(Alfred Hecht)

Teaching aim: To describe the complexity of the physical landscape of Canada, the major physical regions, the impact of glaciation on the Canadian landscape, soils and their land use potential. Keywords: Nature regions, physical landscapes, lowlands, mountains, basins and trenches, geomorphology and morphogenetics, glacial deposits, soils, land use

Some of the world's oldest rocks (3.96 million years in age) have been found in the Canadian Shield [1] the generally low rugged ancient geological nucleus of northern North America that comprises almost one half of Canada. The eastern part of the Shield is high enough to be mountainous and rises to over 2000 m in  Baffin Island [2], but the central part is depressed well below sea level, and forms the Hudson Bay, a large interior sea connected to the Atlantic Ocean by the Hudson Strait. To the west and south of the Shield are younger, flat, sedimentary strata of Paleozoic and more recent age, the Great Plains and the Great Lakes-St. Lawrence Lowland respectively. Along the junction of the Great Plains and the Shield a north to south sequence of extremely large lakes is arrayed, Great Bear, Great Slave, Athabasca, and Winnipeg lakes, all very apparent on a map of Canada. South of the Shield is the greatest group of lakes in the world, the Great Lakes [3], Superior, Michigan, Huron, Erie, and Ontario. The largest, Lake Superior, is so deep that its bottom is well below sea level.

Three great mountain systems form the physical margins of Canada. The Canadian Cordillera on the Pacific coast, over 700 km wide, is composed of numerous ranges, plateaus and valleys. The most famous range, of course, is the Rocky Mountains. The Cordillera is a system of young high mountains, and Mount Robson [4] in the Rockies of British Columbia is 3954 m high, and Mount Logan in the St. Elias range in Yukon is 5959 m, the highest peak in Canada. On the Atlantic coast, in the Atlantic provinces and southeastern Quebec, is the much older and lower Appalachian mountain system, almost 600 km wide, and broken into many peninsulas, gulfs, embayments, and islands. Elevations in most of the ridges are well below 1000 m, although the highest ridge, which is in the Gaspé peninsula of Quebec, rises to over 1200 m. In the extreme north of Canada is another old mountain system, the little-known Innuitian ranges, about 400 km wide, and reaching an elevation of 2616 m in Ellesmere Island. Off the North American land mass in the Atlantic Ocean is a broad continental shelf, important for centuries for its great fisheries [5]. Gas is being produced from these sedimentary strata, and oil is flowing from wells that are 310 km offshore, drilled where the Atlantic has a depth of c. 80 m. The continental shelf in the Arctic Ocean also is known to hold oil and gas [6] reserves, but at the present time they are much too distant from market to be exploited.

Almost all of Canada was covered by ice during the last ice age. High mountains in the west and north have all the classic glacial alpine features [7] so well known in the European Alps. Ice fields still exist in the Canadian Cordillera; the Columbia Ice Field [8] in the Rockies can easily be reached by highway, and is a very popular tourist attraction. In the far north, on Baffin, Ellesmere, and other islands, ice caps remain on the highest slopes.

All farming areas in Canada are on soils produced on parent materials derived from glacial deposits. During the last ice age, continental ice sheets had their main centres of accumulation on the Canadian Shield, with the ice lobes pushing north, west, east, and south. After glaciation [9], the Shield was left as a surface of rounded resistant rock knobs, a disarranged drainage pattern of countless lakes and rivers, marshlands, and some thin patches of glacial drift, often sands and gravels deposited by meltwater, and clays gently dropped in proglacial lakes [10]. On the plains to the west and south of the Shield, the less resistant Paleozoic sedimentary rocks of the lowlands provided much rock material for the advancing ice lobes to erode, and when the broken up materials were subsequently deposited by the ice, deep accumulations of glacial till were laid down in the form of end and ground moraines [11]. After deglaciation, as the climate moderated and vegetation returned, fertile soils were slowly formed on these parent materials. Lacustrine deposits laid down in preglacial lakes today are clay plains used for farming in parts of the prairies and southern Ontario, and also are the basis of agriculture on islands of settlement in the midst of the Shield in Ontario and Quebec. In these northern clay belts, as they are known, the short growing season and frost hazards limit what can be grown because they are located at the climatic limits of commercial agriculture.

Questions for further consideration: On an outline map of Canada sketch the mountain regions of Canada and explain their locations. How was Canada's fertile agricultural lands formed? Why are Canada's glaciers located where they are? Interactive Quiz

[1] http://freespace.virgin.net/john.cletheroe/usa_can/can/canshld.htm
[2] http://sts.gsc.nrcan.gc.ca/clf/landscapes_details.asp?numero=269
[3] http://www.great-lakes.net
[4] http://www.out-there.com/robson/rob-bpk.htm
[5] http://www.ncr.dfo.ca
[6] http://www.nickles.com
[7] http://www.uwsp.edu/geo/faculty/lemke/vgd_alpine/contents.html
[8] http://www.photo.net/photo/pcd1765/columbia-icefield-sunset-37
[9] http://www.entrenet.com/~groedmed/glaciers.html
[10] http://www.mnr.gov.on.ca/mnr/water/p741.html
[11] http://www.homepage.montana.edu/~geol445/hyperglac/depland2/