Dick Brown, age 11, of Decatur, Ga., for his question:

When did the last ice age end?

This was the Wisconsin ice age. Its massive ice sheet was centered around the Great Lakes and across the state of Wisconsin. It was at its peak about 100,000 years ago. Experts think that the last of the ice ages began to relent some 10,000 years ago. About 10,000 years later, the fringes of the great glacier had withdrawn From Labrador, and the region of Niagara Falls was free of its burden of ice. The last of the ice sheet melted from New England about 28,000 years ago, and 5000 years later Minnesota was free of its icy grip. In Europe, central Germany was freed some 17,000 years ago, but there were still remnants of the ice in Sweden some 13,000 years ago.