How is a glacier formed?

Glaciers form where the summers are too cool to melt all the winter snowfall. When summer ends, there is still a layer of last winter's snow and ice on the ground waiting to be covered with new snowfalls. Year by year, the snow piles deeper. The lower layers are crushed and compacted under the heavy weight. Thaws melt the surface, frosts faze the moisture into solid ice.

When the field of ice and frozen snow becomes 150 feet thick, it begins to move. For ice is a fragile mineral and tends to crack and bend under its own weight. An ice field, or flat glacier, pushes outwards from the center. A mountain or valley glacier slides slowly down its slope like a lazy river of ice. The edges of the moving ice field melt away as chilly streams or icy lakes and meantime more snows are adding to the surface of the glacier.