Glacier

A thick mass of ice that forms on land from an accumulation and recrystallization of snow significant enough to persist through the summer and grow year by year. There are two basic types of glaciers: 1) valley (or alpine) glaciers that creep downslope under the influence of gravity, and 2) continental glaciers that flow outward from a thick central area under their own weight.

Arapaho Glacier, Indian Peaks Wilderness