Going to the "Devil City" for adventure is definitely not a trip that can be taken at any time.

On July 23, the news that a Zhejiang University teacher lost contact while conducting field work in the uninhabited area of ​​the Yadan landform in Qinghai attracted widespread attention. He was successfully rescued after being missing for more than 30 hours. It is understood that the place where the teacher lost contact is called the "Devil City", where even locals can easily get lost after entering.

Rescuers escorted the teacher down the mountain. Image source: China National Radio

What is the Yadan landform? How was it formed? How dangerous is this "most unlike-Earth place on Earth"? What should you do if you accidentally stray into it?

The roads in the "Devil City" are difficult to distinguish

Formed by erosion by wind and water

The word "Yardang" originated in the Lop Nur area of ​​China. It was originally a transliteration of the Uyghur language, meaning a hill with steep walls.

The so-called Yardang landform refers to a type of landform dominated by ridges, towers and columns, which is based on river-lake phases formed in the geological history period and not completely consolidated sediments, and is shaped by erosion mainly by wind erosion and supplemented by water erosion. It is mostly distributed on the edge of the desert with flat surface, dry and windy.

Photo by Xinhua News Agency reporter Hu Huhu

Globally, it is distributed on all continents except Oceania and Antarctica, such as Egypt, Libya, and Chad in Africa, the Taklimakan Desert, Qaidam Basin and some deserts in Iran in Asia, the Mojave Desert in North America, and the Ebro River Depression in the semi-arid area of ​​Spain in Europe.

Thanks to the application of high-resolution remote sensing, planetary probes and other technologies, similar Yardang landforms have been found on Mars and Venus. The distribution area of ​​Yardang landforms in my country is more than 20,000 square kilometers, mainly located in the arid and windy areas of the northwest, including the Qaidam Basin, the middle and lower reaches of the Shule River, the area around Lop Nur and the Tuha Basin.

The reason why the Yadan landform is called the "Devil's City" is that its side walls are steep and extremely difficult to climb. These red and yellow mounds of various shapes and sizes are generally 12-20 meters high. Visitors will be amazed and reluctant to leave because of the magical landscape that is so ingenious. However, due to the limited vision, it is as if they have entered a maze created by nature, and the direction of the road is difficult to identify.

On the other hand, the wind howled and the yellow sand covered the sun. Yadan landforms are often located at the wind outlet, also known as the Wind City. Whenever the wind blows, the yellow sand fills the sky, especially after nightfall, the strong wind swirls in the Wind City, and the sharp desert wind makes a terrifying whistle, like the howling of ghosts and wolves, which is creepy. If you are there at this time, you will have a deeper understanding of the origin of the title of "Devil City".

Growth and development is slow and complex

Wind erosion is most intense in young and middle-aged people

The formation process of the Yardang landform is slow and complex, and is typically divided into three stages. The first is the infancy, when the surface of the river-lake deposits was uplifted intermittently and the lake water receded, forming vertical joints or fissures in the strata. The action of flowing water deepened and widened these joints and fissures, forming shallow grooves, and the originally flat terrain became undulating and uneven, and the prototype of the Yardang landform began to appear.

Xinhua News Agency (Photo by Li Hua)

The second is the young and middle-aged period, during which wind erosion is the most intense. The horizontal joints or fissures of the yardang body continue to erode and gradually split. The large yardang body will split into multiple smaller adjacent yardang bodies, forming ridge-shaped, wall-shaped, tower-shaped, and column-shaped yardang landforms. The yardang landforms in this period are strange and colorful, with the most spectacular and mysterious scenery. If the lake water invades again, it can form a more wonderful and dreamy water yardang.

The third is the old age extinction period. With the continuation of erosion, the collapse along the joints is significantly strengthened under the action of gravity, forming Yardang residual hills. The valleys continue to expand, eventually forming a wide valley, and the Yardang landform gradually disappears.

In my country, there are three Yadan landforms known as "Devil City": the "Devil City" in Urho, Karamay City, Xinjiang, the "Devil City" in Nominfengcheng in the Karamay Mountains on the northwestern edge of the General Gobi Desert, and the "Devil City" in Dunhuang.

The more spectacular it is, the easier it is to get lost

Take safety precautions and choose a good date to travel

The areas where Yadan landforms are developed are generally far away from urban areas. Due to the windy seasons and changeable climate, the more spectacular it is, the easier it is to get lost, leading to accidents. Therefore, exploring unfamiliar Yadan landforms is definitely not a trip that can be taken at will, and you should be fully prepared.

Before entering, pay close attention to the weather forecast, choose a good day, hire a professional guide, use modern technologies such as drones and Beidou, and plan the survey route and corresponding emergency safety measures. When traveling, you should ensure that you have enough food, water and medicine, and pay attention to keeping warm while preventing heatstroke . After entering the Yadan landform, follow the route planned in advance, make safety marks, complete the task on time and at a fixed point, and return safely within the specified time.

Source: Popular Science Times

Author: Ren Jinfeng (Senior Engineer of Guangzhou Marine Geological Survey Bureau)

Editor: Wu Tong

Review: Wang Fei

Final judge: Chen Lei