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Canadaâ€™s landscape is very diversified and comprises several distinctive areas, called physiographic regions, each of which has its own topography and geology. This map shows the location of these physiographic regions, including their subregions and divisions.

These are the physiographic regions of Canada:

The Canadian Shield

The landscape of the Shield has been levelled by many long periods of erosion and presents an even, monotonous skyline interrupted by rounded or flat-topped summits and ranges of hills. The surface of the Shield is mainly the result of glaciation and a great proportion of it is covered by water in the form of lakes, ponds and swamps. The most outstanding characteristic of the Shield is the similarity of the terrain, whether you are in Labrador, northern Quebec and Ontario, or the Northwest Territories.

The Canadian Shield is divided into four subregions:

Kazan Region

The Kazan Region is located in the northern part of Manitoba and Saskatchewan, and also covers parts of the Northwest Territories and Nunavut. It consists of vast areas of massive rocks that form flat, broad, sloping uplands, plateaus and lowlands. The Kazan Region is divided into several subregions: the Coronation Hills, the Bathurst Hills and the East Arm Hills; the Boothia Plateau and the Wager Plateau; the Kazan Upland and the Bear-Slave Upland; the Athabasca Plain, the Thelon Plain; and the Back Lowland.

The following photographs are examples of the type of terrain found in the Kazan Region.

Davis Region

The Davis Region extends from Ellesmere Island south and southeastward to northern Labrador. The general aspect of its landscape is that of a broad, old erosion surface almost without surficial deposits. Viewed from an elevated location, the landscape presents an even horizon interrupted by rounded or flat-topped ranges of hills. Along the eastern coast, the relief is generally high. The region is divided into a northern insular part and a southern mainland part. The subdivisions are the Davis Highlands and the Labrador Highlands; the George Plateau and the Melville Plateau; the Frobisher Uplands, the Hall Uplands and the Baffin Uplands; the Baffin Coastal Lowlands and the Whale Lowlands.

The following photographs show examples of the terrain from the Davis Region.

James Region

The James Region exhibits the characteristic features of the Shield that are apparent in major uplands and plateaus. This region spreads from the centre of Manitoba to Labrador, lying south of the Hudson Region. The James Region encompasses several subregions consisting of hills (Port Arthur, Penokean, Mistassini, Labrador and Povungnituk), plateaus (Saglouc, Larch, Caniapiscau and Lake), uplands (Abitibi and Severn), plains (Nipigon and Cobalt) and lowlands (Eastmain).

The following photographs show examples of landscape from the James Region.

Laurentian Region

The Laurentian Region comprises uplands and highlands that rise abruptly above the St. Lawrence Lowlands along their northwestern border. It borders the St. Lawrence Lowlands from Georgian Bay to the Atlantic Ocean and includes the Laurentian Highlands, Mealy Mountains, MÃ©catina Plateau, Hamilton Plateau, Hamilton Upland, Melville Plain and Lake St-Jean Lowlands.

The following photographs show examples of landscape found in the Laurentian Region.

The Hudson Bay Lowland

The Hudson Bay Lowland form the main central depression on the surface of the Canadian Shield. The Hudson Bay Lowland is a low, swampy plain with subdued glacial features and a belt of raised beaches that border the Hudson Bay.

The following photographs show examples of landscape found in the Hudson Bay Lowland.

The Arctic Lands

The Arctic Lands are divided into three subregions:

Innuitian Region

Arctic Coastal Plain

Arctic Lowlands

Innuitian Region

The Innuitian Region is characterized by two zones of mountains that are separated by extensive and discontinuous terrain of more subdued topography formed by plateaus, uplands and lowlands.

The mountain ranges include the Grantland, the Axel Heiberg, and the Victoria and Albert mountains. On central Axel Heiberg Island and northwestern Ellesmere Island, the mountains are nearly buried by ice sheets through which the peaks project as a row of nunataks. Between these two large mountainous zones lies the Eureka Upland. To the south are the Perry Plateau and the Sverdrup Lowlands, a region of low relief, rolling, and scarped lowland.

