Mystery Photo From The Far North

Frank has lately been doing smog checks and related automotive tests in sunny, balmy (-30 degrees) Fairbanks, Alaska. He took a photo of these mysterious formations. Take a guess what caused them (and it wasn't Richard Dreyfuss working over mashed potatoes as in 'Close Encounters of the Third Kind!') My own guess proved wrong. I'll reveal the motive force, as revealed by Frank, next week, when I return from Las Vegas.