When one sketches Canada, several large geographic units stand out. The
first to emerge, because of both its venerable age and its central position
around which everything else is arranged, is the Canadian Shield. From
its throne in east-central Canada, it extends its hills and rocky plateaus
over a good half of the country. All around this base extend shelves whose
rocky layers, of more recent origin, were deposited by seas that no longer
exist.
To the east is the narrow plain of the Great Lakes and the St. Lawrence;
to the west, the rolling plains; to the centre, the Hudson Bay lowlands;
and to the north, the Arctic lowlands. Together, these plains cover one
quarter of the territory. Then, like sentinels posted at the three gates
to Canada, mountain chains arise: the aging Appalachians to the east,
the proud cordillera to the west and the little-known Innuitians to the
north. The last geographic unit consists of the Atlantic, Pacific and
Arctic continental shelves—the submerged part of the continent.
Even though invisible to us, it is of great importance for Canada because
of the immense resources that it contains.
We could not draw the final line in this sketch of Canada without representing
water, which is present everywhere and covers nearly 1 square kilometre
in 11 of Canada's territory. The vast waters of the lakes and the
swift waters of the rivers form intricate networks that are organized
into the four great catchment basins of the Atlantic, the Pacific, the
Arctic and Hudson Bay. A few errant rivers in southern Alberta and Saskatchewan
take the southern route, toward the Gulf of Mexico basin. Two majestic
river systems stand out: in the north, the Mackenzie, with a drainage
area of 1,805,200 square kilometres, and in the east, the St. Lawrence,
which has a drainage area of 839,200 square kilometres.