Zhangye Danxia

Zhangye Danxia National Geopark lies in Gansu province, in the Hexi corridor, at the foot of the Qilian range and beside one of the historic routes of the Silk Road. It is the most famous of the landscapes known as danxia because of its colouring: slopes and ridges striped in red, orange, yellow, greenish and whitish bands running parallel to one another, which have earned it the nickname of the rainbow mountains.

The colours have a mineralogical explanation. The sandstones and conglomerates that make up the massif were laid down in successive layers of differing composition and differing content of iron and other minerals; later oxidation tinted each stratum a different shade. The orogeny that raised Tibet folded and tilted that package of layers, and the subsequent erosion in an arid climate, with no plant cover to mask it, left them exposed at the surface forming wavy patterns. The low light of dawn and dusk, and above all rain, greatly intensify the colours.

The setting is arid and steppe-like, with sparse vegetation, and the area's value is above all geological and scenic rather than biological. It was declared a national geopark and has undergone very rapid tourist growth, managed through walkways and viewpoints that channel visitors and prevent direct trampling of formations that are extremely fragile.