John Cletheroe's
USA and Canada Holiday Hints

Canadian Shield, Precambrian Shield or Laurentian Plateau

Description

The Canadian Shield, also called the Precambrian Shield or the Laurentian Plateau, is a vast horseshoe-shaped area around Hudson Bay covering eastern and central Canada, and a small part of the northern United States. Some 1.9 million square miles, very nearly half of Canada's total area, is occupied by the Canadian Shield.

The rocks of the Canadian Shield were formed in Precambrian times 500 million years ago during a lengthy period when two tectonic plates converged, causing the surface rock to be forced down into the interior of the earth, melt, rise back to the surface and slowly cool. The rocks are igneous and metamorphic and contain large areas of granite.

Due to the effect of glaciation during the most recent ice age which started about two and half million years ago, the Canadian Shield has very thin soil with rocky outcroppings frequently showing. It is mainly undulating land with small hills and with numerous lakes. It is unsuitable for farming, but large parts in the south have forests and mining is also fairly common.

The sphagnum bogs found throughout the Canadian Shield area are called muskegs.

I'm extremely grateful to Jeremy Whitlock (cz725@freenet.carleton.ca) who supplied the following explanation:

The Canadian Shield is also called the Precambrian Shield since it represents the exposed bedrock of the Precambrian Era. It is more correctly called the North American Precambrian Shield, since all continents have a Precambrian Shield (the North American is the most exposed). People in the USA tend to call it the Precambrian Shield, while Canadians prefer Canadian Shield.

A map showing the area of the Canadian Shield is available online (see "External Links" below).

The following is an attempt to describe the area covered by the Canadian Shield. The following are of necessity only approximations.

The entire area of Labrador (i.e. the mainland part of Newfoundland and Labrador), but not the island of Newfoundland.
The entire area of the province of Québec, except for the small part of the Province which lies south of the St Lawrence River. This amounts to about 90% of Québec's land area.
Northern New York State, in particular the Adirondack Mountains.
A large part of Ontario, but excluding the area south of a line drawn east-west approximately through Ottawa, and also excluding an area west of James Bay and south of Hudson Bay. This amounts to about two-third's of Ontario's land area.
Northern Michigan.
Northern Wisconsin.
Northern Minnesota.
A band extending through southeastern, central and northwestern Manitoba.
Approximately the northern half of Saskatchewan.
A very small area in the extreme northeastern corner of Alberta.
That part of Northwest Territories and Nunavut which lies north of Manitoba and Saskatchewan, and also approximately the area north of a line drawn in a northwesterly direction from the northwestern corner of Saskatchewan.
That part of Baffin Island which lies to the northeast of a line drawn from northwest to southeast along the island's main axis.

Superior Upland

That part of the Canadian Shield which lies in northwestern Michigan, northern Minnesota and northern Wisconsin, i.e. south and west of Lake Superior, is called the Superior Upland.

External Links

Canadian Landforms Map The map on this page clearly indicates the major geological regions of Canada, including the Canadian Shield. Checked Oct-98. (For copyright reasons I am reluctant to reproduce the map on this page.)

Alberta

Newfoundland and Labrador

Northwest Territories