Glaciers form through a process that begins with the accumulation of snow in a particular area where it remains year-round without completely melting. Over time, layers of snow build up and compress the snow beneath them. This compression causes the snow to recrystallize and transform from fluffy snowflakes into granular snow, then into firn (a dense, granular snow that has survived at least one melt season), and eventually into dense glacier ice as air pockets between the grains are sealed off
. Key steps in glacier formation include:
- Snow accumulation: Snowfall accumulates in cold regions, typically on high ground or in mountain troughs, where temperatures are low enough that the snow does not fully melt during summer
- Compression and recrystallization: The weight of the overlying snow compresses the lower layers, forcing the snowflakes to recrystallize into grains similar to sugar grains, then firn, and finally dense ice as air is expelled and the snow grains fuse together
- Transformation to ice: Firn becomes glacier ice when the air passages between grains close off, trapping air in bubbles and increasing the density of the ice to about 917 kg/m³. This process can be accelerated by melting and refreezing within the snowpack
- Glacier initiation: When the mass of compressed ice and snow becomes thick enough (often tens of meters), gravity causes the ice to begin flowing downhill, marking the formation of a glacier. This flow distinguishes a glacier from a static snowfield
In summary, glaciers form where snowfall exceeds melting over many years, allowing snow to accumulate, compress, and transform into dense ice that eventually flows under its own weight due to gravity
