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The Canadian Shield, also called the Laurentian Plateau, or Bouclier canadien (French), is a large area of exposed Precambrian
Precambrian
igneous and high-grade metamorphic rocks (geological shield) that forms the ancient geological core of the North American continent (the North American Craton
Craton
or Laurentia). Composed of igneous rock resulting from its long volcanic history, the area is covered by a thin layer of soil.[3] With a deep, common, joined bedrock region in eastern and central Canada, it stretches north from the Great Lakes
Great Lakes
to the Arctic Ocean, covering over half of Canada; it also extends south into the northern reaches of the United States. Human population is sparse, and industrial development is minimal,[4] while mining is prevalent.

Contents

1 Geographical extent 2 Geology 3 Ecology 4 Mining and economics 5 See also 6 References 7 Further reading

Geographical extent[edit] The Canadian Shield
Canadian Shield
is a physiographic division, consisting of five smaller, physiographic provinces: the Laurentian Upland, Kazan Region, Davis, Hudson and James.[1] The shield extends into the United States as the Adirondack Mountains
Adirondack Mountains
(connected by the Frontenac Axis) and the Superior Upland. The Canadian Shield
Canadian Shield
is U-shaped and is a subsection of the Laurentia
Laurentia
craton signifying the area of greatest glacial impact (scraping down to bare rock) creating the thin soils. The Canadian Shield is more than 3.96 billion years old. The Canadian Shield
Canadian Shield
once had jagged peaks, higher than any of today's mountains, but millions of years of erosion have changed these mountains to rolling hills.[5] The Canadian Shield
Canadian Shield
is a collage of Archean
Archean
plates and accreted juvenile arc terranes and sedimentary basins of the Proterozoic
Proterozoic
Eon that were progressively amalgamated during the interval 2.45 to 1.24 Ga, with the most substantial growth period occurring during the Trans-Hudson orogeny, between ca. 1.90 to 1.80 Ga.[6] The Canadian Shield was the first part of North America
North America
to be permanently elevated above sea level and has remained almost wholly untouched by successive encroachments of the sea upon the continent. It is the Earth's greatest area of exposed Archean
Archean
rock. The metamorphic base rocks are mostly from the Precambrian
Precambrian
Supereon (between 4.5 billion and 540 million years ago), and have been repeatedly uplifted and eroded. Today it consists largely of an area of low relief 300 to 610 m (980 to 2,000 ft) above sea level with a few monadnocks and low mountain ranges (including the Torngat and Laurentian Mountains) probably eroded from the plateau during the Cenozoic
Cenozoic
Era. During the Pleistocene
Pleistocene
Epoch, continental ice sheets depressed the land surface (see Hudson Bay), scooped out thousands of lake basins, and carried away much of the region's soil. When the Greenland
Greenland
section is included, the Shield is approximately circular, bounded on the northeast by the northeast edge of Greenland, with Hudson Bay
Hudson Bay
in the middle. It covers much of Greenland, Labrador, most of Quebec
Quebec
north of the St. Lawrence River, much of Ontario including northern sections of the southern peninsula between the Great Lakes, the Adirondack Mountains[7] of New York, the northernmost part of Lower Michigan
Michigan
and all of Upper Michigan, northern Wisconsin, northeastern Minnesota, the central/northern portions of Manitoba
Manitoba
away from Hudson Bay, northern Saskatchewan, a small portion of northeastern Alberta,[8] and the mainland northern Canadian territories to the east of a line extended north from the Saskatchewan/ Alberta
Alberta
border ( Northwest Territories
Northwest Territories
and Nunavut).[2] In total, the exposed area of the Shield covers approximately 8,000,000 km2 (3,088,817 sq mi). The true extent of the Shield is greater still and stretches from the Western Cordillera in the west to the Appalachians in the east and as far south as Texas, but these regions are overlaid with much younger rocks and sediment. The underlying rock structure also includes Hudson Bay.

Canadian Shield
Canadian Shield
geography in the Flin Flon, Manitoba
Manitoba
region. The lake in the background is Big Island Lake.

