Kaskawulsh Rainbow, Canada, 1997

"Just after 7 a.m. one morning ... a rainbow appeared over our camp [on the Kaskawulsh Glacier]. I went for my camera and then saw a huge wall of fog coming straight down the glacier. ... I thought the rainbow would disappear into the mist, but it just turned white.

"There's a technical explanation for this: I was actually seeing a second rainbow, white rather than multicolored because of the way fog droplets scatter light."

—From "Point of View," December 1998, National Geographic magazine