Engineers are building the first bridge over a moving rock glacier

A grizzly bear explodes out of the shadowy brush in entrance of me and bounds up the mountainside, pausing to look again for one soul-shaking second earlier than persevering with over the sunlit ridge along with her two cubs.

Polychrome Pass in Denali National Park, Alaska, is stuffed with such elegant sights. Streams the color of pencil lead crash down from quickly disappearing glaciers into the inexperienced tundra. Golden eagles glide over huge mountains of pink, brown and yellow volcanic rock. Far to the west, clouds …