The internationally recognized geomorphic term “Yardang” was originated from Uygur language which means small hill with steep escarpments, and proposed by Swedish explorer Sven Hedin as a formal technical expression when he was exploring the Lop Nor region of Northwest China in the early 20th century. It represents the ridge-like, castle-like, or hill-like erosional landform with considerable scale in extremely arid region, or some basins in arid region, where the non-completely consolidated sediments were sculptured by the wind and flood.
China owns the largest distribution of Yardangs with about 20,000 km2 in total area. The most representative Yardangs on earth are particularly concentrated in basins in Xinjiang and west of Gansu Province, as well as in the Qaidam Basin in Qinhai Province. These basins are located in the hinterland of the Eurasian continent under an extremely arid temperate continental climate.
The Basin at the middle and lower reaches of the Shule River and Lop Nor locates in the extremely arid triangle region of the Euroasian continent, one of the most arid regions in the world. The annual precipitation is lower than 50 mm. Climate here is with abundant wind and frequent sand/dust storm. The lithology of Yardang stratum are mudstone with fluvio lacustrine facies, siltstone, evaporate of neogene, middle-late pleistocene and the holocene with light brown, gray, white, khaki, and grey-green intercalary strata in some area. It includes Bulongji Yardang and Qiaowan Yardang in Guazhou County, Beihu Yardang and Dunhuang Yardang Geo-park in Dunhuang City, Loulan Yardang, Longcheng Yardang and Bailongdui Yardang in north and northeast Lop Nur basin.The Yardangs in Dunhuang Yardang Geo-park with 251km2 in area, are chartered with concentrated distribution and complex formation. They are composed by fluvio lacustrine silty clay with thin silt interlayer of middle-late pleistocene and alternately sculpted by wind and flood in a long time. Meanwhile, the Yardangs here has the best ornamental value than any other places, where all the respective Yardangs, including the ridge-shaped ones in adolescent period, the castle-shaped ones in adult stage, and isolated hill relics ones in late mature and old period can be visited. There are continuously distributed Yardangs that like grand fleets navigating over the ocean, and delicately sculptured Yardangs in peculiar shapes like sphinx, peacock and the Leaning Tower of Pisa. It was in this place that the term “Yardang” was nominated by Sven Hedin.
The nominated property possesses the most majestic Yardang landscape cluster in the arid and extremely arid desert regions in the temperate zone of the world.
The ridge-shaped Yardangs are magnificent. Hundreds of ridge-shaped Yardang, each could be several kilometers long, stretch over several tens of kilometers, giving the impression of a large fleet group in a vast sea. The representation landscape “fleets” demonstrates the magnificent beauty of Gobi deserts.
The castle-shaped Yardangs have various shapes and colors. Strata where sandstone and mudstone distribute in a staggered pattern form castles of various shapes, such as cubic hills, round hills, and temples shape, by the action of water and wind erosion. They are well-proportioned with ups and downs, preferably showing the desolation beauty of Gobi deserts.
Isolated hill relics Yardangs have peculiar shapes. The most typical ones are towers, columns, beacon tower shapes and mushroom shapes, and animal shapes such as eagle, horse, monkey and turtle, as well as human-like figures such as warriors, old men, children and spirits. The representative Yardangs are "Sphinx", "Peacock" and "the Leaning Tower of Pisa", demonstrating the unique beauty of Gobi deserts.
The nominated property has Yardangs with the most concentrated distribution, the largest scale and types, and the best preservation in the arid and extremely arid desert regions in the temperate zone in terms of geomorphic morphology
Various types of Yardangs can be found in the nominated property, such as the Mesa, Sawback, etc. at an early development stage, as well as ridge-like shapes, whale back shapes and castle shapes, etc. at the peak stage, and isolated hill relics, pagoda forest shapes, cone-like shapes, etc. at the late stage, including the complete geomorphic types of Yardangs in the whole development process. Furthermore, the nominated property includes the three most representative shapes: ridges, castles, and isolated hill relics. All the landform features and diversities are unique in the world. Dunhuang Yardangs developed typical and magnificent geomorphic types acted mainly from wind erosion in the quaternary strata of lacustrine facies, and it is also the typical area with the most concentrated, the largest scaled and the best preserved Yardang landform.