The following photographs show examples of landscape found in the Innuitian Region.

Arctic Coastal Plain

The Arctic Coastal Plain includes the coastal terrain along the shores of the Arctic Ocean from Meighen Island to Alaska. It is divided into three divisions, each of which has distinctive physiographic characteristics:

The Island Coastal Plain extends from Meighen Island to Banks Island, sometimes characterized by hilly terrain that carries an ice cap and sometimes by a low, flat, uniform landscape or by low hills;

The Mackenzie Delta includes not only the delta of the present river but remnants of earlier deltas and features built by the deposition of a mix of sediments coming from the river and from the sea. A multitude of lakes and channels cover the Mackenzie Delta plain and, in the older parts, pingos form the most outstanding features of the landscape;

The Yukon Coastal Plain, which lies at a higher altitude than the Mackenzie Delta, appears to be largely an erosion surface cut into bedrock and mantled by a thin veneer of recent sediments.

The following photographs show examples of the landscape of the Arctic Coastal Plain.

Arctic Lowlands

The Arctic Lowlands include the Lancaster Plateau, Foxe Plain, Boothia Plain, Victoria Lowland and Shaler Mountains.

The surface of the Lancaster Plateau slopes gently southward from about 770 metres on southern Ellesmere Island, across central Devon Island, to an average elevation of 300 to 600 metres on Somerset Island and the Brodeur Peninsula of northwestern Baffin Island. The landscape is uniformed. Farther south, the surface descends still lower until it forms the surface of the Boothia Plain on both sides of the Gulf of Boothia.

Surrounding Foxe Basin, the landscape of the Foxe Plain is low and smooth. It forms a very shallow basin-like area on the old surface, partly covered by very shallow sea. Farther west, the Shaler Mountains rise through the Victoria Lowlands.

The following photographs show examples of the landscape from the Arctic Lowlands.

The Interior Plains

The Interior Plains occupy the region between the Canadian Shield on the east and the mountains of the Cordillera on the west. They join with the Great Lakes - St. Lawrence Lowlands of eastern Canada through the United States and are separated from the Arctic Lowlands by the Amundsen Gulf. The southern part is characterized by semi-arid prairie, the central part is tree covered and the northern part is covered by the tundra. The region is divided into several subdivisions, those in the north being smaller and more varied than those in the south.

In the north, the Horton and Anderson Plains form the Arctic slope. The Peel Plain, which lies southwest of the Mackenzie River, forms a broad, shallow hollow in which some areas have innumerable small lakes and others have none.

West of the Peel Plain, the Peel Plateau rises in steps between the Peel Plain and the Mackenzie Mountains. On the east, the Colville Hills embrace several ridges that stand above the general level of the surrounding plains. Located around Great Bear Lake, the Great Bear Plain has a rolling surface. In contrast, the Great Slave Plain has generally little relief.

Located in the centre of the Interior Plains, the Alberta Plateau consists of a ring of plateaus separated by wide valleys. The two main valleys (Fort Nelson and Peace River lowlands) occupy more than 50 per cent of the area. These two rivers and their main tributaries are more or less entrenched into the valleys.

South of the Athabasca River, the Alberta Plain stretches southeastward to the Canadaâ€"United States boundary. Although a continuation of the Alberta Plateau, it has a more even surface, with a few widely separated groups of low hills, such as Cypress Hills in the south. The Cypress Hills reach an elevation of more than 1400 metres.

The eastern edge of the Alberta Plain forms a step down to Saskatchewan Plain, which is lower and smoother than the Alberta Plain. On the east, the Saskatchewan Plain is bordered by the Manitoba escarpment, overlooking the Manitoba Plain. Streams flowing eastward have deep cut valleys, which divide the Manitoba Plain into a line of separate hills. The Manitoba Plain is largely covered by lakes and includes most of Lake Winnipeg.

The following photographs show examples of landscape from the Interior Plains.

