Zhangye Colorful Hills

The nominated property is located in Zhangye City, Gansu Province, western China. Centered on Su’nan Yugur Autonomous County, it also extends slightly into Linze County and Ganzhou District. Overall, it lies in the transitional zone between the foreland fault belt on the northeastern edge of the Qinghai-Tibet Plateau and the Hexi Corridor, at the junction of the Qilian Orogenic Belt and the Alxa Block (Song et al., 2013). Positioned in the mid-latitude continental interior, it is characterized by a continental arid climate with abundant sunshine, strong solar radiation, large temperature differences between day and night, and four distinct seasons.

Zhangye Colorful Hills, the nominated property, consists of multicolored fluvial-lacustrine rock formations from the Early Cretaceous that have undergone folding (Wang et al., 2022). Within the property are the Upper Member of the Lower Cretaceous Xinminpu Group, the scenic strata, the southern limb of the Aohe Fold, and the Colorful Hills landform. The nominated property covers an area of 4,646 hectares, with a buffer zone of 4,148 hectares.

The scenic strata of the Zhangye Colorful Hills belong to the Upper Member of the Lower Cretaceous Xinminpu Group (K₁xm^b), dating back 114 million to 106 million years. These strata were deposited in a continental fluvial-lacustrine environment. The lithology is primarily siltstone and sandstone interbedded with mudstone, featuring a low degree of cementation and poor resistance to weathering. Consequently, these rocks are prone to fragmentation, making it difficult for steep slopes and cliffs to form. Instead, they tend to form gently rounded, relatively low-lying hill landforms. Within the nominated property, the Zhangye Colorful Hills has experienced various tectonic regimes, including intracontinental extension during the Early Cretaceous, intracontinental compression and deformation during the Late Cretaceous, and the massive uplift and expansion of the plateau. These complex tectonic processes and significant topographic changes resulted in diverse depositional environments. Consequently, brilliantly colored strata—red, purplish red, yellow-green, gray-green, gray-black, and more are formed alternately in striking patterns. In addition, external forces such as wind, water, gravity, and freezing have collectively sculpted this unique landform. Each factor and evolutionary stage played an indispensable role in creating the breathtaking beauty of today’s Zhangye Colorful Hills.

Enriching the variety of hilly landform types, the Zhangye Colorful Hills hold an irreplaceable position among global geomorphological landscapes. They exemplify the remote transfer of tectonic stress from plate margins into the continental interior and serve as a critical window on the leading edge of the Qinghai-Tibet Plateau’s growth and outward expansion. Therefore, they reveal the complexity of the plateau’s tectonic evolution during uplift and embody both the striking “marvel” and expansive “vastness” of natural landscapes. The strata’s colors and rhythmic layering reflect the interplay of time and environment, making them an indispensable natural wonder in the Earth’s evolutionary history.

Criterion (vii): Containing superlative natural phenomena or areas of exceptional natural beauty and aesthetic importance. 

Image Beauty

The spatial morphology of the Zhangye Colorful Hills presents a distinctive planar geometric pattern. Situated in the vast expanses of western China, the resulting visual impact transcends natural scientific understanding and value—it is a comprehensive experience that integrates subjective human perception and emotional response.

Image Beauty of “Wonder” 

The main scenic area of the Zhangye Colorful Hills lies on one limb of a fold, with the strata dipping in a nearly uniform manner and thicknesses that align well with visual perception. On plan view, they form a trumpet-shaped overlapping fold opening toward the southeast. This special planar geometry imparts a surprising and delightful experience: whether climbing to mid-height, viewing from above, or examining remote-sensing images, one perceives a striking visual impact. It stimulates curiosity and a desire to explore, evoking a unique “marvel” in aesthetic appreciation.

Image Beauty of “Vastness”

The landscape of the Zhangye Colorful Hills is predominantly bare soil or gravelly rock without vegetation. The desolate land appears as if splashed with fiery flames, while the imposing rocky hills seem cloaked in brilliant, multi-hued garments. Standing in the nominated property and look around, one sees the overlapping ridges of the Qilian Mountains dissected by numerous valleys, while the corridor basin is flat, broad, and open. Strata of various colors extend continuously with the undulating slopes, resembling countless bolts of colorful silk. They evoke the image of rows of rainbows draped along the Qilian foothills. Under the blue sky and white clouds, this vista of “vastness” appears even more expansive, open, and majestic, inspiring awe at nature’s grand beauty.

