Larry Martin, age 10, of Williams A.F.B., Arizona, for his question:

How does a glacier form?

A great glacier is made of solid ice and may be a mile or two thick. It weighs untold tons. Yet every glacier, large or small, is made from dainty snowflakes. Layers of snow fall one upon another, crushing the snow beneath. The air is squeezed out, frost and weight press the once frothy snow into solid ice.

Ice is a fragile mineral and when a glacier reaches 200 to 300 feet in thickness it begins to feel the stress of its own weight. It cracks in chasms and crevasses. If the glacier is on a slope, it begins to slide down. If it is on flat ground, its weight begins to force it to move outwards from the center.