The nominated property is an outstanding example of the environmental changes as well as the geologic and geomorphic processes in the arid and extremely arid desert regions in the temperate zone
In the nominated property, the major external forces are weathering, wind erosion, flood, gravity collapse, etc. In particular, weathering and flood are active in the early stages, wind erosion is active in the middle stage and gravity collapse occurs in the late stage. The nominated property also presents the complete developing process of Yardang formation from surface weathering in the initial phase, the Yardang rudiment at the early stage, the massive landforms at maturity to disappearance at the end. The property presents the geologic processes of various geographical units, in different stratigraphic sequences, different development periods, and different types under various exogenic forces. It is an outstanding example of the on-going geologic and geomorphic process of Yardang’s generation and destruction, and is the ideal type of Yardang in the world from which the name of the landform was taken. Furthermore, Yardangs are mainly composed of fluvio lacustrine sandstone and mud stone formed in the Quaternary. The stratigraphic sequences constituting Yardang landforms recorded the ancient natural geological section under climate change, and contain important information for studying the Qinghai-Tibet plateau uplift and central Eurasia drying processes.
The nominated property is an important habitat for world endangered wild bactrian camel (Camelus ferus Przewalski)
Wild bactrian camel (Camelus ferus Przewalski) is more endangered than wild giant panda on the earth. Its world population is only about 730-880, 420-470 in China. The artiodactyla wild animals only live at Annanba in Aksai County north of Altun Mountains, Xihu in Dunhuang of Gansu province, Lop nur in Xinjiang province, and Inner Mongolia. The nominated property is an important hideout of wild bactrian camels, and the World Conservation Union has treated them as endangered species listed in the red book, and the convention on international trade has listed them as one of the first-class endangered species of the world. Wild bactrian camels have many special physiological functions that no other animals have. They are hungry, thirsty, heat-cold and aeolian sand resisting, and they are the only rare animals in the world which can drink salt water and eat salt plant for survival. They are intensively-distributed in this nominated property, and criss-cross Yardang landforms can provide hiding places for them.
Criterion (vii): The nomination property presents the most majestic Yardang landscape in the arid and extremely arid desert regions in the temperate zone, including ridge-shaped Yardang landforms like a large fleet of ships in a vast sea, castle-shaped Yardang landforms of various shape combinations and isolated hill relic Yardang landforms with strange shapes and excellent aesthetic values, that contribute to the spectacular beauty of the desolate Gobi desert.
Criterion (viii): The nominated property has various types of Yardangs that representing all the developing processes from the surface weathering, embryonic states, and mature states to disappearance. Furthermore, the nominated property is an outstanding example of wind-erosion, and complex wind and water erosion geomorphic processes in the arid and extremely arid desert regions in the temperate zone, reflecting the central Eurasia drying processes. It also contains important information for studying of the Qinghai-Tibet plateau uplift and central Eurasia drying processes.
The nominated area and buffer zone presents the necessary elements of natural beauty, geomorphic features and geomorphic processes, including castle-like, ridge-like and isolated hill relics Yardangs of great aesthetic importance. Most areas of Dunhuang Yardang are non-populated and no human influence is present.
Yardangs are found mainly at the edge of deserts in arid or extremely arid regions with sparse precipitation, little vegetation and strong wind erosion, such as the desert in west Asia and central Asia, the Sahara Desert and the Namibian Desert in Africa, the western desert in North America, the west coast desert in South America, etc. In China, Yardang are found mainly in basins in north and south Xinjiang Uygur Autonomous Region as well as in the Qaidam Basin in Qinghai Province. The nomination property is where the geomorphic term Yardang was originated and it is also the most concentrated area of Yardang in the world. Compare to Yardangs in other places, Dunhuang Yardangs has various types and geological bases, complex formation mechanisms, and records the central Eurasia drying processes. The nominated area is the most typical example in the world of the environmental changes and geomorphic processes in arid and extremely arid desert regions in the temperate zone, and presents the combinations of different types of Yardang landforms. It is a unique and irreplaceable natural heritage.