The Cordillera

The Cordillera is divided into three large linear zones called the Eastern System, the Interior System and the Western System. Each system is further divided into areas and subdivided into mountains, ranges, plateaus, hills, valleys, trenches, basins and plains. Each has its own geological and physiographic characteristics. The Cordillera is also divided transversely into a number of segments by east-west belts of relatively low terrain.

In the Interior and Western systems, some landforms have been produced by volcanic processes. Most striking, however, are three great shield-like volcanoes in the northwestern part of the Interior Plateau and a group of similar volcanoes on the Stikine Plateau. Also on the Stikine Plateau are a number of flat-topped volcanoes that erupted during the Pleistocene Epoch (the Ice Age between about 80 000 and 10 000 years before the present time). A large number of small volcanoes and cinder cones occur singly, in line or in groups. These range in age from pre-Pleistocene to within a few hundred years of the present and vary in height up to a few tens of metres. For more information, refer to the map on Major Volcanic Areas in Environment / Natural Hazards.

The following photographs are examples of landscape from the Cordillera.

Great Lakes - St. Lawrence Lowlands

The Great Lakes - St. Lawrence Lowlands border the Shield on the southeast, extending from the west end of Lake Huron and the head of Lake Erie northeasterly to the Strait of Belle Isle. They comprise three subregions: the West Lowland, the Central Lowland and the East Lowland. The lowlands are plain-like areas that were all affected by the Pleistocene glaciations and are therefore covered by surficial deposits and other features associated with the ice sheets.

The West Lowland is broken into two parts by the Niagara Escarpment, which extends from the Niagara River on a sinuous westerly and northwesterly course to the Bruce Peninsula and Manitoulin Island. The surface west of the escarpment slopes gradually southwestward through an area of rolling topography of low relief. East of the escarpment, the land rises gently northward from Lake Ontario;

The Central Lowland includes the area between the Ottawa and St. Lawrence rivers, straddling the St. Lawrence as far as the city of QuÃ©bec and extending a short distance beyond the city on the north shore only. The land is rarely more than 150 metres above sea level, except for the Monteregian Hills, which consist of intrusive igneous rocks

Finally, the East Lowland includes Anticosti Island, ÃŽles de Mingan, and several small areas bordering the Gulf of St. Lawrence and the Strait of Belle Isle, as well as the Newfoundland Coastal Lowland.

The following photographs show examples of landscape from the Great Lakes - St. Lawrence Lowlands.

Appalachian Uplands

The Appalachian Uplands extends from southern Quebec and GaspÃ©sie to encompass New Brunswick, Nova Scotia, Prince Edward Island and the island of Newfoundland.

On the island of Newfoundland, the Appalachian Uplands comprises three highlands that form a group called the Newfoundland Highlands. They are rugged with steep slopes and elevations vary from 180 to 820 metres. On the east side, the Atlantic Uplands of Newfoundland lie between 180 and 300 metres in elevation, and the Newfoundland Central Lowland extends from sea level up to 150 metres. Its surface is gently rolling and generally underlain by glacial sediments.

Nova Scotia is divided into three highland areas, three uplands and several small lowlands. The Nova Scotia Highlands include the Cobequid Mountains in the west, the Antigonish Highlands in the centre and the Cape Breton Highlands to the northeast. South of these highlands lay the Nova Scotia Uplands and the Annapolis Lowlands.

New Brunswick comprises three large units: the New Brunswick Highlands; the Chaleur Uplands, which cross the Quebecâ€"New Brunswick border; and the Maritime Plain, which stretches around the coast of New Brunswick and Nova Scotia from the south shore of Chaleur Bay and includes Prince Edward Island and ÃŽles-de-la-Madeleine.

