What appears to be a stroke of thick red paint is actually a remarkable interplay of light and cloud in the Canadian Rockies. Angling through them is part of the Rocky Mountain Trench, a valley that extends from Montana, USA, to just south of the Yukon Territory. Low clouds filled a part of the Trench near the border between the Canadian provinces of Alberta and British Columbia. The light-reflecting nature of the clouds coupled with low sun elevation resulted in this startling effect.