Geology[edit]

Weathered Precambrian
Precambrian
pillow lava in the Temagami Greenstone Belt

The Canadian Shield
Canadian Shield
is among the oldest on earth, with regions dating from 2.5 to 4.2 billion years.[9] The multitude of rivers and lakes in the entire region is caused by the watersheds of the area being so young and in a state of sorting themselves out with the added effect of post-glacial rebound. The Shield was originally an area of very large, very tall mountains (about 12,000 metres or 39,000 feet)[10] with much volcanic activity, but over hundreds of millions of years, the area has been eroded to its current topographic appearance of relatively low relief.[citation needed] It has some of the oldest (extinct) volcanoes on the planet.[citation needed] It has over 150 volcanic belts (now deformed and eroded down to nearly flat plains) whose bedrock ranges from 600 to 1200 million years old.[citation needed] Each belt probably grew by the coalescence of accumulations erupted from numerous vents, making the tally of volcanoes reach the hundreds. Many of Canada's major ore deposits are associated with Precambrian volcanoes. The Sturgeon Lake Caldera in Kenora District, Ontario, is one of the world's best preserved mineralized Neoarchean caldera complexes, which is 2.7 billion years old.[11] The Canadian Shield
Canadian Shield
also contains the Mackenzie dike swarm, which is the largest dike swarm known on Earth.[12]

Typical Canadian Shield: spruce, lakes, bogs, and rock.

Mountains have deep roots and float on the denser mantle much like an iceberg at sea. As mountains erode, their roots rise and are eroded in turn. The rocks that now form the surface of the Shield were once far below the Earth's surface. The high pressures and temperatures at those depths provided ideal conditions for mineralization. Although these mountains are now heavily eroded, many large mountains still exist in Canada's far north called the Arctic
Arctic
Cordillera. This is a vast deeply dissected mountain range, stretching from northernmost Ellesmere Island
Ellesmere Island
to the northernmost tip of Labrador. The range's highest peak is Nunavut's Barbeau Peak
Barbeau Peak
at 2,616 metres (8,583 ft) above sea level.[13] Precambrian
Precambrian
rock is the major component of the bedrock. The North American craton
North American craton
is the bedrock forming the heart of the North American continent and the Canadian Shield
Canadian Shield
is the largest exposed part of the craton's bedrock. The Canadian Shield
Canadian Shield
is part of an ancient continent called Arctica, which was formed about 2.5 billion years ago during the Neoarchean era. It was split into Greenland, Laurentia, Scotland
Scotland
and Siberia
Siberia
and is now roughly situated in the Arctic
Arctic
around the current North Pole. Ecology[edit] The current surface expression of the Shield is one of very thin soil lying on top of the bedrock, with many bare outcrops. This arrangement was caused by severe glaciation during the ice age, which covered the Shield and scraped the rock clean. The lowlands of the Canadian Shield
Canadian Shield
have a very dense soil that is not suitable for forestation; it also contains many marshes and bogs (muskegs). The rest of the region has coarse soil that does not retain moisture well and is frozen with permafrost throughout the year. Forests are not as dense in the north.

Typical landscape in a southern Ontario
Ontario
region with very few old growth trees, due to a history of logging and fires. Black River, Queen Elizabeth II Wildlands Provincial Park.

The Shield is covered in parts by vast boreal forests in the south that support natural ecosystems as well as a major logging industry. This boreal forest area includes ecoregions such as the Eastern Canadian Shield
Canadian Shield
taiga that covers northern Quebec
Quebec
and most of Labrador, and the Midwestern Canadian Shield forests that run westwards from Northwestern Ontario. Hydrographical drainage is generally poor, the soil compacting effects of glaciation being one of the many causes. Tundra
Tundra
typically prevails in the northern regions. Many mammals such as caribou, white-tailed deer, moose, wolves, wolverines, weasels, mink, otters, grizzly bear, polar bears and black bears are present.[14] In the case of polar bears (Ursus maritimus) the Shield area contains many of the denning locations such as the Wapusk National Park.[15] Mining and economics[edit] The Canadian Shield
Canadian Shield
is one of the world's richest areas in terms of mineral ores. It is filled with substantial deposits of nickel, gold, silver, and copper. Throughout the Shield there are many mining towns extracting these minerals. The largest, and one of the best known, is Sudbury, Ontario. Sudbury is an exception to the normal process of forming minerals in the Shield since the Sudbury Basin
Sudbury Basin
is an ancient meteorite impact crater. Ejecta from the meteorite impact was found in the Rove Formation
Rove Formation
in May 2007. The nearby, but less known Temagami Magnetic Anomaly, has striking similarities to the Sudbury Basin. This suggests it could be a second metal-rich impact crater.[16] In northeastern Quebec, the giant Manicouagan Reservoir
Manicouagan Reservoir
is the site of an extensive hydroelectric project (Manic-cinq, or Manic-5). This is one of the largest-known meteorite impact craters on Earth. The Flin Flon
Flin Flon
greenstone belt in central Manitoba
Manitoba
and east-central Saskatchewan
Saskatchewan
is one of the largest Paleoproterozoic volcanic-hosted massive sulfide (VMS) districts in the world, containing 27 copper-zinc-(gold) deposits from which more than 183 million tons[clarification needed] of sulfide have been mined.[17] The Shield, particularly the portion in the Northwest Territories, has recently been the site of several major diamond discoveries. The kimberlite pipes in which the diamonds are found are closely associated with cratons, which provide the deep lithospheric mantle required to stabilize diamond as a mineral. The kimberlite eruptions then bring the diamonds from over 150 kilometres (93 mi) depth to the surface. Currently the Ekati and Diavik mines are actively mining kimberlite diamonds. See also[edit]

