These rare snow balls are formed in snowy weather with a precise combination of snow, ice, temperature, moisture and wind.
They are normally found in certain parts of North America.
Self-rolling snow balls are also known as: snow bales, snow rollers and snow doughnuts.
They get these names from the way that they are formed.
This winter in the UK has been a snowy one so far, and this has caused these snow bales to make an appearance in England.
Ron Trevett and his wife Aileen were walking their dogs close to their home in Yeovil in Somerset.
They managed to photograph these rare natural structures.
“We saw them from a distance on the ridge of the field, and we thought some kids had been playing up there and making giant snowballs, but when we got up there we saw there were no footprints and there were hundreds of them – too many for children to have done it. We realized it must have been the wind.” said Mr Trevett.
In time the snowballs become too heavy and large for the wind to move, or they are get caught on different ground levels.
The snow bails are normally hollow; this is because of the middle layers not being very strong.
The formations can cave in easily if the temperature or wind changes slightly.
Frank Barrow – a lecturer in meteorology, explained that the rolls can only form in a specific set of strange conditions:
“They start off with nice thick layer of snow, with the top snow just on the point of melting either because of general temperature or sunshine on the surface, the top snow layer becomes a bit sticky, and you then need a fairly strong wind. The sticky layer can be peeled off the colder and more powdery snow underneath by the wind forming a roll. – I suppose it is a natural version of making a snowman.”