Snow roller
Encyclopedia
A snow roller is a rare meteorological phenomenon in which large snowball
s 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, leaving what looks like a doughnut
or Swiss roll
. Snow rollers have been seen to grow as large as two feet in diameter.
The following conditions are needed for snow rollers to form:
Because of this last condition, snow rollers are more common in hilly areas. However, the precise nature of the conditions required makes them a very rare phenomenon.
File:Rolling snow.JPG|Snow roller in Krkonoše, near Czech Republic and Poland.
File:Schneeringe1 Foto Kathrin Spiegler.JPG
File:Snow roller Illinois.jpg
File:Umgeworfene Schneerige 4 Foto Olaf Parnieske.JPG
Snowball
A snowball is a spherical object made from snow, usually created by scooping snow with the hands, and compacting it into a roughly fist-sized ball. The snowball is often used to engage in games, such as snowball fights. Snowball fights are usually light-hearted and involve throwing snowballs at...
s are formed naturally as chunks of snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
are blown along the ground by wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
, 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, leaving what looks like a doughnut
Doughnut
A doughnut or donut is a fried dough food and is popular in many countries and prepared in various forms as a sweet snack that can be homemade or purchased in bakeries, supermarkets, food stalls, and franchised specialty outlets...
or Swiss roll
Swiss roll
A Swiss roll or jelly roll is a type of sponge cake roll. The thin cake is made of eggs, flour and sugar and baked in a very shallow rectangular baking tray, called a sheet pan. The cake is removed from the pan and spread with jam or buttercream, rolled up, and served in circular slices.The...
. Snow rollers have been seen to grow as large as two feet in diameter.
The following conditions are needed for snow rollers to form:
- The ground must be covered by a layer of iceIceIce is water frozen into the solid state. Usually ice is the phase known as ice Ih, which is the most abundant of the varying solid phases on the Earth's surface. It can appear transparent or opaque bluish-white color, depending on the presence of impurities or air inclusions...
to which snow will not stick. - The layer of ice must be covered by wet, loose snow with a temperature near the melting pointMelting pointThe melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
of ice. - The wind must be strong enough to move the snow rollers, but not strong enough to blow them too fast.
- Alternatively, gravity can move the snow rollers as when a snowball, such as those that will fall from a tree or cliff, lands on steep hill and begins to roll down the hill.
Because of this last condition, snow rollers are more common in hilly areas. However, the precise nature of the conditions required makes them a very rare phenomenon.
Gallery
File:Rolling snow.JPG|Snow roller in Krkonoše, near Czech Republic and Poland.
File:Schneeringe1 Foto Kathrin Spiegler.JPG
File:Snow roller Illinois.jpg
File:Umgeworfene Schneerige 4 Foto Olaf Parnieske.JPG