A geological layer cake The bright colors of the Zhangye Danxia landscape are a direct record of geological history, beginning with sediment deposition during the Cretaceous Period.%%CITE_1%% For millions of years, this area was a massive inland basin where rivers deposited layers of sand and silt.%%CITE_2%% These sediments, sourced from the surrounding land, formed thick beds of sandstone and siltstone.%%CITE_3%% The total area of this geological park now covers 322 square kilometers.%%CITE_4%%
The distinct colors come from the minerals that cemented these sediment grains together. Groundwater flowing through the porous sandstone carried dissolved minerals. Red, the most dominant color, is caused by hematite, a form of iron oxide created in an oxygen-rich, arid environment. During wetter, warmer periods, different minerals formed. Yellow and brown tones are attributed to goethite and limonite, while green layers contain chlorite or iron silicate clays. These alternating wet and dry periods, driven by long-term climate cycles, created the distinct, multicolored layers in distinct layers. The rock strata of the scenic area belong to the Upper Member of the Lower Cretaceous Xinminpu Group, dating back 106 to 114 million years.
An artist's palette, shaped by force
The second chapter in the mountains' creation began around 55 million years ago with the collision of the Indian and Eurasian tectonic plates. This immense geological force, the same one that began to form the Himalayas, caused the originally flat layers of sandstone to fold, buckle, and tilt dramatically. This tectonic uplift exposed the cross-sections of the colored rock strata to the elements for the first time.
For millions of years since that uplift, erosion has been the final artist. Wind and water, particularly runoff from rainfall, sculpted the tilted and folded layers. The different rock types erode at different rates—a process called differential erosion. Softer sandstone wore away more quickly than harder layers, carving the landscape into the sharp ridges, pillars, and deep valleys seen today. This combination of layered color, tectonic tilting, and prolonged erosion created the unique landform known as Danxia.