Color Beauty

Due to diverse depositional environments, the scenic strata of the Zhangye Colorful Hills exhibits more than thirty distinct colors. At the same time, the thicknesses of differently colored rock layers vary from a few tens of centimeters to several meters. Stacked in succession, these strata produce banded landforms rich in rhythm and layers, forming a uniquely captivating visual spectacle.

Abundant Beauty of Color

Zhangye Colorful Hills exhibit three main color systems—reddish brown, bluish gray, and pale yellow—whose coloration primarily stems from iron-bearing minerals within the strata. Under alternating oxidizing-reducing conditions, Fe²⁺ and Fe³⁺ transform back and forth, migrating repeatedly between solid and liquid phases, thus producing diverse forms of iron. These forms include iron oxides, iron carbonates, iron sulfides, and iron in clay minerals. Specifically, the bluish-gray, grayish-green, and dark green strata contain only clay-mineral iron; the yellow strata mainly host clay-mineral iron and iron sulfides; the light red strata contain both clay-mineral iron and iron oxides; and the dark red strata also hold iron carbonates (Yang et al., 2001; Liu, 2021). It is precisely these special yet typical “geological ingredients” that support and create the brilliant multicolored bands adorning the Colorful Hills, reminiscent of glowing clouds in the sky.

Rhythmic Beauty of Color

Differences in the relative thickness of strata of various color systems, coupled with differential weathering, have shaped a wide variety of landforms. For rock layers mainly of red-brown and blue-gray hues with a stratum thickness ratio of 3:1 and 2:1, they form “white-through-red” stripes on fan-shaped slopes created by weathering, resembling neatly arranged shells. Those with a stratum thickness ratio close to 1:1 form red-and-white alternating banded strata, which, accompanied by the undulations of the strata, look like layer upon layer of colorful waves. For rock layers with main color tones of red, yellow, and gray, the thickness ratio of strata with different color tones is basically 1:1, arranged in rhythms such as red-yellow-gray, red-yellow-gray-yellow, or red-gray-red-yellow-gray, presenting a striking visual impact.

Dynamic Beauty

Through changes, motion, and interplay of light and shadow, the Zhangye Colorful Hills displays a unique sense of beauty that varies dramatically at different times.

In certain places, the rock formations are especially distinctive—some jagged and rugged, others resembling human or animal figures—imbued with fascinating charm. Sunrises and sunsets differ, fair and overcast skies vary, so that each visit yields a new scene, and each departure reveals yet another.

Over the course of a single day, the colors of the landforms also change: In the morning light, they appear gentle and alluring. Under the midday sun, they become dazzlingly vibrant and radiant. At sunset, they deepen into solemn yet magnificent hues. In 2011, the authoritative U.S. magazine, National Geographic named Zhangye Colorful Hills one of the “Top 10 Magical Geographical Wonders in the World.”

Criterion (viii): To be outstanding examples representing major stages of earth’s history, including the record of life, significant ongoing geological processes in the development of landforms, or significant geomorphic or physiographic features. 

1. The nominated property is located on the northeastern edge of the Qinghai-Tibet Plateau, serving as a frontline window for the growth and outward expansion of the plateau (Tapponnier et al., 1990; George et al., 2001; Zhang et al., 2004, 2007; Zheng et al., 2010, 2017; Yin, 2010; Zheng et al., 2013; Yu et al., 2019). The Zhangye Colorful Hills fold, acting as the hanging wall of a thrust fault, has been vertically uplifted as a whole. Additionally, the significantly horizontal attitude of the Cenozoic strata demonstrates the expansion of the northeastern Qinghai-Tibet Plateau is characterized by intense reverse fault activity along regional faults (Zhang et al., 2006; Wang et al., 2014; Zheng et al., 2016; Wang et al., 2022). This provides a prominent example for studying the complexity of tectonic evolution during the uplift of the Qinghai-Tibet Plateau. The lithological combination of the Upper Member of the Xinminpu Group (K₁xm^b) of the Lower Cretaceous within the nominated area, along with Aohe faults, superimposed folds, and associated structural deformations such as wedge faults, reverse faults, and axial plane cleavage, records the intracontinental extension and compressive inversion processes of the Eurasian Plate during the Mesozoic era. It illustrates the far-field effects of plate boundary stresses in the continental interior.

