Zhangye Danxia Landform is concentrated predominantly in Linze and Sunan counties in Gansu Province. It is both the largest and the most typical of China's arid area danxia landforms. Because of aridity, the Zhangye Danxia Landform differs from that of south China. It is very dry and desolate, without any vegetation, so geologists call this "window lattice and palace-shaped Danxia topography”.
Zhangye Danxia Landform is surrounded by colorful hills, which seem to rise and fall like waves: with rock strata of different colors mixed in graceful disarray, it is an imposing and magnificent sight. The Zhangye's palace danxia formations and its colorful hills cover about 300 square kilometers. Its character is unique in China, so it was nominated by the "China National Geographic" as the top 7 Danxia Landforms in the country.
"Danxia Landform" is a broad term used to describe geological formations composed of limestone and conglomerate that have been molded through a series of specific, complex geological processes. These structures are unique to China and are characterized by their deep red hues, steep cliffs, and distinctive shapes.
Magnificence is the first characteristic of it. Most mountains here are composed of precipitous cliffs, and many cliffs are several hundred meters high, giving people a strong sight shock.
Singularity is the second characteristic. In the region, Danxia cliffs, stone walls, stone pillars, stone peaks, low mountains, hills are widely distributed, as well as stone bridges of various shapes. Some peaks are like “couple peaks”, whispering with each other; some are like Skyscrapers, standing straight to the sky; some other are like palaces, appearing splendid in its momentum.
Risk is the third characteristic. There are high mountains with dramatic ups and downs, and deep valleys with ravines and gullies criss-cross. It is very daunting that many peaks are just like cut by the nature.
In addition, the Danxia landform has gorgeous colors due to the organic sediments. You can see various colors, like red, yellow, orange, green, white, black, gray, etc, making the place so colorful and splendid. In the day, the mountains are like brightly colored silks or colorful gemstones. Besides, with the changes of time and weather, the colors vary constantly, adding the visual shock of tourists.
How Did The Rainbow Mountains Form?
The Rainbow Mountains are cretaceous sandstones and siltstones that were deposited in China before the Himalayan Mountains were formed. The sand and silt was deposited with iron and trace minerals that provided it with the key ingredient to form the colors we see today.
What was once a layered horizontal and flat stratigraphy was disrupted by the Indian Plate colliding into the Eurasian Plate approximately 55 million years ago. Much like when two cars get in a wreck and the bumpers fold and break, a similar process folded what was once flat sandstones into the Rainbow Mountains we see today. This process uplifted mountains and exposed sedimentary rocks that were otherwise hidden well below the surface of the earth. Weathering and erosion removed the overlying layers of continental siliciclastic rocks and exposed underlying formations with different mineralogy and chemistry. This causes the striking variation in colors seen across the Rainbow Mountains.
how they got the color we see today.
Precipitated groundwater moves through the sandstone grains and deposits trace minerals in between the grains. This precipitate can build up to a point where there is no longer an pore space between the individual grains, cementing them in place. This process is what imparts the trace minerals mentioned below and allows for the otherworldly coloring of sandstones around the world.
The primary color is a deep red sandstone, not unlike the Fountain Formation that outcrops in the Flatirons, Red Rocks Park, and the Garden of the Gods all in Colorado. The red coloring is due to an iron oxide coating and cementation, also known as hematite (Fe2O3), between the sandstone grains. This is the exact same process that takes place when a piece of metal is left out in the rain and forms a red layer of rust around the outside.
Weathering, mixed with water and oxygen oxidizes elemental iron into iron oxide, which is notable for its dark red coloring. The Rainbow Mountains are largely characterized by this iron oxide staining of its sandstone Danxia formation.
Most of the time iron oxides impart a dark red pigment, however, there are instances where oxides form different colors. For example oxidized limonite or goethite will produce brown or yellow staining of sandstones, magnetite can form black staining of sandstones. If there is iron sulfide present, you will get a metallic yellow color imparted by the sulfur. Meanwhile, green coloring is often due to chlorite or iron silicate clays. These are just some examples of how sandstones can be altered in coloring during diagenesis.