Michelle Gordon, age 14, of Marquette, Mich., for her question:

HOW LARGE IS THE CANADIAN SHIELD?

The Canadian Shield is a huge, rocky region that curves around Hudson Bay like a giant horseshoe. The Shield covers half the land area of Canada. About 1,771,000 square miles of the Shield's 1,864,000 square m ile area lie in Canada.

In Canada, the Shield covers most of Baffin Island, all of Labrador, nine tenths of Quebec, over half of Ontario and Manitoba and large areas in Saskatchewan and the Northwest Territories.

The Shield then dips into the United States to form the Adirondack Mountains of New York and the Superior Uplands of Michigan, Wisconsin and Minnesota.

The Shield is also called the Laurentian Plateau after the Laurentian Mountains of Southern Quebec.

Geoloogists tell us that the rock formations that make up most of the Shield are 500 million to 5 billion years old. Most of the rocks have undergone one or more periods of mountain building.

The Shield is dotted with lakes. Large forests in the southern section rank among Canada's most important natural resources. There's also copper, gold, iron and other minerals.