a. During the Early Cretaceous, the nominated area was located well within the Eurasian Plate, far from its margins. Along the southern edge of the Eurasian Plate, the collision of the Lhasa and Qiangtang terranes generated nearly north-south compressional stresses (Dewey et al., 1988; Ma et al., 2016; Dong et al., 2019). South of the Qilian Mountains, in the Qaidam region, this resulted in a compressional setting with a series of compression-related subsidence basins (the Qaidam Basin) (Zhang, 2020). Meanwhile, north of the Qilian Mountains, the overall eastward displacement of the Alxa Block caused the Hexi Corridor region turning into an approximately east–west extensional environment and leading to the formation of a series of fault-depression basins (Vincent and Allen, 1999; Zhong et al., 2011), including the Jiuquan Basin, Minle Basin, Chaoshui Basin, and Wuwei Basin. The nominated property lies within the Minle Basin, which accumulated nearly 2,500 meters of fluvial-lacustrine clastic strata, referred to as the Xinminpu Group (K₁xm) have been deposited. The Upper Member of this group (K₁xm^b) is precisely the host stratum of the Zhangye Colorful Hills.

b. From the late Early Cretaceous to the early Late Cretaceous, the northward subduction of the Neo-Tethys Ocean produced a northeast–southwest compressional stress (Dong et al., 2019). This caused the Qilian Mountains to uplift (George et al., 2001; Jolivet, 2001). Meanwhile, the Hexi Corridor to the north of the Qilian Mountains, the tectonic regime shifted from extension to compression; the basins ceased to develop (Zhang et al., 2021), and within the nominated property, Late Cretaceous strata are absent. Structural-deformation orientation data indicate that, almost simultaneously, this region also experienced northwest–southeast compressional stress. Under this bidirectional compression, the main body of the nominated property displays a trumpet-shaped, southeast-opening fold in plan view—a classic example of a superimposed fold. The Zhangye Colorful Hills lies on the south limb near the core of this superimposed syncline; relative to the two limbs, this position experiences slower erosion. Consequently, this unique structural form has protected the Colorful Hills. Throughout the Late Cretaceous, the nominated site and most of the surrounding area underwent uplift and denudation, stripping away and leveling all exposed Early Cretaceous strata at the surface.

c. During the Cenozoic, the uplift and outward expansion of the Qinghai-Tibet Plateau exerted intense compressional forces on its northern and eastern margins. Along the northern margin, north of the Qilian Mountains, a series of thrust and strike-slip faults formed (George et al., 2001; An et al., 2020; Li et al., 2020), including the North Qilian Thrust Fault, the Yumushan Thrust Fault, and the Haiyuan Left-Lateral Strike-Slip Fault (Zhang et al., 2006; Wang et al., 2014; Zheng et al., 2016). The nominated property lies between the North Qilian Fault and the Yumushan Fault, both of which underwent strong thrust activity in the Cenozoic, absorbing the powerful compressional stress associated with the plateau’s expansion. As a result, the nominated property, being on the hanging wall of these thrust faults, was uplifted as a whole and did not experience intense horizontal shortening. Within the site, Cenozoic strata are nearly horizontal, resting with angular unconformity atop Early Cretaceous folded strata (Wang et al., 2022). One of the resulting formations, known as the “Little Potala Palace,” exemplifies the property’s structural deformation style during the plateau’s expansion. The overall vertical uplift during the Qinghai-Tibet Plateau’s expansion has maximally preserved the property’s integrity.

2.The scenic strata of the Zhangye Colorful Hills belongs to the Upper Member (K₁xm^b) of the Lower Cretaceous Xinminbao Group which was deposited in a continental fluvial-lacustrine environment. Characterized by fine-grained, muddy to silty particles with a low degree of cementation and poor weathering resistance, these rocks are easily fragmented. They thus tend to form a landform of gently rounded, relatively low-lying hills. During the Cenozoic, the uplift of the Qinghai-Tibet Plateau—a major geological event—brought about a stepwise intensification of aridity in this region (Ding et al., 2017, 2022; Wu et al., 2022). In turn, this leads to weathering processes unique to arid zones—chiefly wind erosion, seasonal fluvial erosion, and freeze-thaw effects—which worked upon the Early Cretaceous strata that had undergone folding, sculpting the Colorful Hills. The sedimentary environment was highly variable, with alternating oxidizing and reducing conditions, causing significant differences in the types and abundances of colors in minerals (hematite, goethite, pyrite, etc.) of the strata (Yang et al., 2001; Liu, 2021). Consequently, the Zhangye Colorful Hills display over thirty brilliant colors. Moreover, the predominant thickness ratios of stratified layers—3:1, 2:1, and 1:1—create striking rhythms and layering, with a vivid sense of order. This combination of colorful strata, rhythmic layering has no known parallels in hilly landscapes worldwide.

