How many years has the Yadan landform been formed, and the Yadan landform formation process

The formation process of Yadan landform: under the long-term geological weathering, wind and flowing water can take away the loose sand layer, and the expansion and contraction effect caused by the drastic temperature difference in the desert area can make the hard mudstone layer crack, and the exposed sand layer is carried away by water and wind, and gradually evolves into a groove. In addition, the erosion of rain and snow water widens and expands the cracks, and the strong winds continue to erode the cracks, and the sand layer slowly forms wind-eroded valleys and depressions, and the hard rocks left behind form island-shaped mounds of different sizes.

Yadan landform is a typical wind-erosion landform, also known as wind-erosion ridge groove, or wind-erosion ridge. "Yadan" was originally a Uyghur language in China, meaning a steep mound.

In the extremely arid areas, the bottom of some dry lakes is often cracked due to drying, and the wind blows along these fissures, and the fissures become larger and larger, so that the originally flat ground develops into many irregular dorsal crucian ridges and wide and shallow grooves, and this fragmented ground becomes the Yadan landform. Some of the landforms look like ancient castles and are commonly known as Devil's Castles.

Two crucial factors are needed to form the Yadan landform: first, the geological basis of the Yadan landform, that is, the lacustrine sedimentary strata; The second is external erosion, that is, the erosion of strong directional winds in the desert and the erosion of flowing water. Over time, the sand layer in the vast Gobi was gradually carried away, leaving behind patches of soil, and this peculiar landform was slowly formed.

Yadan landform is a special landform in Lop Nur area of Xinjiang, which is a typical wind-erosive landform.

1. Lithological conditions: Lithological conditions are the basis for the formation and development of Yadan. Due to the inconsistent definition of Yadan, Yadan formation and development can be on rocks of different hardness and different ages.

2. Environmental conditions: The vast majority of Yadan is found to be distributed in extremely arid areas, with annual precipitation of less than 50 mm, and sparse vegetation in plain areas, with strong wind erosion; or relatively humid depressions, areas with strong salt weathering and groundwater.

3. Dynamic conditions: Dynamic conditions are the key factors in the formation of Yadan landform, and now it mainly focuses on the study of external force conditions, including wind and hydropower.

Yadan landform is a special landform in Lop Nur area of Xinjiang, which is a typical wind-erosive landform.

"Yadan" means "small mountain with steep walls" in Uyghur, and the event was later selected for the "China National Geographic" magazine and the Chinese Geographical Society jointly launched the "Centennial Discoveries of Chinese Geography".

Yadan landform now refers to a kind of wind erosion landform in dry areas, in which the ground formed by the soil-like sediments of rivers and lakes is formed by weathering, intermittent water erosion and wind erosion, forming a combination of wind erosion mounds and wind erosion depressions (trenches) parallel to and intermittently arranged with the prevailing wind direction.

Cross-country through the world's largest Yadan landform group.

The Yadan landform is a typical aeolian landform. Due to the abrasive effect of the wind, the lower part of the hill bag is often subjected to strong denudation, and gradually forms a concave shape. If the rock layer in the upper part of the hill is relatively loose, it is easy to collapse under the action of gravity to form a steep wall, thus forming the Yadan landform, some of which look like an ancient castle, commonly known as the Devil's City.

Yadan landform is a typical wind erosion landform, due to the wind erosion of the lake or alluvial plain in the arid area, the lower part of the hill often suffers from strong denudation, and gradually forms the ground fragmented and concave ridge form, some landforms look like ancient castles, commonly known as the devil's city.

The raised wind-eroded mounds are elongated and arranged in a direction parallel to the main wind direction.

The erosion of temporary flowing water and the erosion of lake water are also one of the important reasons for the formation of Yadan. The Yadan landform is most typical in the northwest of Lop Nur in the Tarim Basin of China.

It refers to the wind blowing away the lake or alluvial plain in the arid area, forming a fragmented ridge terrain on the ground, called Yadan in Uyghur language, and Qiwu means a hillock with steep walls. The raised wind-eroded earth piers are arranged in a long strip shape and are arranged in a direction parallel to the main wind direction. In recent years, studies have shown that the erosion of temporary flowing water and the erosion of lake water are also one of the main reasons for the formation of Yadan.

The Yadan landform is most typical near Loulan in the northwest of Lop Nur.

Yadan landform classification

The purpose of Yadan classification is to classify many Yadan landforms with different morphology, scale, age, development stage and origin, and to determine their location and relationship in the Yadan landform classification system. There are differences in the various classification systems due to the different classification principles employed.

According to the existing research, there are three classification systems in China. Among them, Chen Zongqi divided Yadan into Hubian, Maisai and Yadan according to the shape according to the size and age of formation; According to the cause, Xia Xuncheng divided Yadan into three categories: Yadan with wind erosion, Yadan with water erosion, and Yadan with water erosion followed by wind erosion. Zheng Benxing is divided into red Yadan, white Yadan and yellow Yadan according to the color difference formed by the different geochemical composition of the Yadan formation.

There are two classification systems in foreign countries, except for Cooke et al., which are divided into small, medium and large Yadan according to the morphological size of Yadan, and it is necessary to pay attention to the classification system proposed by Halimov et al. for the Yadan landform in the Qaidam Basin according to the morphology and development stage, which is qualitative and quantitative, which is worthy of reference in the current Yadan landform classification research.

Above** Yadan landform.