But unlike snowballs made by people, snow rollers are typically cylindrical in shape, and are often hollow.
Gravity can also assist snow roller formation.
An inclined surface often needs just a little shove from the wind to get snow rollers in motion.
The top snow layer becomes a bit sticky and you then need a fairly strong wind.
However, the inner layers are weaker as they are formed first and are easily blown away.
Also see:Penitentes: Peculiar Spikey Snow Formation in the Andes
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