A snow roll is a rare meteorological phenomenon in which a large snowball naturally forms as snow chunks that are blown in the ground by the wind, picking up material along the road, in the same way as a large snowball is used on snowmen created. They can be as small as a tennis ball, but they can also be bigger than a car. Most of the snow rolls have a width of several centimeters/centimeter.
Alternative names for snow rollers include: snow bales , snow donuts , and snowballs . Unlike snowball made by people, snow rollers are usually cylindrical, and often empty because the inner layer, which is the first layer formed, is weak and thin compared to the outer layer and can be easily destroyed, leaving what looks like a donut or Swiss rolls.
The following conditions are required for the snow roll to be formed:
- There should be a relatively thin surface layer of wet and wet snow, with the temperature near the melting point of ice.
- Below this thin layer of wet snow there must be a substrate in which a thin layer of wet snow surface will not stick, like ice or powdered snow.
- The wind must be strong enough to move the snow roller, but not strong enough to blow it up.
- Alternatively, gravity can move snow rollers when a snowball, as it falls from a tree or cliff, lands on a steep hill and starts rolling down a hill.
Due to this latter condition, snow rollers are more common in hilly areas. However, the precise nature of the necessary conditions makes them a very rare phenomenon.
The term snow roll also applies to horse drawers used in the mid to late 19th century (though tractor-pull samples are still in limited use today, especially in ski resorts) for snow-packing. It is mainly used in areas with high snow accumulation for access to horses and horse drawn carriages or carriages equipped with skis or runners. It is essentially a huge, large, wooden wheel loaded with rocks or concrete.
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Source of the article : Wikipedia