In Quebec, the Chaleur Uplands are bounded on the north by the Notre-Dame Mountains, which extend from near Thetford Mines to Baie de GaspÃ©. In the Notre-Dame Mountains area, there are the Chic-Chocs Mountains which have the highest elevation at more than 1230 metres in the north. To the southwest, the summits are lower, like the areas of MÃ©gantic Hills and Sutton Mountains, which merge with the Eastern Quebec Uplands. The Sutton Mountains are a continuation of the Green Mountains of Vermont; and the MÃ©gantic Hills lie astride the Canadaâ€"United States boundary and are part of the larger White Mountains of the New England states.

The following photographs show examples of landscapes from the Appalachian Uplands.

Definitions of underlined terms

Arete

Steep-sided mountain ridge also spelled arÃªte

Escarpment

A long steep slope at the edge of a plateau

Esker

Sinuous ridges composed of glacial material deposited by meltwater currents in englacial tunnels. Their orientation is generally parallel to the direction of glacial flow, and they sometimes exceed 100 kilometres in length.

Fjord

Deep and narrow glacial valley invaded by sea water after the retreat of the glacier

Ground ice

Ice formed into the ground

Horn

A pyramidal peak with three or more distinct faces steepened by glacial undercutting

Ice wedge

Piece of ice, generally has the shape of a wedge with the apex pointing towards the bottom. This ice is vertically foliated and is generally white.

Igneous rock

Rocks that are formed from molten materials that come from the depths of the Earth. They are also referred to as magmatic rocks.

Nunatak

Inuit-derived word describing a mountain completely surrounded by an ice cap

Patterned ground

Ground where the surface presents regular patterns such as circles, polygons or parallel lines

Permafrost

A layer of permanently frozen soil and rock. The active layer of permafrost refers to that portion of the ground that freezes in winter and thaws in summer; this layer is usually less than one metre in depth.

Pingo

Small hills with an ice core growing by water injection; they are covered with soil and vegetation

Pleistocene

An epoch of the Quaternary period, after the Pliocene of the Tertiary and before the Holocene. Pleistocene was between about 80 000 and 10 000 years before the present time.

Precambrian rock

Rock that originates from the geologic period in history from about 4.5 to 5 billion years ago to about 570 million years ago. Precambrian rock covers about 75% of the land area of the earth.

Sedimentary rock

Sedimentary rocks are the product of the consolidation of loose sediment that has accumulated in beds. These sediments settle gradually under the weight of overlying beds and are transformed into solid sedimentary rock by cementation.

Surficial deposits

Unconsolidated materials covering the ground

Thermokarst

Karst-like topographic feature produced in a permafrost region by the local melting of ground ice and the subsequent settling of the ground.

Till

Any sediment that is transported and deposited by a glacier without being sorted by meltwater. It consists of clay, sand and large rock fragments that are deposited in irregular sheets or in ridges called moraines.

Tundra

The treeless area to the north of the boreal forest. Tundra vegetation includes low, matted and erect shrubs and herbs such as cottongrass.

Physiographic Regions

Map Source

Map. Physiographic Regions of Canada. 1254A. Scale 1:5M compiled by H.S. Bostock. 1967. Geological Survey of Canada.

Map References

Bone, R. M. 2003. The regional geography of Canada. Don Mills, Ont: Oxford University Press.

Douglas, R.J.W. (Scientific Editor). 1972. Geology and Economic Minerals of Canada. Geological Survey of Canada.

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The Atlas of Canada - Physiographic Regions

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Canadaâ€™s landscape is very diversified and comprises several distinctive areas, called physiographic regions, each of which has its own topography and geology. This map shows the location of these physiographic regions, including their subregions and divisions.

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How Was the Canadian Shield Formed?

The mountains of the Canadian Shield were subsequently eroded by weather such as wind and rain. Comparable to sandpaper on wood, these forces slowly wore down the mountains, so that by about 800 million years ago, the low-relief surface of the Shield had been created. In the case of the Grenville Mountains, it's estimated that tens of kilometres of rock may have been worn down.

These weathering processes were interrupted by a number of ice ages occurring over the last 2.5 million years. Like weather, as glaciers grow and move they also smooth the landscape, as well as move sediment. When they retreat, glaciers release the material they've been transporting and the deposited sediments become the origin of soils.

