This winter, snow is on a roll.

This week, people in Ottawa, Canada, were mystified when an unusual cold weather phenomenon began plowing through their yards. It looked like the snow was garnering a mind of its own, inexplicably balling itself into donut-shaped spirals and rolling across the icy ground. But this rare occurrence is a natural phenomenon rather than Frosty the Snowman coming to life; it has a name, and it's called "snow rollers."

Also known as "snow bales," "wind snowballs," or "snow donuts," snow rollers are the cold weather equivalent of tumbleweeds. They form when wind pushes snow across the ground, gathering it into a hollow cylinder. Although some formations appear more squashed than others, bigger snow rollers can