The Aohe Fold region of the Zhangye Colorful Hills has served as a model site for the long-term geomorphic evolution within the interior of the Asian continent since the Early Cretaceous, encompassing extension and compression, sedimentation and deformation, and uplift and denudation. It is an outstanding example of significant geomorphic features shaped by past and ongoing endogenic (internal) and exogenic (external) geological processes. By broadening and enriching the variety of known hilly landforms, the Zhangye Colorful Hills hold an irreplaceable position among the world’s geomorphological landscapes.

The Early Cretaceous strata in the nominated property are extensively and continuously developed, with excellent exposures. Different lithological assemblages record all the changes in the basin’s depositional environment, thereby comprehensively reflecting the basin’s depositional history from a stratigraphic and structural deformation perspective. Having initially formed as an Early Cretaceous extensional basin, the nominated area later experienced compressional modification, resulting in superimposed folds. Different types of compressional structural deformation, including wedge faults, high-angle thrust faults, and axial-plane cleavage, are observable on both limbs of the folds. These features record two directions of compressional stress during the late Early Cretaceous to the early Late Cretaceous. Cenozoic strata in the nominated property lie nearly horizontally, unconformably over the folded Early Cretaceous strata, demonstrating a predominantly vertical uplift associated with the Qinghai-Tibet Plateau’s expansion. The Early Cretaceous strata are continuous and well-preserved, and meanwhile retain evidence of structural changes from the basin’s sedimentation through its subsequent deformation, they provide a complete record of the basin’s evolutionary process—from deposition to later modification.

 Zhangye Colorful Hills, as a typical erosional landform in northwest China’s arid regions, exhibit integrity through the interaction of multiple erosional processes and the coexistence of diverse landform types. Weathering, wind erosion, and fluvial erosion are the principal forces shaping these Colorful Hills. These processes interact and influence each other, collectively shaping the diverse landscapes. From the nearly vertical strata "Sleeping Beauty," Monocline “Scallop-shaped Hill”, “Rainbow-like Screen,” to the “Fairy’s Slipper” in Peach Blossom Gully, various multicolored hills showcase combinations of different strata attitudes and slope morphologies. Additionally, a Pair of Stone Pillars features such as the Hanging Mud Strip “Yugur Tassels,” clastic rock pillars “Cowherd and Weaver Girl”, as well as collapse, landslide landforms, and sinkholes further enhance the landscape diversity of Zhangye Colorful Hills, making it a comprehensive and varied erosional landform system.

Principles for Defining the Nominated Property and Buffer Zone Boundaries

1. Including all elements required to express its Outstanding Universal Value;
2. Ensure a complete representation of the OUV and the geological heritage’s features and processes;
3. Maintain integrity by aligning, whenever possible, the boundaries of the nominated site with stratigraphic boundaries, ridgelines, valleys, foothills, and rivers.
4. Ensuring that areas designated as protected regions coincide with existing protected areas or are encompassed within them;
5. Maximizing the avoidance of human activities that could negatively impact the heritage value to maintain the site's natural condition;
6. Positioning the buffer zone around the nomination area to provide additional protection and management buffers;

The nominated site encompasses the outcrops of the Zhangye Colorful Hills and the tectonic system, covering the complete range of Early Cretaceous strata and structural deformations at different stages. The buffer zone is delineated based on the boundaries of the national geopark, considering stratigraphic lines, ridges, valleys, rivers, and other geomorphological elements.

Located within Zhangye National Geopark, the nominated property is protected and managed in accordance with the relevant requirements of the "Overall Plan for Zhangye National Geopark" and "Overall Plan for Zhangye Global Geopark."

The nominated Zhangye Colorful Hills site fully includes the Aohe Fold and the erosion landform system's geo-heritage that reflect the heritage's value. In terms of elements, scope, and value, it is complete and meets the requirements for integrity, protection, and management as stipulated in the Operational Guidelines for the Implementation of the World Heritage Convention.