The most recent glaciation to affect the area was the Wisconsin glaciation that began around 110,000 years ago. During this glaciation, the Shield was covered by the Laurentide Ice Sheet, a giant expanse of ice as much as 3 km thick. As the ice retreated from the southern part of present-day Canada - a process that began as recently as 11,000 years ago - it cut the basins of the Great Lakes as well as the thousands of lakes throughout the Canadian Shield.

Geology

The Shield can be divided into seven geologically distinct regions sometimes referred to as provinces. They are the Nain, Grenville, Southern, Superior, Churchill, Slave and Bear provinces. Each is home to rock of different ages, types and formation characteristics, as well as different mineral deposits. The Southern Province, for example, is home to the mining district of Sudbury, Ontario, known for its production of copper and nickel. North of this region, the Superior Province is one of Canada's most important sources of metals, including deposits of copper, gold, iron and silver. The Bear province includes deposits of copper and uranium, while the Slave province is being explored and mined for diamonds. The Churchill and Grenville provinces contain deposits of uranium, lead and zinc. Finally, the Nain province is the smallest of the seven regions, and is not a major mineral producer.

DID YOU KNOW?
The Canadian Shield contains some of the oldest rocks on Earth. In 2008, researchers estimated rock found on the northern shore of Hudson Bay, 40 km south of Inukjuak, to be 4.28 billion years old. Its age means the rock was created approximately 300million years after the formation of Earth. Previously, the oldest rocks in the world were thought to be southeast of Great Bear Lake, in the Northwest Territories. These rocks were estimated to be 4 billion years old.

Physical Features and Landforms

In addition to the thousands of small lakes throughout the Shield, the region also borders many of the larger lakes and waterways of Canada: the eastern shores of Great Bear Lake, Great Slave Lake, Lake Athabasca and Lake Winnipeg; the northern shores of Lake of the Woods, Lake Superior and Lake Huron; and the north shore of the St. Lawrence River.

Vegetation

The Canadian Shield is dominated by the boreal forest ecosystem. Common coniferous trees include white and black spruce; jack, red, white and eastern white pine; balsam fir; tamarack; eastern hemlock; and eastern red cedar. Deciduous trees include red and mountain maple; white and paper birch; trembling aspen; black ash; and balsam poplar.

North of the boreal forest is the Arctic tundra ecozone, characterized by low-growing vegetation and few to no trees. Because most of the tundra is underlain by permafrost, vegetation is not able to put down deep roots, stunting growth.

Wildlife

A wide range of wildlife calls the Canadian Shield home. Lakes and rivers in the south house a variety of fish species including trout, burbot and northern pike. In addition to fish, lakes are often spotted with a mix of waterfowl including wood ducks, Canada geese and American black ducks. Other birds include boreal owls , great horned owls, blue jays and white-throated sparrows, while mammals include caribou, deer, wolves, lynx, moose, black bears and beavers .

Moving north into the tundra, wildlife, like vegetation, becomes increasingly sparse. Animals in the Arctic portion of the Shield include polar bears, Arctic fox, Arctic hares, snowy owls and rock ptarmigan.

Natural Resources

The Canadian Shield is rich in natural resources, including minerals, forests and freshwater. Mining began in the region in the mid-19th century and was key to Canada's economic development. Various minerals and precious stones have been mined or continue to be mined on the Shield, including gold, silver, copper, zinc, nickel, iron, uranium and diamonds.

The first modern hard-rock mine in the Canadian Shield, near Madoc, Ontario, opened in 1866 after gold was found there. Substantial gold discoveries were also made in Ontario at Kirkland Lake in 1906 and Timmins in 1912, and in Québec at Rouyn-Noranda in 1920. Around the same time, silver was discovered near Cobalt , Ontario, in 1903. The town prospered during the silver rush of the early 20th century, before going into decline in the 1920s. While gold mines still operate near Kirkland Lake and Timmins, there are no longer any active mines in Colbalt or Rouyn-Noranda - a reality not uncommon for early mining towns.

