whom the river was named and whose father had led the Okanagan migration into the valley in the late 18th century. The Scw'exmx intermarried with the Okanagans, and also with the Nicola Athapaskans, a now-extinct Athapaskan-speaking people who migrated into the valley in the 17th Century.

The British Columbia Interior, BC Interior or Interior of British Columbia, usually referred to only as the Interior, is one of the three main regions of the Canadian province of British Columbia, the other two being the Lower Mainland, which comprises the overlapping areas of Greater Vancouver and the Fraser Valley, and the Coast, which includes Vancouver Island and also including the Lower Mainland.

The Nicola Athapaskans, also known as the Nicola people or Stuwix, were an Athabascan people who migrated into the Nicola Country of what is now the Southern Interior of British Columbia from the north a few centuries ago but were slowly reduced in number by constant raiding from peoples from outside the valley, with the survivors, the last of whom lived near Nicola Lake, assimilated to the Scw'exmx-Syilx Nicola people by the end of the 19th century. The term Nicola for them is a misnomer, though a common one used by ethnologists and linguists - it commemorates a famous Okanagan chief who once held sway over the valley and its peoples as well as over the Kamloops Shuswap).

Skihist Mountain mountain in Canada

Skihist Mountain, also sometimes referred to as Skihist Peak, is the highest mountain in the Cantilever Range and in southwestern British Columbia, Canada. It is located on the southern boundary of Stein Valley Nlaka'pamux Heritage Park, about 20 km (12 mi) west of Lytton. It is the highest summit in the Lillooet Ranges, which lie between the Lillooet and Fraser Rivers, south of the Gates Valley and Seton and Anderson Lakes.

The Similkameen Country, also referred to as the Similkameen Valley or Similkameen District, but generally referred to simply as The Similkameen or more archaically, Similkameen, is a region roughly coinciding with the basin of the river of the same name in the Southern Interior of British Columbia. The term "Similkameen District" also refers to the Similkameen Mining District, a defunct government administrative district, which geographically encompasses the same area, and in more casual terms may also refer to the Similkameen electoral district, which was combined with the Grand Forks-Greenwood riding by the time of the 1966 election. The Similkameen Country has deep historical connections to the Boundary Country and the two are sometimes considered one region, partly as a result of the name of the electoral district. It is also sometimes classed as being part of the Okanagan region, which results from shared regional district and other administrative boundaries and names. The term "Similkameen District" may also historically refer to the Similkameen Division Yale Land District, which also includes Osoyoos and the Boundary Country to Osoyoos' east.

The Thompson Country, also referred to as The Thompson and in some ways as the Thompson Valley and historically known as the Couteau Country or Couteau District, is a historic geographic region of the Southern Interior of British Columbia, more or less defined by the basin of the Thompson River, a tributary of the Fraser and focused on the city of Kamloops.

The Nicola Country, also known as the Nicola Valley and often referred to simply as The Nicola, and originally Nicolas' Country or Nicholas' Country, adapted to Nicola's Country and simplified since, is a region in the Southern Interior of British Columbia, Canada. It is the main subregion of the larger Thompson Country and is often referred to separately, or in combination forms, notably the Thompson-Nicola Regional District. The combination Nicola-Similkameen is also common.


  1. 1 2 "Thompson Plateau". BC Geographical Names.
  2. James Alexander Teit (1975). "Introduction, Historical and Geographical". In Franz Boas. The Jesup North Pacific Expedition: Volume 4 - The Thomson Indians of British Columbia. AMS PRESS INC. pp. 166–181. ISBN   0-404-58115-3.
  3. 1 2 James Alexander Teit (1975). "Introduction, Historical and Geographical". In Franz Boas. The Jesup North Pacific Expedition: Volume 4 - The Thomson Indians of British Columbia. AMS PRESS INC. p. 174. ISBN   0-404-58115-3.
  4. John D. Greenough, Murray A. Roed, ed. (2004). Okanagan Geology. Kelowna Geology Committee. pp. 24–25. ISBN   0-9699795-2-5.
  5. Stuart S. Holland (1976). Landforms of British Columbia, Bulletin 48 (PDF) (Report). Province of British Columbia. pp. 71–72. Retrieved 14 November 2015.