The Western World Daily Readings on Geography Chapter 33 North America Physical Geography I

CHAPTER 33 North America Physical Geography I The Canadian Shield PETER . 52 by Bonce Noun Propel Many if not most regions of continents have a physical basis and in North America , the Canadian Shield exemplifies this . The Shield is a three million square mile ( eight million square kilometer ) area of ancient geology , directly linked with Canada , climates , and cultures . Ringing Hudson Bay , the Shield is the fundamental surface for nearly all of Labrador , and , before extending into parts of , and the Northwest and Territories . These same Precambrian era ( beginning billion years ago ) rocks extend for hundreds of miles under the sedimentary strata of surrounding regions , such as the Great Plains and Central Lowlands . 151

152 JOEL QUAM AND SCOTT CAMPBELL The Shield location globally and within North America not only has affected its , but also its climate and therefore its soils and vegetation . In turn , human activities ca be separated ' from the physical characteristics because resource 71 availability and exploitation , transportation and accessibility , settlement patterns and growth , and even cultures and lifestyles are so strongly affected by this environment . Most ofthe rocks exposed in the Shield are over 600 million years old some are older than four billion years . Their formation during the Precambrian period ( sometimes referred to as the ' I ' or hidden life eon ) means that in the Shield there are virtually no ' fossil fuels ( or fossils ) but instead it holds an abundance of metal deposits . Native copper ( pure copper ) was found and used long ago by the indigenous peoples around Lake Superior ( especially Michigan Upper Peninsula ) while more recent mines were critical to the development of both countries . Gold , silver , nickel , and iron deposits have been major economic activities for two centuries the iron deposits in Minnesota Range supported the American steel industry from the late through the century , while mines did the same for Canada . Erosion over millions of years exposed Shield rocks by removing mountains of soil and rock . Not only did this expose the deeper older rocks and allow easier access to mineral resources ( including diamonds in recent decades ) but also it helps explain the hydrology of the region . First , the rocks of the Shield are mostly igneous ( often granitic ) and are relatively impermeable . The surface works like a shield in blocking water from passing through the rock , and rain tend to either runoff downslope ( rivers ) or be trapped in lower areas as lakes . Second , glacial activity , either through erosion or deposition , has created deranged ( random ) stream patterns and depressions for thousands of lakes . Minnesota may be the Land of Lakes check the license plate but is the land of lakes ! Canada claims to have the greatest amount of lakes in the world Finland disagrees . us ?

man can The Canadian Shield . Cartography . The role of lakes and rivers created by glaciers and the Shield has changed over the centuries , but these waterways have always been vital to the inhabitants . During France early colonization of Canada , access to the interior was either on foot or by canoe and the French were famous for their travels to . obtain pelts from the natives ( now known in Canada as , I ' First Nations ) Settlers , especially in , used the long lot system where property included Georgian Bay , Canadian Shield Photo by Michael on frontage for access and then extended onshore . In the last century a cottage culture developed where having a summer place on the water was part of the

NORTH AMERICA PHYSICAL GEOGRAPHY 153 Canadian dream , for the wealthy at first , but then for the middle class . Fishing in Canadian waters now attracts millions of tourists each year and facilities provide over half of Canada electricity . Winters in the Canadian Shield range from cold ( averaging ) around the Great Lakes to extremely cold ( averaging ) near the Arctic Ocean , but summers though short can be warm to hot . Despite the lakes and rivers , Shield climates are classified as ' so that seasonal extremes are the rule . The extreme northern latitudes are a factor . Winter days are extremely short ( sometimes nonexistent ) and the long summer days ( up to 24 hours ) allow vegetation to exist at the Arctic , attracting insects and the migrating birds that feed upon them ( Canada Geese and Tundra Swans . The early fur trade in the Shield relied on the heavier pelts of those animals that live through the brutally cold winters . True tundra occurs in a climate that is found only on the northern shores of the Shield and lacks the forests that dominate the rest . Since most of the air masses in the Shield lack moisture , there is surprisingly little precipitation ( and also little evaporation ) but the remaining Shield climates can support pines , firs , and some deciduous trees . In Canada two climates Taiga and Boreal Forest dominate the Canadian Shield taiga forests are shorter , less dense and to the north of boreal forests . The harsh weather of the Shield limits the variety of trees and has resulted in huge expanses of and firs the best trees for the pulp mills that cover and . Most Shield soils are relatively thin , relatively infertile , and relatively acidic . The glaciers of the last Ice Age removed the existing soils and the development of new soils has been slowed by the climate . In short , agriculture is limited to the few places where rivers or lakes have deposited fertile silt , such as the Clay Belt south of Hudson Bay ( where the former Lake once stood . Farther north in the Shield much of the soil is frozen round ( permafrost ) which creates huge problems for construction during summer , melt . In the summer peat bogs ( containing decayed vegetation ) and swamps appear in the Shield and are a major concern for global warming the increased decomposition of peat from higher temperatures adds even more carbon dioxide to the atmosphere . The geology ofthe Canadian Shield , combined with the history of the rise and fall of the Ice Age and with the northern latitudes of Canada , creates a large swath of Canada that has a plethora of mineral resources exploited for wealth , a network of waterways used for transportation and tourism , and a landscape better suited for forests than for agriculture . Did You Know ?

During the Cold War following , the US was concerned about a nuclear attack by the Soviets ( Russians ) Since the shortest air route for Soviet bombers to reach America was across the North Pole and Canada , to monitor this potential Soviet threat , a system of radar stations was placed across the Shield . This DEW Line ( Distant Early Warning Line ) has since been transitioned to the North Warning System , but the relative location of the Shield means it remains important to US defense strategies . Hudson Bay was a bay before the last Ice Age and eventually in the future it wo be a bay either . This is due to isostatic rebound , the gradual rise of land after the departure of glaciers or ice sheets . Photo by Francis ' on .

154 JOEL QUAM AND SCOTT CAMPBELL CITED AND ADDITIONAL BIBLIOGRAPHY , Michael . 2016 . Georgian Bay , Canadian Shield . Generic ( Francis . 2016 . Drizzle Dripping on the Canadian Shield . Generic ( Jeff . 2020 . The Canadian College of .