Canadian Shield

The Canadian Shield is an enormous circular landform in North America, stretching at least two million square miles across much of Canada. The shield was formed billions of years ago when plates in Earth's crust collided and pushed upward. Other natural forces, including glaciers and erosion, wore away at the exposed rock. In modern times, much of the rock is still exposed or covered by only thin layers of soil. The Canadian Shield is notable for its thousands of small lakes and heavily forested areas. Humans have lived in the region since prehistoric Aboriginal groups, and now the Shield is home to millions of Canadians. Canada values the shield region mostly for its natural resources, including lumber, minerals, and hydroelectric power derived from its rivers.

Background

The Canadian Shield formed early in Earth's history as tectonic plates, huge sections of the planet's crust, shifted and collided. More than three billion years ago, plates met in what is today North America. The enormous power of the plates pushing together forced up rock and other material into mountain-like masses reaching from what is now Mexico to Greenland.

Over millions of years, natural forces such as erosion and glaciers wore down the peaks of these rocky landforms. Meanwhile, other processes of nature caused much of the exposed plate to be covered with soil. In many areas, this soil gathered into very thick coverings that eventually gave rise to grass, trees, and other plant life. Animals and later humans ultimately moved into these areas.

One huge section of Earth's rocky crust remained largely exposed or just thinly covered with soil. Scientists today refer to this area as the Canadian Shield. The Shield is a circular formation of about two million square miles, occupying roughly half of Canada's total land mass. According to some calculations, the Shield may be even larger. The landform is named "Shield" after its rounded shape, which looks somewhat like a warrior's shield. Some observers have also likened it to a horseshoe shape.

Much of the Canadian Shield is still exposed rock, and researchers have determined that some of this rock is among the oldest ever discovered on Earth. Some rock formations near the Hudson Bay are likely more than 4.25 billion years old. During the eons since then, most formations avoided extensive soil coverings and were heavily affected by glaciers and erosion. Glaciers, enormous blocks of ice that slowly move across a landscape, carved hundreds of lakes, rivers, and other landforms throughout the Canadian Shield.

Overview

The Canadian Shield is an important part of North America. Humans have inhabited the region since ancient times, starting with many groups of Aboriginal people including the Cree, Métis, Dene, and Inuit. Europeans began exploring the area in the 1500s and traded for furs and land with native groups before beginning their own colonies. In the 1800s, the area was mapped and criss-crossed with railroads servicing the growing towns and mining operations in the region. In modern times, millions of Canadians live along the great shield-shaped land.

The physical form of the Canadian Shield in modern times clearly reflects the forces of its creation deep in prehistory. One of the main features of the Shield is its long, rolling hills, which are the product of both tectonic shifts and glaciers. Some hills were formed from rock pushed upward by tectonic plates. Other hills were carved into the landform by passing glaciers—these often bear visible scars from ancient glacial impacts—or were formed by sediments left behind by melting glaciers.

Another important legacy of the glaciers are the many bodies of water carved into the bedrock by huge ice sheets. The Canadian Shield is dotted with thousands of lakes. Most of the lakes are small, but many exceed 35 square miles. In addition, parts of some of the largest waterways in North America extend into the Canadian Shield. These bodies of water include the St. Lawrence River, Lake Superior, and Lake Huron to the south, and Lake Winnipeg, Great Slave Lake, and Great Bear Lake to the west.

The scouring glaciers were also partly responsible for the fact that the Canadian Shield has only a thin layer of soil over its tectonic bedrock. Despite this, in temperate areas of the shield, this soil is deep enough to support roots for many boreal forest plants, including deciduous and coniferous trees. Some of these trees include varieties of coniferous spruce, fir, cedar, and pine, and deciduous birch, poplar, and maple trees. In areas, the boreal forests of the Canadian Shield grow deep and tall. However, the cold northern reaches of the shield, affected by frigid climates, long-term ice coverings, and the lack of deep soil for roots, is host to only the most basic plant growth.

The abundant waterways and forests of the Canadian Shield host a wide variety of wildlife. In the coldest regions, Arctic animals include species of polar bear, fox, hare, and small and medium-sized birds. In the more temperate zones, a wider variety of animals may be found, including moose, bear, beaver, deer, and caribou. The lakes support pike, trout, and other fish, and the skies are frequented by a variety of geese, ducks, owls, and small birds such as sparrows and blue jays.

The landscapes of the Canadian Shield are rich with a variety of natural resources. The abundant forests offer a huge variety of lumber, and much of the human industry in the area is devoted to logging. Similarly, the lakes and rivers provide not only valuable freshwater, but also the potential for hydropower. In many areas, hydroelectric stations including dams at Labrador and Churchill Falls create large amounts of clean energy for local residents.

Another valuable natural resource is the minerals found in the ancient bedrock and glacial sediments. Precious metals including silver, gold, and palladium, and precious stones including diamonds may be found in the Canadian Shield, along with other useful and valuable materials such as lead, uranium, copper, and iron. Some of these metals were formed by meteorite impacts in prehistoric times. Different regions of the Canadian Shield have their own sets of mineral resources. Mining is an extensive industry in the shield.

Bibliography

"Canadian Landforms." Canadian Geographic / The Canadian Atlas Online, www.canadiangeographic.com/atlas/themes.aspx?id=canadianlandforms&lang=En. Accessed 20 Sept. 2017.

Eyles, Nick. Canadian Shield: The Rocks that Made Canada. Fitzhenry & Whiteside, 2011.

James-Abra, Erin and Jamie Bastedo. "Canadian Shield." Historica Canada / The Canadian Encyclopedia, 8 March 2017, www.thecanadianencyclopedia.ca/en/article/shield/. Accessed 20 Sept. 2017.

Miall, Andrew D. "Geological Regions." Historica Canada / The Canadian Encyclopedia, 6 July 2015, www.thecanadianencyclopedia.ca/en/article/geological-regions/. Accessed 20 Sept. 2017.

Mortillaro, Nicole. "Traces of Earth's Original Crust found in Canadian Shield." CBC News, 19 March 2017, www.cbc.ca/news/technology/earth-original-crust-canadian-shield-1.4028576. Accessed 20 Sept. 2017.

"The Canadian Shield Region." Alberta Online Encyclopedia, www.abheritage.ca/abnature/shield/shield.htm. Accessed 20 Sept. 2017.

"Welcome, Tourist, to the Canadian Shield." Calgary Board of Education, projects.cbe.ab.ca/ict/2learn/jwfech/geography/north/canadian‗shield/Canadian Shield Notes.htm. Accessed 20 Sept. 2017.