A glacier is a vast sheet of ice frozen solid from snowflakes and liquid moisture. Its mother is wet, runny water and even when frozen stiff, the solid ice acts in some ways like its busy mother. Glaciers move like rivers in slow motion and it takes most of them a year to flow as far and as fast as a river flows in a few minutes.

Most mountain glaciers flow fastest because they can slide down the slopes. The center of a flat ice field flows faster than the edges. A big glacier in Alaska flows seven feet a day and, in summer time, another flows 30 feet a day. Greenland's mountain glaciers may move almost 100 feet a day and there are slowpoke glaciers that move less than one foot in a week.