How do ice fields form in mountainous regions?

In mountainous regions, ice fields and glaciers form through the long-term accumulation of snow and other solid precipitation in areas where annual snowfall exceeds the amount lost to melting during the summer.1

The transformation of this snow into dense glacier ice involves several stages:

• Densification: As snow accumulates year after year, the weight of overlying layers compresses the snow beneath it. Intricate snow crystals break down, evaporate, and condense into more rounded grains that fit together tightly.213
• Firn Formation: Snow that survives a full melting season is known as firn (or névé). As this material continues to be buried and compressed, its density increases.3
• Recrystallization: Under the stress of the overlying weight, the grains undergo recrystallization, growing in size and changing shape to minimize stress. Once the density reaches approximately 830 to 840 kilograms per cubic meter, air spaces between the grains are sealed off, rendering the material impermeable to fluids and marking the transition into true glacier ice.3

This process is influenced by local temperature and wetness, with liquid water often accelerating the transition through melting and refreezing cycles.31