Today, the largest concentration of active mines on the Shield - and in the world - is located around Sudbury, Ontario. Metals mined here include copper, nickel, gold and palladium.

Kimberlites - formations where diamonds can be located - are scattered throughout the Shield, with the largest deposit located near Lac de Gras, Northwest Territories, about 300 km northeast of Yellowknife. Canada's first diamond mine - called Ekati - opened there in 1998.

DID YOU KNOW?
Sudbury, Ontario, was hit by a meteorite about 1.85 billion years ago, creating a crater known as the Sudbury Structure. The basin is 60 km long and 30 km wide and home to the rich metal resources found in the area. Metals such as copper and nickel are the result of the Earth's crust melting after the meteorite hit.

Given the prominence of the boreal forest throughout the Canadian Shield, forestry is also a prominent industry. Many of the small towns and villages scattered throughout northern Ontario and Québec were founded around pulp and paper mills and other forestry-related activities (e.g., Atikokan, Ontario).

Human History

The Canadian Shield is the traditional territory of several Indigenous peoples. The Innu made their home on the Shield in what is now Québec and Labrador, while the Cree, Anishinaabeg and Métis occupied large swaths of the region through Québec, Ontario, Manitoba, Saskatchewan and Alberta. The traditional territory of the Dene and Inuit includes the sections of the Shield now covered by the Northwest Territories and Nunavut. As Europeans began to settle and colonize the country, beavers found in the Shield region became a source for the fur trade ( see also Exploration). Learning from Indigenous people, coureurs de bois, voyageurs and explorers used the birchbark canoe to travel and trade along the Shield's many waterways. Later, beginning in the mid-1800s, railway construction meant blasting through Canadian Shield rock, exposing valuable minerals in the process. While the bare rock, thin soils, muskeg and insects of the Shield made living there difficult, the development of resource-based industries, such as mining and forestry, promoted increased settlement. Hydroelectric developments such as those at Churchill Falls, Labrador, James Bay, Québec, and Kettle Rapids, Manitoba, continue to feed electricity to urban centres in the south.

The historic mapping of this area was done by Alexander Murray, who, in 1851-52, examined the geology around the Gananoque, Ottawa and St. Lawrence rivers, as well as the perimeter of the Shield from Kingston to Lake Superior. ( See also Geological Survey of Canada.)

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The Canadian Shield refers to the exposed portion of the continental crust underlying the majority of North America. The crust, also known as the North American...

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History, politics, arts, science & more: the Canadian Encyclopedia is your reference on Canada. Articles, timelines & resources for teachers, students & public.

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The Interior Plains is a vast physiographic region that spreads across the Laurentian craton of central North America. The region extends from the Gulf Coast region to the Arctic Ocean along the east flank of the Rocky Mountains. In Canada the region separates the Rocky Mountains from the Canadian Shield.

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A cordillera is a major system of often parallel mountain ranges that includes the intervening plateaus, valleys and plains.

The term is Spanish and dates from the early 18th century. It derives from the Old Spanish word cordilla, which was the diminutive form of cuerda (meaning "cord," "string" or "rope"), from the Latin chorda. The Spanish used the plural term cordilleras to refer to the parallel Andean mountain ranges of South America. While cordilleras of this definition are found around the world, outside of North and South America, the singular term typically refers to individual mountain ranges.

On the North American continent, the westernmost physiographic region that extends from Mexico to Alaska is commonly called the Western Cordillera, Cordilleran region, or simply Cordillera. The Canadian portion of this system includes the Rocky Mountains and the Coast Mountains. While the Canadian Cordillera covers most of British Columbia and Yukon, it also extends into parts of Alberta and the Northwest Territories.

The Arctic Cordillera is a series of mountain ranges in northeastern Nunavut and northern Labrador. This is also the name of the region's ecozone ( see Natural Regions).

