A rare environmental process is being blamed for huge quantities of giant snowballs suddenly appearing on a beach in Siberia, Russia. Videos and photos emerged recently of the Gulf of Ob in western Siberia depicting a beach covered in giant balls of snow that appear to have washed ashore.

The snowballs started showing up a couple weeks ago and stretched over 11 miles of coastline, according to reports. They can be small, about the size of a regular snowball, or as large as several feet across. A video show by an individual named Valery Togo, which you can view below, provides an idea of just how large of an area they cover.

Scientists say a rare environmental process where small pieces of ice form and then are rolled by wind and water are the likely cause of these giant snowballs. They were spotted as recently as 2010 in Lake Michigan.

“As a rule, first there is a primary natural phenomenon — sludge ice, slob ice,” said Sergei Lisenkov, a press secretary of the Arctic and Antarctic Research Institute, according to Russian TV as reported by the BBC. “Then comes a combination of the effects of the wind, the lay of the coastline, and the temperature and wind conditions. It can be such an original combination that it results in the formation of balls like these.”