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How does snow gradually change into glacier ice?
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iceberg
Tourist boat in front of a massive iceberg near the coast of Greenland.
The transformation of snow into glacier ice is a gradual process of densification driven by pressure, temperature, and time.
The Stages of Transformation
- Snowpack: Initially, snow crystals are intricate, unstable shapes. Over time, evaporation and condensation cause these grains to round and fit more closely together. Wind may also break crystal points, further increasing density.1
- Firn: Snow that survives a melting season is known as firn. This intermediate, granular stage typically has a density greater than 500 kilograms per cubic meter.12
- Glacier Ice: As burial depth increases, the weight of overlying snow causes further compaction and recrystallization. When the density reaches approximately 830 to 840 kilograms per cubic meter, air spaces between grains are sealed off, making the material impermeable to fluids. This marks the transition to glacier ice.12
The speed of this transition varies significantly based on the environment, ranging from a few years in warm, wet climates to thousands of years in cold, polar regions.1