LOS ANGELES — On a hazy summer afternoon, before the giant thunder clouds have had chance to unleash their fury, one of the most breath-taking sights you can witness is the Painted Desert of northern Arizona looming iridescently out of the mist. Even after swooping among the spectacular outcrops, mesas and buttes of Sedona, or nosing along the rim of the Grand Canyon, from the cockpit of a light aircraft 4,000 feet (1,200 metres) above the ground nothing can compare with the Painted Desert’s palette of multi-coloured rock formations stretching off to the horizon.

The blues, grays and lavenders come from the geologically rapid formation of sediments when water covered the land over 200m years ago. The reds, ochres and pinks hail from the much slower deposition during the Triassic’s dryer periods, when erosion and oxidation had time to work their magic. The pigments that give the fine-grained rocks their hues come largely from the iron and manganese compounds they contain. Other colours found along the desert’s southern fringe stem from the fossilised remains of a prehistoric coniferous forest. How such naked beauty could ever be labeled ‘badlands