Yellowstone National Park is full of natural wonders, and visitors this week can count snow rollers among them.
The park on Tuesday shared an image showing what it described as “nature’s snowballs,” or snow rollers, adorning a slope between Mammoth and the Norris Geyser Basin.
Snow rollers are formed, according to the park, “when the right amount of snow, wind, temperature, and moisture come together to form a snowball or doughnut shape.”
These doughnut shapes sometimes roll downslope, creating snow-roller trails (see images).
The park described this as a “rare winter phenomenon” and added that snow rollers typically form in open spaces near incline bottoms, where fresh powder is blown by wind across an icy surface.
RELATED: Tour company documents rare Yellowstone cougar sighting
According to National Geographic, snow rollers are also referred to as “snow bales,” “wind snowballs,” and “snow doughnuts.”
–Top image courtesy of yellowstone National Park; second image showing a snow roller in Rocky Mountain National Park is courtesy of Wikimedia Commons