030_Chapter 23 The Canadian Shield - CHAPTER 23 The Canadian Shield M any regions of the United States have their Canadian counterparts and vice versa

030_Chapter 23 The Canadian Shield - CHAPTER 23 The...

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CHAPTER 23The Canadian ShieldMany regions of the United States have their Canadian counterparts, andvice versa. Both countries have rockbound Atlantic coasts and mountains fring-ing the Pacific. They share the Great Plains, the Rocky Mountains, and the GreatLakes. Apart from its cold northern fringes, what most distinguishes Canada'sgeography from the United States is Canada's lack of a populated heartland. Inthe center of the continent, where the United States has industrial cities and ex-panses of farmland, Canada has only boreal forest. Between Washington, D.C.,and Omaha, a distance of approximately 1,30o miles, lies a substantial share ofAmerican industry and agriculture. To take a similar distance, of the 1,50o milesbetween Ottawa and Winnipeg, across the middle of Canada, all but a few mileson either end is part of the unpopulated Canadian Shield (map 23.1).Before the Canadian Pacific Railway was completed in 1885, continuous landtravel across Canada was not even possible. The Shield formed so effective a bar-rier between southern Ontario on the east and the prairie frontier of Manitobaon the west that all traffic across the Dominion of Canada had to detour throughthe United States. Travel across the rocky, swampy Shield terrain north of LakeSuperior was so difficult that no wagon routes for trade or migration, similar tothe Oregon or Santa Fe Trails in the United States, ever developed. When a rail-road finally was constructed around the northern edge of Lake Superior, itsroute had to be blasted out of the granitic Shield rocks that form the lake'snorthern margin.Today many populated sections of North America have no agriculture, andthus its presence is not absolutely associated with human settlement. But in the19th century, land that was impossible to farm held little interest for European-derived settlers. Nonfarming areas, including almost all of the Shield withinCanada, simply were bypassed. Substantial areas of the Shield north of Lake Su-perior consist of rocky, barren ground (fig. 23.1). Where cultivable soils exist,they are limited in productivity by their acidic nature, having developed onsands weathered from granitic rock and from a forest litter of boreal conifers,both of which produce infertility of the soil. (In the Canadian soil nomencla-ture, these soils are known as Podzols and are the equivalent of Spodosols of theUnited States.) Where even these limits can be overcome, the circumstance of avery short growing season, with late-spring and early autumn freezes, adds yetanother impediment.The general climatic model of Canada is that of a high-latitude continent376
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with fairly warm currents along its west coast and a cool current along its eastcoast. The ecosystem boundaries in Canada's interior trend in a northwest-southeast direction, with warmer conditions prevailing on the west at a givenlatitude. The effect of continentality—being in the interior of a land mass—creates larger seasonal temperature differences in continental interiors than
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