Photo-Fire in the Sky

Fire in the Sky
This picture was taken on a warm Sunny afternoon in July 1980 at Three Valley Gap which is located 12 miles west of Revelstoke, British Columbia, Canada. The woman and her sister were standing in the motel park with a steep mountain wall behind them. Why is the mountain cut off vertically and what are the strange swirling lights in the sky? The camera was a Balda Folding Roll Film Camera, 120 size Kodacolor, 1/200 of a second at F- 11.