Geography of Canada
Canada
portal

Athabasca Basin Platform Oldest rock Basement Platform basement Volcanology of Canada Glacial
Glacial
history of Minnesota

References[edit]

^ a b The Atlas of Canada. "Physiographic Regions Map" (JP2). Natural Resources Canada. Retrieved 2017-08-01.  ^ a b Encyclopædia Britannica. "Canadian Shield". Archived from the original on 2015-06-24. Retrieved 2009-02-10.  ^ Stephen Marshak. Essentials of Geology. 3rd ed. ^ " Canadian Shield
Canadian Shield
Archived 2006-08-21 at the Wayback Machine." in Columbia Encyclopedia. 6th ed., 2005. ^ James-Abra, Erin. "Canadian Shield". Canadian Encyclopedia. Archived from the original on 11 January 2018. Retrieved 24 January 2018.  ^ Corrigan, D. (2008). "Metallogeny and Tectonic Evolution of the Trans-Hudson Orogen" (PDF). Archived from the original (PDF) on April 9, 2008. Retrieved 2008-03-05.  ^ Peterson Field Guide to Geology of Eastern North America
North America
by Roberts, David & Roger Tory Peterson. ^ Alberta
Alberta
Heritage - Alberta
Alberta
Online Encyclopedia Archived 2010-12-08 at Archive-It
Archive-It
- The Canadian Shield
Canadian Shield
Region of Alberta ^ Tsuyoshi Iizuka, at al., Geology and Zircon Geochronolgy of the Acasta Gneiss Complex, Precambrian
Precambrian
Research, 153 (2007) pp. 179 - 208 ^ Clark, Bruce W. (1999). "Geologic History". Making Connections: Canada's geography. Scarborough, Ontario: Prentice Hall Ginn Canada. p. 95. ISBN 0-13-012635-7.  ^ Caldera
Caldera
Volcanoes Archived 2012-06-16 at WebCite Retrieved on 2007-07-20 ^ Mark Pilkington and Walter R. Roest, Removing varying directional trends in aeromagnetic data, Geophysics, vol. 63 no. 2 (1998), pp. 446–453. ^ "Barbeau Peak". Bivouac.com.  ^ World Wildlife Fund (2001). "Northern Canadian Shield
Canadian Shield
taiga". WildWorld Ecoregion Profile. National Geographic Society. Archived from the original on 2010-03-08.  ^ C. Michael Hogan (2008) Polar Bear: Ursus maritimus, Globaltwitcher.com, ed. Nicklas Stromberg Archived December 24, 2008, at the Wayback Machine. ^ 3-D Magnetic Imaging using Conjugate Gradients: Temagami anomaly Archived 2009-07-11 at the Wayback Machine. Retrieved on 2008-03-12 ^ Norris, Jessica (2007). "Report on the 2007 Diamond
Diamond
Drilling Program McClarty Lake Project, Manitoba" (PDF). Aurora Geosciences Ltd. Archived from the original (PDF) on 2008-05-30. Retrieved 2008-02-22. 

