Cathy Elizabeth Woods, age 10, of Timmonsville, South Carolina, for her question:

What is an alpine glacier?

Glaciers come in assorted shapes and sizes    but all of them are fields of frozen snow. Some bury the polar regions under thick, massive ice caps and some spread over the plains at the feet of lofty mountain ranges. Others form long tongues of ice in the high valleys and gorges of mountainous regions. All glaciers have rugged surfaces and all of them are on the move.

Strictly speaking, an alpine glacier is a valley glacier. This may be misleading because we tend to think that valleys are long ditches, either in the level plains or at the feet of tall mountains. It is true that most of the valleys we know are of this type. But mountain climbers know that there are numerous valleys high among the lofty peaks of the mountains. As a rule, the steep sides of the pointed peaks are grooved with deep canyons and gorges. There are more of these lofty mountain valleys between one jagged peak and the next.

This is where we find most of the world's valley glaciers. Some people call them alpine glaciers because there are so many of them among the steep sided peaks of the Alps in Central Europe. At least 1,200 alpine valley glaciers have been counted in the Alps. There are more of them in our lofty northwestern mountains, especially in Alaska, and others in the Andes of Peru. There are also valley glaciers in Tibet between the mighty peaks of the high Himalayas.

Glacial ice is actually a rocky mineral, but. it is very weak and fragile. Any glacier that is 200 to 300 feet thick cannot support its own weight. It cracks and bends and moves somewhat like a lazy river    in fact, a valley glacier is actually a frozen river. The slope of the valley gorge guides it downhill. In the Alps, some of the glaciers creep down at a rate of one foot a day. When summer comes to Alaska, some of the valley glaciers glide downhill at 40 feet a day or even faster.

Ice, of course, melts when the temperature rises above freezing point. In torrid and temperate zones, the weather is warm high up the mountain slopes. This causes the lower tips of valley glaciers to start melting far up in the mountains. Chilly streams and icy waterfalls come gushing down to the base of the slopes and wander away as rivers. In polar regions, through much of the year even the lowlands are icy cold. There the valley glaciers stay frozen and spread their ice over the low¬lands. They form piedmont glaciers, shaped like covered frypans. The valley glaciers that feed them look like panhandles.

All glaciers have rough, cruel surfaces cracked with treacherous crevasses, sometimes several hundred feet deep. But valley glaciers are beautiful to behold, especially when seen from afar. They hang like white streamers between the dark rugged peaks. In the sunshine they sparkle like glittering jewels. A closer view shows that the snow white streamers have frayed edges. Feathery fingers of ice come down to join them from smaller gorges higher up the slopes.