See also Geological Regions; Vegetation Regions; Spanish Exploration

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A cordillera is a major system of often parallel mountain ranges that includes the intervening plateaus, valleys and plains. The term is Spanish and dates from the early 18th century. It derives from the Old Spanish word cordilla, which was the diminutive form of cuerda (meaning "cord," "string" or "rope"), from the Latin chorda.

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The Appalachian Region started its development in the Paleozoic geologic era about 300 million years ago. This region covers many areas such as, New Brunswick, Nova Scotia, Prince Edouard Island,…

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St. Lawrence Lowland is a plain along the St. Lawrence River between Québec City in the east and Brockville, Ontario, in the west, including the Ottawa River valley west to Renfrew, Ontario.

The topography of the Lowlands is the result of weathering and erosion by rivers of the nearby flat-lying early sedimentary rock (photo by Thomas Kitchin).

St. Lawrence Lowland is a plain along the St. Lawrence River between Québec City in the east and Brockville, Ontario, in the west, including the Ottawa River valley west to Renfrew, Ontario. The lowland's total area is 46,000 km ² (5,000 km 2 of which is in the United States). It is 450 km long west to east and 100 km wide in the western half, narrowing to 35 km at Québec. In addition, an arm extends 130 km south into the Lake Champlain valley.

Geological History

The details of the lowland's present landscape are the result of the last continental glaciation, followed by marine submergence, emergence and, finally, river erosion and deposition. Evidence of early glaciation has been obliterated by later ones, but deposits exposed in valleys near Lac Saint-Pierre indicate that an early interval of weathering and deposition of river gravels was followed by at least two episodes of glaciation. These were separated by a non-glacial interval during which peat and lake sediments accumulated. This interval lasted from about 70,000 to possibly 34,000 years ago.

The last major glacial advance covered the region prior to 18,000 years ago. This ice sheet eventually retreated with minor re-advances, intermittently uncovering the south and southwest parts of the lowlands, which were then inundated by pro-glacial lakes. Residual glacier ice obstructing the St. Lawrence Valley near Québec disintegrated 13,000 years ago and the sea flooded the region, forming a body of water known as the Champlain Sea.

From 13,000 to 10,000 years ago the St. Lawrence Lowland rose rapidly (as much as 20 m per century) in response to the disappearance of the ice mass. The highest relict strand lines of the Champlain Sea are now 230 m above sea level on the north side of the lowlands and 75 m lower on the south side.

The sea withdrew 9,500 years ago and for a short time a lake with a surface at 40 m (present elevation) occupied the central part of the basin. It drained when the St. Lawrence River eroded its channel past Québec deeper, and the present course of the river became established around 6,500 years ago.

Geography

Altitudes range from 15 m above sea level along the St. Lawrence River northeast of Montréal to 150 m along the borders with the Laurentian Mountains to the north, the Adirondacks to the south and the gradual transitions to the Appalachians in the southeast and the Precambrian Shield of Ontario in the west.

Tributaries of the St. Lawrence that drain the lowland from the south are the Châteauguay, Richelieu, Yamaska, Saint-François, Nicolet, Bécancour and Chaudière rivers, and from the north, l'Assomption, Maskinongé, Saint-Maurice, Batiscan and Sainte-Anne rivers. Tributaries of the Ottawa River crossing the lowland are the South Nation, Rideau, Mississippi, Madawaska and Bonnechere rivers.

The large-scale topographic features are the result of subaerial weathering and erosion by rivers, during the last 100 million years, of the nearly flat-lying early Paleozoic sedimentary rocks of the lowland. The rocks from oldest (lowest) to youngest (uppermost) are sandstone, dolomite, limestone and shale, ranging from 520 to 480 million years old. These sediments are in a basin surrounded by older, more resistant crystalline rocks. Below the sedimentary rocks is an ancient surface of moderate relief that was eroded on the older Precambrian rocks.

