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Snow RollerA snow roller is a rare meteorological phenomenon in which large snowballs are formed naturally as chunks of snow are blown along the ground by wind, picking up material along the way, in much the same way that the large snowballs used in snowmen are made. Unlike snowballs made by people, snow rollers are typically cylindrical in shape, and are often hollow since the inner layers, which are the first layers to form, are weak and thin compared to the outer layers and can easily be blown away. Snow rollers can grow as large as a foot in diameter. The following conditions are needed for snow rollers to form: - The ground must be covered by a layer of ice that snow will not stick to.
- The layer of ice must be covered by wet, loose snow with a temperature near the melting point of water.
- The wind must be strong enough to move the snow rollers, but not strong enough to blow them too fast.
- The ground must have a slope, at least where the snow rollers start rolling.
Because of this last condition, snow rollers are more common in hilly areas. However, the precice nature of the conditions required makes them a very rare phenomenon. External links
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