Geologists believe that Danxia topography is formed as a result of movement in the earth’s crust. This makes rock layers appear in different colors, textures, shapes, sizes, and patterns. The combination of differences in density and erosion creates towering peaks, cave holes and stone halls.
Danxia formations are green, yellow, blue and many other colors, though their appellation comes from the red rocks of Mount Danxia in Guangdong. Experts say that they are the result of red sandstone and other rocks undergoing metamorphic processes for millions of years.
The Guardian featured Zhangye's Danxia Landforms in pictures, and called this fantastic landscape: "China's rainbow mountains". See http://www.theguardian.com/world/gallery/2013/aug/01/rainbow-mountains-china-in-pictures.