The lowland is dominated by the Monteregian Hills, a series of isolated mountains in a belt about 20 km wide extending east from Montréal to the Appalachians. They are, from west to east, Mont-Royal (231 m), Saint-Bruno (213 m), Saint-Hilaire (404 m), Saint-Grégoire (229 m), Rougemont (366 m), Yamaska (411 m), Shefford (518 m) and Brome (548 m). All are erosional remnants of igneous intrusions of the early Cretaceous age (144-97.5 million years ago). Whether any volcanoes existed above the intrusions is unknown because no direct evidence remains.

Igneous dikes and sills radiate from the Monteregian Hills, and some support terraces around the mountains, and form parts of the Lachine Rapids in the St. Lawrence River. Hills of Precambrian crystalline rocks project through the sedimentary rocks of the lowland 30-50 km west of Montréal at the Oka Hills (260 m), Rigaud Mountain (213 m) and a hill near Saint-André-Est (137 m). An estimated 800-1,200 m of rock has been eroded from the lowland in the last 100 million years. The north boundary is an eroded fault line escarpment in many places.

The lowland is part of a rift valley originating in Cretaceous times, and is a region of high earthquake probability where major damage can be expected; during historical times about 10 major earthquakes have occurred in each century.

Soil

Much of the St. Lawrence Lowland is underlain by clay deposited in the Champlain Sea. It is as thick as 60 m along the north side near the former glacier margin and becomes progressively thinner until it virtually disappears. When subjected to excessive water percolation from rain or snowmelt, the clay becomes unstable and often subsides in earth-flow landslides, which have caused much loss of life and property.

The west and south parts of the lowland are underlain by glacial deposits (till) rather than marine clay. Wave action has removed the silt and clay from the till, leaving behind sand and gravel, so that beach deposits are common on the hills in this region. Around the margins of the lowland are numerous sand and gravel beaches, spits and bars representing former water levels. Fossils are abundant in Champlain Sea deposits, including foraminifera, molluscs and vertebrates such as seals and whales, and indicate that these waters were similar to those of the present Labrador coast and Gulf of St. Lawrence.

In the lower, central part of the lowland, areas of sand north and east of Montréal are remnants of former deltas of the Ottawa and St. Lawrence rivers. Low terraces covered by river sands occur in the east part of the lowland. Some of the sand has been formed into dunes; locally these have elongated, sharp crests as high as 18 m and are called "crêtes de coq." The aeolian sand is stabilized by vegetation. Along the Ottawa and St. Lawrence rivers from Ottawa to Lac Saint-Pierre are trough-like abandoned river channels as wide as 2 km, with banks as high as 10 m.

On the plain east of Montréal, roughly parallel to the St. Lawrence, are ridges of bouldery sand 1.5-4.5 m high and 30 m wide, which appear to be material transported and pushed up by floating river ice during the river's early stages. The ridges have provided excellent building sites and road locations, and many rural communities are built on them.

Much of the lowland is good agricultural land. Its clay has been used for brick and tile manufacture, and the sand and gravel deposits are exploited for road metal and construction material. The rocks of the lowland have been quarried for building stone, silica, cement, lime, crushed stone and concrete aggregate and for making brick and tile.

Settlement

The lowland was occupied by ​Iroquoian-speaking people at the time Jacques Cartier arrived in 1535. The farmlands were settled in the pattern of narrow strips fronting on the river, characteristic of the seigneurial system. Industry began near Trois-Rivières where bog iron was exploited in 1737. The St. Lawrence Lowland now cradles the largest part of the population of Québec.

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St. Lawrence Lowland is a plain along the St. Lawrence River between Québec City in the east and Brockville, Ontario, in the west, including the Ottawa River valley west to Renfrew, Ontario. The topography of the Lowlands is the result of weathering and erosion by rivers of the nearby flat-lying early sedimentary rock (photo by Thomas Kitchin).

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7 Regions of Canada | Song For Kids | Social Studies

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The Great Lakes-St. Lawrence Lowlands - Regions of Canada - Social Studies

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