"This spruce tree and a flock of passing waxwings was highlighted by a setting sun pillar," says Standley. "It was a beautiful sight."
Sun pillars are caused by ice in the air. Plate-shaped ice crystals flutter down from freezing clouds like leaves falling from trees. They act like thousands of little mirrors reflecting the light of the setting sun into a towering pillar--or Christmas-tree finder, as the case may be.