Glaciers are formed when snow remains in the same place all year round.
Each year the new layer of snow compresses the previous layers. The compression forces the snow to re-crystallize, forming grains around the same shape and size as grains of sugar. Gradually the grain grow larger and the air pockets between the grains get smaller.
This causes the snow to slowly compact and increase in density. After about two winters the snow turns into firn which is and intermediate state between snow and glacier ice. At this point it is about half as dense as water.
Over time, larger ice crystals form and become so compressed that the air pockets are very tiny. In very old glacial ice, crystals can reach several inches in length. For most glaciers this process takes over a hundred years.
Each year the new layer of snow compresses the previous layers. The compression forces the snow to re-crystallize, forming grains around the same shape and size as grains of sugar. Gradually the grain grow larger and the air pockets between the grains get smaller.
This causes the snow to slowly compact and increase in density. After about two winters the snow turns into firn which is and intermediate state between snow and glacier ice. At this point it is about half as dense as water.
Over time, larger ice crystals form and become so compressed that the air pockets are very tiny. In very old glacial ice, crystals can reach several inches in length. For most glaciers this process takes over a hundred years.
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