The+Canadian+Shield

THE CANADIAN SHIELD media type="file" key="The Canadian Shield.mp3" width="240" height="20"  media type="custom" key="21995286"

The Canadian Shield is the geographic foundation of Canada. The Shield underlies not only much of Canada but also parts of the United States. More than half of Canada is covered by the Shield, about 4 800 000 km. Some of the world's oldest rocks (3.96 billion years old) are located in the Shield near Great Slave Lake. Today, most of the Shield is relatively flat with rounded hills of rock which are actually the roots of ancient mountains.

 Two types of rock, igneous and metamorphic, form most of the Shield. They contain valuable minerals in great quantities. Because of the vast deposits of lead, gold, nickel, copper, zinc, and other important metals, the Canadian Shield is often called the storehouse of Canada's metallic minerals. In addition, diamonds have recently been found where ancient volcanoes once existed.

 1. a) What types of rock make up the platform on which the Canadian Shield is built?  b) What is the topography of the Shield like?

**What does it look like? Check this out; **  media type="custom" key="4985799"  Read on below to find out WHY it looks the way it does...

How were mineral deposits formed in the rock of the Shield? Minerals were present in magma (molten rock) beneath the earth's crust. As magma rose toward the surface, it forced its way into cracks and cavities in the Shield rock. This process of magma slowly rising toward the surface took thousands or millions of years. As it cooled, some minerals were deposited in the magma itself. Other deposits were formed when minerals, dissolved in very hot water, were forced deep into cracks in the surrounding rock. This process allowed minerals to be deposited in high concentrations which makes mining worthwhile.

2. What geologic processes caused the minerals to be deposited near the surface?

As the minerals slowly cooled, they separated into layers according to their density. The lighter ones floated on top of the heavier ones. Those that had similar density floated to the same level. Nickel and copper are often found together because they have similar densities.

 Mining companies are attracted to the Shield because of the presence of metallic minerals. Many cities and towns, such as Sudbury in Ontario, Thompson in Manitoba, and Yellowknife in the Northwest Territories, rely on the mining industry for jobs. The mineral ores are smelted to remove waste materials. The concentrated minerals are shipped to factories in Canada and other parts of the world where they are used to manufacture products we use every day.

 3. a) Why is the Shield called Canada's storehouse of metallic minerals? <span style="background-color: #e9e5e5; font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;"> b) Using your own words, describe how mineral deposits form.

<span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;">While the Shield is well-suited to mining, it is ill-suited to farming because it has very thin soils. However, it is ideal for recreation because of its scenic rivers, waterfalls, lakes, rock outcrops, and vast forests. The action of the glaciers affected the drainage of the Shield. The scraping and gouging action of the ice created depressions in the bedrock. These depressions filled with water to form the hundreds of thousands of lakes that now dot the Shield. Because the bedrock is impervious, water does not pass through it. The glaciers deposited sand, gravel, and clay which dammed rivers or forced them to flow in different directions. The result is a very disorganized pattern of winding rivers, lakes, and swamps. These rivers and swamps are the breeding ground for the many blackflies and mosquitoes found in the Shield. People visit the Shield to canoe, fish, hunt, and "get back to nature." The tourist industry is very important to the towns and cities in the southern parts of the Shield.

<span style="background-color: #e9e5e5; font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;">4. Describe the effects of glaciers on: <span style="background-color: #e9e5e5; font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;"> a) <span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 20px; line-height: 29px;">the drainage of the Shield <span style="background-color: #e9e5e5; font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;">b) the land's surface material, such as soil, rocks, and gravel

<span style="font-family: 'Arial Black',Gadget,sans-serif; font-size: 150%;">The Shield's plentiful water flows have made it an excellent source of water-generated energy, and the pattern of drainage has affected where hydro-electrical plants are located. The centre of the Shield is much lower than its outer portion. This gives it the appearance of a saucer, with Hudson Bay occupying the low-lying centre. As a result, most of the rivers of the Shield flow toward its centre and into Hudson Bay. Hydroelectric generating stations have been built where the rivers tumble from the Shield onto the Hudson Bay Lowlands. The energy produced by these stations is transmitted by power lines to cities and towns both on and off the Shield.