The Zhangye Danxia

Twenty-four million years of layers, tipped on end and cut open

In the northern foothills of the Qilian Mountains in Gansu, at the northernmost edge of the Tibetan Plateau, where the range drops to the flat basin of the Hexi Corridor, the hills are striped. Bands of rust red, brown, yellow and even green run across ridges several hundred metres tall, smooth and sharp-edged, as if someone had poured the landscape in layers. This is the Zhangye Danxia, protected within Zhangye National Geopark, 322 square kilometres in Linze and Sunan counties of Zhangye.

The colours were made long ago. The rocks are sandstones and other sediments laid down during the Cretaceous, tens of millions of years ago; iron oxide stained the sandstone deep red as it formed, and other oxides gave the browns, yellows and greens of different beds. Folding and faulting have since lifted and tilted them, exposing layers that would otherwise have stayed out of sight, much of the deformation thought to be the work of India colliding with Eurasia about 50 million years ago, more than 2,000 kilometres away, though recent research suggests some of the crumpling is older still. Wind and water then carved the tilted layer cake into towers, pillars and ravines that show the stripes edge-on. About 150 kilometres to the northwest the same red Cretaceous sandstones appear again, but there, as one geologist told NASA, they lack the tilted colourful beds and small-scale rugged ground that make the park.

Fame came quickly. In 2005 reporters from 34 major Chinese media outlets voted Zhangye one of the most beautiful Danxia landforms in China, and in 2009 Chinese National Geography magazine named it among the country's six most beautiful landforms. It became a provisional geopark in 2012 and a national one on 16 June 2016, and it is now a UNESCO Global Geopark.

Most visitors go to the Linze Danxia Scenic Area, the core of the park, about 30 kilometres west of downtown Zhangye and 20 kilometres south of the Linze county seat, where boardwalks and roads lead between the formations. A second area, Binggou, on the north bank of the Liyuan River, opened in August 2014 after an investment of 100 million yuan, and a third lies at Sunan.