Further reading[edit]

Library resources about Canadian Shield

Resources in your library Resources in other libraries

Schwartzenberger, Tina (2005), The Canadian Shield, Weigl Educational ISBN 1-55388-141-9 Pazynych V.G. Formation of placer gold deposits in Canadian Shield during late Wisconsin
Wisconsin
glaciation

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Continental glaciations

General

Canadian Shield Glacial
Glacial
history of Minnesota Lake Agassiz Lake Chicago Lake Tight Last Glacial
Glacial
Maximum Laurentide Ice Sheet List of prehistoric lakes Post-glacial rebound Proglacial lake Teays River Timeline of glaciation

Landforms

Erosional

Fjord Glacial
Glacial
striae Ribbon lake Roche moutonnée Tunnel valley U-shaped valley

Depositional

Drumlin Drumlin
Drumlin
field Erratic block Moraine Pulju moraine Rogen moraine Terminal moraine Till plain Veiki moraine

Glacifluvial

Diluvium Esker Giant current ripples Kame Kame
Kame
delta Kettle hole Outwash fan Sandur

North American places

Canada

Arrowhead Provincial Park, Ontario Big Rock (glacial erratic), Alberta Cypress Hills (Canada), Saskatchewan Eramosa River, Ontario Eskers Provincial Park, British Columbia Foothills Erratics Train, Alberta Lion's Head Provincial Park, Ontario Origin of the Oak Ridges Moraine, Ontario Ovayok Territorial Park, Nunavut

United States

Chippewa Moraine
Moraine
State Recreation Area, Wisconsin Coteau des Prairies, South Dakota Devil's Lake State Park, Wisconsin Glacial
Glacial
Lake Wisconsin, Wisconsin Glacial
Glacial
Lakes State Park, Minnesota Horicon Marsh
Horicon Marsh
State Wildlife Area, Wisconsin Ice Age Floods National Geologic Trail, Idaho, Oregon & Washington Ice Age National Scientific Reserve, Wisconsin Ice Age Trail, Wisconsin Interstate State Park, Minnesota
Minnesota
& Wisconsin Kelleys Island, Ohio Kettle Moraine
Moraine
State Forest, Wisconsin Lake Bonneville, Utah Lake Lahontan, Nevada Lake Missoula, Montana Mill Bluff State Park, Wisconsin Oneida Lake, New York Two Creeks Buried Forest State Natural Area, Wisconsin Withrow Moraine
Moraine
and Jameson Lake Drumlin
Drumlin
Field, Washington Yosemite National Park, California

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Antarctica Hardangerfjord Killary Harbour Lambert Glacier Monte Rosa Ross Ice Shelf Svalbard

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Wisconsin
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Africa

African Alpine System (Atlas Mountains) African massive (Sahara Mid-African) South African Platform (Kalahari Region Lunda Swell Matabele Upland Veldt High Karoo Damara–Nama Upland Namib Desert Cape Mountains Natal Terrace Belt Mozambique Plain Madagascar) East African Highlands

Rift Valley Abyssinian

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Arctic
Lowlands Atlantic Plain Canadian Shield Hudson Bay
Hudson Bay
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Mountain
System Rocky Mountain
Mountain
System Sierra Madre System Baja California Peninsula Buried Ranges Central Meseta Gulf Coastal Lowlands Neovolcanic Plateau Chiapas–Guatemala Highlands Gulf Coast Plain
Plain
and Yucatán Peninsula Andean Mountain
Mountain
System Brazilian Highlands Guiana Shield Amazon Plain Orinoco Basin Paraná–Paraguay Plain Patagonian Plateau

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East Antarctica West Antarctica

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West Australian Shield East Australian Shield East Australian Cordillera

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Fenno-Scandian Shield Central European Uplands Alpine System Great European Plain Ural Mountains Middle East Eastern Highlands Fertile Crescent West Siberian Plain Central Siberian Upland Eastern Highlands Northern Asian Mountains North Indian Plain Himalayan Mountain
Mountain
System Deccan Plateau Central Asian Lowlands

See also: Physical geography
Physical geography
and Physiographic regions of the world

Coordinates: 52°00′N 71°00′W / 52.000°N 71.000°W / 52.000; -71.000

Authority control

WorldCat Identities VIAF: 239998762 LCCN: sh85019

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