Borderlands: Eastern Physiographic Regions

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Abstract

Canada’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 the eastern physiographic regions which include the Appalachian Region and the St. Lawrence Lowlands.

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The physical geography of Canada comprises two great parts: the Shield and the Borderlands. The Shield consists of a core of old, massive, Precambrian crystalline rocks. The Borderlands areas are formed by younger rocks and surround the Shield like two rings. The inner ring comprises a chain of lowlands, plains and plateaus of generally flat-lying sedimentary rocks. The outer ring consists of discontinuous areas of mountains and plateaus in which the younger rocks are deformed. Each of these areas is divided into regions, each of which comprises many smaller subdivisions that are distinctive based on their topography and geology.

The Eastern Physiographic Regions

The Appalachian Region

The Appalachian Region extends from southern Quebec and Gaspésie to encompass New Brunswick, Nova Scotia, Prince Edward Island and the island of Newfoundland. It is divided into a large number of physiographic units, the physiography being dominated by a well-developed peneplain that is generally highest in the northwest and slopes gently southeastward to the ocean.

On the island of Newfoundland, the Appalachian Region 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 Quebec–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 Îles-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 Gaspé. 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 Mégantic 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 Mégantic Hills lie astride the Canada–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 Region.

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Gros Morne National Park, Newfoundland and Labrador

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Cape Breton Island, Nova Scotia

The St. Lawrence Lowlands

The 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 units: the West St. Lawrence Lowland, the Central St. Lawrence Lowland and the East St. Lawrence 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 St. Lawrence 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 St. Lawrence Lowland includes the area between the Ottawa and St. Lawrence rivers, straddling the St. Lawrence as far as the city of Québec 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 St. Lawrence Lowland includes Anticosti Island, Îles 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 St. Lawrence Lowlands.

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Trois-Rivières, Quebec

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Sainte-Anne-de-la-Pérade, Quebec